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ION WG                                               M. Maher, A. Mankin
Category: internet-draft                                   November 1996
draft-ietf-ion-sig-uni4.0-01.txt                 Expires: April 10, 1996



        ATM Signalling Support for IP over ATM - UNI 4.0 Update


Status of this Memo

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   Rim).


Abstract

   This memo describes how to efficiently use the ATM call control
   signalling procedures defined in UNI 4.0 [UNI96] to support IP over
   ATM environments as described in RFC 1577 [LAUB94] and in [KATZ96].
   Among the new features found in UNI 4.0 signalling are Available Bit
   Rate (ABR) signalling and traffic parameter negotiation.  This
   initial draft highlights the features of UNI 4.0 signalling that
   provide IP entities capabilities for requesting ATM service in sites
   with SVC support, whether it is private ATM or publicly provisioned
   ATM, in which case the SVC support is probably configured inside
   PVPs.

   This document is only relevant to IP when used as the well know "best
   effort" connectionless service. In particular, this means that this
   document does not pertain to IP in the presence of implemented IP
   Integrated Services (ISS).  The topic of IP with ISS over ATM will be
   handled by a different specification or set of specifications being
   worked on in the IISSL WG.




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   This specification is follow-on to RFC 1755, "ATM Signaling Support
   for IP over ATM", which is based on UNI signalling 3.1. Readers are
   assumed to be familiar with RFC 1755.

                             Table of Contents

     1.  Conventions ...............................................   2
     2.  Overview ..................................................   3
     3.  Use of Protocol Procedures ................................   3
         3.1  VC Teardown...........................................   3
     4.  Overview of Call Establishment Message Content ............   3
     5.  Description of Information Elements .......................   4
         5.1  ATM Adaptation Layer Parameters ......................   4
         5.2  Broadband Low Layer Information  .....................   5
         5.3  Traffic Management Issues and Related IEs.............   5
              5.3.1  ATM Traffic Descriptor ........................   7
              5.3.2  Traffic Parameter Negotiation ..................  7
              5.3.3  Broadband Bearer Capability ....................  7
              5.3.4  QoS Parameter ..................................  8
                     5.3.4.1  Signalling of Individual QoS Parameters  8
         5.6  ATM Addressing Information ...........................   8
     6.  ABR Signalling In More Detail  ............................   9
     7.  Frame Discard Capability ..................................   9
     8.  Security Consideration ....................................  10
     9.  Open Issues ...............................................  10
     10. Acknowledgements...........................................  10
     11. References ................................................  10
     12. Authors ...................................................  11
     Appendix A  Sample Signaling Messages .........................  12
     Appendix B  Combinations of Traffic Related Parameters ........  14



   1.  Conventions

   The following language conventions are used in the items of specifi-
   cation in this document:

   o   MUST, SHALL, or MANDATORY -- the item is an absolute requirement
       of the specification.

   o   SHOULD or RECOMMEND -- this item SHOULD generally be followed for
       all but exceptional circumstances.

   o   MAY or OPTIONAL -- the item is truly optional and MAY be followed
       or ignored according to the needs of the implementor.





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   2.  Overview

   UNI Signalling version 4.0 is the ATM Forum follow-on specification
   to UNI Signalling 3.1. Among the new features in UNI 4.0, those of
   particular interest to IP over ATM environments are:

       o ABR Signalling for Point-to-Point Calls
       o Traffic Parameter Negotiation
       o Frame Discard Support
       o Leaf Initiated Join (LIJ) Capability
       o ATM Anycast Capability
       o Switched Virtual Path (VP) Service

   This draft highlights the first three capabilities listed above. The
   last three capabilities are not discussed because models for their
   use in IP over ATM environments have not yet been defined or IP
   imposes no special requirements on them.


   3.  Use of Protocol Procedures

   Section 3 in RFC 1755 introduces requirements of virtual circuit (VC)
   management intended to prevent VC thrashing, excessive VC consump-
   tion, and other related problems. This section updates RFC 1755's
   requirements related to VC teardown.


