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Internet Engineering Task Force (IETF) A. Farrel Request for Comments: 6123 Old Dog Consulting Category: Historic February 2011 ISSN: 2070-1721

               Inclusion of Manageability Sections in
        Path Computation Element (PCE) Working Group Drafts


 It has often been the case that manageability considerations have
 been retrofitted to protocols after they have been specified,
 standardized, implemented, or deployed.  This is sub-optimal.
 Similarly, new protocols or protocol extensions are frequently
 designed without due consideration of manageability requirements.
 The Operations Area has developed "Guidelines for Considering
 Operations and Management of New Protocols and Protocol Extensions"
 (RFC 5706), and those guidelines have been adopted by the Path
 Computation Element (PCE) Working Group.
 Previously, the PCE Working Group used the recommendations contained
 in this document to guide authors of Internet-Drafts on the contents
 of "Manageability Considerations" sections in their work.  This
 document is retained for historic reference.

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for the historical record.
 This document defines a Historic Document for the Internet community.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are a candidate for any level of Internet
 Standard; see Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at

Farrel Historic [Page 1] RFC 6123 Manageability Sections in PCE Drafts February 2011

Copyright Notice

 Copyright (c) 2011 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 ( in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

1. Introduction

 This document is produced for historic reference.
 When new protocols or protocol extensions are developed, it is often
 the case that not enough consideration is given to the manageability
 of the protocols or to the way in which they will be operated in the
 network.  The result is that manageability considerations are only
 understood once the protocols have been implemented and sometimes not
 until after they have been deployed.
 The resultant attempts to retrofit manageability mechanisms are not
 always easy or architecturally pleasant.  Furthermore, it is possible
 that certain protocol designs make manageability particularly hard to
 Recognizing that manageability is fundamental to the utility and
 success of protocols designed within the IETF, and that simply
 defining a MIB module does not necessarily provide adequate
 manageability, this document was developed to define recommendations
 for the inclusion of Manageability Considerations sections in all
 Internet-Drafts produced within the PCE Working Group.  It was the
 intention that meeting these recommendations would ensure that proper
 consideration was given to the support of manageability at all stages
 of the protocol development process from Requirements and
 Architecture through Specification and Applicability.
 It is clear that the presence of such a section in an Internet-Draft
 does not guarantee that the protocol will be well-designed or
 manageable.  However, the inclusion of this section will ensure that
 the authors have the opportunity to consider the issues, and, by
 reading the material in this document, they will gain some guidance.

Farrel Historic [Page 2] RFC 6123 Manageability Sections in PCE Drafts February 2011

 This document was developed within the PCE Working Group and was used
 to help guide the authors and editors within the working group to
 produce Manageability Considerations sections in the Internet-Drafts
 and RFCs produced by the working group.
 [RFC5706] presents general guidance from the IETF's Operations Area
 for considering Operations and Management of new protocols and
 protocol extensions.  It has been adopted by the PCE Working Group to
 provide guidance to editors and authors within the working group, so
 this document is no longer required.  However, the working group
 considers that it will be useful to archive this document as Historic
 for future reference.

1.1. Requirements Notation

 This document is not a protocol specification.  The key words "MUST",
 "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be
 interpreted as described in [RFC2119] in order that the contents of a
 Manageability Considerations section can be clearly understood.

1.2. What Is Manageability?

 In this context, "manageability" is used to refer to the interactions
 between a network operator (a human or an application) and the
 network components (hosts, routers, switches, applications, and
 protocols) performed to ensure the correct operation of the network.
 Manageability issues are often referred to under the collective
 acronym, FCAPS [X.700], which stands for the following:
  1. Fault management
  2. Configuration
  3. Accounting
  4. Performance
  5. Security
 Conventionally, Security is already covered an Internet-Draft in its
 own Security Considerations section, and this document does not in
 any way diminish the need for that section.  Indeed, as pointed out
 in Section 6, a full consideration of other aspects of manageability
 may increase the text that should be supplied in the Security
 Considerations section.
 The author of a Manageability Considerations section should certainly
 consider all aspects of FCAPS.  The author should reflect on how the
 manageability of a new protocol impacts the manageability and
 operation of the entire network.  Specific optional subsections (see

