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rfc:rfc3127

Network Working Group D. Mitton Request for Comments: 3127 Nortel Networks Category: Informational M. St.Johns

                                                Rainmaker Technologies
                                                            S. Barkley
                                                                 UUNET
                                                             D. Nelson
                                                    Enterasys Networks
                                                              B. Patil
                                                                 Nokia
                                                            M. Stevens
                                                     Ellacoya Networks
                                                              B. Wolff
                                                          Databus Inc.
                                                             June 2001
           Authentication, Authorization, and Accounting:
                        Protocol Evaluation

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

 This memo represents the process and findings of the Authentication,
 Authorization, and Accounting Working Group (AAA WG) panel evaluating
 protocols proposed against the AAA Network Access Requirements, RFC
 2989.  Due to time constraints of this report, this document is not
 as fully polished as it might have been desired.  But it remains
 mostly in this state to document the results as presented.

Mitton, et al. Informational [Page 1] RFC 3127 AAA Protocol Evaluation Process June 2001

Table of Contents

 1.  Process Description  . . . . . . . . . . . . . . . . . . . . . .3
 1.1  WG Co-Chair's Note  . . . . . . . . . . . . . . . . . . . . . .3
 1.2  Chairman's Note . . . . . . . . . . . . . . . . . . . . . . . .4
 1.3  Members Statements  . . . . . . . . . . . . . . . . . . . . . .4
 1.4  Requirements Validation Process . . . . . . . . . . . . . . . .6
 1.5  Proposal Evaluation . . . . . . . . . . . . . . . . . . . . . .7
 1.6  Final Recommendations Process . . . . . . . . . . . . . . . . .7
 2.  Protocol Proposals . . . . . . . . . . . . . . . . . . . . . . .8
 3.  Item Level Compliance Evaluation  . . . . . . . . . . . . . . . 8
 3.1  General Requirements . . . . . . . . . . . . . . . . . . . . . 9
 3.2  Authentication Requirements. . . . . . . . . . . . . . . . . .11
 3.3  Authorization Requirements . . . . . . . . . . . . . . . . . .12
 3.4  Accounting Requirements  . . . . . . . . . . . . . . . . . . .12
 3.5  MOBILE IP Requirements . . . . . . . . . . . . . . . . . . . .13
 4.  Protocol Evaluation Summaries . . . . . . . . . . . . . . . . .14
 4.1  SNMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
 4.2  Radius++ . . . . . . . . . . . . . . . . . . . . . . . . . . .14
 4.3  Diameter . . . . . . . . . . . . . . . . . . . . . . . . . . .14
 4.4  COPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
 4.5  Summary Recommendation   . . . . . . . . . . . . . . . . . . .14
 5.  Security Considerations . . . . . . . . . . . . . . . . . . . .14
 6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . .15
 7.  Authors' Addresses. . . . . . . . . . . . . . . . . . . . . . .15
 A.  Appendix A - Summary Evaluations  . . . . . . . . . . . . . . .17
 B.  Appendix B - Review of the Requirements . . . . . . . . . . . .18
 B.1 General Requirements. . . . . . . . . . . . . . . . . . . . . .18
 B.2 Authentication Requirements . . . . . . . . . . . . . . . . . .19
 B.3 Authorization Requirements. . . . . . . . . . . . . . . . . . .19
 B.4 Accounting Requirements . . . . . . . . . . . . . . . . . . . .20
 C.  Appendix C - Position Briefs  . . . . . . . . . . . . . . . . .21
 C.1  SNMP PRO Evaluation  . . . . . . . . . . . . . . . . . . . . .21
 C.2  SNMP CON Evaluation  . . . . . . . . . . . . . . . . . . . . .28
 C.3  RADIUS+ PRO Evaluation . . . . . . . . . . . . . . . . . . . .33
 C.4  RADIUS+ CON Evaluation . . . . . . . . . . . . . . . . . . . .37
 C.5  Diameter PRO Evaluation  . . . . . . . . . . . . . . . . . . .44
 C.6  Diameter CON Evaluation  . . . . . . . . . . . . . . . . . . .50
 C.7  COPS PRO Evaluation  . . . . . . . . . . . . . . . . . . . . .55
 C.8  COPS CON Evaluation  . . . . . . . . . . . . . . . . . . . . .59
 D.  Appendix D - Meeting Notes  . . . . . . . . . . . . . . . . . .66
 D.1  Minutes of 22-Jun-2000 Teleconference  . . . . . . . . . . . .66
 D.2  Minutes of 27-Jun-2000 Teleconference  . . . . . . . . . . . .68
 D.3  Minutes of 29-Jun-2000 Teleconference  . . . . . . . . . . . .73
 D.4  Minutes of 06-Jul-2000 Teleconference  . . . . . . . . . . . .78
 D.5  Minutes of 11-Jul-2000 Teleconference  . . . . . . . . . . . .80
 Full Copyright Statement  . . . . . . . . . . . . . . . . . . . . .84

Mitton, et al. Informational [Page 2] RFC 3127 AAA Protocol Evaluation Process June 2001

1. Process Description

 Due to time constraints, the original draft of this document was
 rushed to meet the publication deadline of the June 2000 Pittsburgh
 meeting.  Since the meeting has passed, we do not wish to
 substantially revise the findings within this document, so that we
 don't give the appearance of changing information after the
 presentation.  Only additional descriptions of the process,
 formatting, layout editing and errors of fact have been corrected in
 subsequent revisions.

1.1. WG Co-Chair's Note:

 After the AAA WG re-charter was approved, and the Network Access
 Requirements document passed AAA WG Last Call, a Solicitation of
 Protocol Submissions was issued on 4/13/2000.  The Solicitation was
 sent to the AAA WG mailing list, as well as to other IETF WG mailing
 lists related to AAA, including NASREQ, Mobile IP, RAP, and SNMPv3.
 Submissions were solicited effective immediately.  Authors of
 candidate protocols were requested to notify the AAA WG chairs of
 their intent to submit a candidate protocol.  It was suggested that
 this notification be sent by May 1, 2000.
 Protocol submissions and compliance description documents were to be
 submitted in Internet Draft format by email to internet-
 drafts@ietf.org.  The deadline for submissions was June 1, 2000.  To
 be considered as a candidate, submissions needed to include an
 unqualified RFC 2026 statement, as described at:
 http://www.ietf.org/Sec10.txt
 In order to assist the AAA WG in evaluating the protocol submissions
 and compliance description documents, the AAA WG chairs then formed
 an evaluation team, which was announced on May 20, 2000.  The job of
 the team was be to put together an Internet Draft documenting their
 evaluation of the protocol submissions.  The goal is to have a first
 draft available prior to the July 14, 2000 submission deadline for
 IETF 48.
 In composing the evaluation draft, the evaluation team was asked to
 draw from the protocol specifications, the compliance descriptions,
 and other relevant documents, the Network Access Requirements
 document, RFC 2989.
 Mike St. Johns was asked to chair the evaluation team.  The chairs of
 WGs related to AAA were also invited to join the team.  These
 included Dave Mitton, co-chair of NASREQ WG, Basavaraj Patil, co-
 chair of Mobile IP WG, and Mark Stevens, co-chair of the RAP WG.

Mitton, et al. Informational [Page 3] RFC 3127 AAA Protocol Evaluation Process June 2001

 Additional members of the evaluation team were chosen to represent
 the interests of network operators as well as developers of AAA
 client and server software.
 As usual, the IESG advised the evaluation team.  IESG advisors
 included Randy Bush and Bert Wijnen, Directors of the Operations and
 Management Area.

1.2. Chairman's Note:

 This document is the result of 6 weeks of intense work by the panel
 listed below.  Our mission was to evaluate the various AAA proposals
 and provide recommendations to the AAA working group and to the IESG
 on the viability of each of the proposals.
 The evaluation process had three distinct phases.  1) Validate the
 AAA requirements document [AAAReqts] against the base requirements
 documents for NASREQ, MOBILEIP and ROAMOPS.  2) Evaluate each of the
 SNMP, Radius++, Diameter and COPS proposal claims against the
 validated requirements.  3) Provide final recommendations based on
 side by side comparison for each proposal on a requirement by
 requirement basis.
 In general, the ONLY information the evaluators were allowed to use
 throughout the process was that provided in the source documents (the
 requirements document and the proposal) or documents referenced by
 the source documents.  In other words, if it wasn't written down, it
 generally didn't exist.  Our cutoff for acceptance of information was
 1 June 2000 - any submissions after that time were not considered in
 the panel's deliberations.

1.3. Members Statements

 The group was chaired by Michael St.Johns.  David Mitton was the
 document editor.  Following are the background statements and any
 conflicts of interest from them and the rest of the panel.
 Michael St. Johns, Rainmaker Technologies
 I have no known conflicts of interest with respect to the AAA
 process.  I have neither advocated nor participated in the creation
 of any of the submissions.  My company is a service company (ISP) and
 will not be involved in the manufacture or sale  of AAA enabled
 products.  Other than my participation as the chair of the AAA
 evaluation process, I have not had any contact with the AAA standards
 process.

Mitton, et al. Informational [Page 4] RFC 3127 AAA Protocol Evaluation Process June 2001

 David Mitton, Nortel Networks
 I have been Nasreq WG co-chair and author of several Nasreq drafts.
 As well as, previously contributed to several RADIUS drafts.
 I have been a RADIUS NAS implementor and Technical Prime on our
 Server products, so know it extremely well.  In my current job role I
 am involved with Nortel's IP Mobility products, which support
 Diameter.
 I have written a presentation on COPS vs NASreq Requirements for a
 Nasreq meeting, but have not implemented it, nor consider myself an
 through expert on the subject.
 Stuart Barkley, UUNET
 I've been working for 5 years at UUNET on various parts of our dialup
 network.  I have extensive experience with designing, developing and
 operating our SNMP based usage data gathering system.  I've also been
 involved in our radius based authentication and authorization systems
 in an advisory position.
 I've participated in radius/roamops/nasreq/aaa groups for the past
 several years.  I'm not an author or contributer on any of the
 requirements or protocol documents being presented although I have
 been peripherally involved in these working groups.
 Dave Nelson, Enterasys Networks
 Very active in the RADIUS WG, especially during the early years.  No
 involvement in the AAA submission.  Have not contributed to the
 development of Diameter.
 No involvement with SNMPv3 or the AAA submission.  David Harrington,
 a proponent, works in a different group within my company.  We have
 not discussed the submission.  No involvement with the COPS protocol.
 Basavaraj Patil, Nokia
 I am a contributor to the AAA requirements document (RFC 2977)
 submitted by the Mobile IP WG.  I was a member of the team that was
 constituted to capture the Mobile IP requirements for AAA services.
 As part of the co-chairing activity of the Mobile IP WG I have
 realized the need for AAA services by Mobile IP and hence closely
 followed the work done in the AAA WG, RADIUS, RoamOps and TR45.6.

Mitton, et al. Informational [Page 5] RFC 3127 AAA Protocol Evaluation Process June 2001

 My present work at Nokia does involve looking at AAA protocols (to
 some extent at least) for use in wireless networks.  I have also done
 some work with AAA protocols such as Diameter in my previous job at
 Nortel Networks.
 Mark Stevens, Ellacoya Networks
 I am the co-chair of the IETF RAP working group which is the working
 group that has developed the COPS protocol.  I have not contributed
 to the documents describing how COPS can satisfy AAA requirements.
 I participated in early AAA working group meetings, but have not been
 an active participant since the group's rechartering.  The company
 that currently employees me builds devices might benefit from being
 AAA enabled.
 Barney Wolff, Databus Inc.
 I have implemented RADIUS client, proxy and server software, under
 contract to AT&T.  That software is owned by AT&T and I have no
 financial interest in it.
 I have been a member of the RADIUS WG for several years, and consider
 myself an advocate for RADIUS against what I consider unjustified
 attacks on it.
 I've never worked for any of the companies whose staff have produced
 any of the proposals, although I obviously might at some future time.

1.4. Requirements Validation Process

 For each of the base requirements documents, the chair assigned a
 team member to re-validate the requirement.  The process was fairly
 mechanical; the evaluator looked at what was said in [AAAReqts], and
 verified that the references and supporting text in the basis
 document supported the requirement in [AAAReqts] as stated.  Where
 the reference was wrong, too general, missing or otherwise did not
 support the requirement, the evaluator either deleted or downgraded
 the requirement.  The results of that process were sent to the AAA
 mailing list and are also included in this document in the
 appendixes.  The group's used [AAAReqts] as modified by our
 validation findings to evaluate the AAA proposals.

Mitton, et al. Informational [Page 6] RFC 3127 AAA Protocol Evaluation Process June 2001

1.5. Proposal Evaluation

 For each of the four proposals, the chair assigned two panel members
 to write evaluation briefs.  One member was assigned to write a 'PRO'
 brief and could take the most generous interpretation of the
 proposal; he could grant benefit of doubt.  The other member was
 assigned to write a 'CON' brief and was required to use the strictest
 criteria when doing his evaluation.
 Each brief looked at each individual requirement and evaluated how
 close the proposal came in meeting that requirement.  Each item was
 scored as one of an 'F' for failed to meet the requirement, 'P' for
 partially meeting the requirement, or 'T' for totally meeting the
 requirement.  The proposals were scored only on the information
 presented.  This means that a particular protocol might actually meet
 the specifics of a requirement, but if the proposal did not state,
 describe or reference how that requirement was met, in might be
 scored lower.
 The panel met by teleconference to discuss each proposal and the PRO
 and CON briefs.  Each of the briefers discussed the high points of
 the brief and gave his summary findings for the proposal.  We then
 discussed each individual requirement line-by-line as a group.  At
 the conclusion, the members provided their own line-by-line
 evaluations which were used to determine the consensus evaluation for
 the specific requirement relative to that proposal.  The meeting
 notes from those teleconferences as well as the individual briefs are
 included in the appendixes.

1.6. Final Recommendations Process

 The panel met for one last time to compare the results for the four
 proposals and to ensure we'd used consistent evaluation criteria.  We
 did a requirement by requirement discussion, then a discussion of
 each of the protocols.
 The final phase was for each member to provide his final summary
 evaluation for each of the protocols.  Each proposal was scored as
 either Not Acceptable, Acceptable Only For Accounting, Acceptable
 with Engineering and Fully Acceptable.  Where a proposal was
 acceptable with engineering, the member indicated whether it would be
 a small, medium or large amount.
 It should be noted that score indicated the opinion of the team
 member.  And they may have taken into consideration background
 knowledge or additional issues not captured in the minutes presented
 here.

Mitton, et al. Informational [Page 7] RFC 3127 AAA Protocol Evaluation Process June 2001

 Each member's scores were used within the group to develop the
 group's consensus.

2. Protocol Proposals

 The following proposal documents were submitted to the AAA WG for
 consideration by the deadline.
  1. SNMP:
    [SNMPComp] "Comparison of SNMPv3 Against AAA Network Access
                Requirements", Work in Progress.
  1. RADIUS Enhancements:
    [RADComp]  "Comparison of RADIUS Against AAA Network Access
                Requirements", Work in Progress.
    [RADExt]   "Framework for the extension of the RADIUS(v2)
                protocol", Work in Progress.
  1. Diameter
    [DIAComp]  "Comparison of Diameter Against AAA Network Access
                Requirements", Work in Progress.
  1. COPS for AAA:
    [COPSComp] "Comparison of COPS Against the AAA NA Requirements",
                Work in Progress.
    [COPSAAA]  "COPS Usage for AAA", Work in Progress.

3. Item Level Compliance Evaluation

 For each requirement item, the group reviewed the proposal's level of
 compliance.  Where the proposal was lacking, the evaluators may have
 made supposition on how hard it would be to resolve the problem.  The
 following shows the consensus results for each requirement item.
 Key:
 T = Total Compliance, Meets all requirements fully
 P = Partial Compliance, Meets some requirements
 F = Failed Compliance, Does not meet requirements acceptably
 Where two are shown eg: P/T, there was a tie.

Mitton, et al. Informational [Page 8] RFC 3127 AAA Protocol Evaluation Process June 2001

 The sub-section numbering corresponds to the requirements document
 section and item numbers.  This relative numbering was also used in
 the Protocol Position presentations, here in the appendices.

3.1 General Requirements

 3.1.1 Scalability - SNMP:P, RADIUS:P, Diameter:T, COPS:T
 SNMP was downgraded due to a lack of detail of how the current agent
 model would be adapted to a client request based transaction.  The
 RADIUS proposal did not address the problem adequately.  There are
 open issues in all proposals with respect to webs of proxies.
 3.1.2 Fail-over - SNMP:P, RADIUS:P, Diameter:P, COPS:T/P
 The group particularly noted that it didn't think any protocol did
 well in this requirement.  Insufficient work has been done to specify
 link failure detection and primary server recovery in most
 submissions.  COPS has some mechanisms but not all.  How these
 mechanisms would work in a web of proxies has not been addressed.
 3.1.3 Mutual Authentication  - SNMP:T, RADIUS:T/P, Diameter:T, COPS:T
 Many of the submissions missed the point of the requirement.  There
 should be a way for the peers to authenticate each other, end-to-end,
 or user-to-server.   However, the group questions who really needs
 this feature, and if it could be done at a different level.
 Mutual authentication in RADIUS is only between hops.
 3.1.4 Transmission Level Security  - SNMP:T, RADIUS:P, Diameter:T,
 COPS:T
 All protocols have methods of securing the message data.
 3.1.5 Data Object Confidentiality  - SNMP:P, RADIUS:P, Diameter:T,
 COPS:T
 This requirement usually comes from third-party situations, such as
 access outsourcing.
 Diameter and COPS both use CMS formats to secure data objects.  The
 group is concerned if this method and it's support is perhaps too
 heavy weight for NAS and some types of edge systems.

