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Internet Engineering Task Force (IETF) F. Baker Request for Comments: 5865 J. Polk Updates: 4542, 4594 Cisco Systems Category: Standards Track M. Dolly ISSN: 2070-1721 AT&T Labs

                                                              May 2010
            A Differentiated Services Code Point (DSCP)
                   for Capacity-Admitted Traffic


 This document requests one Differentiated Services Code Point (DSCP)
 from the Internet Assigned Numbers Authority (IANA) for a class of
 real-time traffic.  This traffic class conforms to the Expedited
 Forwarding Per-Hop Behavior.  This traffic is also admitted by the
 network using a Call Admission Control (CAC) procedure involving
 authentication, authorization, and capacity admission.  This differs
 from a real-time traffic class that conforms to the Expedited
 Forwarding Per-Hop Behavior but is not subject to capacity admission
 or subject to very coarse capacity admission.

Status of This Memo

 This is an Internet Standards Track document.
 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).  Further information on
 Internet Standards is available in 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

Baker, et al. Standards Track [Page 1] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

Copyright Notice

 Copyright (c) 2010 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.
 This document may contain material from IETF Documents or IETF
 Contributions published or made publicly available before November
 10, 2008.  The person(s) controlling the copyright in some of this
 material may not have granted the IETF Trust the right to allow
 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified
 outside the IETF Standards Process, and derivative works of it may
 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .  3
   1.1.  Definitions . . . . . . . . . . . . . . . . . . . . . . .  4
   1.2.  Problem   . . . . . . . . . . . . . . . . . . . . . . . .  6
 2.  Candidate Implementations of the Admitted Telephony
     Service Class   . . . . . . . . . . . . . . . . . . . . . . .  7
   2.1.  Potential implementations of EF in this model . . . . . .  7
   2.2.  Capacity admission control  . . . . . . . . . . . . . . .  9
   2.3.  Recommendations on implementation of an Admitted
         Telephony Service Class . . . . . . . . . . . . . . . . . 10
 3.  Summary: changes from RFC 4594  . . . . . . . . . . . . . . . 11
 4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
 5.  Security Considerations . . . . . . . . . . . . . . . . . . . 12
 6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . 12
 7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . 13
   7.1.  Normative References  . . . . . . . . . . . . . . . . . . 13
   7.2.  Informative References  . . . . . . . . . . . . . . . . . 13

Baker, et al. Standards Track [Page 2] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

1. Introduction

 This document requests one Differentiated Services Code Point (DSCP)
 from the Internet Assigned Numbers Authority (IANA) for a class of
 real-time traffic.  This class conforms to the Expedited Forwarding
 (EF) [RFC3246] [RFC3247] Per-Hop Behavior.  It is also admitted using
 a CAC procedure involving authentication, authorization, and capacity
 admission.  This differs from a real-time traffic class that conforms
 to the Expedited Forwarding Per-Hop Behavior but is not subject to
 capacity admission or subject to very coarse capacity admission.
 In addition, this document recommends that certain classes of video
 described in [RFC4594] be treated as requiring capacity admission.
 Real-time traffic flows have one or more potential congestion points
 between the endpoints.  Reserving capacity for these flows is
 important to application performance.  All of these applications have
 low tolerance to jitter (aka delay variation) and loss, as summarized
 in Section 2, and most (except for multimedia conferencing) have
 inelastic flow behavior from Figure 1 of [RFC4594].  Inelastic flow
 behavior and low jitter/loss tolerance are the service
 characteristics that define the need for admission control behavior.
 One of the reasons behind the requirement for capacity admission is
 the need for classes of traffic that are handled under special
 policies.  Service providers need to distinguish between special-
 policy traffic and other classes, particularly the existing Voice
 over IP (VoIP) services that perform no capacity admission or only
 very coarse capacity admission and can exceed their allocated
 The requested DSCP applies to the Telephony Service Class described
 in [RFC4594].
 Since video classes have not had the history of mixing admitted and
 non-admitted traffic in the same Per-Hop Behavior (PHB) as has
 occurred for EF, an additional DSCP code point is not recommended
 within this document for video.  Instead, the recommended "best
 practice" is to perform admission control for all traffic in three of
 the video classes from [RFC4594]:
 o  The Interactive Real-Time Traffic (CS4, used for Video
    conferencing and Interactive gaming),
 o  The Broadcast TV (CS3) for use in a video on demand context, and
 o  The AF4 Multimedia Conferencing (video conferencing).