Farrel Historic [Page 3] RFC 6123 Manageability Sections in PCE Drafts February 2011

 Section 2.3) should be added as necessary to describe features of
 FCAPS that are pertinent but are not covered by the recommended
 subsections.  More discussion of what manageability is and what may
 be included in a Manageability Considerations section can be found in
 As part of documenting the manageability considerations for a new
 protocol or for protocol extensions, authors should consider that one
 of the objectives of specifying protocols within the IETF is to
 ensure interoperability of implementations.  This interoperability
 extends to the manageability function so that it is an ideal that
 there should be implementation independence between management
 applications and managed entities.  This may be promoted by the use
 of standardized management protocols and by the specification of
 standard information models.
 Note that, in some contexts, reference is made to the term
 "management plane".  This is used to describe the exchange of
 management messages through management protocols (often transported
 by IP and by IP transport protocols) between management applications
 and the managed entities such as network nodes.  The management plane
 may use distinct addressing schemes, virtual links or tunnels, or a
 physically separate management control network.  The management plane
 should be seen as separate from, but possibly overlapping with, the
 control plane, in which signaling and routing messages are exchanged,
 and the forwarding plane (sometimes called the data plane or user
 plane), in which user traffic is transported.

2. Presence and Placement of Manageability Considerations Sections

 Note that examples of the sections described here can be found in the
 documents listed in Appendix A.

2.1. Null Manageability Considerations Sections

 In the event that there are no manageability requirements for an
 Internet-Draft, the draft SHOULD still contain a Manageability
 Considerations section.  The presence of this section indicates to
 the reader that due consideration has been given to manageability and
 that there are no (or no new) requirements.
 In this case, the section SHOULD contain a simple statement such as
 "There are no new manageability requirements introduced by this
 document" and SHOULD briefly explain why that is the case with a
 summary of manageability mechanisms that already exist.

Farrel Historic [Page 4] RFC 6123 Manageability Sections in PCE Drafts February 2011

 Note that a null Manageability Considerations section may take some
 effort to compose.  It is important to demonstrate to the reader that
 no additional manageability mechanisms are required, and it is often
 hard to prove that something is not needed.  A null Manageability
 Considerations section SHOULD NOT consist only of the simple
 statement that there are no new manageability requirements.
 If an Internet-Draft genuinely has no manageability impact, it should
 be possible to construct a simple null Manageability Considerations
 section that explains why this is the case.

2.2. Recommended Subsections

 If the Manageability Considerations section is not null, it SHOULD
 contain at least the following subsections.  Guidance on the content
 of these subsections can be found in Section 3 of this document.
  1. Control of Function through Configuration and Policy
  2. Information and Data Models, e.g., MIB modules
  3. Liveness Detection and Monitoring
  4. Verifying Correct Operation
  5. Requirements on Other Protocols and Functional Components
  6. Impact on Network Operation
 In the event that one or more of these subsections is not relevant,
 it SHOULD still be present and SHOULD contain a simple statement
 explaining why the subsection is not relevant.  That is, null
 subsections are allowed, and each should be formed following the
 advice in Section 2.1.

2.3. Optional Subsections

 The list of subsections above is not intended to be prescriptively
 limiting.  Other subsections can and SHOULD be added according to the
 requirements of each individual Internet-Draft.  If a topic does not
 fit comfortably into any of the subsections listed, the authors
 should be relaxed about adding new subsections as necessary.

2.4. Placement of Manageability Considerations Sections

 The Manageability Considerations section SHOULD be placed immediately
 before the Security Considerations section in any Internet-Draft.

Farrel Historic [Page 5] RFC 6123 Manageability Sections in PCE Drafts February 2011

3. Guidance on the Content of Subsections

 This section gives guidance on the information to be included in each
 of the recommended subsections listed above.  Note that, just as
 other subsections may be included, so additional information MAY also
 be included in these subsections.