Mitton, et al. Informational [Page 9] RFC 3127 AAA Protocol Evaluation Process June 2001

 3.1.6 Data Object Integrity  - SNMP:F, RADIUS:P, Diameter:T, COPS:T
 How to guard the data object from changes was not adequately
 described in the SNMP proposal.  The RADIUS solution was not very
 strong either.
 3.1.7 Certificate Transport  - SNMP:T, RADIUS:T, Diameter:T, COPS:T
 All protocols can figure out some way to transport a certificate.
 3.1.8 Reliable AAA Transport  - SNMP:P, RADIUS:P, Diameter:T, COPS:T
 The requirement does not give a definition of "how reliable" it must
 be.
 The SNMP and RADIUS proposals lacked in providing solutions to
 message retransmission and recovery.
 3.1.9 Run over IPv4  - SNMP:T, RADIUS:T, Diameter:T, COPS:T
 3.1.10 Run over IPv6  - SNMP:P, RADIUS:T, Diameter:T, COPS:T
 The SNMP proposal indicated that this area is still in the
 experimental stages.
 3.1.11 Support Proxy and Routing Brokers  - SNMP:F, RADIUS:P,
 Diameter:T, COPS:P
 The SNMP proposal did not address this requirement.  COPS claims
 support, but does not work through some of the issues.  Diameter was
 the only protocol that attempted to address this area to a fair
 extent.
 3.1.12 Auditability - SNMP:F, RADIUS:F, Diameter:T, COPS:P
 We treated this requirement as something like "non-repudiation".
 There is a concern that digital signatures may be too computationally
 expensive for some equipment, and not well deployed on those
 platforms.
 The SNMP and RADIUS proposals did not attempt to work this
 requirement.  COPS suggests that a History PIB will help solve this
 problem but gives no description.

Mitton, et al. Informational [Page 10] RFC 3127 AAA Protocol Evaluation Process June 2001

 3.1.13 Shared Secret Not Required  - SNMP:P/T, RADIUS:T, Diameter:T,
 COPS:T
 The requirement is interpreted to mean that any application level
 security can be turned off in the presence of transport level
 security.
 Pretty much every protocol can use an enveloping secure transport
 that would allow them not to use an internal secret.
 3.1.14 Ability to Carry Service Specific Attributes  - SNMP:T,
 RADIUS:T, Diameter:T, COPS:T

3.2 Authentication Requirements

 3.2.1 NAI Support  - SNMP:T, RADIUS:T, Diameter:T, COPS:T
 3.2.2 CHAP Support  - SNMP:T, RADIUS:T, Diameter:T, COPS:T
 3.2.3 EAP Support  - SNMP:T, RADIUS:T, Diameter:T, COPS:T
 3.2.4 PAP/Clear-text Passwords  - SNMP:T, RADIUS:T, Diameter:T,
 COPS:T
 The requirement for clear-text passwords comes from one-time-password
 systems and hard-token (SecurID) systems.
 3.2.5 Reauthentication on demand - SNMP:T, RADIUS:P, Diameter:P,
 COPS:T
 To supply this, the proposal must have asynchronous peer-to-peer
 capabilities, and there must defined operation for such state
 changes.
 We also distinguished event-driven Reauthentication from timer-driven
 (or lifetime-driven).  Also concerned about how this would work in a
 proxy environment.
 3.2.6 Authorization w/o Authentication - SNMP:P, RADIUS:T/P,
 Diameter:T, COPS:T
 This requirement really means authorization with trivial
 authentications (e.g. by assertion or knowledge).

Mitton, et al. Informational [Page 11] RFC 3127 AAA Protocol Evaluation Process June 2001

3.3 Authorization Requirements

 3.3.1 Static and Dynamic IP Addr Assignment - SNMP:P/F, RADIUS:T,
 Diameter:T, COPS:T
 There is difficulty in interpreting what is static or dynamic with
 respect to the viewpoint of the client, server, administrator or
 user.
 3.3.2 RADIUS Gateway Capability  - SNMP:P, RADIUS:P, Diameter:T/P,
 COPS:P
 It was noted that any new capability in a new AAA protocol would not
 be able to map directly back to RADIUS.  But this is already a
 problem within a RADIUS environment.
 3.3.3 Reject Capability  - SNMP:T/P/F, RADIUS:T, Diameter:T, COPS:P
 3.3.4 Preclude Layer 2 Tunneling  - SNMP:F, RADIUS:T, Diameter:T,
 COPS:T
 3.3.5 Reauthorization on Demand  - SNMP:P/F, RADIUS:P, Diameter:T/P,
 COPS:T
 Some evaluators wondered how the server will know that re-
 authorization is supposed to be done?  Will it interface to something
 external, or have sufficient internals?
 3.3.6 Support for Access Rules & Filters  - SNMP:P, RADIUS:P,
 Diameter:P, COPS:T/P
 Only the Diameter proposal actually tackled this issue, but the group
 felt that the rules as designed were too weak to be useful.  There
 was also concern about standardizing syntax without defining
 semantics.
 3.3.7 State Reconciliation - SNMP:F, RADIUS:P/F, Diameter:P, COPS:T/P
 All of the protocols were weak to non-existent on specifying how this
 would be done in a web of proxies situation.
 3.3.8 Unsolicited Disconnect  - SNMP:T, RADIUS:P, Diameter:T, COPS:T

3.4 Accounting Requirements

 3.4.1 Real Time Accounting  - SNMP:T, RADIUS:T, Diameter:T, COPS:T

Mitton, et al. Informational [Page 12] RFC 3127 AAA Protocol Evaluation Process June 2001

 3.4.2 Mandatory Compact Encoding  - SNMP:T, RADIUS:T, Diameter:T,
 COPS:T
 3.4.3 Accounting Record Extensibility  - SNMP:T, RADIUS:T,
 Diameter:T, COPS:T
 3.4.4 Batch Accounting  - SNMP:T, RADIUS:F, Diameter:P, COPS:P
 Some members of the group are not sure how this fits into the rest of
 the AAA protocol, which is primarily real-time and event driven.
 Would this be better met with FTP?
 3.4.5 Guaranteed Delivery   - SNMP:T, RADIUS:T, Diameter:T, COPS:T
 3.4.6 Accounting Timestamps       - SNMP:T, RADIUS:T, Diameter:T,
 COPS:T
 3.4.7 Dynamic Accounting  - SNMP:T, RADIUS:T, Diameter:T, COPS:T

3.5 MOBILE IP Requirements

 3.5.1 Encoding of MOBILE IP Registration Messages  - SNMP:T,
 RADIUS:T/P, Diameter:T, COPS:T
 3.5.2 Firewall Friendly   - SNMP:F, RADIUS:T, Diameter:P, COPS:P
 There was considerable discussion about what it means to be "firewall
 friendly".  It was suggested that not making the firewall look into
 packets much beyond the application port number.  Protocols such as
 SNMP and COPS are at a disadvantage, as you must look far into the
 packet to understand the intended operation.  Diameter will have the
 disadvantage of SCTP, which is not well deployed or recognized at the
 moment.
 SNMP and COPS also have the problem that they are used for other
 types of operations than just AAA.
 Should firewalls have AAA Proxy engines?
 We didn't look at "NAT friendly" issues either.
 COPS:T
 The group is not clear on how this requirement impacts the actual
 protocol.  Raj explained it to us, but we mostly took it on faith.

Mitton, et al. Informational [Page 13] RFC 3127 AAA Protocol Evaluation Process June 2001

4. Protocol Evaluation Summaries

4.1. SNMP

 SNMP is generally not acceptable as a general AAA protocol.  There
 may be some utility in its use for accounting, but the amount of
 engineering to turn it into a viable A&A protocol argues against
 further consideration.

4.2. Radius++

 Radius++ is not considered acceptable as an AAA protocol.  There is a
 fairly substantial amount of engineering required to make it meet all
 requirements, and that engineering would most likely result in
 something close to the functionality of Diameter.

4.3. Diameter

 Diameter is considered acceptable as an AAA protocol.  There is some
 minor engineering required to bring it into complete compliance with
 the requirements but well within short term capabilities.  Diameter
 might also benefit from the inclusion of a broader data model ala
 COPS.

4.4. COPS

 COPS is considered acceptable as an AAA protocol.  There is some
 minor to medium engineering required to bring it into complete
 compliance with the requirements.

4.5. Summary Recommendation

 The panel expresses a slight preference for Diameter based on the
 perception that the work for Diameter is further along than for COPS.
 However, using SCTP as the transport mechanism for Diameter places
 SCTP on the critical path for Diameter.  This may ultimately result
 in COPS being a faster approach if SCTP is delayed in any way.

5. Security Considerations

 AAA protocols enforce the security of access to the Internet.  The
 design of these protocols and this evaluation process took many
 security requirements as critical issues for evaluation.  A candidate
 protocol must meet the security requirements as documented, and must
 be engineered and reviewed properly as developed and deployed.

Mitton, et al. Informational [Page 14] RFC 3127 AAA Protocol Evaluation Process June 2001

6. References

 [AAAReqts] Aboba, B., Clahoun, P., Glass, S., Hiller, T., McCann, P.,
            Shiino, H., Walsh, P., Zorn, G., Dommety, G., Perkins, C.,
            Patil, B., Mitton, D., Manning, S., Beadles, M., Chen, X.,
            Sivalingham, S., Hameed, A., Munson, M., Jacobs, S., Lim,
            B., Hirschman, B., Hsu, R., Koo, H., Lipford, M.,
            Campbell, E., Xu, Y., Baba, S. and E. Jaques, "Criteria
            for Evaluating AAA Protocols for Network Access", RFC
            2989, April 2000.
 [AAAComp]  Ekstein, TJoens, Sales and Paridaens, "AAA Protocols:
            Comparison between RADIUS, Diameter and COPS", Work in
            Progress.
 [SNMPComp] Natale, "Comparison of SNMPv3 Against AAA Network Access
            Requirements", Work in Progress.
 [RADComp]  TJoens and DeVries, "Comparison of RADIUS Against AAA
            Network Access Requirements", Work in Progress.
 [RADExt]   TJoens, Ekstein and DeVries, "Framework for the extension
            of the RADIUS (v2) protocol", Work in Progress,
 [DIAComp]  Calhoun, "Comparison of Diameter Against AAA Network
            Access Requirements", Work in Progress.
 [COPSComp] Khosravi, Durham and Walker, "Comparison of COPS Against
            the AAA NA Requirements", Work in Progress.
 [COPSAAA]  Durham, Khosravi, Weiss and Filename, "COPS Usage for
            AAA", Work in Progress.

7. Authors' Addresses

 David Mitton
 Nortel Networks
 880 Technology Park Drive
 Billerica, MA 01821
 Phone: 978-288-4570
 EMail: dmitton@nortelnetworks.com

Mitton, et al. Informational [Page 15] RFC 3127 AAA Protocol Evaluation Process June 2001

 Michael StJohns
 Rainmaker Technologies
 19050 Pruneridge Ave, Suite 150
 Cupertino, CA 95014
 Phone: 408-861-9550 x5735
 EMail: stjohns@rainmakertechnologies.com
 Stuart Barkley
 UUNET
 F1-1-612
 22001 Loudoun County Parkway
 Ashburn, VA  20147  US
 Phone: 703-886-5645
 EMail: stuartb@uu.net
 David B. Nelson
 Enterasys Networks, Inc. (a Cabletron Systems company)
 50 Minuteman Road
 Andover, MA 01810-1008
 Phone: 978-684-1330
 EMail: dnelson@enterasys.com
 Basavaraj Patil
 Nokia
 6000 Connection Dr.
 Irving, TX 75039
 Phone: +1 972-894-6709
 EMail: Basavaraj.Patil@nokia.com
 Mark Stevens
 Ellacoya Networks
 7 Henry Clay Drive
 Merrimack, NH  03054
 Phone: 603-577-5544 ext. 325
 EMail: mstevens@ellacoya.com
 Barney Wolff, Pres.
 Databus Inc.
 15 Victor Drive
 Irvington, NY 10533-1919 USA
 Phone: 914-591-5677
 EMail: barney@databus.com

Mitton, et al. Informational [Page 16] RFC 3127 AAA Protocol Evaluation Process June 2001

Appendix A - Summary Evaluations Consensus Results by Requirement

           and Protocol
 Requirement Section         SNMP      Radius++  Diameter  COPS
         1.1.1                P         P         T         T
         1.1.2                P         P         P       T/P
         1.1.3                T       T/P         T         T
         1.1.4                T         P         T         T
         1.1.5                P         P         T         T
         1.1.6                F         P         T         T
         1.1.7                T         T         T         T
         1.1.8                P         P         T         T
         1.1.9                T         T         T         T
         1.1.10               P         T         T         T
         1.1.11               F         P         T         P
         1.1.12               F         F         T         P
         1.1.13             P/T         T         T         T
         1.1.14               T         T         T         T
         1.2.1                T         T         T         T
         1.2.2                T         T         T         T
         1.2.3                T         T         T         T
         1.2.4                T         T         T         T
         1.2.5                T         P         P         T
         1.2.6                P       T/P         T         T
         1.3.1              P/F         T         T         T
         1.3.2                P         T       T/P         P
         1.3.3            T/P/F         T         T         P
         1.3.4                F         T         T         T
         1.3.5              P/F         P       T/P         T
         1.3.6                P         P         P       T/P
         1.3.7                F       P/F         P       T/P
         1.3.8                T         P         T         T
         1.4.1                T         T         T         T
         1.4.2                T         T         T         T
         1.4.3                T         T         T         T
         1.4.4                T         F         P         P
         1.4.5                T         T         T         T
         1.4.6                T         T         T         T
         1.4.7                T         T         T         T
         1.5.1                T       T/P         T         T
         1.5.2                F         T         P         P
         1.5.3                F         P         T         T

Mitton, et al. Informational [Page 17] RFC 3127 AAA Protocol Evaluation Process June 2001

Appendix B - Review of the Requirements

 Comments from the Panel on then work in progress, "Criteria for
 Evaluating AAA Protocols for Network Access" now revised and
 published as RFC 2989.  This became the group standard interpretation
 of the requirements at the time.

B.1 General Requirements

 Scalability - In clarification [a], delete "and tens of thousands of
 simultaneous requests."  This does not appear to be supported by any
 of the three base documents.
 Transmission level security - [Table] Delete the ROAMOPS "M" and
 footnote "6".  This appears to be an over generalization of the
 roaming protocol requirement not necessarily applicable to AAA.
 Data object confidentiality - [Table] Delete the MOBILE IP "S" and
 footnote "33".  The base document text does not appear to support
 this requirement.
 Reliable AAA transport mechanism - In clarification [h] delete
 everything after the "...packet loss" and replace with a ".".  The
 requirements listed here are not necessarily supported by the base
 document and could be mistakenly taken as requirements for the AAA
 protocol in their entirety.
 Run over IPv4 - [Table] Replace the MOBILE IP footnote "17" with
 footnote "33".  This appears to be a incorrect reference.
 Run over IPv6 - [Table] Replace the MOBILE IP footnote "18" with a
 footnote pointing to section 8 of [8].  This appears to be an
 incorrect reference.
 Auditability - Clarification [j] does not appear to coincide with the
 NASREQ meaning of Auditability.  Given that NASREQ is the only
 protocol with an auditability requirement, this section should be
 aligned with that meaning.
 Shared secret not required - [Table] General - This section is
 misleadingly labeled.  Our team has chosen to interpret it as
 specified in clarification [k] rather than any of the possible
 interpretations of "shared secret not required".  We recommend the
 tag in the table be replaced with "Dual App and Transport Security
 Not Required" or something at least somewhat descriptive of [k].
 Delete the NASREQ "S" and footnote "28" as not supported by the
 NASREQ document.  Delete the MOBILE IP "O" and footnotes "34" and 39"
 as not supported.

Mitton, et al. Informational [Page 18] RFC 3127 AAA Protocol Evaluation Process June 2001

B.2 Authentication Requirements

 NAI Support - [Table] Replace MOBILE IP footnote "38" with "39".
 This appears to be a more appropriate reference.
 CHAP Support - [Table] Delete MOBILE IP "O" as unsupported.
 EAP Support - [Table] Delete MOBILE IP "O" as unsupported.
 PAP/Clear-Text Support - [Table] Replace NASREQ footnote "10" with
 "26" as being more appropriate.  Replace ROAMOPS "B" with "O".  The
 reference text appears to not explicitly ban this and specifically
 references clear text for OTP applications.  Delete MOBILE IP "O" as
 unsupported.
 Re-authentication on demand - Clarification [e] appears to go beyond
 the requirements in NASREQ and MOBILE IP.  [Table] Delete MOBILE IP
 footnote "30" as inapplicable.
 Authorization Only without Authentication - Clarification [f] does
 not include all NASREQ requirements, specifically that unneeded
 credentials MUST NOT be required to be filled in.  Given that there
 are no other base requirements (after deleting the MOBILE IP
 requirement) we recommend that clarification [f] be brought in line
 with NASREQ.  [Table] Delete MOBILE IP "O" and footnote "30".  The
 referenced text does not appear to support the requirement.

B.3 Authorization Requirements

 Static and Dynamic... - Clarification [a] appears to use a
 particularly strange definition of static and dynamic addressing.
 Recommend clarification here identifying who (e.g. client or server)
 thinks address is static/dynamic.  [Table] ROAMOPS "M" appears to be
 a derived requirement instead of directly called out.  The footnote
 "1" should be changed to "5" as being more appropriate.  A text
 clarification should be added to this document identifying the
 derived requirement.
 RADIUS Gateway capability - [Table] Delete the MOBILE IP "O" and
 footnote "30".  The referenced text does not appear to support the
 requirement.
 Reject capability - [Table] Delete the NASREQ "M" and footnote "12".
 The NASREQ document does not appear to require this capability.

Mitton, et al. Informational [Page 19] RFC 3127 AAA Protocol Evaluation Process June 2001

 Reauthorization on Demand - [Table] Delete the MOBILE IP "S" and
 footnotes "30,33" The referenced text does not support this
 requirement.
 Support for Access Rules... - Clarification [e] has a overbroad list
 of requirements.  NASREQ only requires 5-8 on the list, and as The
 MOBILE IP requirement is not supported by its references, this
 clarification should match NASREQ requirements.  [Table] Delete the
 MOBILE IP "O" and footnotes "30,37" as not supported.
 State Reconciliation - Clarification [f] should be brought in line
 with NASREQ requirements.  The clarification imposes overbroad
 requirements not required by NASREQ and NASREQ is the only service
 with requirements in this area.