Baker, et al. Standards Track [Page 3] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

 Other video classes are believed not to have the current problem of
 confusion with unadmitted traffic and therefore would not benefit
 from the notion of a separate DSCP for admitted traffic.  Within an
 ISP and on inter-ISP links (i.e., within networks whose internal
 paths are uniform at hundreds of megabits per second or faster), one
 would expect all of this traffic to be carried in the Real-Time
 Traffic (RTP) class described in [RFC5127].

1.1. Definitions

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 document are to be interpreted as described in RFC 2119 [RFC2119].
 The following terms and acronyms are used in this document.
 PHB:   A Per-Hop Behavior (PHB) is the externally observable
        forwarding behavior applied at a Differentiated Services
        compliant node to a DS behavior aggregate [RFC2475].  It may
        be thought of as a program configured on the interface of an
        Internet host or router, specified in terms of drop
        probabilities, queuing priorities or rates, and other handling
        characteristics for the traffic class.
 DSCP:  The Differentiated Services Code Point (DSCP), as defined in
        [RFC2474], is a value that is encoded in the DS field, and
        that each DS Node MUST use to select the PHB that is to be
        experienced by each packet it forwards [RFC3260].  It is a
        6-bit number embedded into the 8-bit TOS (type of service)
        field of an IPv4 datagram or the Traffic Class field of an
        IPv6 datagram.
 CAC:   Call Admission Control includes concepts of authorization and
        capacity admission.  "Authorization" refers to any procedure
        that identifies a user, verifies the authenticity of the
        identification, and determines whether the user is authorized
        to use the service under the relevant policy.  "Capacity
        Admission" refers to any procedure that determines whether
        capacity exists supporting a session's requirements under some
        In the Internet, these are separate functions; while in the
        Public Switched Telephone Network (PSTN), they and call
        routing are carried out together.

Baker, et al. Standards Track [Page 4] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

 UNI:   A User/Network Interface (UNI) is the interface (often a
        physical link or its virtual equivalent) that connects two
        entities that do not trust each other, and in which one (the
        user) purchases connectivity services from the other (the
        Figure 1 shows two user networks connected by what appears to
        each of them to be a single network ("The Internet", access to
        which is provided by their service provider) that provides
        connectivity services to other users.
        UNIs tend to be the bottlenecks in the Internet, where users
        purchase relatively low amounts of bandwidth for cost or
        service reasons, and as a result are most subject to
        congestion issues and therefore issues requiring traffic
        conditioning and service prioritization.
 NNI:   A Network/Network Interface (NNI) is the interface (often a
        physical link or its virtual equivalent) that connects two
        entities that trust each other within limits, and in which the
        two are seen as trading services for value.  Figure 1 shows
        three service networks that together provide the connectivity
        services that we call "the Internet".  They are different
        administrations and are very probably in competition, but
        exchange contracts for connectivity and capacity that enable
        them to offer specific services to their customers.
        NNIs may not be bottlenecks in the Internet if service
        providers contractually agree to provision excess capacity at
        them, as they commonly do.  However, NNI performance may
        differ by ISP, and the performance guarantee interval may
        range from a month to a much shorter period.  Furthermore, a
        peering point NNI may not have contractual performance
        guarantees or may become overloaded under certain conditions.
        They are also policy-controlled interfaces, especially in BGP.
        As a result, they may require a traffic prioritization policy.
 Queue: There are multiple ways to build a multi-queue scheduler.
        Weighted Round Robin (WRR) literally builds multiple lists and
        visits them in a specified order, while a calendar queue
        (often used to implement Weighted Fair Queuing, or WFQ) builds
        a list for each time interval and queues at most a stated
        amount of data in each such list for transmission during that
        time interval.  While these differ dramatically in
        implementation, the external difference in behavior is
        generally negligible when they are properly configured.
        Consistent with the definitions used in the Differentiated
        Services Architecture [RFC2475], these are treated as