3.1. Control of Function through Configuration and Policy

 This subsection describes the functional elements that may be
 controlled through configuration and/or policy.
 For example, many protocol specifications include timers that are
 used as part of the operation of the protocol.  These timers often
 have default values suggested in the protocol specification and do
 not need to be configurable.  However, it is often the case that the
 protocol requires that the timers can be configured by the operator
 to ensure specific behavior by the implementation.
 Even if all configurable items have been described within the body of
 the document, they SHOULD be identified in this subsection, but a
 reference to another section of the document is sufficient if there
 is a full description elsewhere.
 Other protocol elements are amenable to control through the
 application of local or network-wide policy.  It is not the intention
 that this subsection should give details of policy implementation
 since that is covered by more general policy framework specifications
 such as [RFC3060] and [RFC3460].  Additionally, specific frameworks
 for policy as applicable within protocol or functional architectures
 are also normally covered in separate documents, for example,
 However, this section SHOULD identify which protocol elements are
 potentially subject to policy and should give guidance on the
 application of policy for successful operation of the protocol.
 Where this material is already described within the body of the
 document, this subsection SHOULD still identify the issues and
 reference the other sections of the document.

3.2. Information and Data Models

 This subsection SHOULD describe the information and data models
 necessary for the protocol or the protocol extensions.  This
 includes, but is not necessarily limited to, the MIB modules
 developed specifically for the protocol functions specified in the

Farrel Historic [Page 6] RFC 6123 Manageability Sections in PCE Drafts February 2011

 Where new or extended MIB modules are recommended, it is helpful if
 this section can give an overview of the items to be modeled by the
 MIB modules.  This does not require an object-by-object description
 of all of the information that needs to be modeled, but it could
 explain the high-level "object groupings" (perhaps to the level of
 suggesting the MIB tables) and certainly should explain the major
 manageable entities.  For example, a protocol specification might
 include separate roles for "sender" and "receiver" and might be
 broken into a "session" and individual "transactions"; if so, this
 section could list these functionalities as separate manageable
 [RFC3444] may be useful in determining what information to include in
 this section.
 The description in this section can be by reference where other
 documents already exist.
 It should be noted that the significance of MIB modules may be
 decreasing, but there is still a requirement to consider the managed
 objects necessary for successful operation of the protocol or
 protocol extensions.  This means that due consideration should be
 given not only to what objects need to be managed but also to what
 management model should be used.  There are now several options,
 including the MIB/SNMP (Simple Network Management Protocol) model and
 the Network Configuration Protocol (NETCONF) model, being developed
 by the NETCONF Data Modeling Language (NETMOD) Working Group [YANG].

3.3. Liveness Detection and Monitoring

 Liveness detection and monitoring apply both to the control plane and
 the data plane.
 Mechanisms for detecting faults in the control plane or for
 monitoring its liveness are usually built into the control plane
 protocols or inherited from underlying data plane or forwarding plane
 protocols.  These mechanisms do not typically require additional
 management capabilities but are essential features for the protocol
 to be usable and manageable.  Therefore, this section SHOULD
 highlight the mechanisms in the new protocol or protocol extensions
 that are required in order to ensure liveness detection and
 monitoring within the protocol.
 Further, when a control plane fault is detected, there is often a
 requirement to coordinate recovery action through management
 applications or at least to record the fact in an event log.  This
 section SHOULD identify the management actions expected when the
 protocol detects a control plane fault.

Farrel Historic [Page 7] RFC 6123 Manageability Sections in PCE Drafts February 2011

 Where the protocol is responsible for establishing data or user plane
 connectivity, liveness detection and monitoring usually need to be
 achieved through other mechanisms.  In some cases, these mechanisms
 already exist within other protocols responsible for maintaining
 lower layer connectivity, but it will often be the case that new
 procedures are required so that failures in the data path can be
 detected and reported rapidly, allowing remedial action to be taken.
 This section SHOULD refer to other mechanisms that are assumed to
 provide monitoring of data plane liveness and SHOULD identify
 requirements for new mechanisms as appropriate.
 This section SHOULD describe the need for liveness and detection
 monitoring, SHOULD highlight existing tools, SHOULD identify
 requirements and specifications for new tools (as appropriate for the
 level of the document being written), and SHOULD describe the
 coordination of tools with each other, with management applications,
 and with the base protocol being specified.