B.4 Accounting Requirements

 Real-Time accounting - [Table] Replace MOBILE IP footnote [39] with a
 footnote pointing to section 3.1 of [3] as being more appropriate.
 Mandatory Compact Encoding - [Table] Delete MOBILE IP "M" and
 footnote "33" as the reference does not support the requirement.
 Accounting Record Extensibility - [Table] Delete NASREQ "M" and
 footnote "15" as the reference does not support the requirement.
 Accounting Time Stamps - [Table] Delete MOBILE IP "S" and footnote
 "30" as they don't support the requirement.  Replace MOBILE IP
 footnote "40" with a footnote pointing to section 3.1 of [3] as being
 more appropriate.
 Dynamic Accounting - [Table] Replace the NASREQ footnote "18" with a
 footnote pointing to section 8.4.1.5 of [3].  Delete the MOBILE IP
 "S" and footnote "30" as the reference does not support the
 requirement.
 Footnote section.
 [40] should be pointing to 6.1 of [4].
 [41] should be pointing to 6.2.2 of [4].
 [45] should be pointing to 6.4 of [4].
 [46] should be pointing to 8 of [4].

Mitton, et al. Informational [Page 20] RFC 3127 AAA Protocol Evaluation Process June 2001

Appendix C - Position Briefs

C.1 SNMP PRO Evaluation

 Evaluation of SNMP AAA Requirements
 PRO Evaluation
 Evaluator - Stuart Barkley
 Ref [1] is "Comparison of SNMPv3 Against AAA Network Access
 Requirements", aka 'the document'
 Ref [2] is the aaa eval criteria as modified by us, aka 'the
 requirements'
 The document uses T to indicate total compliance, P to indicate
 partial compliance and F to indicate no compliance.  For each section
 I've indicated my grade for the section.  If there is a change, I've
 indicated that and the grade given by the authors.
 1 Per item discussion
 1.1 General Requirements
 1.1.1 Scalability - Grade T
 The document indicates that SNMP can adequately handle that scale
 from the requirements document.  Since most current uses are ppp
 connections and SNMP is already capable of handling the interface
 table and other per session tables it is clear that basic capacity
 exists.  Additions to support other tables and variables scales in a
 simple linear fashion with the number of additional variables and
 protocol interactions.  Regardless of the final selected protocol
 handling the scaling required is not a trivial undertaking.  SNMP can
 draw upon existing network management practices to assist in this
 implementation.
 1.1.2 Fail-over - Grade T
 SNMP is of vital importance to the operation of most networks.
 Existing infrastructures can handle required failover or other
 redundant operations.
 1.1.3 Mutual Authentication - Grade T
 The use of shared secrets described in the document is a well
 understood method of integrity control.  Although shared secrets
 don't necessarily provide full authentication since other parties may
 also have the same secrets, the level of authentication is sufficient
 for the task at hand.  In many cases the SNMP infrastructure will

Mitton, et al. Informational [Page 21] RFC 3127 AAA Protocol Evaluation Process June 2001

 already exist and shared secrets should already be properly managed
 on an operational network.  A failure of the SNMP shared secret
 approach regardless of the AAA protocol will likely leave equipment
 and systems open to substantial misuse bypassing any more elaborate
 AAA authentication.
 1.1.4 Transmission Level Security - Grade T
 SNMPv3 provides many additional security options which were not
 available or were more controversial in previous SNMP versions.
 1.1.5 Data Object Confidentiality - New Grade P (from T)
 The document discusses SNMPv3 which can provide data confidentially
 for data passing over the wire.  There is substantial implied AAA
 architecture (brokers and proxies) in the requirements that full
 conformance is difficult to determine.  In particular, the evaluator
 has difficulty with the concept of "the target AAA entity for whom
 the data is ultimately destined", but will concede that the desired
 requirement is only partially met (most especially with the transfer
 of a PAP password).
 1.1.6 Data Object Integrity - New Grade T (from P)
 SNMP has full capabilities that allow the authentication of the data.
 Brokers, proxies or other intermediaries in the data chain can verify
 the source of the information and determine that the data has not
 been tampered with.  The document downgrades the grade to P because
 of confusion over the integrity checking role of intermediaries.
 1.1.7 Certificate Transport - Grade T
 The requirements require the capability of transporting certificates
 but do not have any specific use for the certificates.  The
 requirements make assumptions that the protocol selected will be
 dependent upon certificates, but this is not necessarily true.  SNMP
 can transport arbitrary objects and can transport certificates if
 necessary.  The document indicates some issues with size of
 certificates and current maximum practical data sizes, however if the
 compact encoding requirement extends to the internal certificate
 information this should be less of an issue.
 1.1.8 Reliable AAA Transport - New Grade T (from P)
 The requirements is stated rather strongly and makes substantial
 assumptions of AAA protocol architecture and based upon current
 protocols and their failings.  SNMP allows for great flexibility in
 retransmission schemes depending upon the importance of the data.

Mitton, et al. Informational [Page 22] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.9 Run over IPv4 - Grade T
 SNMP has operated in this mode for many years.
 1.1.10 Run over IPv6 - New Grade T (from P)
 SNMP must support IPv6 for many other systems so support for this
 should be possible by the time the requirement becomes effective.
 The document indicates that experimental versions satisfying this
 requirement are already in existence.
 1.1.11 Support Proxy and Routing Brokers - New Grade T (from P)
 The requirements make significant assumptions about the final
 architecture.  It is well within the capabilities of SNMP to provide
 intermediaries which channel data flows between multiple parties.
 The document downgrades SNMPs compliance with this requirement due to
 issues which are covered more specifically under "Data Object
 Confidentially" which the evaluator has downgraded to P.
 1.1.12 Auditability - New Grade T (from F)
 Data flows inside SNMP are easily auditable by having secondary data
 flows established which provide copies of all information to
 auxiliary servers.  The document grades this as a failure, but this
 support is only minor additions within a more fully fleshed out set
 of data flows.
 1.1.13 Shared Secret Not Required - Grade T
 Shared secrets are not required by SNMP.  They are desirable in many
 instances where a lower level does not provide the necessary
 capabilities.  The document supplies pointers to various security
 modes available.
 1.1.14 Ability to Carry Service Specific Attributes - Grade T
 SNMP has long had the ability for other parties to create new
 unambiguous attributes.
 1.2 Authentication Requirements
 1.2.1 NAI Support - Grade T
 SNMP easily supports this.  NAIs were defined to be easily carried in
 existing protocols.

Mitton, et al. Informational [Page 23] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.2.2 CHAP Support - Grade T
 SNMP can easily provide objects to pass the necessary information for
 CHAP operation.
 1.2.3 EAP Support - New Grade T (from P)
 SNMP can easily provide objects to pass the necessary information for
 EAP operation.  As with CHAP or PAP MIB objects can be created to
 control this operation thus the upgrade from the document grade.
 1.2.4 PAP/Clear-text Passwords - New Grade P (from T)
 SNMP can easily provide objects to pass the necessary information for
 PAP operation.  The requirement about non-disclosure of clear text
 passwords make assumptions about the protocol implementation.  The
 choice to use clear text passwords is inherently insecure and forced
 protocol architecture don't really cover this.  This requirement
 grade is downgraded to P (partial) because the document does not
 really address the confidentially of the data at application proxies.
 1.2.5 Reauthorization on demand - Grade T
 SNMP can easily provide objects to control this operation.
 1.2.6 Authorization w/o Authentication - New Grade T (from T)
 The document makes an incorrect interpretation of this requirement.
 However, SNMP makes no restriction which prevents to desired
 requirements.  No actual change of grade is necessary, since both the
 actual requirements and the incorrect interpretation are satisfied by
 SNMP.
 1.3 Authorization Requirements
 1.3.1 Static and Dynamic IP Addr Assignment - Grade T
 SNMP can easily provide objects to control this operation.
 1.3.2 RADIUS Gateway Capability - Grade T
 As the document describes, with the addition of any necessary
 compatibility variables SNMP can be gatewayed to RADIUS applications.

Mitton, et al. Informational [Page 24] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.3.3 Reject Capability - Grade T
 Any of the active components in the SNMP based structure could decide
 to reject and authentication request for any reason.  Due to mixing
 different levels of requirements the document doesn't attempt to
 directly address this, instead indicating that a higher level
 application can cause this operation.
 1.3.4 Preclude Layer 2 Tunneling - New Grade T (from ?)
 Nothing in SNMP explicitly interacts with the selection of any
 tunneling mechanisms the client may select.  The document author was
 unclear about the needs here.
 1.3.5 Reauth on Demand - Grade T
 SNMP can easily provide objects to control this operation.
 1.3.6 Support for ACLs - Grade T
 The document indicates that should it be desired SNMP can provide
 objects to control these operations.  In addition, active components
 can apply substantial further configurable access controls.
 1.3.7 State Reconciliation - Grade T
 The requirements describe an over broad set of required capabilities.
 The document indicates concern over incompatibilities in the
 requirements, however SNMP can provide methods to allow active
 components to reacquire lost state information.  These capabilities
 directly interact with scalability concerns and care needs to be
 taken when expecting this requirement to be met at the same time as
 the scalability requirements.
 1.3.8 Unsolicited Disconnect - Grade T
 The document indicates that SNMP can easily provide objects to
 control this operation.
 1.4 Accounting Requirements
 1.4.1 Real Time Accounting - Grade T
 SNMP can provide this mode of operation.  The document outlines
 methods both fully within SNMP and using SNMP to interface with other
 transfer methods.  Many providers already use SNMP for real time

Mitton, et al. Informational [Page 25] RFC 3127 AAA Protocol Evaluation Process June 2001

 notification of other network events.  This capability can directly
 interact with scalability concerns and implementation care needs to
 be taken to make this properly interact is large scale environments.
 1.4.2 Mandatory Compact Encoding - Grade T
 The document indicates the possibility of controlling external
 protocols to handle data transmissions where the BER encoding of SNMP
 objects would be considered excessive.  SNMP BER encoded protocol
 elements are generally in a fairly compact encoding form compared
 with text based forms (as used in some existing radius log file
 implementations).  This interacts with the general requirement for
 carrying service specific attributes and the accounting requirement
 for extensibility.  With careful MIB design and future work on SNMP
 payload compression the SNMP coding overhead can be comparable with
 other less extensible protocols.
 1.4.3 Accounting Record Extensibility - Grade T
 SNMP has a strong tradition of allowing vendor specific data objects
 to be transferred.
 1.4.4 Batch Accounting - Grade T
 There are many methods which a SNMP based system could use for batch
 accounting.  The document discusses SNMP parameters to control the
 batching process and indicates that certain existing MIBs contain
 examples of implementation strategies.  SNMP log tables can provide
 accounting information which can be obtained in many methods not
 directly related to real time capabilities.  The underlying system
 buffering requirements are similar regardless of the protocol used to
 transport the information.
 1.4.5 Guaranteed Delivery - Grade T
 SNMP is very amenable to providing guaranteed delivery.  Particularly
 in a pull model (versus the often assumed push model) the data
 gatherer can absolutely know that all data has been transfered.  In
 the common push model the data receiver does not know if the
 originator of the data is having problems delivering the data.
 1.4.6 Accounting Timestamps - Grade T
 Timestamps are used for many SNMP based operations.  The document
 points at the DateAndTime textual convention which is available for
 use.  As with all environments the timestamps accuracy needs
 evaluation before the information should be relied upon.

Mitton, et al. Informational [Page 26] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.4.7 Dynamic Accounting - Grade T
 As long as there is some way to relate multiple records together
 there are no problems resolving multiple records for the same
 session.  This interacts with the scalability requirement and care
 must be taken when implementing a system with both of these
 requirements.
 1.5 MOBILE IP Requirements
 1.5.1 Encoding of MOBILE IP Registration Messages - Grade T
 SNMP can easily provide objects to transfer this information.
 1.5.2 Firewall Friendly - New Grade T (from P)
 SNMP is already deployed in many operational networks.  SNMPv3
 addresses most concerns people had with the operation of previous
 versions.  True SNMPv3 proxies (as opposed to AAA proxies) should
 become commonplace components in firewalls for those organizations
 which require firewalls.
 1.5.3 Allocation of Local Home Agent - New Grade T (from ?)
 SNMP is not concerned with the LHA.  This can be under control of the
 Local network to meet its needs.
 2. Summary Discussion
 SNMP appears to meet most stated requirements.  The areas where the
 SNMP proposal falls short are areas where specific AAA architectures
 are envisioned and requirements based upon that architecture are
 specified.
 Scaling of the protocol family is vital to success of a AAA suite.
 The SNMP protocol has proved scalable in existing network management
 and other high volume data transfer operations.  Care needs to be
 taken in the design of a large scale system to ensure meeting the
 desired level of service, but this is true of any large scale
 project.
 3. General Requirements
 SNMP is well understood and already supported in many ISP and other
 operational environments.  Trust models already exist in many cases
 and can be adapted to provide the necessary access controls needed by
 the AAA protocols.  Important issues with previous versions of SNMP
 have been corrected in the current SNMPv3 specification.

Mitton, et al. Informational [Page 27] RFC 3127 AAA Protocol Evaluation Process June 2001

 The SNMP proposal is silent on the specific data variables and
 message types to be implemented.  This is largely due to the
 requirements not specifying the necessary data elements and the time
 constraints in extracting that information from the base document
 set.  Such a data model is necessary regardless of the ultimate
 protocol selected.
 4. Summary Recommendation
 SNMP appears to fully meet all necessary requirements for the full
 AAA protocol family.

C.2 SNMP CON Evaluation

 Evaluation of SNMP AAA Requirements
 CON Evaluation
 Evaluator - Michael StJohns
 Ref [1] is "Comparison of SNMPv3 Against AAA Network Access
 Requirements", aka 'the document'
 Ref [2] is the aaa eval criteria as modified by us.
 The document uses T to indicate total compliance, P to indicate
 partial compliance and F to indicate no compliance.  For each section
 I've indicated my grade for the section.  If there is no change, I've
 indicated that and the grade given by the authors.
 Section 1 - Per item discussion
 1.1 General Requirements
 1.1.1 Scalability - Although the document indicates compliance with
 the requirement, its unclear how SNMP actually meets those
 requirements.  The document neither discusses how SNMP will scale,
 nor provides applicable references.  The argument that there is an
 existence proof given the deployed SNMP systems appears to assume
 that one manager contacting many agents maps to many agents (running
 AAA) contacting one AAA server.  A server driven system has
 substantially different scaling properties than a client driven
 system and SNMP is most definitely a server (manager) driven system.
 Eval - F
 1.1.2 Fail-over - The document indicates the use of application level
 time outs to provide this mechanism, rather than the mechanism being
 a characteristic of the proposed protocol.  The protocol provides
 only partial compliance with the requirement.  Eval - P

Mitton, et al. Informational [Page 28] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.3 Mutual Authentication - There is some slight handwaving here,
 but the protocol's USM mode should be able to support this
 requirement.  Eval - No Change (T)
 1.1.4 Transmission Level Security - The authors should elaborate on
 the specific use of the SNMPv3 modes to support these requirements,
 but the text is minimally acceptable.  Eval - No Change (T)
 1.1.5 Data Object Confidentiality - The authors describe a mechanism
 which does not appear to completely meet the requirement.  VACM is a
 mechanism for an end system (agent) to control access to its data
 based on manager characteristics.  This mechanism does not appear to
 map well to this requirement.  Eval - P
 1.1.6 Data Object Integrity - There appears to be some handwaving
 going on here.  Again, SNMP does not appear to be a good match to
 this requirement due to at least in part a lack of a proxy
 intermediary concept within SNMP.  Eval - F
 1.1.7 Certificate Transport - The document does indicate compliance,
 but notes that optimization might argue for use of specialized
 protocols.  Eval - No Change (T)
 1.1.8 Reliable AAA Transport - The document indicates some confusion
 with the exact extent of this requirement.  Given the modifications
 suggested by the eval group to the explanatory text in [2] for the
 related annotation, the point by point explanatory text is not
 required.  The document does indicate that the use of SNMP is
 irrespective of the underlying transport and the support of this
 requirement is related at least partially to the choice of transport.
 However, SNMP over UDP - the most common mode for SNMP - does not
 meet this requirement.  Eval - No Change (P)
 1.1.9 Run over IPv4 - While the evaluator agrees that SNMPv3 runs
 over V4, the authors need to point to some sort of reference.  Eval -
 No Change (T)
 1.1.10 Run over IPv6 - The document indicates both experimental
 implementations and future standardization of SNMPv3 over IPv6.  Eval
 - No Change (P)
 1.1.11 Support Proxy and Routing Brokers - The section of the
 document (5.5.3) that, by title, should have the discussion of SNMP
 proxy is marked as TBD.  The section notes that the inability to
 completely comply with the data object confidentiality and integrity
 requirements might affect the compliance of this section and the
 evaluator agrees.  Eval - F

Mitton, et al. Informational [Page 29] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.12 Auditability - The document indicates no compliance with this
 requirement.  Eval - No Change (F)
 1.1.13 Shared Secret Not Required - Slight handwaving here, but
 SNMPv3 does not necessarily require use of its security services if
 other security services are available.  However, the interaction with
 VACM in the absence of USM is not fully described and may not have
 good characteristics related to this requirement.  Eval - P
 1.1.14 Ability to Carry Service Specific Attributes - SNMP complies
 via the use of MIBs.  Eval - No Change (T)
 1.2 Authentication Requirements
 1.2.1 NAI Support - The document indicates that MIB objects can be
 created to meet this requirement, but gives no further information.
 Eval - P
 1.2.2 CHAP Support - The document indicates that MIB objects can be
 created to meet this requirement, but gives no further information.
 Given the normal CHAP model, its unclear exactly how this would work.
 Eval - F
 1.2.3 EAP Support - The document notes that EAP payloads can be
 carried as specific MIB objects, but also notes that further design
 work would be needed to fully incorporate EAP.  Eval - No Change (P)
 1.2.4 PAP/Clear-text Passwords - The document notes the use of MIB
 objects to carry the clear text passwords and the protection of those
 objects under normal SNMPv3 security mechanisms.  Eval - No Change
 (T)
 1.2.5 Reauthorization on demand - While there's some handwaving here,
 its clear that the specific applications can generate the signals to
 trigger reauthorization under SNMP.  Eval - No Change (T)
 1.2.6 Authorization w/o Authentication - The author appears to be
 confusing the AAA protocol authorization with the AAA user
 authorization and seems to be over generalizing the ability of SNMP
 to deal with general AAA user authorization.  Eval - F
 1.3 Authorization Requirements
 1.3.1 Static and Dynamic IP Addr Assignment - The reference to MIB
 objects without more definite references or descriptions continues to
 be a negative.  While the evaluator agrees that MIB objects can
 represent addresses, the document needs to at least lead the reader
 in the proper direction.  Eval - F