Baker, et al. Standards Track [Page 5] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

        equivalent in this document, and the lists of WRR and the
        classes of a calendar queue will be referred to uniformly as
                                  ,-''           `--.
                               ,-'                   `-.
         ,-------.           ,',-------.                `.
       ,'         `.       ,','         `.                `.
      /  User       \ UNI / /   Service   \                 \
     (    Network    +-----+    Network    )                 `.
      \             /  ;    \             /                    :
       `.         ,'   ;     `.         .+                     :
         '-------'    /        '-------'  \ NNI                 \
                     ;                     \                     :
                     ;     "The Internet"   \  ,-------.         :
                    ;                        +'         `.        :
      UNI: User/Network Interface           /   Service   \       |
                   |                       (    Network    )      |
      NNI: Network/Network Interface        \             /       |
                    :                        +.         ,'        ;
                     :                      /  '-------'         ;
                     :                     /                     ;
         ,-------.    \        ,-------.  / NNI                 /
       ,'         `.   :     ,'         `+                     ;
      /  User       \ UNI   /   Service   \                    ;
     (    Network    +-----+    Network    )                 ,'
      \             /     \ \             /                 /
       `.         ,'       `.`.         ,'                ,'
         '-------'           `.'-------'                ,'
                               `-.                   ,-'
                                  `--.           _.-'
                    Figure 1: UNI and NNI Interfaces

1.2. Problem

 In short, the Telephony Service Class, described in [RFC4594],
 permits the use of capacity admission in implementing the service,
 but present implementations either provide no capacity admission
 services or do so in a manner that depends on specific traffic
 engineering.  In the context of the Internet backbone, the two are
 essentially equivalent; the edge network depends on specific
 engineering by the service provider that might not be present,
 especially in a mobile environment.

Baker, et al. Standards Track [Page 6] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

 However, services are being requested of the network that would
 specifically make use of capacity admission, and would distinguish
 among users or the uses of available Voice-over-IP or Video-over-IP
 capacity in various ways.  Various agencies would like to provide
 services as described in RFC [RFC4190] or in Section 2.6 of
 This requires the use of capacity admission to differentiate among
 users to provide services to them that are not afforded to non-
 capacity admitted customer-to-customer IP telephony sessions.

2. Candidate Implementations of the Admitted Telephony Service Class

2.1. Potential Implementations of EF in This Model

 There are at least two possible ways to implement isolation between
 the Capacity Admitted PHB and the Expedited Forwarding PHB in this
 model.  They are to implement separate classes as a set of
 o  Multiple data plane traffic classes, each consisting of a policer
    and a queue, with the queues enjoying different priorities, or
 o  Multiple data plane traffic classes, each consisting of a policer
    but feeding into a common queue or multiple queues at the same
 We will explain the difference and describe in what way they differ
 in operation.  The reason this is necessary is that there is current
 confusion in the industry.
 The multi-priority model is shown in Figure 2.  In this model,
 traffic from each service class is placed into a separate priority
 queue.  If data is present in more than one queue, traffic from one
 of them will always be selected for transmission.  This has the
 effect of transferring jitter from the higher-priority queue to the
 lower-priority queues, and reordering traffic in a way that gives the
 higher-priority traffic a smaller average queuing delay.  Each queue
 must have its own policer, however, to protect the network from
 errors and attacks; if a traffic class thinks it is carrying a
 certain data rate but an abuse sends significantly more, the effect
 of simple prioritization would not preserve the lower priorities of
 traffic, which could cause routing to fail or otherwise impact a
 service level agreement (SLA).