   3.1.  VC Teardown

   In environments running layer 3 (L3) signalling protocols, such as
   RSVP [RSVP], over ATM, data VCs might correspond to L3 reserved flows
   (even if the VC is a 'best effort' VC). In such environments it is
   beneficial for VCs to be torn down only when the L3 reservation has
   expired. In other words, it is more efficient for the sender of a L3
   reserved flow to initiate VC tear-down when the receiver(s) has
   ceased refreshing the reservation.  To support such L3 behavior, sys-
   tems implementing a Public ATM UNI interface and serving as the
   _called_ party of a VC, MUST NOT use a configurable inactivity timer
   to clear connections that are idle for some period of time.


   4.  Overview of Call Establishment Message Content

   Signalling messages are structured to contain mandatory and optional
   variable length information elements (IEs).  A SETUP message which
   establishes an ATM connection to be used for IP and multiprotocol
   interconnection calls MUST contain the following IEs:




Maher, Mankin                                                   [Page 3]

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        AAL Parameters
        ATM Traffic Descriptor
        Broadband Bearer Capability
        Broadband Low Layer Information
        QoS Parameter
        Called Party Number
        Calling Party Number

   and MAY, under certain circumstance contain the following IEs :

        Calling Party Subaddress
        Called Party Subaddress
        Transit Network Selection

        (New in UNI 4.0:)
        Minimum Acceptable ATM Traffic Descriptor
        Alternative ATM Traffic Descriptor
        ABR Setup Parameters
        ABR Additional Parameters
        Connection Scope Selection
        Extended QoS Parameters
        End-to-End Transit Delay

   In UNI 4.0, like UNI 3.1, the AAL Parameters and the Broadband Low
   Layer Information IEs are optional in a SETUP message.  However, in
   support of IP over ATM these two IEs MUST be included. Appendix A
   shows a sample setup message.


   5.  Description of Information Elements

   This section describes the coding of, and procedures surrounding,
   information elements in SETUP and CONNECT messages. The first two IEs
   described, ATM Adaptation Layer Parameters and Broadband Low Layer
   Information, are categorized as having significance only to the end-
   points of an ATM call supporting IP. That is, the network does not
   process these IEs.


   5.1.  ATM Adaptation Layer (AAL) Parameters

   The AAL Parameters IE carries information about the ATM adaptation
   layer to be used on the connection. The parameters specified in this
   IE are the same as specified in [PER95].







Maher, Mankin                                                   [Page 4]

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          Format and field values of AAL Parameters IE

          ----------------------------------------------------------
          | aal_parameters                                         |
          ----------------------------------------------------------
          |  aal_type                    5        (AAL 5)          |
          |  fwd_max_sdu_size_identifier 140                       |
          |  fwd_max_sdu_size            65,535   (desired IP MTU) |
          |  bkw_max_sdu_size_identifier 129                       |
          |  bkw_max_sdu_size            65,535   (desired IP MTU) |
          |  sscs_type identifier        132                       |
          |  sscs_type                   0        (null SSCS)      |
          ----------------------------------------------------------

   This shows maximum size MTUs.  In practice, most sites have used 9180
   IP MTUs for ATM [RFC1626].


   5.2.  Broadband Low Layer Information

   Selection of an encapsulation to support IP over an ATM VCC is done
   using the Broadband Low Layer Information (B-LLI) IE, along with the
   AAL Parameters IE, and the B-LLI negotiation procedure.  B-LLI nego-
   tiation is described in [PER95] in Appendix D. The procedures remain
   the same for this UNI 4.0 based specification.

          Format of B-LLI IE indicating LLC/SNAP encapsulation

          ----------------------------------------------------------
          | bb_low_layer_information                               |
          ----------------------------------------------------------
          |  layer_2_id                 2                          |
          |  user_information_layer     12  (lan_llc - ISO 8802/2) |
          ----------------------------------------------------------



   5.3.  Traffic Management Issues and Related IEs

   The ATM Forum Traffic Management Sub-working group has completed ver-
   sion 4.0 of their specification [TMGT96]. This latest version focuses
   primarily on the definition of the ABR service category. As opposed
   to the Unspecified Bit Rate (UBR) traffic class, ABR uses a rate-
   based flow control mechanism to assure certain traffic guarantees
   (bandwidth and delay).  There has been much debate on whether IP
   benefits from ABR, and if so, how IP should use ABR. The Integrated
   Internet Services (IIS) and RSVP models in IP add complexity to this
   issue because mapping IIS traffic classes to ATM traffic classes is



Maher, Mankin                                                   [Page 5]

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   not straightforward.