Mitton, et al. Informational [Page 30] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.3.2 RADIUS Gateway Capability - The transport and manipulation of
 Radius objects appears to be only a part of what is required.  Eval -
 P
 1.3.3 Reject Capability - Again, a clarification of how SNMP might
 accomplish this requirement would be helpful.  The overall document
 lacks a theory of operation for SNMP in an AAA role that might have
 clarified the various approaches.  Eval - F
 1.3.4 Preclude Layer 2 Tunneling - Document indicates lack of
 understanding of this requirement.  Eval - F
 1.3.5 Reauth on Demand - See response in 1.3.3 above.  None of the
 text responding to this requirement, nor any other text in the
 document, nor any of the references describes the appropriate
 framework and theory.  Eval - F
 1.3.6 Support for ACLs - The response text again references MIB
 objects that can be defined to do this job.  There is additional
 engineering and design needed before this is a done deal.  Eval - P
 1.3.7 State Reconciliation - The text fails to address the basic
 question of how to get the various parts of the AAA system back in
 sync.  Eval - F
 1.3.8 Unsolicited Disconnect - Assuming that the NAS is an SNMP agent
 for an AAA server acting as an SNMP manager the evaluator concurs.
 Eval - No Change (T).
 1.4 Accounting Requirements
 1.4.1 Real Time Accounting - SNMP Informs could accomplish the
 requirements.  Eval - No Change (T)
 1.4.2 Mandatory Compact Encoding - This is a good and reasonable
 response.  SNMP can vary the style and type of reported objects to
 meet specific needs.  Eval - No Change (T).
 1.4.3 Accounting Record Extensibility - MIBs are extensible.  Eval -
 No Change (T)
 1.4.4 Batch Accounting - MIBs provide data collection at various
 times.  Eval - No Change (T)
 1.4.5 Guaranteed Delivery - There's some weasel wording here with
 respect to what guaranteed means, but the description of mechanisms
 does appear to meet the requirements.  Eval - No Change (T)

Mitton, et al. Informational [Page 31] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.4.6 Accounting Timestamps - Accounting records can use the
 DateAndTime Textual Convention to mark their times.  Eval - No Change
 (T)
 1.4.7 Dynamic Accounting - The author may have partially missed the
 point on this requirement.  While the number of records per session
 is not of great interest, the delivery may be.  The author should go
 a little more into depth on this requirement.  Eval - No Change (T)
 1.5 MOBILE IP Requirements
 1.5.1 Encoding of MOBILE IP Registration Messages - Registration
 messages can probably be encoded as SNMP messages.  Eval - No Change
 (T)
 1.5.2 Firewall Friendly - There's a chicken and egg problem with the
 response to the requirement in that the author hopes that SNMP as an
 AAA protocol will encourage Firewall vendors to make SNMP a firewall
 friendly protocol.  Eval - F
 1.5.3 Allocation of Local Home Agent - The author disclaims an
 understanding of this requirement.  Eval - F
 2. Summary Discussion
 The documents evaluation score was substantially affected by a lack
 of any document, reference or text which described a theory of
 operation for SNMP in AAA mode.  Of substantial concern are the items
 relating to the AAA server to server modes and AAA client to server
 modes and the lack of a map to the SNMP protocol for those modes.
 The evaluator also notes that the scaling issues of SNMP in SNMP
 agent/manager mode are in no way indicative of SNMP in AAA
 client/server mode.  This has a possibility to substantially impair
 SNMPs use in an AAA role.
 However, SNMP may have a reasonable role in the Accounting space.
 SNMP appears to map well with existing technology, and with the
 requirements.
 3. General Requirements
 SNMP appears to meet the general requirements of an IP capable
 protocol, but may not have a proper field of use for all specific
 requirements.

Mitton, et al. Informational [Page 32] RFC 3127 AAA Protocol Evaluation Process June 2001

 4. Summary Recommendation
 Recommended in Part.  SNMP is NOT RECOMMENDED for use as either an
 authentication or authorization protocol, but IS RECOMMENDED for use
 as an accounting protocol.

C.3 RADIUS+ PRO Evaluation

 Evaluation of RADIUS AAA Requirements PRO Evaluation
 Evaluator - Mark Stevens
 Ref [1] is "Comparison of RADIUS Against AAA Network Access
 Requirements"
 Ref [2] is "Framework for the extension of the RADIUS(v2) protocol"
 Ref [3] is the aaa eval criteria as modified by us.
 The documents uses T to indicate total compliance, P to indicate
 partial compliance and F to indicate no compliance.
 For each section I've indicated my grade for the section.  I have
 indicated whether or not my evaluation differs from the statements
 made with respect to RADIUS++.  The evaluation ratings as given below
 may differ from the evaluations codified in the document referred to
 as, "Comparison of RADIUS Against AAA Network Access Requirements"
 without any indication.
 1.1 General Requirements
 1.1.1 [a] Scalability - In as much as a protocol's scalability can be
 measured, the protocol seems to transmit information in a fairly
 efficient manner.So, in that the protocol appears not to consume an
 inordinate amount of bandwidth relative to the data it is
 transmitting, this protocol could be considered scalable.  However,
 the protocol has a limit in the number of concurrent sessions it can
 support between endpoints.  Work arounds exist and are in use.  Eval
 - P (no change)
 1.1.2 [b] Fail-over - The document indicates the use of application
 level time outs to provide this mechanism, rather than the mechanism
 being a characteristic of the proposed protocol.  The fail-over
 requirement indicates that the protocol must provide the mechanism
 rather than the application.  The implication is that the application
 need not be aware that the fail-over and subsequent correction when
 it happens.  The application using the RADIUS++ protocol will be
 involved in fail-over recovery activities.  The protocol layer of the
 software does not appear to have the capability built-in.  Given the
 wording of the requirement: Eval - P (changed from T)

Mitton, et al. Informational [Page 33] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.3 [c] Mutual Authentication - The RADIUS++ protocol provides
 shared-secret as a built-in facility for mutual authentication.  The
 authors of the document suggest the use of IPSec to obtain mutual
 authentication functions.  The RADIUS++ protocol provides no road
 blocks to obtaining mutual authentication between instances of AAA
 applications, however the protocol provides no facilities for doing
 so.
 1.1.4 [d] Transmission Level Security - The RADIUS++ protocol
 provides no transmission level security features, nor does it
 preclude the use of IPSec to obtain transmission level security.
 Eval - P (no change)
 1.1.5 [e] Data Object Confidentiality - The document describes a
 RAIDUS++ message designed to server as an envelope in which encrypted
 RADIUS messages (attributes) may be enclosed.  Eval - T (no change)
 1.1.6 [f] Data Object Integrity - Using visible signatures, the
 RADIUS++ protocol appears to meet this requirement.  Eval - T (no
 change)
 1.1.7 [g] Certificate Transport - The document indicates compliance
 through the use of the CMS-Data Radius Attribute (message).  Eval - T
 (no change)
 1.1.8 [h] Reliable AAA Transport - The document points out that
 RADIUS++ can be considered a reliable transport when augmented with
 Layer 2 Tunneling Protocol.  The protocol itself does not provide
 reliability features.  Reliability remains the responsibility of the
 application or a augmenting protocol.  Eval - P (no change)
 1.1.9 [i] Run over IPv4 - Eval - T (no change)
 1.1.10 [j] Run over IPv6 - an IPv6 Address data type must be defined.
 Eval - T (no change)
 1.1.11 [k] Support Proxy and Routing Brokers - There is no mechanism
 for rerouting requests, but an extension can be made to do so.  Eval
 - T (no change)
 1.1.12 [l] Auditability - The document indicates no compliance with
 this requirement.  Eval - F (no change)
 1.1.13 [m] Shared Secret Not Required - RADIUS++ can be configured to
 run with empty shared secret values.  Eval - T (no change)

Mitton, et al. Informational [Page 34] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.14 [n] Ability to Carry Service Specific Attributes - Vendor
 escape mechanism can be used for this purpose..  Eval - T  (no
 change)
 1.2 Authentication Requirements
 1.2.1 [a] NAI Support -  Eval - T (no change)
 1.2.2 [b] CHAP Support - Subject to dictionary attacks.  Eval - P
 (changed from T)
 1.2.3 [c] EAP Support - Eval - T (no change)
 1.2.4 [d] PAP/Clear-text Passwords - No end-to-end security, but
 potential for encapsulation exists within current paradigm of the
 protocol.  -  Eval -T (no change)
 1.2.5 [e] Reauthentication on demand -   The RADIUS protocol
 supports re-authentication.  In  case  re-authentication is initiated
 by the user or AAA client, the AAA client can send a new
 authentication request.  Re-authentication can be initiated from the
 visited or home AAA server by sending a challenge message to the AAA
 client.  Eval - T (no change)
 1.2.6 [f] Authorization w/o Authentication - A new message type can
 be created to enable RADIUS++ to support Aw/oA .  Eval - T (no
 change)
 1.3 Authorization Requirements
 1.3.1[a] Static and Dynamic IP Addr Assignment - Both supported.
 IPv6 would require the definition of a new address data type.  Eval -
 P (no change)
 1.3.2 [b] RADIUS Gateway Capability - The transport and manipulation
 of RADIUS objects appears to be only a part of what is required.
 Requirement seems to be worded to preclude RADIUS.  Eval - P (changed
 from T)
 1.3.3 [c] Reject Capability -  Eval -T
 1.3.4 [d] Preclude Layer 2 Tunneling -  I do not see a definition in
 the AAA eval criteria document.  Eval - ?

Mitton, et al. Informational [Page 35] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.3.5 [e] Reauthorization on Demand - Implementation in the field
 demonstrate that extensions to RADIUS can support the desired
 behavior.  Re-authentication is currently coupled to re-
 authorization.  Eval - P (no change)
 1.3.6 [f] Support for ACLs - Currently done in the applications
 behind the RADIUS end points, not the within the protocol.  RADIUS++
 could define additional message types to deal with expanded access
 control within new service areas.  Eval - P (no change)
 1.3.7 [g] State Reconciliation -  Eval - F (no change)
 1.3.8 [h] Unsolicited Disconnect - RADIUS++ extensions to support.
 Eval - T. (no change)
 1.4 Accounting Requirements
 1.4.1 [a] Real Time Accounting -  Eval - T (no change)
 1.4.2 [b] Mandatory Compact Encoding -  Eval - T (no change)
 1.4.3 [c] Accounting Record Extensibility -  Eval - T (no change)
 1.4.4 [d] Batch Accounting - RADIUS++ offers no new features to
 support batch accounting.  Eval - F No change)
 1.4.5 [e] Guaranteed Delivery - Retransmission algorithm employed.
 Eval - T (no change)
 1.4.6 [f] Accounting Timestamps - RADIUS++ extensions support
 timestamps.  Eval - T (no change)
 1.4.7 [g] Dynamic Accounting - RADIUS++ extensions to support.  Eval
 - T (no change)
 1.5 MOBILE IP Requirements
 1.5.1 [a] Encoding of MOBILE IP Registration Messages - RADIUS++
 extensions can be made to include registration messages as an opaque
 payload.  Eval - T (no change)
 1.5.2 [b] Firewall Friendly -  RADIUS  is  known  to  be  operational
 in environments where firewalls acting as a proxy are active.  Eval -
 T (no change)
 1.5.3 [c] Allocation of Local Home Agent -Requirement statement needs
 some clarification and refinement.  Eval - F (no change)

Mitton, et al. Informational [Page 36] RFC 3127 AAA Protocol Evaluation Process June 2001

 2. Summary Discussion
 The RADIUS protocol, and its associated extensions, is  presently not
 fully  compliant  with  the AAA Network Access requirements.
 However, it is  possible with a small effort to extend present
 procedures to meet the requirements as listed in, while maintaining a
 high level  of interoperability  with  the  wide  deployment  and
 installed base of RADIUS clients and servers.
 3. General Requirements
 RADIUS++ the protocol and the application meet the majority of the
 requirements and can be extended to meet the requirements where
 necessary.
 4. Summary Recommendation
 RADIUS++ as it could be developed would provide a level of backward
 compatibility that other protocols cannot achieve.  By extending
 RADIUS in the simple ways described in the documents listed above,
 the transition from existing RADIUS-based installations to RADIUS++
 installations would be easier.  Although accounting continues to be
 weaker than other approaches, the protocol remains a strong contender
 for continued use in the areas of Authorization and Authentication.

C.4 RADIUS+ CON Evaluation

 Evaluation of RADIUS++ (sic) AAA Requirements CON Evaluation
 Evaluator - David Nelson
 Ref [1] is "Comparison of RADIUS Against AAA Network Access
 Requirements", a.k.a. 'the document'
 Ref [2] is "Framework for the extension of the RADIUS(v2) protocol",
 a.k.a. 'the protocol'
 Ref [3] is the AAA evaluation criteria as modified by us.
 Ref [4] is RFC 2869.
 Ref [5] is an expired work in progress "RADIUS X.509 Certificate
 Extensions".
 Ref [6] is RFC 2868
 The document uses T to indicate total compliance, P to indicate
 partial compliance and F to indicate no compliance.  Evaluator's
 Note:  The document [1] pre-dates the protocol [2].  It is clear from
 reading [2], that some of the issues identified as short comings in
 [1] are now addressed in [2].  The evaluator has attempted to take
 note of these exceptions, where they occur.

Mitton, et al. Informational [Page 37] RFC 3127 AAA Protocol Evaluation Process June 2001

 Section 1 - Per item discussion
 1.1 General Requirements
 1.1.1 Scalability - The document [1] indicates partial compliance,
 largely in deference to the "tens of thousands of simultaneous
 requests" language in [3], that has been deprecated.  The issue of
 simultaneous requests from a single AAA client is addressed in [1],
 indicating that the apparent limitation of 256 uniquely identifiable
 outstanding request can be worked around using well known techniques,
 such as the source UDP port number of the request.  The document
 claims "P", and the evaluator concurs.
 1.1.2 Fail-over - The document [1] indicates the use of application
 level time outs to provide the fail-over mechanism.  Since the AAA
 protocol is indeed an application-layer protocol, this seems
 appropriate.  There are significant issues of how to handle fail-
 over in a proxy-chain environment that have not been well addressed,
 however.  The document claims "T", and the evaluator awards "P".
 1.1.3 Mutual Authentication - The document [1] indicates that mutual
 authentication exists in the presence of a User-Password or CHAP-
 Password attribute in an Access-Request packet or the Message-
 Authenticator [4] in any packet.  Once again, this addresses hop-by-
 hop authentication of RADIUS "peers", but does not fully address
 proxy-chain environments, in which trust models would need to be
 established.  The document further indicates that strong mutual
 authentication could be achieved using the facilities of IPsec.  This
 claim would apply equally to all potential AAA protocols, and cannot
 be fairly said to be a property of the protocol itself.  The document
 claims "T", and the evaluator awards "F".
 1.1.4 Transmission Level Security - The document [1] indicates that
 transmission layer security, as defined in [3], is provided in the
 protocol, using the mechanisms described in section 1.1.3.  It should
 be noted that this requirement is now a SHOULD in [3].  The document
 claims "P", and the evaluator concurs.
 1.1.5 Data Object Confidentiality - The document [1] indicates that
 end-to-end confidentiality is not available in RADIUS, but goes on to
 say that it could be added.  The protocol [2] actually makes an
 attempt to specify how this is to be done, in section 4.3.2.2 of [2],
 using a CMS-data attribute, based in large part upon RFC 2630.  The
 evaluator has not, at this time, investigated the applicability of
 RFC 2630 to the AAA work.  The document claims "F", but in light of
 the specifics of the protocol [2], the evaluator awards "P".

Mitton, et al. Informational [Page 38] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.6 Data Object Integrity - The document [1] indicates that end-
 to-end integrity is not available in RADIUS, but goes on to say that
 it could be added.  The protocol [2] actually makes an attempt to
 specify how this is to be done, in section 4.3.2.1 of [2], using a
 CMS-data attribute, based in large part upon RFC 2630.  The evaluator
 has not, at this time, investigated the applicability of RFC 2630 to
 the AAA work.  The document claims "F", but in light of the specifics
 of the protocol [2], the evaluator awards "P".
 1.1.7 Certificate Transport - The document [1] indicates that
 certificate transport is not available in RADIUS, but goes on to say
 that it could be added.  The protocol [2] actually makes an attempt
 to specify how this is to be done, in section 4.3.2.3 of [2], using a
 CMS-data attribute, based in large part upon RFC 2630.  The evaluator
 has not, at this time, investigated the applicability of RFC 2630 to
 the AAA work.  Other relevant work in the area of certificate support
 in RADIUS may be found in an expired work in progress, "RADIUS X.509
 Certificate Extensions" [5].  The document claims "F", but in light
 of the specifics of the protocol [2], the evaluator awards "P".
 1.1.8 Reliable AAA Transport - The document [1] indicates that RADIUS
 provides partial compliance with the requirements of the original AAA
 requirements document.  However, in [3], the requirement has been
 simplified to "resilience against packet loss".  Once again, the
 evaluator finds that the protocol [2] meets this criteria on a hop-
 by-hop basis, but fails to effectively address these issues in a
 proxy-chain environment.  The document claims "P", and the evaluator
 awards "F".
 1.1.9 Run over IPv4 - RADIUS is widely deployed over IPv4.  The
 document claims "T", and the evaluator concurs.
 1.1.10 Run over IPv6 - The document [1] indicates that adoption of a
 limited number of new RADIUS attributes to support IPv6 is
 straightforward.  Such discussion has transpired on the RADIUS WG
 mailing list, although that WG is in the process of shutting down.
 The document claims "P", and the evaluator concurs.
 1.1.11 Support Proxy and Routing Brokers - The document [1] indicates
 that RADIUS is widely deployed in proxy-chains of RADIUS servers.
 This is equivalent to the Proxy Broker case, but the Routing Broker
 case is a different requirement.  The protocol [2] does not describe
 any detail of how a Routing Broker might be accommodated, although it
 opens the door by indicating that the RADIUS++ protocol is peer-to-
 peer, rather than client/server.  The document claims "P", and the
 evaluator awards "F".