Baker, et al. Standards Track [Page 7] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

                      policers    priorities  |`.
              Admitted EF <=> ----------||----+  `.
                                          high|    `.
            Unadmitted EF <=> ----------||----+     .'-----------
                            .             medium  .'
               rate queues  |`.         +-----+ .' Priority
            AF1------>||----+  `.      /  low |'   Scheduler
                            |    `.   /
            AF2------>||----+     .'-+
                            |   .'
            CS0------>||----+ .' Rate Scheduler
                            |'   (WFQ, WRR, etc.)
              Figure 2: Implementation as a Data Plane Priority
 The multi-policer model is shown in Figure 3.  In this model, traffic
 from each service class is policed according to its SLA requirements,
 and then placed into a common priority queue.  Unlike the multi-
 priority model, the jitter experienced by the traffic classes in this
 case is the same, as there is only one queue, but the sum of the
 traffic in this higher-priority queue experiences less average jitter
 than the elastic traffic in the lower-priority.
                     policers    priorities  .
             Admitted EF <=> -------\        |`.
                                     --||----+  `.
           Unadmitted EF <=> -------/    high|    `.
                           .                 |     .'--------
              rate queues  |`.         +-----+   .'
           AF1------>||----+  `.      /  low | .' Priority
                           |    `.   /       |'   Scheduler
           AF2------>||----+     .'-+
                           |   .'
           CS0------>||----+ .' Rate Scheduler
                           |'   (WFQ, WRR, etc.)
           Figure 3: Implementation as a Data Plane Policer
 The difference between the two operationally is, as stated, the
 issues of loss due to policing and distribution of jitter.
 If the two traffic classes are, for example, voice and video,
 datagrams containing video data can be relatively large (often of
 variable sizes up to the path MTU), while datagrams containing voice
 are relatively small, on the order of only 40 to 200 bytes, depending
 on the codec.  On lower-speed links (less than 10 MBPS), the jitter
 introduced by video to voice can be disruptive, while at higher

Baker, et al. Standards Track [Page 8] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

 speeds, the jitter is nominal compared to the jitter requirements of
 voice.  Therefore, at access network speeds, [RFC4594] recommends the
 separation of video and voice into separate queues, while at optical
 speeds, [RFC5127] recommends that they use a common queue.
 If, on the other hand, the two traffic classes are carrying the same
 type of application with the same jitter requirements, then giving
 one preference in this sense does not benefit the higher-priority
 traffic and may harm the lower-priority traffic.  In such a case,
 using separate policers and a common queue is a superior approach.

2.2. Capacity Admission Control

 There are at least six major ways that capacity admission is done or
 has been proposed to be done for real-time applications.  Each will
 be described below, and Section 3 will judge which ones are likely to
 meet the requirements of the Admitted Telephony service class.  These
 o  Drop Precedence used to force sessions to voluntarily exit,
 o  Capacity admission control by assumption or engineering,
 o  Capacity admission control by call counting,
 o  Endpoint capacity admission performed by probing the network,
 o  Centralized capacity admission control via bandwidth broker, and
 o  Distributed capacity admission control using protocols such as
    Resource Reservation Protocol (RSVP) or Next Steps in Signaling
 The problem with dropping traffic to force users to hang up is that
 it affects a broad class of users -- if there is capacity for N calls
 and the N+1 calls are active, data is dropped randomly from all
 sessions to ensure that offered load doesn't exceed capacity.  On
 very fast links, that is acceptable, but on lower speed links it can
 seriously affect call quality.  There is also a behavioral issue
 involved here, in which users who experience poor quality calls tend
 to hang up and call again, making the problem better -- then worse.
 The problem with capacity admission by assumption, which is widely
 deployed in today's VoIP environment, is that it depends on the
 assumptions made.  One can do careful traffic engineering to ensure
 needed bandwidth, but this can also be painful, and has to be
 revisited when the network is changed or network usage changes.