   This document attempts only to present the required IP to ATM signal-
   ling interface for IP over ATM systems that do not support IIS as
   yet.  It is an attempt to cause IP over ATM vendors to support enough
   options for signalling the traffic characteristics of VCs serving
   non-IIS IP datagrams. This specification also aims to give guidance
   to ATM system administrators so that they can configure their IP over
   ATM entities to conform to the varied services that their ATM pro-
   vider may have sold to them.  By definition, IP without IIS cannot be
   expected to provide a signalling interface that is flexible and
   allows application specific traffic descriptors. The topic of IP over
   ATM signalling for IP _with_ IIS is to presented other specifications
   produced by the ISSLL WG of the IETF.


   An IP over ATM interface may be configured to support all the defined
   ATM Service Categories (ASC). They are:

    - CBR
    - CBR with CLR specified (loss-permitting CBR)
    - ABR
    - UBR
    - real time VBR
    - non-real time VBR

   The ATM Traffic Descriptor IE, Broadband Bearer Capability IE, and
   the QoS Parameter IE together define the signalling view of ATM
   traffic management. Additionally, the Extended QoS parameters IE and
   the End-to-end Transit Delay IE may be used to provide more specifics
   about traffic requirements, however this note does not provide expli-
   cit recommendations on their use.  Annex 9 of [TMGT96] describes a
   set of allowable combinations of traffic and QoS related paramenters
   defined for UNI 4.0 signalling.  This set includes all forms of non-
   IIS IP signalling configurations that MUST be implemented in ATM
   endsystems to accommodate varied sites' needs. The principle is that
   IP over ATM service may be available in different sites by different
   types of procured ATM service; for one site, a CBR PVP might be
   cost-effective and then the SVCs that IP over ATM without IIS must
   establish must be CBR.  Similarly, VBR or ABR PVPs could be pro-
   visioned.  The intent of this document is to specify the use of the
   most sensible parameters within this non-IIS configuration.  For
   instance, for non-IIS VBR, the SCR value may need to be hand-
   configured for IP users, or for ABR, the PCR value may be link-rate
   with a 0 MCR.

   For the reader's convenience, we have replicated the tables found in
   Annex 9 of [TMGT96] in Appendix B of this document. Ideally this



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   document could recommend specific values for the various table param-
   eters that would offer the most sensible IP over ATM service.
   Nevertheless, it is not possible to mandate specific values given the
   varied scenarios of procured ATM service.


   5.3.1.  ATM Traffic Descriptor

   Even with the newly defined ABR ASC, the most convenient model of IP
   behavior still corresponds to the Best Effort Capability.  Best
   effort service MAY be requested by including the forward and backward
   peak cell rate (CLP=0+1) and the Best Effort Indicator fields in the
   ATM Traffic Descriptor IE. As stated above, this may not be the
   choice that a site's configuration allows.

   In support of ABR service two new subfields have been added to the
   Traffic Descriptor IE, forward and backward 'Minimum Cell Rate'
   fields.


   5.3.2.  Traffic Parameter Negotiation

   UNI 4.0 allows certain traffic parameters to be negotiated during the
   call establishment phase Traffic parameters cannot be 'renegotiated'
   after the call is active. Two new IEs make negotiation possible:

     - the Minimum Acceptable ATM Traffic Descriptor IE allows
       negotiation of PCR parameters

     - the Alternative ATM Traffic Descriptor IE allows negotiation of
       other traffic parameters

   A SETUP or CONNECT message may include ONLY one of the above IEs.
   That is, the calling party may only offer an 'alternative' or
   'minimum' to the requested traffic parameters. (See Section 8 of
   [UNI96].) IP over ATM entities SHOULD take advantage of this capabil-
   ity whenever possible. In order to do so, IP over ATM entities SHOULD
   specify PCR _equal_ to the link rate in the ATM Traffic Descriptor IE
   of the SETUP message and a minimum of zero PCR in the Minimum Accept-
   able ATM Traffic Descriptor IE.


   5.3.3.  Broadband Bearer Capability

   A new field in UNI signalling 4.0 called, 'ATM Transfer Capability'
   (ATC), has been defined in the Broadband Bearer Capability IE for the
   purpose of explicitly specifying the desired ATM traffic category.
   The figure below shows the allowable ATC values.