Mitton, et al. Informational [Page 39] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.12 Auditability - The document [1] indicates no compliance with
 this requirement.  The document claims "F", and the evaluator
 concurs.
 1.1.13 Shared Secret Not Required - The document [1] indicates that
 RADIUS may effectively skirt the requirement of application-layer
 security by using a value of "zero" for the pre-shared secret.  While
 this is a bit creative, it does seem to meet the requirement.  The
 document claims "T" and the evaluator concurs.
 1.1.14 Ability to Carry Service Specific Attributes - RADIUS has a
 well defined Vendor-Specific Attribute, which, when properly used,
 does indeed provide for the ability to transport service-specific
 attributes.  The document claims "T", and the evaluator concurs.
 1.2 Authentication Requirements
 1.2.1 NAI Support - The document [1] indicates that RADIUS specifies
 the NAI as one of the suggested formats for the User-Name attribute.
 The document claims "T", and the evaluator agrees.
 1.2.2 CHAP Support - CHAP support is widely deployed in RADIUS.  The
 document claims [1] "T", and the evaluator concurs.
 1.2.3 EAP Support - The document [1] indicates that EAP support in
 RADIUS is specified in [4].  The document claims [1] "T", and the
 evaluator concurs.
 1.2.4 PAP/Clear-text Passwords - The document [1] indicates that
 RADIUS provides protection of clear-text passwords on a hop-by-hop
 basis.  The protocol [2] indicates how additional data
 confidentiality may be obtained in section 4.3.2.2 of [2], using a
 CMS-data attribute, based in large part upon RFC 2630.  The evaluator
 has not, at this time, investigated the applicability of RFC 2630 to
 the AAA work.  The document claims [1] "F", but in light of the
 specifics of the protocol [2], the evaluator awards "P".
 1.2.5 Reauthentication on demand - The document [1] indicates that
 RADIUS may accomplish re-authentication on demand by means of an
 Access-Challenge message sent from a server to a client.  The
 evaluator disagrees that this is likely to work for a given session
 once an Access-Accept message has been received by the client.  The
 document claims "T", and the evaluator awards "F".
 1.2.6 Authorization w/o Authentication - This requirement, as applied
 to the protocol specification, mandates that non- necessary
 authentication credentials not be required in a request for
 authorization.  The actual decision to provide authorization in the

Mitton, et al. Informational [Page 40] RFC 3127 AAA Protocol Evaluation Process June 2001

 absence of any authentication resides in the application (e.g. AAA
 server).  RADIUS does require some form of credential in request
 messages.  The document [1] claims "F", and the evaluator concurs.
 1.3 Authorization Requirements
 1.3.1 Static and Dynamic IP Addr Assignment - The document [1]
 indicates that RADIUS can assign IPv4 addresses, and can easily be
 extended to assign IPv6 addresses (see section 1.1.10).  Of greater
 concern, however, is the issue of static vs. dynamic addresses.  If
 dynamic address has the same meaning as it does for DHCP, then there
 are issues of resource management that RADIUS has traditionally not
 addressed.  The document claims "P", and the evaluator concurs.
 1.3.2 RADIUS Gateway Capability - The document [1] maintains that a
 RADIUS++ to RADIUS gateway is pretty much a tautology.  The document
 claims "T", and the evaluator concurs.
 1.3.3 Reject Capability - The document [1] maintains that RADIUS
 Proxy Servers, and potentially RADIUS++ Routing Brokers, have the
 ability to reject requests based on local policy.  The document
 claims "T" and the evaluator concurs.
 1.3.4 Preclude Layer 2 Tunneling - The document [1] indicates that
 [6] defines support for layer two tunneling in RADIUS.  The document
 claims "T", and the evaluator concurs.
 1.3.5 Reauth on Demand - The document [1] indicates that RADIUS
 provides this feature by means of the Session-Timeout and
 Termination- Action attributes.  While this may, in fact, be
 sufficient to provide periodic re-authorization, it would not provide
 re- authorization on demand.  The protocol [2] does not address this
 further.  The document claims "P", and the evaluator awards "F".
 1.3.6 Support for ACLs - The document [1] describes the attributes in
 RADIUS that are used to convey the access controls described in [3].
 Certain of these (e.g. QoS) are not currently defined in RADIUS, but
 could easily be defined as new RADIUS attributes.  The document
 claims "P", and the evaluator concurs.
 1.3.7 State Reconciliation - The document [1] addresses each of the
 sub- items, as listed in the original AAA requirements document.  In
 reviewing the document against the modified requirements of [3],
 there is still an issue with server-initiated state reconciliation
 messages.  While the protocol [2] makes provision for such messages,
 as servers are allowed to initiate protocol dialogs, no detailed

Mitton, et al. Informational [Page 41] RFC 3127 AAA Protocol Evaluation Process June 2001

 message formats are provided.  This is an area that has traditionally
 been a short coming of RADIUS.  The document claims "P", and the
 evaluator awards "F".
 1.3.8 Unsolicited Disconnect - Much of the discussion from the
 previous section applies to this section.  The document [1] claims
 "F", and the evaluator concurs.
 1.4 Accounting Requirements
 1.4.1 Real Time Accounting - RADIUS Accounting is widely deployed and
 functions within the definition of real time contained in [3].  The
 document [1] claims "T", and the evaluator concurs.
 1.4.2 Mandatory Compact Encoding - RADIUS Accounting contains TLVs
 for relevant accounting information, each of which is fairly compact.
 Note that the term "bloated" in [3] is somewhat subjective.  The
 document [1] claims "T", and the evaluator concurs.
 1.4.3 Accounting Record Extensibility - RADIUS Accounting may be
 extended by means of new attributes or by using the Vendor-Specific
 attribute.  While it has been argued that the existing attribute
 number space is too small for the required expansion capabilities,
 the protocol [2] addresses this problem in section 3.0, and its
 subsections, of [2].  The document [1] claims "T", and the evaluator
 concurs.
 1.4.4 Batch Accounting - RADIUS has no explicit provisions for batch
 accounting, nor does the protocol [2] address how this feature might
 be accomplished.  The document [1] claims "F", and the evaluator
 concurs.
 1.4.5 Guaranteed Delivery - RADIUS Accounting is widely deployed and
 provides guaranteed delivery within the context of the required
 application-level acknowledgment.  The document [1] claims "T", and
 the evaluator concurs.
 1.4.6 Accounting Timestamps - The document [1] indicates that this
 feature is specified in [4] as the Event-Timestamp attribute.  The
 document claims [1] "T", and the evaluator concurs.
 1.4.7 Dynamic Accounting - The document [1] indicates that this
 requirement is partially met using the accounting interim update
 message as specified in [4].  In addition, there was work in the
 RADIUS WG regarding session accounting extensions that has not been
 included in [4], i.e., some expired works in progress.  The document
 claims [1] "P", and the evaluator concurs.

Mitton, et al. Informational [Page 42] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.5 MOBILE IP Requirements
 1.5.1 Encoding of MOBILE IP Registration Messages - The document [1]
 claims "F", and the evaluator concurs.
 1.5.2 Firewall Friendly - The document [1] indicates that RADIUS
 deployment is know to have occurred in fire-walled environments.  The
 document claims "T", and the evaluator concurs.
 1.5.3 Allocation of Local Home Agent - The document [1] claims "F",
 and the evaluator concurs.
 2. Summary Discussion
 The document [1] and the protocol [2] suffer from having been written
 in a short time frame.  While the protocol does provide specific
 guidance on certain issues, citing other relevant documents, it is
 not a polished protocol specification, with detailed packet format
 diagrams.  There is a pool of prior work upon which the RADIUS++
 protocol may draw, in that many of the concepts of Diameter were
 first postulated as works in progress within the RADIUS WG, in an
 attempt to "improve" the RADIUS protocol.  All of these works in
 progress have long since expired, however.
 3. General Requirements
 RADIUS++ meets many of the requirements of an AAA protocol, as it is
 the current de facto and de jure standard for AAA.  There are long-
 standing deficiencies in RADIUS, which have been well documented in
 the RADIUS and NASREQ WG proceedings.  It is technically possible to
 revamp RADIUS to solve these problems.  One question that will be
 asked, however, is:  "What significant differences would there be
 between a finished RADIUS++ protocol and the Diameter protocol?".
 4. Summary Recommendation
 Recommended in part.  What may possibly be learned from this
 submission is that it is feasible to have a more RADIUS-compliant
 RADIUS-compatibility mode in Diameter.

Mitton, et al. Informational [Page 43] RFC 3127 AAA Protocol Evaluation Process June 2001

C.5 Diameter PRO Evaluation

 Evaluation of Diameter against the AAA Requirements
 PRO Evaluation
 Evaluator - Basavaraj Patil
 Ref [1] is "Diameter Framework Document".
 Ref [2] is "Diameter NASREQ Extensions".
 Ref [3] is the AAA evaluation criteria as modified by us.
 Ref [4] is "Diameter Accounting Extensions".
 Ref [5] is "Diameter Mobile IP Extensions".
 Ref [6] is "Diameter Base Protocol".
 Ref [7] is "Diameter Strong Security Extension".
 Ref [8] is "Comparison of Diameter Against AAA Network Access
 Requirements".
 The document uses T to indicate total compliance, P to indicate
 partial compliance and F to indicate no compliance.
 Evaluator's note : The Diameter compliance document [8] claims Total
 "T" compliance with all the requirements except :  - 1.2.5 - 1.5.2
 Section 1 - Per item discussion
 1.1 General Requirements
 1.1.1 Scalability
 Diameter is an evolution of RADIUS and has taken into consideration
 all the lessons learned over many years that RADIUS has been in
 service.  The use of SCTP as the transport protocol reduces the need
 for multiple proxy servers (Sec 3.1.1 Proxy Support of [1]) as well
 as removing the need for application level acks.  The use and support
 of forwarding and redirect brokers enhances  scalability.  Evaluator
 concurs with the "T" compliance on this requirement.
 1.1.2 Fail-over
 Again with the use of SCTP, Diameter is able to detect disconnect
 indications upon which it switches to an alternate server (Sec 4.0
 [6]).  Also Requests and Responses do not have to follow the same
 path and this increases the reliability.  Evaluator concurs with the
 "T" compliance on this requirement.

Mitton, et al. Informational [Page 44] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.3 Mutual Authentication
 The compliance document quotes the use of symmetric transforms for
 mutual authentication between the client and server (Sec 7.1 of
 [6]).  The use of IPSec as an underlying security mechanism and
 thereby use the characteristics of IPSec itself to satisfy this
 requirement is also quoted.  Evaluator concurs with the "T"
 compliance on this requirement.
 1.1.4 Transmission Level Security
 Although this requirement has been deprecated by the AAA evaluation
 team the document complies with it based on the definition (referring
 to hop-by-hop security).  Section 7.1 of [6] provides the details of
 how this is accomplished in Diameter.  Evaluator concurs with the "T"
 compliance on this requirement.
 1.1.5 Data Object Confidentiality
 This requirement seems to have come from Diameter.  Ref [7] explains
 in detail the use of Cryptographic Message Syntax (CMS) to achieve
 data object confidentiality.  A CMS-Data AVP is defined in [7].
 Evaluator concurs with the "T" compliance on this requirement.
 1.1.6 Data Object Integrity
 Using the same argument as above and the hop-by-hop security feature
 in the protocol this requirement is completely met by Diameter.
 Evaluator concurs with the "T" compliance on this requirement.
 1.1.7 Certificate Transport
 Again with the use of the CMS-Data AVP, objects defined as these
 types of attributes allow the transport of certificates.  Evaluator
 concurs with the "T" compliance on this requirement.
 1.1.8 Reliable AAA Transport
 Diameter recommends that the protocol be run over SCTP.  SCTP
 provides the features described for a reliable AAA transport.
 Although the compliance is not a perfect fit for the definition of
 this tag item, it is close enough and the functionality achieved by
 using SCTP is  the same.  Evaluator concurs with the "T" compliance
 on this requirement.

Mitton, et al. Informational [Page 45] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.9 Run over IPv4
 Is an application layer protocol and does not depend on the
 underlying version of IP.  Evaluator concurs with the "T" compliance
 on this requirement.
 1.1.10 Run over IPv6
 Is an application layer protocol and does not depend on the
 underlying version of IP.  Evaluator concurs with the "T" compliance
 on this requirement.
 1.1.11 Support Proxy and Routing Brokers
 Section 3.1.1/2 of the framework document [1] provides an explanation
 of how Diameter supports proxy and routing brokers.  In fact it
 almost appears as though the requirement for a routing broker came
 from Diameter.  Evaluator concurs with the "T" compliance on this
 requirement.
 1.1.12 Auditability
 With the use of CMS-Data AVP [7] a trail is created when proxies are
 involved in the transaction.  This trail can provide auditability.
 Evaluator concurs with the "T" compliance on this requirement.
 1.1.13 Shared Secret Not Required
 With the use of IPSec as the underlying security mechanism, Diameter
 does not require the use of shared secrets for message
 authentication.  Evaluator concurs with the "T" compliance on this
 requirement.
 1.1.14 Ability to Carry Service Specific Attributes
 The base protocol [6] is defined by Diameter and any one else can
 define specific extensions on top of it.  Other WGs in the IETF can
 design an extension on the base protocol with specific attributes and
 have them registered by IANA.  Evaluator concurs with the "T"
 compliance on this requirement.

Mitton, et al. Informational [Page 46] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.2 Authentication Requirements
 1.2.1 NAI Support
 The base protocol [6] defines an AVP that can be used to support
 NAIs.  Diameter goes one step further by doing Message forwarding
 based on destination NAI AVPs.  Evaluator concurs with the "T"
 compliance on this requirement.
 1.2.2 CHAP Support
 Reference [2] section 3.0 describes the support for CHAP.  Evaluator
 concurs with the "T" compliance on this requirement.
 1.2.3 EAP Support
 Reference [2] section 4.0 describes the support for EAP.  Evaluator
 concurs with the "T" compliance on this requirement.
 1.2.4 PAP/Clear-text Passwords
 Reference [2] section 3.1.1.1 describes the support for PAP.
 Evaluator concurs with the "T" compliance on this requirement.
 1.2.5 Reauthentication on demand
 The use of Session-Timeout AVP as the mechanism for reauthentication
 is claimed by the compliance document.  However no direct references
 explaining this in the base protocol [6] document were found.
 Evaluator deprecates the compliance on this to a "P"
 Note: However this is a trivial issue.
 1.2.6 Authorization w/o Authentication
 Diameter allows requests to be sent without having any authentication
 information included.  A Request-type AVP is defined in [2] and it
 can specify authorization only without containing any authentication.
 Evaluator concurs with the "T" compliance on this requirement.

Mitton, et al. Informational [Page 47] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.3 Authorization Requirements
 1.3.1 Static and Dynamic IP Addr Assignment
 The base protocol includes an AVP for carrying the  address.
 References [6.2.2 of 2] and [4.5 of 5] provide detailed  explanations
 of how this can be done.  Evaluator concurs with the "T" compliance
 on this requirement.
 1.3.2 RADIUS Gateway Capability
 One of the basic facets of Diameter is to support backward
 compatibility and act as a RADIUS gateway in certain environments.
 Evaluator concurs with the "T" compliance on this requirement.
 1.3.3 Reject Capability
 Based on the explanation provided in the compliance document for this
 requirement evaluator concurs with the "T" compliance on this
 requirement.
 1.3.4 Preclude Layer 2 Tunneling
 Ref [2] defines AVPs supporting L2 tunnels  Evaluator concurs with
 the "T" compliance on this requirement.
 1.3.5 Reauth on Demand
 A session timer defined in [6] is used for reauthorization.  However
 Diameter allows reauthorization at any time.  Since this is a peer-
 to-peer type of protocol any entity can initiate a reauthorization
 request.  Evaluator concurs with the "T" compliance on this
 requirement.
 1.3.6 Support for ACLs
 Diameter defines two methods.  One that supports backward
 compatibility for RADIUS and another one with the use of a standard
 AVP with the filters encoded in it.  Evaluator concurs with the "T"
 compliance on this requirement.
 1.3.7 State Reconciliation
 A long explanation on each of the points defined for this tag item in
 the requirements document.  Evaluator concurs with the "T" compliance
 for this requirement.

Mitton, et al. Informational [Page 48] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.3.8 Unsolicited Disconnect
 The base protocol [6] defines a set of session termination messages
 which can be used for unsolicited disconnects.  Evaluator concurs
 with the "T" compliance on this requirement.
 1.4 Accounting Requirements
 1.4.1 Real Time Accounting
 Evaluator concurs with the "T" compliance based on explanations in
 [4].
 1.4.2 Mandatory Compact Encoding
 Use of Accounting Data Interchange Format (ADIF)-Record-AVP for
 compact encoding of accounting data.  Evaluator concurs with the "T"
 compliance.
 1.4.3 Accounting Record Extensibility
 ADIF can be extended.  Evaluator concurs with the "T" compliance.
 1.4.4 Batch Accounting
 Sec 1.2 of [4] provides support for batch accounting.
 1.4.5 Guaranteed Delivery
 Sections 2.1/2 of [4] describe messages that are used to guarantee
 delivery of accounting records.  Evaluator concurs with the "T"
 compliance.
 1.4.6 Accounting Timestamps
 Timestamp AVP [6] is present in all accounting messages.  Evaluator
 concurs with the "T" compliance.
 1.4.7 Dynamic Accounting
 Interim accounting records equivalent to a call-in-progress can be
 sent periodically.  Evaluator concurs with the "T" compliance.