3.4. Verifying Correct Operation

 An important function that Operations and Management (OAM) can
 provide is a toolset for verifying the correct operation of a
 protocol.  To some extent, this may be achieved through access to
 information and data models that report the status of the protocol
 and the state installed on network devices.  However, it may also be
 valuable to provide techniques for testing the effect that the
 protocol has had on the network by sending data through the network
 and observing its behavior.
 Thus, this section SHOULD include details of how the correct
 operation of the protocols described by the Internet-Draft can be
 tested, and, in as far as the Internet-Draft impacts on the operation
 of the network, this section SHOULD include a discussion about how
 the correct end-to-end operation of the network can be tested and how
 the correct data or forwarding plane function of each network element
 can be verified.
 There may be some overlap between this section and that describing
 liveness detection and monitoring since the same tools may be used in
 some cases.

3.5. Requirements on Other Protocols and Functional Components

 The text in this section SHOULD describe the requirements that the
 new protocol puts on other protocols and functional components as
 well as requirements from other protocols that have been considered

Farrel Historic [Page 8] RFC 6123 Manageability Sections in PCE Drafts February 2011

 in designing the new protocol.  This is pertinent to manageability
 because those other protocols may already be deployed and operational
 and because those other protocols also need to be managed.
 It is not appropriate to consider the interaction between the new
 protocol and all other protocols in this section, but it is important
 to identify the specific interactions that are assumed for the
 correct functioning of the new protocol or protocol extensions.

3.6. Impact on Network Operation

 The introduction of a new protocol or extensions to an existing
 protocol may have an impact on the operation of existing networks.
 This section SHOULD outline such impacts (which may be positive),
 including scaling concerns and interactions with other protocols.
 For example, a new protocol that doubles the number of active,
 reachable addresses in use within a network might need to be
 considered in the light of the impact on the scalability of the IGPs
 operating within the network.
 A very important feature that SHOULD be addressed in this section is
 backward compatibility.  If protocol extensions are being introduced,
 what impact will this have on a network that has an earlier version
 of the protocol deployed? Will it be necessary to upgrade all nodes
 in the network? Can the protocol versions operate side by side? Can
 the new version of the protocol be tunneled through the old version?
 Can existing services be migrated without causing a traffic hit or is
 a "maintenance period" required to perform the upgrade? What are the
 configuration implications for the new and old protocol variants?
 Where a new protocol is introduced, issues similar to backward
 compatibility may exist and SHOULD be described.  How is migration
 from an old protocol to the new protocol achieved? Do existing
 protocols need to be interfaced to the new protocol?

3.7. Other Considerations

 Anything that is not covered in one of the recommended subsections
 described above but is needed to understand the manageability
 situation SHOULD be covered in an additional section.  This may be a
 catch-all section named "Other Considerations" or may be one or more
 additional optional sections as described in Section 2.3.

Farrel Historic [Page 9] RFC 6123 Manageability Sections in PCE Drafts February 2011

4. IANA Considerations

 This document does not introduce any new codepoints or name spaces
 for registration with IANA.  It makes no request to IANA for action.
 Internet-Drafts SHOULD NOT introduce new codepoints, name spaces, or
 requests for IANA action within the Manageability Considerations

5. Manageability Considerations

 This document defines Manageability Considerations sections
 recommended for inclusion in all PCE Working Group Internet-Drafts.
 As such, the whole document is relevant to manageability.
 Note that the impact of the application of this document to Internet-
 Drafts produced within the PCE Working Group should be that PCE
 protocols and associated protocols are designed and extended with
 manageability in mind.  This should result in more robust and more
 easily deployed protocols.
 However, since this document does not describe any specific protocol,
 protocol extensions, or protocol usage, no manageability
 considerations need to be discussed here.
 (This is an example of a null Manageability Considerations section).