Maher, Mankin                                                   [Page 7]

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          Format and field values of Broadband Bearer Capability IE

          -------------------------------------------------------------
          | bb_bearer_capability                                      |
          ------------------------------------------------------------|
          |  spare                       0                            |
          |  bearer_class                16    (bcob-x,c,a or VP)     |
          |  transfer_capability         cbr, rt-vbr, nrt-vbr, abr    |
          |  susceptibility_to_clipping  0     (not suscept)          |
          |  spare                       0                            |
          |  user_plane_configuration    pt-to-pt, pt-to-mpt          |
          -------------------------------------------------------------


   5.3.4.  QoS Parameter

   Inclusion of the QoS Parameter IE is optional in UNI 4.0 signalling.
   It may be omitted from a SETUP message when the Extended QoS Parame-
   ters IE, discussed in the next section, is included. This specifica-
   tion makes no explicit recommendation on the use of the QoS related
   IEs.


   5.3.4.1.  Two IEs for Signalling of Individual QoS Parameters

   UNI 4.0 allows for signalling of individual QoS parameters for the
   purpose of giving the the network and called party a more exact
   description of the desired delay and cell loss characteristics. The
   two individual QoS related IEs, Extended QoS Parameters IE and End-
   to-End Transit Delay IE, can be used in the SETUP and CONNECT signal-
   ling messages in place of the 'generic' QoS Parameter IE. Note that
   inclusion of these two IEs depends on the type of ATM service
   category requested (see Annex 9 in [TMGT96]).



   5.4.  ATM Addressing Information

   ATM addressing information is carried in the Called Party Number,
   Calling Party Number, and, under certain circumstance, Called Party
   Subaddress, and Calling Party Subaddress IE. The ATM Forum ILMI
   Specification 4.0 provides the procedure for an ATM endsystem to
   learn its own ATM address from the ATM network, for use in populating
   the Calling Party Number IE.







Maher, Mankin                                                   [Page 8]

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          Format and field values of Called Party Number IE

          ----------------------------------------------------------
          | called_party_number                                    |
          ----------------------------------------------------------
          |  type_of_number      (international number / unknown)  |
          |  addr_plan_ident     (ISDN / ATM Endsystem Address)    |
          |  addr_number         (E.164 / ATM Endsystem Address)   |
          ----------------------------------------------------------


   6.  ABR Signalling In More Detail

   The IEs and procedures pertaining to ABR signalling are briefly
   described in this section. Nevertheless, this document makes no
   specific recommendation on when to use the ABR service category for
   IP VCCs or give suggestions on appropriate values for the various
   parameters in the ABR related IEs.

   Two new IEs have been defined for ABR signalling:

      o ABR Setup Parameters
      o ABR Additional Parameters

   These IEs may be optionally included in a SETUP or CONNECT message.
   The ABR Setup Parameters IE contains the following subfields:

      - Forward/Backward ABR Initial Cell Rate
      - Forward/Backward ABR Transient Buffer Exposure
      - Cumulative RM Fixed Round Trip Time
      - Forward/Backward Rate Increment Factor
      - Forward/Backward Rate Decrease Factor

   The ABR Additional Parameters IE contains one subfield:

      - Forward/Backward Additional Parameters Record

   The Additional Parameters Record value is a compressed encoding of a
   set of ABR parameters (see TMGT96).


   7.  Frame Discard Capability

   The frame discard capabilty in UNI 4.0 is primarily based on the
   'Partial Packet Discard' strategy [ROM94]. Its use is defined for any
   of the ATM services, except for loss-less CBR.  Frame discard signal-
   ling MUST be supported by all IP over ATM entities and it is RECOM-
   MENDED that frame discard be signalled for all IP SVCs because it has



Maher, Mankin                                                   [Page 9]

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   been proven to increase throughput under network congestion. Signal-
   ling for frame discard is done by setting the frame discard bit in
   the 'Traffic Management Options' subfield in the Traffic Descriptor
   IE.  It is possible that not all network entities in the SVC path
   support frame discard, but it is required that they all forward the
   signalling.



   8.  Security Considerations

   The ATM Forum has established an ATM Security sub-working group for
   the purpose of defining security mechanisms in ATM. It is therefore
   premature to begin defining IP over ATM signalling's use of ATM secu-
   rity.  IP Security (RFC1825) can be applied to IP datagrams over any
   medium.