Mitton, et al. Informational [Page 49] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.5 MOBILE IP Requirements
 1.5.1 Encoding of MOBILE IP Registration Messages
 Ref [5] provides details of how Diameter can encode MIP messages.
 Evaluator concurs with the "T" compliance.
 1.5.2 Firewall Friendly
 Some handwaving here and a possible way of solving the firewall
 problem with a Diameter proxy server.  Document claims "T", evaluator
 deprecates it to a "P"
 1.5.3 Allocation of Local Home Agent
 Diameter can assign a local home agent in a visited network in
 conjunction with the FA in that network.  Evaluator concurs with the
 "T"
 Summary Recommendation
 Diameter is strongly recommended as the AAA protocol.  The experience
 gained from RADIUS deployments has been put to good use in the design
 of this protocol.  It has also been designed with extensibility in
 mind thereby allowing different WGs to develop their own specific
 extension to satisfy their requirements.  With the use of SCTP as the
 transport protocol, reliability is built in.  Security has been
 addressed in the design of the protocol and  issues that were
 discovered in RADIUS have been fixed.  Diameter also  is a session
 based protocol which makes it more scalable.  The support for
 forwarding and redirect brokers is well defined and  this greatly
 improves the scalability aspect of the protocol.
 Lastly the protocol has been implemented by at least a few people and
 interop testing done.  This in itself is a significant step and a
 positive point for Diameter to be the AAA protocol.

C.6 Diameter CON Evaluation

 Evaluation of Diameter against the AAA Requirements
 CON Brief
 Evaluator: Barney Wolff

Mitton, et al. Informational [Page 50] RFC 3127 AAA Protocol Evaluation Process June 2001

 Section 1 - Per item discussion
 1.1 General Requirements
 1.1.1 Scalability - P (was T)  The evaluator is concerned with
 scalability to the small, not to the large.  Diameter/SCTP may prove
 difficult to retrofit to existing NAS equipment.
 1.1.2 Fail-over - P (was T)  SCTP gives an indication of peer
 failure, but nothing in any Diameter or SCTP document the evaluator
 was able to find even mentions how or when to switch back to a
 primary server to which communication was lost.  After a failure, the
 state machines end in a CLOSED state and nothing seems to trigger
 exit from that state.  It was not clear whether a server, on
 rebooting, would initiate an SCTP connection to all its configured
 clients.  If not, and in any case when the communication failure was
 in the network rather than in the server, the client must itself,
 after some interval, attempt to re-establish communication.  But no
 such guidance is given.
 Of course, the requirement itself fails to mention the notion of
 returning to a recovered primary.  That is a defect in the
 requirement.  The evaluator has had unfortunate experience with a
 vendor's RADIUS implementation that had exactly the defect that it
 often failed to notice recovery of the primary.
 1.1.3 Mutual Authentication - T
 1.1.4 Transmission Level Security - T
 1.1.5 Data Object Confidentiality - P (was T).  Yes, the CMS data
 type is supported.  But the work in progress, "Diameter Strong
 Security Extension", says:
    Given that asymmetric transform operations are expensive, Diameter
    servers MAY wish to use them only when dealing with inter-domain
    servers, as shown in Figure 3.  This configuration is normally
    desirable since Diameter entities within a given administrative
    domain MAY inherently trust each other.  Further, it is desirable
    to move this functionality to the edges, since NASes do not
    necessarily have the CPU power to perform expensive cryptographic
    operations.
 Given all the fuss that has been made about "end-to-end"
 confidentiality (which really means "NAS-to-home_server"), the
 evaluator finds it absurd that the proposed solution is acknowledged
 to be unsuited to the NAS.

Mitton, et al. Informational [Page 51] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.6 Data Object Integrity - P (was T).  See above.
 1.1.7 Certificate Transport - T
 1.1.8 Reliable AAA Transport - T
 1.1.9 Run over IPv4 - T
 1.1.10 Run over IPv6 - T
 1.1.11 Support Proxy and Routing Brokers - T
 1.1.12 Auditability - T (based on our interpretation as non-
 repudiation, rather than the definition given in reqts)
 1.1.13 Shared Secret Not Required - T
 1.1.14 Ability to Carry Service Specific Attributes - T
 1.2 Authentication Requirements
 1.2.1 NAI Support - T
 1.2.2 CHAP Support - T
 1.2.3 EAP Support - T
 1.2.4 PAP/Clear-text Passwords - T
 1.2.5 Reauthentication on demand - P (was T).  No mechanism was
 evident for the server to demand a reauthentication, based for
 example on detection of suspicious behavior by the user.  Session-
 timeout is not sufficient, as it must be specified at the start.
 1.2.6 Authorization w/o Authentication - T
 1.3 Authorization Requirements
 1.3.1 Static and Dynamic IP Addr Assignment - T
 1.3.2 RADIUS Gateway Capability - P (was T).  RADIUS has evolved from
 the version on which Diameter was based.  EAP is a notable case where
 the convention that the Diameter attribute number duplicates the
 RADIUS one is violated.  No protocol, not even RADIUS++, can claim a
 T on this.
 1.3.3 Reject Capability - T (The evaluator fails to understand how
 any AAA protocol could rate anything other than T on this.)

Mitton, et al. Informational [Page 52] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.3.4 Preclude Layer 2 Tunneling - T
 1.3.5 Reauth on Demand - P (was T).  As with reauthentication, there
 is no evident mechanism for the server to initiate this based on
 conditions subsequent to the start of the session.
 1.3.6 Support for ACLs - P (was T).  The evaluator finds the Filter-
 Rule AVP laughably inadequate to describe filters.  For example, how
 would it deal with restricting SMTP to a given server, unless all IP
 options are forbidden so the IP header length is known?  No real NAS
 could have such an impoverished filter capability, or it would not
 survive as a product.
 1.3.7 State Reconciliation - P (was T).  It is difficult for the
 evaluator to understand how this is to work in a multi-administration
 situation, or indeed in any proxy situation.  Furthermore, SRQ with
 no session-id is defined to ask for info on all sessions, not just
 those "owned" by the requester.
 1.3.8 Unsolicited Disconnect - T
 1.4 Accounting Requirements
 1.4.1 Real Time Accounting - T
 1.4.2 Mandatory Compact Encoding - T
 1.4.3 Accounting Record Extensibility - T
 1.4.4 Batch Accounting - P (was T).  The evaluator suspects that
 simply sending multiple accounting records in a single request is not
 how batch accounting should or will be done.
 1.4.5 Guaranteed Delivery - T
 1.4.6 Accounting Timestamps - T  (The evaluator notes with amusement
 that NTP time cycles in 2036, not 2038 as claimed in the Diameter
 drafts.  It's Unix time that will set the sign bit in 2038.)
 1.4.7 Dynamic Accounting - T
 1.5 MOBILE IP Requirements
 1.5.1 Encoding of MOBILE IP Registration Messages - T
 1.5.2 Firewall Friendly - F (was T).  Until such time as firewalls
 are extended to know about or proxy SCTP, it is very unlikely that
 SCTP will be passed.  Even then, the convenient feature of being able

Mitton, et al. Informational [Page 53] RFC 3127 AAA Protocol Evaluation Process June 2001

 to send a request from any port, and get the reply back to that port,
 means that a simple port filter will not be sufficient, and
 statefulness will be required.  Real friendship would require that
 both source and dest ports be 1812.
 1.5.3 Allocation of Local Home Agent - T
 2. Summary Discussion
 In some areas, Diameter is not completely thought through.  In
 general, real effort has gone into satisfying a stupendous range of
 requirements.
 3. General Requirements
 Diameter certainly fails the KISS test.  With SCTP, the drafts add up
 to 382 pages - well over double the size of RADIUS even with
 extensions.  The evaluator sympathizes with the political instinct
 when faced with a new requirement no matter how bizarre, to say "we
 can do that" and add another piece of filigree.  But the major places
 where Diameter claims advantage over RADIUS, namely "end-to-end"
 confidentiality and resource management, are just the places where
 some hard work remains, if the problems are not indeed intractable.
 More specifically, the evaluator sees no indication that specifying
 the separate transport protocol provided any advantage to defray the
 large increase in complexity.  Application acks are still required,
 and no benefit from the transport acks was evident to the evaluator.
 Nor was there any obvious discussion of why "sequenced in-order"
 delivery is required, when AAA requests are typically independent.
 SCTP offers out-of-order delivery, but Diameter seems to have chosen
 not to use that feature.
 Whether TLV encoding or ASN.1/BER is superior is a religious
 question, but Diameter manages to require both, if the "strong"
 extension is implemented.  The evaluator has a pet peeve with length
 fields that include the header, making small length values invalid,
 but that is a minor point.
 Finally, interoperability would be greatly aided by defining a
 standard "dictionary" format by which an implementation could adopt
 wholesale a set of attributes, perhaps from another vendor, and at
 least know how to display them.  That is one of the advantages of
 MIBs.

Mitton, et al. Informational [Page 54] RFC 3127 AAA Protocol Evaluation Process June 2001

 4. Summary Recommendation
 Diameter is clearly close enough to meeting the myriad requirements
 that it is an acceptable candidate, though needing some polishing.
 Whether the vast increase in complexity is worth the increase in
 functionality over RADIUS is debatable.

C.7 COPS PRO Evaluation

 Evaluation of COPS AAA Requirements
 PRO Evaluation
 Evaluator - David Nelson
 Ref [1] is "Comparison of COPS Against the AAA NA Requirements", work
 in progress, a.k.a. 'the document'
 Ref [2] is RFC 2748 a.k.a. 'the protocol'
 Ref [3] is the AAA evaluation criteria as modified by us.
 Ref [4] is "AAA Protocols: Comparison between RADIUS, Diameter, and
 COPS"  work in progress.
 Ref [5] is "COPS Usage for AAA", work in progress.
 This document uses T to indicate total compliance, P to indicate
 partial compliance and F to indicate no compliance.
 Section 1 - Per item discussion
 1.1 General Requirements
 1.1.1 Scalability - The document [1] claims "T", and the evaluator
 concurs.
 1.1.2 Fail-over - The document [1] claims "T", and the evaluator
 concurs.
 1.1.3 Mutual Authentication - The document claims "T", and the
 evaluator concurs.
 1.1.4 Transmission Level Security - The document [1] indicates that
 transmission layer security, as defined in [3], is provided in the
 protocol, using the mechanisms described in [2].  It should be noted
 that this requirement is now a SHOULD in [3].  The document claims
 "T", and the evaluator concurs.
 1.1.5 Data Object Confidentiality - The document [1] indicates that
 end-to-end confidentiality is provided using a CMS-data attribute,
 based in large part upon RFC 2630.  The evaluator has not, at this
 time, investigated the applicability of RFC 2630 to the AAA work.
 The document claims "T", and the evaluator concurs.

Mitton, et al. Informational [Page 55] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.6 Data Object Integrity - The document [1] indicates that data
 object integrity is provided using a CMS-data attribute, based in
 large part upon RFC 2630.  The evaluator has not, at this time,
 investigated the applicability of RFC 2630 to the AAA work.  The
 document claims "T", and the evaluator concurs.
 1.1.7 Certificate Transport - The document [1] indicates that
 certificate transport is provided using a CMS-data attribute, based
 in large part upon RFC 2630 and RFC 1510.  The evaluator has not, at
 this time, investigated the applicability of RFC 2630 to the AAA
 work.  The document claims "T", and the evaluator concurs.
 1.1.8 Reliable AAA Transport - The document [1] indicates that COPS
 uses TCP, which certainly meets the requirements for a reliable
 transport.  The document claims "T", and the evaluator concurs.
 1.1.9 Run over IPv4 - The document [1] claims "T", and the evaluator
 concurs.
 1.1.10 Run over IPv6 - The document [1] claims "T", and the evaluator
 concurs.
 1.1.11 Support Proxy and Routing Brokers - Reasonable detail of proxy
 operations is provided in [5].  The document [1] claims "T", and the
 evaluator concurs.
 1.1.12 Auditability - The document [1] alludes to a History PIB that
 would enable auditing without explaining how it would work.  The AAA
 Extension [5] does not provide additional insight.  The document
 claims "T", and the evaluator awards "P".
 1.1.13 Shared Secret Not Required - The document [1] claims "T" and
 the evaluator concurs.
 1.1.14 Ability to Carry Service Specific Attributes -  The document
 [1] claims "T", and the evaluator concurs.
 1.2 Authentication Requirements
 1.2.1 NAI Support - The document [1] indicates that NAI is to be
 supported in the Information Model, but notes that for cases where
 certificates are in use, the more restrictive syntax of RFC 2459
 applies.  The document claims "T", and the evaluator awards "P".
 1.2.2 CHAP Support - The document [1] claims "T", and the evaluator
 concurs.

Mitton, et al. Informational [Page 56] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.2.3 EAP Support - The document [1] claims "T", and the evaluator
 concurs.
 1.2.4 PAP/Clear-text Passwords - The document [1] indicates
 compliance, presumably using a CMS-data attribute, based in large
 part upon RFC 2630.  The evaluator has not, at this time,
 investigated the applicability of RFC 2630 to the AAA work.  The
 document claims "T", and the evaluator concurs.
 1.2.5 Reauthentication on demand - The document [1] claims "T", and
 the evaluator concurs.
 1.2.6 Authorization w/o Authentication - This requirement, as applied
 to the protocol specification, mandates that non- necessary
 authentication credentials not be required in a request for
 authorization.  The actual decision to provide authorization in the
 absence of any authentication resides in the application (e.g. AAA
 server).  The document [1] claims "T", and the evaluator concurs.
 1.3 Authorization Requirements
 1.3.1 Static and Dynamic IP Addr Assignment -  The document [1]
 claims "T", and the evaluator concurs.
 1.3.2 RADIUS Gateway Capability - The document [1] claims "T", and in
 the absence of any detailed discussion of how this is accomplished,
 in either [1] or [5], the evaluator awards "P".
 1.3.3 Reject Capability - The document claims [1] "T" and the
 evaluator concurs.
 1.3.4 Preclude Layer 2 Tunneling - The document [1] claims "T", and
 in the absence of any detailed discussion of how this is
 accomplished, in either [1] or [5], the evaluator awards "P".
 1.3.5 Reauth on Demand -  The document [1] claims "T", and the
 evaluator concurs.
 1.3.6 Support for ACLs - The document [1] "T", and the evaluator
 concurs.
 1.3.7 State Reconciliation - The document [1] "T", and the evaluator
 concurs.
 1.3.8 Unsolicited Disconnect - The document [1] claims "T", and the
 evaluator concurs.

Mitton, et al. Informational [Page 57] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.4 Accounting Requirements
 1.4.1 Real Time Accounting -  The document [1] claims "T", and the
 evaluator concurs.
 1.4.2 Mandatory Compact Encoding - Note that the term "bloated" in
 [3] is somewhat subjective.  The document [1] claims "T", and the
 evaluator concurs.
 1.4.3 Accounting Record Extensibility -  The document [1] claims "T",
 and the evaluator concurs.
 1.4.4 Batch Accounting - The protocol [2] [5] does not address how in
 detail this feature might be accomplished.  The document [1] claims
 "T", and the awards "P".
 1.4.5 Guaranteed Delivery - Guaranteed delivery is provided by TCP.
 The document [1] claims "T", and the evaluator concurs.
 1.4.6 Accounting Timestamps - The document [1] claims "T", and the
 evaluator concurs.
 1.4.7 Dynamic Accounting - The document [1] claims "T", and the
 evaluator concurs.
 1.5 MOBILE IP Requirements
 1.5.1 Encoding of MOBILE IP Registration Messages - The document [1]
 claims "T", and the evaluator concurs.
 1.5.2 Firewall Friendly - The document [1] claims "T", and the
 evaluator concurs.
 1.5.3 Allocation of Local Home Agent - The document [1] claims "T",
 and the evaluator concurs.
 2. Summary Discussion
 It may appear, upon initial inspection, that the evaluator has not
 lent a critical eye to the compliance assertions of the document [1].
 First, this memo is a "PRO" brief, and as such reasonable benefit of
 doubt is to be given in favor of the protocol submission.  Second,
 there is a fundamental conceptual issue at play.  The COPS-PR model
 provides a sufficient set of basic operations and commands, a
 stateful model, the ability for either "peer" to initiate certain
 kinds of requests, as well as an extensible command set, to be able
 to support a wide variety of network and resource management
 protocols.  The details of protocol specific messages is left to

Mitton, et al. Informational [Page 58] RFC 3127 AAA Protocol Evaluation Process June 2001

 Policy Information Base (PIB) data objects.  Since no AAA PIB has
 been written, the evacuator can only (optimistically) assess the
 inherent capabilities of the base protocol to accomplish the intended
 requirements of [3], given a reasonable set of assumptions about what
 an AAA PIB might look like.
 In some sense, this akin to asserting that a given algorithm can be
 correctly implemented in a specific programming language, without
 actually providing the code.
 The PIB model used by COPS is a powerful and flexible model.  The
 protocol document [5] spends a considerable amount of time
 enumerating and describing the benefits of this data model, and
 explaining its roots in Object Oriented (OO) design methodology.
 Analogies are made to class inheritance and class containment, among
 others.  It's always hard to say bad things about OO.
 3. General Requirements
 COPS-AAA would appear to meet (totally or partially) all of the
 requirements of [3], at least as can be determined without the
 benefit of an AAA PIB.
 4. Summary Recommendation
 Recommended with reservation.  Before final acceptance of COPS-AAA,
 someone is going to have to write the AAA PIB and evaluate its
 details.

C.8 COPS CON Evaluation

 Evaluation of COPS against the AAA Requirements
 CON Evaluation
 Evaluator - David Mitton
 The Primary document discussed here is [COPSComp] and the arguments
 therein based on the proposal [COPSAAA].
 [COPSComp] "Comparison of COPS Against the AAA NA Requirements", Work
 in Progress.
 [COPSAAA] "COPS Usage for AAA", Work in Progress.
 [EksteinProtoComp] "AAA Protocols: Comparison between RADIUS,
 Diameter, and COPS", Work in Progress.