Baker, et al. Standards Track [Page 9] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

 The problem with call-counting-based admission control is that it
 gets exponentially worse the farther you get from the control point
 (e.g., it lacks sufficient scalability on the outskirts of the
 There are two fundamental problems with depending on the endpoint to
 perform capacity admission: it may not be able to accurately measure
 the impact of the traffic it generates on the network, and it tends
 to be greedy (e.g., it doesn't care).  If the network operator is
 providing a service, he must be able to guarantee the service, which
 means that he cannot trust systems that are not controlled by his
 The problem with capacity controls via a bandwidth broker is that
 centralized servers lack far away awareness, and also lack effective
 real-time reaction to dynamic changes in all parts of the network at
 all instances of time.
 The problem with mechanisms that do not enable the association of a
 policy with the request is that they do not allow for multi-policy
 services, which are becoming important.
 The operator's choice of admission procedure MUST, for this DSCP,
 ensure the following:
 o  The actual links that a session uses have enough bandwidth to
    support it.
 o  New sessions are refused admission if there is inadequate
    bandwidth under the relevant policy.
 o  A user is identified and the correct policy is applied if multiple
    policies are in use in a network.
 o  Under periods of network stress, the process of admission of new
    sessions does not disrupt existing sessions, unless the service
    explicitly allows for disruption of calls.

2.3. Recommendations on Implementation of an Admitted Telephony

    Service Class
 When coupled with adequate Authentication, Authorization, and
 Accounting (AAA) and capacity admission procedures as described in
 Section 2.2, either of the two PHB implementations described in
 Section 2.1 is sufficient to provide the services required for an
 Admitted Telephony service class.  If preemption is required, Section of [RFC4542] provides the tools for carrying out the
 preemption.  If preemption is not in view, or if used in addition to

Baker, et al. Standards Track [Page 10] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

 preemptive services, the application of different thresholds
 depending on call precedence has the effect of improving the
 probability of call completion by admitting preferred calls at a time
 when other calls are being refused.  Routine and priority traffic can
 be admitted using the same DSCP value, as the choice of which calls
 are admitted is handled in the admission procedure executed in the
 control plane, not the policing of the data plane.
 On the point of what protocols and procedures are required for
 authentication, authorization, and capacity admission, we note that
 clear standards do not exist at this time for bandwidth brokers, NSIS
 has not been finalized at this time and in any event is limited to
 unicast sessions, and that RSVP has been standardized and has the
 relevant services.  We therefore RECOMMEND the use of a protocol,
 such as RSVP, at the UNI.  Procedures at the NNI are business matters
 to be discussed between the relevant networks, and are RECOMMENDED

3. Summary: Changes from RFC 4594

 To summarize, there are two changes to [RFC4594] discussed in this
 Telephony class: The Telephony Service Class in RFC 4594 does not
                  involve capacity admission, but depends on
                  application layer admission that only estimates
                  capacity, and does that through static engineering.
                  In addition to that class, a separate Admitted
                  Telephony Class is added that performs capacity
                  admission dynamically.
 Video classes:   Capacity admission is added to three video classes.
                  These are the Interactive Real-Time Traffic class,
                  Broadcast TV class when used for video on demand,
                  and the Multimedia Conferencing class.

4. IANA Considerations

 IANA assigned a DSCP value to a second EF traffic class consistent
 with [RFC3246] and [RFC3247] in the "Differentiated Services Field
 Codepoints" registry.  It implements the Telephony Service Class
 described in [RFC4594] at lower speeds and is included in the Real-
 Time Treatment Aggregate [RFC5127] at higher speeds.  The code point
 value should be from pool 1 within the dscp-registry.  The value is
 parallel with the existing EF code point (101110), as IANA assigned

Baker, et al. Standards Track [Page 11] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

 the code point 101100 -- keeping the (left-to-right) first 4 binary
 values the same in both.  The code point described in this document
 is referred to as VOICE-ADMIT and has been registered as follows:
 Sub-registry: Pool 1 Codepoints
 Reference: [RFC2474]
 Registration Procedures: Standards Action
    Name         Space    Reference
    ---------    -------  ---------
    VOICE-ADMIT  101100   [RFC5865]
 This traffic class REQUIRES the use of capacity admission, such as
 RSVP services together with AAA services, at the User/Network
 Interface (UNI); the use of such services at the NNI is at the option
 of the interconnected networks.