   9.  Open Issues

   Description of Leaf Initiated Join (LIJ) signalling is not discussed
   because the use of LIJ in IP over ATM has not been defined.  [those
   various drafty bits]


   10.  Acknowledgements

   The authors would like to thank the members of the ION working group
   for their input.

REFERENCES

   [PER95] Perez Maher, M. et al, ""ATM Signaling Support for IP over
       ATM", RFC1755, February 1995

   [LAUB93] Laubach, M., "Classical IP and ARP over ATM", RFC1577,
       Hewlett-Packard Laboratories, December 1993

   [UNI96] ATM Forum, "ATM User-Network Interface Specification Version
       4.0", Prentice Hall, Upper Saddle River, NJ, specification final-
       ized July 1996; expected publication, late 1996; available at
       ftp://ftp.atmforum.com/pub.

   [UNI94] ATM Forum, "ATM User-Network Interface Specification Version
       3.1", Prentice Hall, Upper Saddle River, NJ, 1995






Maher, Mankin                                                  [Page 10]

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   [TMGT96] ATM Forum, "ATM Forum Traffic Management Specification Ver-
       sion 4.0", Prentice Hall, Upper Saddle River NJ; specification
       finalized April 1996; expected publication, late 1996; available
       at ftp://ftp.atmforum.com/pub.

   [RSVP] R. Braden, L. Zhang, S. Berson, S. Herzog and S. Jamin,
       "Resource ReSerVation Protocol (RSVP) - Version 1 Functional
       Specification", Internet Draft, May 1996, <draft-ietf-rsvp-spec-
       14.txt>

   [KATZ96] "NBMA Next Hop Resolution Protocol (NHRP)", Katz, Pisci-
       tello, Cole, Luciani, draft-ietf-rolc-nhrp-08.txt. Work in Pro-
       gress.

   [BRAD89] Braden, R., Editor, "Requirements for Internet Hosts -- Com-
       munication Layers", RFC 1122, USC/Information Science Institute,
       October 1989.

   [BRAD94] Braden, R., Clark, D, Shenker, S., "Integrated Service in
       the Internet Architecture:  An Overview", RFC 1633,
       USC/Information Science Institute, June 1994.

   [HEIN93] Heinanen, J., "Multiprotocol Encapsulation over ATM Adapta-
       tion Layer 5", RFC 1483, Telecom Finland, July 1993.

   [ISO8473] ISO/IEC 8473, Information processing systems - Data commun-
       ications - Protocol for providing the connectionless-mode network
       service, 1988.

   [ISO9577] Information Technology - Telecommunication and information
       exchange between systems - Protocol identification in the network
       layer ISO/IEC TR9577 (International Standards Organization:
       Geneva, 1990)

   [ROM94] Romanow, A., and Floyd, S., Dynamics of TCP Traffic over ATM
       Networks.  IEEE JSAC, V. 13 N. 4, May 1995, p. 633-641. Abstract.
       An earlier version appeared in SIGCOMM '94, August 1994, pp. 79-
       88.

   [PART92] Partridge, C., "A Proposed Flow Specification", RFC1363,
       BBN, September 92


Authors' Addresses

   Maryann Perez Maher, Allison Mankin      {maher|mankin}@isi.edu
   4350 N. Fairfax Drive, Suite 620
   Arlington VA 22203



Maher, Mankin                                                  [Page 11]

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   Appendix A. A Sample UNI 4.0 SETUP Message

      +--------------------------------------------------------------------+
                                    SETUP

        Information Elements/
          Fields                         Value/(Meaning)
        --------------------             ---------------

       aal_parameters
          aal_type                         5        (AAL 5)
          fwd_max_sdu_size_ident         140
          fwd_max_sdu_size               (xmit IP MTU value)
          bkw_max_sdu_size_ident         129
          bkw_max_sdu_size         (recv IP MTU, 0 for disallowing return traff
ic)
          sscs_type identifier           132
          sscs_type                        0        (null SSCS)

       traffic_descriptor
          fwd_peak_cell_rate_0_1_ident   132
          fwd_peak_cell_rate_0_1         (link rate)
          bkw_peak_cell_rate_0_1_ident   133
          bkw_peak_cell_rate_0_1         (link rate)
          traff_mngt_options_ident       191
          fwd_frame_discard                1      (on)
          bkw_frame_discard                1      (on if return traffic indicat
ed)
          spare                            0
          tagging_bkw                      1      (on)
          tagging_fwd                      1      (on if return traffic indicat
ed)
          best_effort_indication         190      (on)