6. Security Considerations

 This document is Historic and describes the format and content of
 Internet-Drafts.  As such, it introduces no new security concerns.
 However, there is a clear overlap between security, operations, and
 management.  The manageability aspects of security SHOULD be covered
 within the mandatory Security Considerations of each Internet-Draft.
 New security considerations introduced by the Manageability
 Considerations section MUST be covered in the Security Considerations
 Note that fully designing a protocol before it is implemented
 (including designing the manageability aspects) is likely to result
 in a more robust protocol.  That is a benefit to network security.
 Retrofitting manageability to a protocol can make the protocol more
 vulnerable to security attacks, including attacks through the new
 manageability facilities.  Therefore, the use of this document is
 RECOMMENDED in order to help ensure the security of all protocols to
 which it is applied.

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7. Acknowledgements

 This document is based on earlier work exploring the need for
 Manageability Considerations sections in all Internet-Drafts produced
 within the Routing Area of the IETF.  That document was produced by
 Avri Doria and Loa Andersson working with the current author.  Their
 input was both sensible and constructive.
 Peka Savola provided valuable feedback on an early versions of the
 original document.  Thanks to Bert Wijnen, Dan Romascanu, David
 Harrington, Lou Berger, Spender Dawkins, Tom Petch, Matthew Meyer,
 Dimitri Papdimitriou, Stewart Bryant, and Jamal Hadi Salim for their
 Thanks to the PCE Working Group for adopting the ideas contained in
 this document and for including Manageability Considerations sections
 in their Internet-Drafts and RFCs.

8. References

8.1. Normative References

 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
           Requirement Levels", BCP 14, RFC 2119, March 1997.

8.2. Informative References

 [RFC3060] Moore, B., Ellesson, E., Strassner, J., and A. Westerinen,
           "Policy Core Information Model -- Version 1 Specification",
           RFC 3060, February 2001.
 [RFC3460] Moore, B., Ed., "Policy Core Information Model (PCIM)
           Extensions", RFC 3460, January 2003.
 [RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
           Information Models and Data Models", RFC 3444, January
 [RFC5394] Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash,
           "Policy-Enabled Path Computation Framework", RFC 5394,
           December 2008.
 [RFC5706] Harrington, D., "Guidelines for Considering Operations and
           Management of New Protocols and Protocol Extensions", RFC
           5706, November 2009.
 [X.700]   CCITT Recommendation X.700 (1992), Management framework for
           Open Systems Interconnection (OSI) for CCITT applications.

Farrel Historic [Page 11] RFC 6123 Manageability Sections in PCE Drafts February 2011

 [YANG]    Bjorklund, M., Ed., "YANG - A Data Modeling Language for
           the Network Configuration Protocol (NETCONF)", RFC 6020,
           October 2010.

Farrel Historic [Page 12] RFC 6123 Manageability Sections in PCE Drafts February 2011

Appendix A. Example Manageability Considerations Sections

 Readers are referred to the following documents for example
 Manageability Considerations sections that received positive comments
 during IESG review:
 Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation Element
 (PCE)-Based Architecture", RFC 4655, August 2006.
 Le Roux, J., Ed., "Requirements for Path Computation Element (PCE)
 Discovery", RFC 4674, October 2006.
 Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. Zhang,
 "OSPF Protocol Extensions for Path Computation Element (PCE)
 Discovery", RFC 5088, January 2008.
 Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path Computation Element
 (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009.
 Bradford, R., Ed., Vasseur, JP., and A. Farrel, "Preserving Topology
 Confidentiality in Inter-Domain Path Computation Using a Path-Key-
 Based Mechanism", RFC 5520, April 2009.
 Oki, E., Takeda, T., Le Roux, JL., and A. Farrel, "Framework for PCE-
 Based Inter-Layer MPLS and GMPLS Traffic Engineering", RFC 5623,
 September 2009.

Author's Address

 Adrian Farrel
 Old Dog Consulting

Farrel Historic [Page 13]

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