Mitton, et al. Informational [Page 59] RFC 3127 AAA Protocol Evaluation Process June 2001

 References: (in order of relevancy)
 [COPSBase]  Durham, D., Boyle, J., Cohen, R., Herzog, S., Rajan, R.
             and A. Sastry, "The Common Open Policy Service Protocol",
             RFC 2748, January 2000.
 [COPSFwork] Yavatkar, R., Pendarakis, D. and R. Guerin, "A Framework
             for Policy-based Admission Control", RFC 2753, January
             2000.
 [COPSPR]    "COPS Usage for Policy Provisioning", Work in Progress.
 [COPSSPPI]  "Structure of Policy Provisioning Information (SPPI)",
             Work in Progress.
 [COPSCMS]   "COPS Over CMS", Work in Progress.
 [COPSTLS]   "COPS Over TLS", Work in Progress.
 [COPSGSS]   "COPS Extension for GSS-API based Authentication
             Support", Work in Progress.
 Other COPS & RSVP RFCs & drafts not listed as not directly relevant.
 Compliance: T==Total, P==Partial, F=Failed
 Section 1 - Per item discussion
 Initial Note: [COPSComp] claims "unconditional compliance" with all
 requirements.
 1.1 General Requirements
 1.1.1 Scalability - P (was T) The evaluator is concerned with
 scalability of many always-on TCP connections to a server supporting
 a lot of clients, particularly with the heartbeat messages.  The
 claim that the request handle is "unbounded" sounds fishy.
 1.1.2 Fail-over - P (was T) COPS gives an indication of peer failure,
 and has mechanisms to restart state, but there seems to be a bias
 toward a single state server.  COPS has decided that synchronizing
 state between multiple hot servers is out of scope.
 Because COPS uses TCP, it is at the mercy of the TCP timers of the
 implementation which can be significant.  Connection timeout
 reporting to the application may be delayed beyond the client
 authentication timeouts.  Tuning the Keep-Alive message to a tighter
 period will increase the session and system overhead.

Mitton, et al. Informational [Page 60] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.3 Mutual Authentication - P (was T) The explanation is sort of
 for message object integrity.  It does not describe authentication
 techniques.  The evaluator assumes that COPS peers would authenticate
 each other at Client-Open time.  But cannot understand how this would
 work if proxies are involved.
 1.1.4 Transmission Level Security - T
 1.1.5 Data Object Confidentiality - T  Seems almost a carbon copy of
 the Diameter capabilities.  This evaluator echoes the high overhead
 concerns of the Diameter evaluator for the CMS capability.  TLS is
 not mentioned here, but is piled on later.
 1.1.6 Data Object Integrity - T  See above.
 1.1.7 Certificate Transport - T
 1.1.8 Reliable AAA Transport - T (maybe P) COPS meets this
 requirement as well as any other protocol we've evaluated.  That is
 it does have one application level ACK.  Statements such as "TCP
 provides guaranteed delivery" are incorrect.  COPS does attempt to
 identify outages by using a keep-alive message between TCP peers.
 1.1.9 Run over IPv4 - T
 1.1.10 Run over IPv6 - T
 1.1.11 Support Proxy and Routing Brokers - P (was T)  How client
 types are supported forward is not well understood by this evaluator.
 Does each client type require the Broker to make a different client
 Open request to it's upstream servers?  What about routing brokers?
 1.1.12 Auditability - P (was T)  (based on our interpretation as
 non-repudiation, rather than the definition given in reqts) The
 explanation of a History PIB is incomplete and therefore
 inconclusive.
 1.1.13 Shared Secret Not Required - T  Except this clause in
 [COPSAAA] 6.2 page 14 "COPS MUST be capable of supporting TLS"
 1.1.14 Ability to Carry Service Specific Attributes - P (was T)
 a) COPS only allows a small number of unique objects to be added.
    256 Object "classes" or types, with 256 subtypes or versions.
    Client types are 16 bits long, where the high bit indicates
    "enterprise" specific values.  But pertain to a COPS peer-

Mitton, et al. Informational [Page 61] RFC 3127 AAA Protocol Evaluation Process June 2001

    connection session.  The client type seems to just identify the
    information model for the message. eg. it will be fixed to one
    value for AAA.
 b) Service specific objects are not the same as Vendor Specific
    Objects.  They pertain to objects within a client type.
 c) The PIB model leads to a different model interoperability.
    Because most vendor product differ in some way, each PIB will be
    different, and sharing common provisioning profiles will be a
    rather difficult mapping problem on the server.
 d) It's not clear the different client types can be mixed or that
    other objects definitions can be used from other defined client
    types.  It's really unclear how the client type of a connection
    propagates in a proxy situation.
 1.2 Authentication Requirements
 1.2.1 NAI Support - T  The requirement that RFC 2459 (X.509 profiles)
 be met presumes that Auth servers would not have a mapping or local
 transformation.
 1.2.2 CHAP Support - T  An Information Model is being invoked, which
 I don't see really fleshed out anywhere.  [COPSAAA] does a bit of
 handwaving and definitions but doesn't deliver much meat.
 Nonetheless, this could be handled ala RADIUS.
 1.2.3 EAP Support - P (was T)  Again with the non-existent
 Information Model.  To do EAP, this evaluator thinks another Request
 or Decision type is needed here to indicate to proxies that an
 extended message exchange is in progress.
 1.2.4 PAP/Clear-text Passwords - T
 1.2.5 Reauthentication on demand - T
 1.2.6 Authorization w/o Authentication - T
 The comment "Please note: with existing algorithms, any authorization
 scheme not based on prior authentication is meaningless" is
 meaningless out of application context.
 1.3 Authorization Requirements
 1.3.1 Static and Dynamic IP Addr Assignment - T

Mitton, et al. Informational [Page 62] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.3.2 RADIUS Gateway Capability - P (was T).  It would be interesting
 to see RADIUS attributes wrapped in some COPS "Information Model".
 1.3.3 Reject Capability - T
 1.3.4 Preclude Layer 2 Tunneling - T
 More work for the "Information Model" author!
 1.3.5 Reauthorization on Demand - T
 1.3.6 Support for Access Rules & Filters - P (was T)  Yet more work
 for the "Information Model" author, including some design issues
 which alluded the RADIUS and Diameter designers.  At least an attempt
 was made in Diameter.  There is nothing here.
 1.3.7 State Reconciliation - P (was T).  It is difficult for the
 evaluator to understand how well the COPS mechanisms work in a
 multi-administration situation, or in any proxy situation.  Multi-
 server coordination, if allowed, seems to be lacking a description.
 1.3.8 Unsolicited Disconnect - T
 1.4 Accounting Requirements
 1.4.1 Real Time Accounting - T
 1.4.2 Mandatory Compact Encoding - T  This evaluator does not believe
 that ADIF is a compact format.  But does believe that the Information
 Model author can design a PIB with accounting statistics that will
 satisfy this requirement.
 1.4.3 Accounting Record Extensibility - P (was T)  By defining a
 vendor/device specific PIB for additional elements.
 1.4.4 Batch Accounting - P (was T)  Offered description does not seem
 to match the requirement.
 1.4.5 Guaranteed Delivery - P (was T)  TCP does NOT "guarantee
 delivery", only application Acks can do that.  If these acks can be
 generated similar to the description here, then this requirement is
 met.

Mitton, et al. Informational [Page 63] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.4.6 Accounting Timestamps - T  Another item for the "Information
 Model" author.
 1.4.7 Dynamic Accounting - T  Event and interim accounting can be
 supported.
 1.5 MOBILE IP Requirements
 1.5.1 Encoding of MOBILE IP Registration Messages - P (was T)  Yet
 more work for the "Information Model" author.  Hope he can handle it.
 1.5.2 Firewall Friendly - P (was T)  I guess.  Because it uses TCP
 and can be identified by known connection port.  But there is an
 issue with respect to the impact level of mixed COPS traffic coming
 through a common firewall port.
 1.5.3 Allocation of Local Home Agent - P (was T)  Just add another
 element to that "Information Model" definition.
 2. Summary Discussion
 COPS was designed to do some things similar to what we want and be
 somewhat flexible, but with a totally different set of assumptions on
 how many clients and requests would be funneled through the
 infrastructure and the acceptable overhead.  This evaluator is not
 sure that it scales well to the fast evolving access market where
 every product doesn't implement a small set of common features, but a
 large set of overlapping ones.
 3. General Requirements
 COPS started out with small and easily met set of design goals for
 RSVP and DiffServe, and is evolving as a new hammer to hit other
 nails [COPSPR].  As COPS implementors get more operational
 experience, it is interesting to see more reliability fixes/features
 quickly get patched in.
 Understanding COPS requires that you read a number RFCs and drafts
 which do not readily integrate well together.  Each application of
 COPS has spawned a number of drafts.  It's not clear if one wants to
 or can implement a single COPS server that can service AAA and other
 application clients.
 The COPS authors seem to overly believe in the goodness of TCP, and
 rely on it to solve all their transport problems, with concessions to
 application keep-alive messages to probe the connection status and
 sequence numbers to prevent replay attacks.  This evaluator believes
 this type of approach may work for many networks but really doesn't

Mitton, et al. Informational [Page 64] RFC 3127 AAA Protocol Evaluation Process June 2001

 scale well in larger configurations.  End-to-end application acks are
 the only guaranteed delivery solution, particularly where distributed
 state is involved.
 COPS falls into an in between place on encoding.  It has small number
 of simple data object blobs which are concatenated ala
 RADIUS/Diameter TLVs to form a flexible message layout.  However,
 they attempt to limit the number of objects by making them
 arbitrarily complex ala SNMP MIBs, and defining yet another data
 structuring language for these PIBs.  There is a lot of computer
 science style grandstanding in [COPSAAA] Section 1.2, but no
 translation into how a set of data objects can be used to meet these
 wonderful features in operation.  (or even if we needed them) This
 will be the crux of the interoperability issue.  RADIUS
 implementations interoperate because they at least, understand a
 common set of functional attributes from the RFCs.  And vendor extent
 ions can be simply customized in as needed via dictionaries.  If PIB
 definitions are needed for every piece and version of access
 equipment, before you can use it, then the bar for ease of
 configuration and use has been raised quite high.
 Support for PIB definition and vendor extensions will be on the same
 order as MIB integration in SNMP management products and put the
 supposed complexity of Diameter to shame.
 4. Summary Recommendation
 COPS has a structure that could be made to serve as a AAA protocol,
 perhaps by just copying the features of RADIUS and Diameter into it.
 The author of [COPSAAA] and [COPSComp] has not done the whole job yet
 and some of the missing pieces are vexing even for those already in
 the field.
 While some of the synergy with other COPS services is attractive,
 this evaluator is concerned about the liabilities of combining AAA
 services with the new emerging COPS applications in a single server
 entity will introduce more complexity than needed and opportunities
 to have progress pulled into other rat-holes. (eg. Policy Frameworks)

Mitton, et al. Informational [Page 65] RFC 3127 AAA Protocol Evaluation Process June 2001

Appendix D - Meeting Notes

 The minutes of the team meetings as recorded by various members.

D.1 Minutes of 22-Jun-2000 Teleconference

 Recorded by: Mark Stevens
 Arguments for and against SNMP as an AAA protocol were given.  Stuart
 Barkley gave a summary of the pro argument.  Mike St. Johns gave a
 summary of the con argument.  Dave Nelson asked for "instructions to
 the jury" in an effort to determine what evidence could and could not
 be used in making decisions.
 The AAA evaluation criteria is weak in some areas and in others it
 appears to be written with what might be interpreted as undue
 influence from the NASREQ working group.
 Mike St. Johns offered that we must restrict ourselves to considering
 only the evidence provided in the compliance documents and any
 supporting documents to which they may refer.
 In summary: AAA evaluation criteria document, AAA evaluation criteria
 source documents, protocol response documents and reference
 documents.
 The question as to what the group should do with malformed
 requirements came up.  The consensus seemed to be that we would use
 the requirements as adjusted in our last meeting where the
 requirements made no sense.
 The floor was then given to Stuart Barkley for the pro SNMP argument.
 Highlights:
  • In most areas the requirements are met by SNMP.
  • Confidentiality and Certificate transport mechanisms may be weak,

but workable.

  • With regard to Authentication, every technique can be supported

although support for PAP or cleartext passwords is weak.

  • With regard to Authorization, there is nothing in the requirements

that cannot be supported.

  • Accounting everything supported, although there is no specific

consideration for compact encoding. SNMP not as bloated as ASCII

    or XML based encoding schemes.  Requirement for compact encoding
    weakly indicated in requirements anyway.  Server-specific
    attributes needed, but compact encoding preclude w/o tradeoffs.

Mitton, et al. Informational [Page 66] RFC 3127 AAA Protocol Evaluation Process June 2001

  • With regard to mobile IP requirement, everything works well,

although firewall friendliness is a judgment call.

  • Proxy mechanisms of SNMPv3 mitigates problems w/ firewalls.
  • Scalability is ok.
  • Overall, meets most requirements and shortfalls are minor.
  • In some cases requirements seemed to expressed in a manner that

"stacks" the odds against SNMP.

  • SNMP is deployed everywhere already.
  • The protocol has a well-understood behavior despite the tedium of

MIB definition, so it has the advantage of not requiring the

    creation of a new infrastructure.
 *  AAA response document is silent on architecture and MIB
    definition, but there is too much work to do at this stage of
    evaluation.  Not having done the MIB definitions and architecture
    is not a limitation of the protocol.
 *  SNMP is a good candidate.
 Mike St. Johns took the floor to give a summary of the con argument.
  • Neither the requirements, core documents nor response document

specify the mechanism of operation.

  • Liberties were taken in the assertion that the server to server

interaction requirements were met.

  • The scaling arguments are weak.
  • Fail-over arguments are weak.
  • Security aspects work well with the manager/server paradigm, but

not well in bidirectional interactions among peers.

  • The authentication requirements not understood by authors of the

response document. * SNMP is just data moving protocol.

  • Message formats not specified.
  • What is the method for supporting authentication? Storing the

information is handled, but what do the nodes do with it?

  • The protocol certainly shined in the area of meeting accounting

requirements.

  • Although SNMP could certainly play a role in the accounting space,

it is unusable in the areas of Authorization and Authentication.

  • The response document does not address how the problem will be

solved.

  • It does not address the scalability issues that may arise in the

transition from a manager-agent mode of operation to a client-

    server model.
 The group then examined each requirement against SNMP in a line-by-
 line exercise.

Mitton, et al. Informational [Page 67] RFC 3127 AAA Protocol Evaluation Process June 2001

D.2 Minutes of 27-Jun-2000 Teleconference

 Attendees - All (Mike St. John, Dave Mitton, Dave Nelson, Mark
 Stevens, Barney Wolff, Stuart Barkley, Steven Crain, Basavaraj Patil)
 Minutes recorded by : Basavaraj Patil
 Evaluation of RADIUS++ AAA Requirements
 Pro : Mark Stevens
 Con : Dave Nelson
  1. Question raised on if all meetings held so far have been recorded.

Last week's meeting was recorded by Mark. Previous meetings have

    been recorded by Mike.  All of these minutes should be available
    in the archive.
  1. Dave Nelson mentioned that Pat Calhoun has responded on the AAA WG

mailing list to the changes made to the requirements document by

    the evaluation team.  Pat's response includes arguments for
    inclusion of some of the requirements that were deleted by the
    eval team.
  1. Mike concluded that we can reinstate these requirements after

reviewing Pat's comments in detail and the RFCs referenced. The

    intent is to take Pat's comments/document and review it between
    now and next Thursday (July 6th) and integrate the comments based
    on the findings at that time.
 Voting Procedure for evaluation : No voting during the discussion.
 All votes MUST be submitted to Mike by COB, June 28th, 00.
  1. Dave Nelson's summary of the Con statement for RADIUS++.

Overview of the points on which the evaluator disagrees with the

    compliance statement.
    Conclusion from Dave : Not recommended (Details in the con
    statement).
    Q: Is it possible to use it for accounting?
    A: Authentication and Authorization could be separated, but
    Accounting is the weak link in this protocol and hence is not
    suitable.
  1. Mark Steven's summary of the Pro statement

Agreed with most of the observations made by Dave Nelson. The

    biggest thing going for it is that it has been running in this
    environment for a while and it does meet most of the requirements

Mitton, et al. Informational [Page 68] RFC 3127 AAA Protocol Evaluation Process June 2001

    in the document.  Transition will be easy and backwards
    compatibility is a key plus point.
 Point-by-point Discussion:
 General (1.1):
 1.1.1 Scalability
 BW - There is no actual limit on the number of outstanding requests.
 The protocol itself does not limit the number.
 DN -Simultaneous requests is not the same as outstanding requests.
 Discussion of workarounds that have been implemented to overcome this
 problem.
 1.1.2 Fail-over
 DN - This is an application layer protocol and uses application level
 time-outs to provide fail-over solutions.  Analogy and discussion on
 the use of round-trip-timer in TCP.
 Example of how robust a network can be based on a machine at MIT that
 was decommissioned and a new one with the same name installed in the
 network.
 Discussion of environments where proxies for primary, secondary and
 tertiaries exist and the possible effect of flooding messages in the
 event of a fail-over detection.
 1.1.3 Mutual Authentication
 No Discussion.  Accepted as stated.
 1.1.4 Transmission level security
 This requirement was deleted from the list by the evaluation team.
 It was deleted because it is an overgeneralization of Roam Ops.
 DN - There is a concern regarding what this really means.  Referred
 to what Pat is saying about this on the list and the need for it to
 be reinstated.
 Suggestion to change the tag in the requirements document to hop-by-
 hop security.

Mitton, et al. Informational [Page 69] RFC 3127 AAA Protocol Evaluation Process June 2001

 Does the Roamops group use transmission level security to imply hop-
 by-hop security?
 1.1.5 Data Object Confidentiality
 Mike explained the concept of Cryptographic Message Syntax (CMS -
 RFC2630).  There are some issues regarding the use of CMS at an end
 point.  Symmetric or Asymmetric keys can be used.
 There does not seem to be a problem with the suggested usage of CMS
 in RADIUS++.
 1.1.6/7 Data Object Integrity/Certificate Transport
 No discussion.  (I guess everyone concurs with the statement in the
 compliance document and the reviewers comments).
 1.1.8 Reliable AAA Transport
 BW - Radius provides reliability at the application layer by doing
 retransmissions.  So why is there a need for a reliable AAA transport
 protocol?
  1. Is it packet loss that the protocol needs to be concerned about?
 DN - This requirement is tied to the failover issue.  Explanation of
 the negative impact of retransmissions in a network, especially in
 the case of a web of proxies.
 Conclusion is that this requirement deals with packet loss.
 1.1.9/10 Run over IPv4/6
 Running over IPv6 should be a trivial issue.
 1.1.11 Support Proxy and Routing Brokers
  1. Discussion on what this requirement means and analogy to DNS

servers in a network.