       minimum_acceptable_traffic_descriptor
          fwd_peak_cell_rate_0_1_ident   132
          fwd_peak_cell_rate_0_1           0
          bkw_peak_cell_rate_0_1_ident   133
          bkw_peak_cell_rate_0_1           0

       bb_bearer_capability     /* a coding for specifying UBR like service */
          spare                            0
          bearer_class                    16        (BCOC-X)
          spare                            0
          atm_transfer_capability         10        (nrt-vbr)
          timing_requirements             10        (timing not required)
          susceptibility_to_clipping       0        (not susceptible to clippin
g)
          spare                            0
          user_plane_configuration         0        (point_to_point)





Maher, Mankin                                                  [Page 12]

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       bb_low_layer_information
          layer_2_id                       2
          user_information_layer          12       (lan_llc - ISO 8802/2)


       qos_parameter
          qos_class_fwd                    0        (class 0)
          qos_class_bkw                    0        (class 0)

       called_party_number
          type_of_number                   (international number / unknown)
          addr_plan_ident                  (ISDN / ATM Endsystem Address)
          number                           (E.164 / ATM Endsystem Address)

       calling_party_number
          type_of_number                   (international number / unknown)
          addr_plan_ident                  (ISDN / ATM Endsystem Address)
          presentation_indic               (presentation allowed)
          spare                            0
          screening_indic                  (user_provided verified and passed)
          number                           (E.164 / ATM Endsystem Address)

      +--------------------------------------------------------------------+

                                  Figure 1.
                        Sample contents of SETUP message

























Maher, Mankin                                                  [Page 13]

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   Appendix B. Combinations of Traffic Related Parameters

   This appendix contains a copy of the five tables found in Annex 9 of
   [TMGT96] which show the allowable combinations of traffic and QoS related
   parameters in a UNI 4.0 SETUP message.

      +--------------------------------------------------------------------+
      |ATM Service Category|                     CBR                       |
      |--------------------|---------------|---------------|---------------|
      | Conformance        |CBR.1 (note 10)|   (note 4)    |   (note 4)    |
      |--------------------|---------------|---------------|---------------|
      | Bearer Capability  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | BB Bearer Class    |  A |  X  | VP |  A |  X  | VP^|  A |  X  | VP^|
      |--------------------|---------------|----|-----|----|----|-----|----|
      | ATM Transfer       |               |    | 4,5,|    |    | 4,5,|    |
      | Capability (note 1)|       7       | abs| or 6|  5 | abs| or 6|  5 |
      |--------------------|---------------|---------------|---------------|
      | Traffic Descriptor |               |               |               |
      |  for a given dir.  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0)        |               |               |       S       |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0+1)      |       S       |       S       |       S       |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0)   |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0+1) |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | Best Effort        |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | Tagging            |       N       |       N       |      Y/N      |
      |--------------------|---------------|---------------|---------------|
      | Frame Discard      |      Y/N      |      Y/N      |      Y/N      |
      |--------------------|---------------|---------------|---------------|
      | QoS Classes        |       *       |       *       |       *       |
      |--------------------|---------------|---------------|---------------|
      | Transit Delay      |       0       |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | Peak-to-Peak CDV   |       0       |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0)        |               |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0+1)      |       0       |               |               |
      +--------------------------------------------------------------------+






Maher, Mankin                                                  [Page 14]