5. Security Considerations

 A major requirement of this service is effective use of a signaling
 protocol, such as RSVP, with the capabilities to identify its user as
 either an individual or a member of some corporate entity, and assert
 a policy such as "normal", "routine", or some level of "priority".
 This capability, one has to believe, will be abused by script kiddies
 and others if the proof of identity is not adequately strong or if
 policies are written or implemented improperly by the carriers.  This
 goes without saying, but this section is here for it to be said.
 Many of the security considerations from RFC 3246 [RFC3246] apply to
 this document, as well as the security considerations in RFC 2474 and
 RFC 4542.  RFC 4230 [RFC4230] analyzes RSVP, providing some gap
 analysis to the NSIS WG as they started their work.  Keep in mind
 that this document is advocating RSVP at the UNI only, while RFC 4230
 discusses (mostly) RSVP from a more complete point of view (i.e., e2e
 and edge2edge).  When considering the RSVP aspect of this document,
 understanding Section 6 of RFC 4230 is a good source of information.

6. Acknowledgements

 Kwok Ho Chan, Georgios Karagiannis, Dan Voce, and Bob Briscoe
 commented and offered text.  The impetus for including video in the
 discussion, which initially only targeted voice, is from Dave

Baker, et al. Standards Track [Page 12] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

7. References

7.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
            "Definition of the Differentiated Services Field (DS
            Field) in the IPv4 and IPv6 Headers", RFC 2474, December
 [RFC3246]  Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,
            J., Courtney, W., Davari, S., Firoiu, V., and D.
            Stiliadis, "An Expedited Forwarding PHB (Per-Hop
            Behavior)", RFC 3246, March 2002.

7.2. Informative References

 [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
            and W. Weiss, "An Architecture for Differentiated
            Service", RFC 2475, December 1998.
 [RFC3247]  Charny, A., Bennet, J., Benson, K., Boudec, J., Chiu, A.,
            Courtney, W., Davari, S., Firoiu, V., Kalmanek, C., and K.
            Ramakrishnan, "Supplemental Information for the New
            Definition of the EF PHB (Expedited Forwarding Per-Hop
            Behavior)", RFC 3247, March 2002.
 [RFC3260]   Grossman, D., "New Terminology and Clarifications for
            Diffserv", RFC 3260, April 2002.
 [RFC4190]  Carlberg, K., Brown, I., and C. Beard, "Framework for
            Supporting Emergency Telecommunications Service (ETS) in
            IP Telephony", RFC 4190, November 2005.
 [RFC4504]  Sinnreich, H., Ed., Lass, S., and C. Stredicke, "SIP
            Telephony Device Requirements and Configuration", RFC
            4504, May 2006.
 [RFC4542]  Baker, F. and J. Polk, "Implementing an Emergency
            Telecommunications Service (ETS) for Real-Time Services in
            the Internet Protocol Suite", RFC 4542, May 2006.
 [RFC4594]  Babiarz, J., Chan, K., and F. Baker, "Configuration
            Guidelines for DiffServ Service Classes", RFC 4594, August

Baker, et al. Standards Track [Page 13] RFC 5865 DSCP for Capacity-Admitted Traffic May 2010

 [RFC5127]  Chan, K., Babiarz, J., and F. Baker, "Aggregation of
            DiffServ Service Classes", RFC 5127, February 2008.
 [RFC4230]  Tschofenig, H. and R. Graveman, "RSVP Security
            Properties", RFC 4230, December 2005.

Authors' Addresses

 Fred Baker
 Cisco Systems
 Santa Barbara, California  93117
 Phone: +1-408-526-4257
 James Polk
 Cisco Systems
 Richardson, Texas  75082
 Phone: +1-817-271-3552
 Martin Dolly
 AT&T Labs
 Middletown Township, New Jersey  07748
 Phone: +1-732-420-4574

Baker, et al. Standards Track [Page 14]

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