  1. RADIUS can be extended to support this requirement and from the

compliance document this does not appear to be fully cooked yet.

 1.1.12 Auditability
 No Discussion

Mitton, et al. Informational [Page 70] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.13 Shared Secret Not Required
 This seems to be a trivial issue to be addressed in RADIUS++.
 1.1.14 Ability to carry Service Specific Attributes
 No Discussion
 Authentication Requirements:
 1.2.1 NAI Support
 Trivial - Total compliance.
 1.2.2 CHAP Support
 Comment : RADIUS support of CHAP could be better and the response
 needs to be encrypted.
 1.2.3/4 EAP/PAP
 No Discussion
 1.2.5 Reauthentication on Demand
 DN - Document claims that the server can reauthenticate by issuing an
 Access-challenge.  There is a change to the state machine and the
 suggested solution is too simplistic.  Also backwards compatibility
 would be an issue.
 1.2.6 Authorization w/o Authentication
 DN - This is trivial to fix, but this is not mentioned in the
 compliance document.
 Authorization Requirements:
 1.3.1 Static and Dynamic IP Addr assignment
  1. RADIUS does not rise to the demands of being a resource manager
  2. RADIUS assigns an address and it stays assigned for the session.

There is no concept of leasing.

 1.3.2 RADIUS Gateway Capability
 This is a requirement written that is not applicable to RADIUS
 itself.

Mitton, et al. Informational [Page 71] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.3.3/4/5/6/7/8
 Call dropped.  Somebody else needs to fill in here.  (Mike ????)
 Accounting Requirements:
 1.4.1 Real time accounting
 No dissent.  No discussion
 1.4.2 Mandatory compact encoding
 Comment made regarding ASN.1 and XML in this context
 1.4.3 Accounting Record Extensibility
 No discussion
 1.4.4 Batch Accounting
 No specific wording in the document to show how this can be done.
 Basically it is real time accounting without the real time
 constraint.
 It may be a trivial issue.
 1.4.5/6 Guaranteed Delivery/Accounting Timestamps
 No Discussion
 1.4.7 Dynamic Accounting
 There is ongoing discussion in the AAA WG on this requirement.  The
 RADIUS WG is also discussing this (comment).  The idea here is to be
 able to send the equivalent of a phonecall in progress type of
 messages.
 Mobile IP Requirements:
 1.5.1 Encoding of Mobile IP Reg. Messages
 May be trivial.  Discussion on what this requirement really is.  Is
 it just the ability to carry the reg. message as payload? Does the
 AAA protocol have to delve into the reg. message and behave
 differently.

Mitton, et al. Informational [Page 72] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.5.2 Firewall Friendly
 No Discussion
 1.5.3 Allocation of Local Home Agents
 This concept needs to be clarified as the author writing the
 compliance statement did not understand it either.
 If you notice anything that I recorded here as something
 misinterpreted, please feel free to make corrections.

D.3 Minutes of 29-Jun-2000 Teleconference

 Attendees: Mike St. John, Dave Mitton, Dave Nelson, Barney Wolff,
 Stuart Barkley, Steven Crain, Basavaraj Patil.
 Missing: Mark Stevens.
 Minutes recorded by: Stuart Barkley
 Evaluation of Diameter AAA Requirements
 Advocates:
 Pro: Basavaraj Patil
 Con: Barney Wolff
 Summary discussion:
 PRO summary (Basavaraj Patil):
    session based
    lightweight base + extensions
    has implementation experience
    based upon radius
    fixes specific problems with radius,
    interoperates with radius
    looks like requirements are written for diameter
 CON summary (Barney Wolff):
    meets most needs, designed with requirements in mind
 issues:  scalability in small devices (strong crypto specifically)
    failover (need guidance on failover recovery procedures)

Mitton, et al. Informational [Page 73] RFC 3127 AAA Protocol Evaluation Process June 2001

    Data object confidentiality has been expressed as very important,
    diameter glosses over it referring to rfc2630, cost to run on NAS
    device
    ACL: filter style syntax seems inadequate
    state reconciliation: difficult over global multiple
    administrative domains
    batch accounting: implementation doesn't meet intended need
    firewall friendly: until firewalls support SCTP will be failure
 summary very close
 concerns:
 size and complexity needs almost all extensions to actually support
 needs separation of SCTP and data (as per IESG suggestion?)
 application vs transport acks
 Point-by-point Discussion:
 General (1.1):
 1.1.1 Scalability
    Handles large number of requests
    SCTP reduces proxy needs (how? what is justification for this
    statement?)
    Scalability in large
 1.1.2 Fail-over
    Recovery from SCTP failure needs discussion (Note to DM: Include
    in final document considerations)
 1.1.3 Mutual Authentication
    No Discussion
 1.1.4 Transmission level security
    No Discussion

Mitton, et al. Informational [Page 74] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.5/6 Data Object Confidentiality/Data Object Integrity
    Crypto in NAS
    NAS needs knowledge of when to use crypto
    One Time Passwords
 1.1.7 Certificate Transport
    No Discussion
 1.1.8 Reliable AAA Transport
    No Discussion
 1.1.9/10 Run over IPv4/6
    No Discussion
 1.1.11 Support Proxy and Routing Brokers
    No Discussion
 1.1.12 Auditability
    No Discussion
 1.1.13 Shared Secret Not Required
    No Discussion
 1.1.14 Ability to carry Service Specific Attributes
    No Discussion
 Authentication Requirements:
 1.2.1 NAI Support
    No Discussion
 1.2.2 CHAP Support
    No Discussion
 1.2.3/4 EAP/PAP
    No Discussion

Mitton, et al. Informational [Page 75] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.2.5 Reauthentication on Demand
    No Discussion
 1.2.6 Authorization w/o Authentication
    No Discussion
 Authorization Requirements:
 1.3.1 Static and Dynamic IP Addr assignment
    No Discussion
 1.3.2 RADIUS Gateway Capability
    Protocol requirement or implementation/application requirement?
    Which RADIUS versions are to be supported?  Which subset?
 1.3.3 Reject Capability
    No Discussion
 1.3.4 Preclude L2TP
    No Discussion
 1.3.5 Reauthorize on demand
    Raj to look at this again
 1.3.6 Support for ACLs
    Standardizes syntax not semantics.
    Standardizes semantics in NASREQ extension, but is very weak
 1.3.7 State reconciliation
    Appears to be weak in that server must "query the world" to
    restore its state
    Just in time reconciliation
    Simultaneous usage limitations
    More discussion needed

Mitton, et al. Informational [Page 76] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.3.8 Unsolicited disconnect
    No Discussion
 Accounting Requirements:
 1.4.1 Real time accounting
    No Discussion
 1.4.2 Mandatory compact encoding
    Is ADIF compact?
    Is ADIF UTF-8 compatible?
 1.4.3 Accounting Record Extensibility
    No Discussion
 1.4.4 Batch Accounting
    Diameter okay for small batches.  Specification doesn't seem
    suitable for large batch transfers (100,000+ records)
 1.4.5 Guaranteed Delivery
    No Discussion
 1.4.6 Accounting Timestamps
    No Discussion
 1.4.7 Dynamic Accounting
    No Discussion
 Mobile IP Requirements:
 1.5.1 Encoding of Mobile IP Reg. Messages
    Taken of faith
 1.5.2 Firewall Friendly
    Issues with SCTP being supported initially through firewalls

Mitton, et al. Informational [Page 77] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.5.3 Allocation of Local Home Agents
    Still lack of understanding of the AAA protocol requirements here
    (versus just being a roaming attribute)
 Overall summary:
 Diameter seems to meet most requirements and is a likely candidate to
 support AAA requirements.
 Other matters:
 Votes on Diameter should be in by Sunday evening.  Same format as
 before.  Mike will tally up as both majority and average votes.
 Should different requirements have different weight?
 Possibility of SNMP reconsideration as per ADs?  To close off our
 task in timeframe allocated, should not reopen submissions or
 discussions.  Could cause to drag on for long time causing us to miss
 our July 15 date.
 Possibility of needing a few extra days to finish report due to
 editing and review needs of the group.  Mike to ask ADs to consider
 slight time extension possibility.
 "No discussion" means that the topic was mentioned but there we no
 objections/issues raised on that requirement being met.
 These are based upon my notes.  Please send any corrections to the
 list.

D.4 Minutes of 06-Jul-2000 Teleconference

 Minutes of AAA-Team Telecon 7/6/00
 By: Barney Wolff
 Pro review of COPS - Dave Nelson
    Likes the object model.
    No apparent showstoppers.
    Will resend review with typos corrected.

Mitton, et al. Informational [Page 78] RFC 3127 AAA Protocol Evaluation Process June 2001

 Con review of COPS - Dave Mitton
    Architecture is mostly there.
    Strong dependency on info model, sceptical of object model.
    Problem with info model in multi-vendor, multi-administration
    environment.
    How does server speak to multiple client flavors?
    Will resend review with typos corrected.
 Comment by Mike StJ "replace SNMP with COPS" - :) I think.
 Per-Item discussion
 1.1.1 Scalability - concern re always-on TCP.  Direction to DM - add
 general issue of number of connections.
 1.1.2 Failover - No hot backup, but true of all protocols.  (ie, no
 explicit mention of server-server protocol that might keep a backup
 server in sync so it could take over instantly.)
 1.1.3 Mutual Authentication - perhaps relies on TLS.  Draft does not
 otherwise support this.
 1.1.8 Reliable AAA Transport - TCP + appl heartbeat.
 1.1.11 Proxy & Routing Brokers - client-type interaction with proxy
 is questionable.  (In later discussion, it appears client-type is a
 field in the request, and perhaps all AAA is one type, so may not be
 an issue.)
 1.1.13 Shared secret not req'd - runs over TLS, no multiple levels of
 security.
 1.2.1 NAI Support - some uncertainty on the impact of RFC 2459 (X.509
 profiles) on this - may restrict NAI in some way?
 1.2.3 EAP Support - multi-pass handshake needs work.
 1.2.6 Authorization without Authentication - Mike comments the
 requirement is broken.  BW comment (post-meeting) - the requirement
 appears intended specifically to chastise RADIUS for requiring User-
 Name and some sort of password in an Access-Request, even if it's
 sent pre-connect, on receipt of DNIS, for example.  Sure it's silly,
 but does it really matter whether an attribute is absent or filled
 with "NONE"?  This was just nasty sniping at RADIUS on somebody's
 part, imho.
 1.3.2 RADIUS Gateway - skepticism was expressed.

Mitton, et al. Informational [Page 79] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.3.4 Preclude L2 Tunnels - too much handwaving.
 1.3.6 Access Rules - lots of work needed.
 1.3.7 State Reconciliation - multi-server coordination is an issue.
 1.4.4 Batch Accounting - for small batches, perhaps.
 1.4.5 Guaranteed Delivery - application acks are an area of mystery.
 1.5.2 Firewall-Friendly - COPS like any Swiss-Army-Knife protocol
 (SNMP) requires the firewall to look inside the packets, because
 passing AAA may be allowed but not other protocol uses.  So it would
 be a big help, for both COPS and SNMP, to define a different port for
 its AAA application.

D.5 Minutes of 11-Jul-2000 Teleconference

 Present:  Mike, Bernard, Paul, Bert, Raj, Dave N., Dave M., Barney,
 Stuart, Mark
 Recorded By: Dave Nelson
 Mike St. Johns set the ground rules.
 An item by item review of the summary results was held.
 1.1.1 Question as to why SNMP and RADIUS++ are "P"?  There are issues
 regarding scaling of retries in a web of proxies (multi-layer proxy;
 primary, secondary tertiary servers at each level).
 1.1.2 No protocol did very well.  Similar issues as above, e.g. web
 of proxies.  Recovery of state from a previously failed primary
 server?
 1.1.3 Question as to how serious is the need for this requirement?
 May be some legitimate requirements from Mobile IP.  Is this
 requirement an AAA-level issue?
 1.1.4 Called hop-by-hop or transmission level?
 1.1.5 Most protocols evaluated used CMS to meet this requirement.
 Question as to applicability of CMS for NASes and other edge devices?
 There is a requirement for object by object confidentiality.
 consider three-party scenarios.

Mitton, et al. Informational [Page 80] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.1.6 Question as to why SNMP did not rate the same as for item
 1.1.5?  The evaluation is based on what was contained in the
 submission documents, rather than capabilities of the protocol
 itself.  Too much hand waving.
 1.1.7 No comments.
 1.1.8 Question as to meaning of "reliable"?  Discussion of transport
 protocols was deferred to later in the meeting.
 1.1.9 No comments.
 1.1.10 SNMP received "P" because of hand waving in the submission
 documents.
 1.1.11 SNMP received "F" because this section of the submission
 document indicated "t.b.d.".  Diameter was the only protocol
 submission to completely address this item.
 1.1.12 We treated this requirement as "non-repudiation".  There is a
 concern that digital signatures are computationally expensive and are
 not globally available.  COPS has more work to do on this item.
 1.1.13 Question that "no shared secrets" should be interpreted to
 mean that an alternative key management mechanism is available?  We
 treated this as meaning that application-layer security could be
 turned off in deference to transport layer security.  There had been
 discussion of the use of IKE in the AAA protocol.
 1.1.14 No comments.
 1.2.1 No comments.
 1.2.2 No comments.
 1.2.3 No comments.
 1.2.4 Is there a need for a clear-text "password" for service such as
 OTP, SecurID, et. al.?   It was noted that all plain passwords are
 exposed in clear-text at the NAS or other edge device, which is no
 more inherently trustworthy than any AAA server or proxy.
 1.2.5 We distinguished event-driven reauthentication from timer-
 driven (or lifetime-driven).  How is this requirement to be met in a
 proxy environment?
 1.2.6 We asserted that this requirement is an oxymoron.

Mitton, et al. Informational [Page 81] RFC 3127 AAA Protocol Evaluation Process June 2001

 1.3.1 We had difficulty in determining what "static" meant, and from
 which reference point it was measured.
 1.3.2 We agreed that NAIs could be handled, possibly with some
 restrictions.
 1.3.3 No comment.
 1.3.4 The SNMP submission documents contained significant hand
 waving.
 1.3.5 Similar comments as to item 1.2.5.  The question was raised as
 to how the server knows when to send this request?
 1.3.6 We found that the notation in Diameter was weak, and of a least
 common denominator nature.  In general, there was concern about
 achieving interoperability when the syntax was standardized but the
 semantics were not.  This area needs further work.
 1.3.7 Question as to how this requirement is achieved via proxies?
 1.4.1 No comment.
 1.4.2 No comment.
 1.4.3 No comment.
 1.4.4 There was significant skepticism regarding batch accounting as
 part of the AAA protocol.  How large are the "batches"?  Should this
 requirement be met using FTP or something similar?
 1.4.5 No comment.
 1.4.6 No comment.
 1.4.7 No comment.
 1.5.1 No comment.
 1.5.2 There was some discussion of what constitutes firewall
 friendly.  It was suggested that the firewall didn't want to look
 into packets much past the application protocol address (e.g. UDP or
 TCP port number).  Protocols such as SNMP and COPS that have usage
 other than AAA are at a disadvantage, since the firewall must look
 deep into the application PDU to determine the intended purpose of
 the packet.  Diameter suffers from reliance of SCTP, which is not
 widely deployed or widely recognized by firewalls.  Should firewalls

Mitton, et al. Informational [Page 82] RFC 3127 AAA Protocol Evaluation Process June 2001

 also be AAA proxy engines?  Has this issue anything to do with
 interoperability with NAT?
 1.5.3 We had some confusion as to what the requirement actually was.
 Raj seemed to be able to explain it, but the rest of us had to take
 it on faith.
 A poll was taken on overall acceptability and effort for each of the
 protocols submitted, for requirements conformance.
 Each member indicated their evaluation in the form of (Acceptable,
 Not-Acceptable) with qualifiers for (Accounting, or effort to change)
 This information will be summarized in the final report.
 A general wrap-up discussion was held.
 It was considered important that as much of the thought processes and
 rationales be placed in the final report as is feasible.  Mike St.
 John will work with Dave Mitton on the ID.  We really need to meet
 the IETF July 14 submission deadline, even if we have to issue an
 update on the AAA WG mailing list.  All agreed that the process went
 fairly well.  In future evaluations of this nature, it would be well
 for the evaluators to follow the requirements documents closely, for
 the submitters to create accurate and complete conformance documents,
 and to allow a "re-spin" cycle to correct errors and omissions in the
 requirements documents and conformance documents.
 A discussion of the transport protocol was held.
 The issue with transport is congestion control.  There has been a
 problem with streams-oriented applications over TCP.  The IESG is
 increasingly sensitive to this issue in new protocols.  It was noted
 that AAA was a transaction-oriented application.  Other request-
 response applications, such as DNS, seem to scale welt to Internet-
 scale using simple application-level retries and UDP transport.  TCP
 has problems with head-of-line blocking, especially when multiple
 sessions are using a single TCP connection.  AAA typically will send
 3 or 4 iterations and then indicate a failure to the upper layers.
 It won't continue retransmissions in the face of congestion, like
 TCP.  It was noted that bulk data transfer may not best be
 implemented in the AAA protocol.  Concern was voiced that SCTP is not
 a widely implemented protocol.  AAA will implement congestion control
 by limiting the number of outstanding requests.  Some RADIUS
 implementations send lots of traffic when they encounter
 misconfigured shared secrets, but this is likely caused by a lack of
 proper error recovery.  Diameter, as currently drafted, relies on
 SCTP.  Can AAA run over UDP?  The IESG didn't say "no"; their issue
 is addressing congestion control.

Mitton, et al. Informational [Page 83] RFC 3127 AAA Protocol Evaluation Process June 2001

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Mitton, et al. Informational [Page 84]

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