Internet-Draft   IP over ATM Signalling - UNI 4.0 Update    November 1996


      +--------------------------------------------------------------------+
      |ATM Service Category|                 Real Time VBR                 |
      |--------------------|---------------|---------------|---------------|
      | Conformance        |VBR.1 (note 10)|     VBR.2     |     VBR.3     |
      |--------------------|---------------|---------------|---------------|
      | Bearer Capability  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | BB Bearer Class    |  C |  X  | VP |  C |  X  | VP |  C |  X  | VP |
      |--------------------|---------------|----|-----|----|----|-----|----|
      | ATM Transfer       |               |    |  1  |    |    |  1  |    |
      | Capability         |      19       |  9 | or 9|  9 |  9 | or 9|  9 |
      |--------------------|---------------|---------------|---------------|
      | Traffic Descriptor |               |               |               |
      |  for a given dir.  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0)        |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0+1)      |       S       |       S       |       S       |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0)   |               |       S       |       S       |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0+1) |      S        |               |               |
      |--------------------|---------------|---------------|---------------|
      | Best Effort        |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | Tagging            |       N       |       N       |      Y/N      |
      |--------------------|---------------|---------------|---------------|
      | Frame Discard      |      Y/N      |      Y/N      |      Y/N      |
      |--------------------|---------------|---------------|---------------|
      | QoS Classes        |       *       |       *       |       *       |
      |--------------------|---------------|---------------|---------------|
      | Transit Delay(nt.2)|       0       |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | Peak-to-Peak CDV   |       0       |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0)        |               |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0+1)      |       0       |               |               |
      +--------------------------------------------------------------------+












Maher, Mankin                                                  [Page 15]

Internet-Draft   IP over ATM Signalling - UNI 4.0 Update    November 1996


      +--------------------------------------------------------------------+
      |ATM Service Category|                 Real Time VBR                 |
      |--------------------|---------------|---------------|---------------|
      | Conformance        |  (note 4,7)   |   (note 4,8)  |    (note 4)   |
      |--------------------|---------------|---------------|---------------|
      | Bearer Capability  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | BB Bearer Class    |       X       |       X       |   X | C or VP^|
      |--------------------|---------------|---------------|-----|---------|
      | ATM Transfer       |               |               |     |         |
      | Capability         |    1 or 9     |     1 or 9    | 1or9|    9    |
      |--------------------|---------------|---------------|---------------|
      | Traffic Descriptor |               |               |               |
      |  for a given dir.  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0)        |       S       |               |               |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0+1)      |       S       |       S       |       S       |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0)   |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0+1) |               |               |       S       |
      |--------------------|---------------|---------------|---------------|
      | Best Effort        |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | Tagging            |      Y/N      |       N       |       N       |
      |--------------------|---------------|---------------|---------------|
      | Frame Discard      |      Y/N      |      Y/N      |      Y/N      |
      |--------------------|---------------|---------------|---------------|
      | QoS Classes        |       *       |       *       |       *       |
      |--------------------|---------------|---------------|---------------|
      | Transit Delay(nt.2)|       0       |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | Peak-to-Peak CDV   |       0       |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0) (nt.11)|       0       |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0+1)(nt11)|               |               |               |
      +--------------------------------------------------------------------+












Maher, Mankin                                                  [Page 16]

Internet-Draft   IP over ATM Signalling - UNI 4.0 Update    November 1996


      +--------------------------------------------------------------------+
      |ATM Service Category|               Non-Real Time VBR               |
      |--------------------|---------------|---------------|---------------|
      | Conformance        |VBR.1 (note 10)|     VBR.2     |     VBR.3     |
      |--------------------|---------------|---------------|---------------|
      | Bearer Capability  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | BB Bearer Class    |  C |  X  | VP |C |    X   | VP|C |    X   | VP|
      |--------------------|---------------|--|--------|---|--|--------|---|
      | ATM Transfer       |               |  |abs,0,2,|abs|  |abs,0,2,|abs|
      | Capability         |      11       |ab| 8,10   |10 |ab| 8,10   |10 |
      |--------------------|---------------|---------------|---------------|
      | Traffic Descriptor |               |               |               |
      |  for a given dir.  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0)        |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0+1)      |       S       |       S       |       S       |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0)   |               |       S       |       S       |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0+1) |       S       |               |               |
      |--------------------|---------------|---------------|---------------|
      | Best Effort        |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | Tagging            |       N       |       N       |       Y       |
      |--------------------|---------------|---------------|---------------|
      | Frame Discard      |      Y/N      |      Y/N      |      Y/N      |
      |--------------------|---------------|---------------|---------------|
      | QoS Classes        |       *       |       *       |       *       |
      |--------------------|---------------|---------------|---------------|
      | Transit Delay(nt.2)|    (note 3)   |   (note 3)    |    (note 3)   |
      |--------------------|---------------|---------------|---------------|
      | Peak-to-Peak CDV   |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0)        |               |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0+1)      |       0       |               |               |
      +--------------------------------------------------------------------+












Maher, Mankin                                                  [Page 17]

Internet-Draft   IP over ATM Signalling - UNI 4.0 Update    November 1996


      +--------------------------------------------------------------------+
      |ATM Service Category|               Non-Real Time VBR               |
      |--------------------|---------------|---------------|---------------|
      | Conformance        |  (note 4,7)   |   (note 4,8)  |    (note 4)   |
      |--------------------|---------------|---------------|---------------|
      | Bearer Capability  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | BB Bearer Class    |   C   |   X   |   C   |   X   |C |    X   |VP^|
      |--------------------|-------|-------|-------|-------|--|--------|---|
      | ATM Transfer       |       |abs,0,2|       |abs,0,2|  |abs,0,2,|abs|
      | Capability         | abs   |8 or 10|       |8 or 10|ab| 8 or10 |10 |
      |--------------------|---------------|---------------|---------------|
      | Traffic Descriptor |               |               |               |
      |  for a given dir.  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0)        |       S       |               |               |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0+1)      |       S       |       S       |       S       |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0)   |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0+1) |               |               |       S       |
      |--------------------|---------------|---------------|---------------|
      | Best Effort        |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | Tagging            |     Y/N       |       N       |       N       |
      |--------------------|---------------|---------------|---------------|
      | Frame Discard      |      Y/N      |      Y/N      |      Y/N      |
      |--------------------|---------------|---------------|---------------|
      | QoS Classes        |       *       |       *       |       *       |
      |--------------------|---------------|---------------|---------------|
      | Transit Delay(nt.2)|    (note 3)   |   (note 3)    |    (note 3)   |
      |--------------------|---------------|---------------|---------------|
      | Peak-to-Peak CDV   |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0)        |       0       |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0+1)      |               |               |               |
      +--------------------------------------------------------------------+












Maher, Mankin                                                  [Page 18]

Internet-Draft   IP over ATM Signalling - UNI 4.0 Update    November 1996


      +--------------------------------------------------------------------+
      |ATM Service Category|     ABR       |              UBR              |
      |--------------------|---------------|---------------|---------------|
      | Conformance        |     ABR       |     UBR.1     |     UBR.2     |
      |--------------------|---------------|---------------|---------------|
      | Bearer Capability  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | BB Bearer Class    |  C |  X  | VP |C |    X   | VP|C |    X   | VP|
      |--------------------|---------------|--|--------|---|--|--------|---|
      | ATM Transfer       |               |  |abs,0,2,|abs|  |abs,0,2,|abs|
      | Capability         |      12       |ab| 8,10   |10 |ab| 8,10   |10 |
      |--------------------|---------------|---------------|---------------|
      | Traffic Descriptor |               |               |               |
      |  for a given dir.  |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0)        |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | PCR (CLP=0+1)      |       S       |       S       |       S       |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0)   |               |       S       |       S       |
      |--------------------|---------------|---------------|---------------|
      | SCR, MBS (CLP=0+1) |       S       |               |               |
      |--------------------|---------------|---------------|---------------|
      | ABR MCR            |    (note 6)   |               |               |
      |--------------------|---------------|---------------|---------------|
      | Best Effort        |               |  S (note 9)   |   S (note 9)  |
      |--------------------|---------------|---------------|---------------|
      | Tagging            |       N       |       N       |       N       |
      |--------------------|---------------|---------------|---------------|
      | Frame Discard      |      Y/N      |      Y/N      |      Y/N      |
      |--------------------|---------------|---------------|---------------|
      | QoS Classes        |       0       |       0       |       0       |
      |--------------------|---------------|---------------|---------------|
      | Transit Delay(nt.2)|               |               |               |
      |--------------------|---------------|---------------|---------------|
      | Peak-to-Peak CDV   |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0)        |               |               |               |
      |--------------------|---------------|---------------|---------------|
      | CLR (CLP=0+1)      |               |               |               |
      +--------------------------------------------------------------------+



      ab, abs = absent.

      Y/N = either "Yes" or "No" is allowed.




Maher, Mankin                                                  [Page 19]

Internet-Draft   IP over ATM Signalling - UNI 4.0 Update    November 1996


      * = allowed QoS class values are a network option. Class 0 is always
          for alignment with ITU-T.

      ^ = (note 5).

      See Annex 9 of [TMGT96] for comments on "note"s.













































Maher, Mankin                                                  [Page 20]