ION WG                                                    M.Maher, A.Mankin
Category: internet-draft                                          June 1996
draft-ietf-ion-sig-uni4.0-00.txt                      Expires: Dec 13, 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
   time.  It is inappropriate to use Internet-Drafts as reference
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   To learn the current status of any Internet-Draft, please check the
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   (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific
   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) and RSVP.  The topic of IP with ISS over
   ATM will be handled by a different specification or set of
   specifications being worked on in the ISSLL WG.




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INTERNET-DRAFT      IP over ATM Signalling - UNI 4.0 Update    June 1996


   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.




   1.  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 enviroments 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 mainly because models for
   their use in IP over ATM environments have not yet been defined.


   2.  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:

        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



Maher, Mankin                                                   [Page 2]


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        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.


   3.  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.


   3.1.  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].

          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].






Maher, Mankin                                                   [Page 3]


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   3.2.  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) |
          ----------------------------------------------------------



   3.3.  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
   not straightforward.

   This draft attempts only to present the required IP to ATM signalling
   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 sys-
   tem administrators so that they can configure their IP over ATM enti-
   ties to conform to the varied services that their ATM provider may
   have sold to them.  By definition, IP without IIS cannot be expected
   to provide a signalling interface that is flexible and allows appli-
   cation specific traffic descriptors. The topic of IP over ATM signal-
   ling 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:



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

   [We don't think it's likely that realtime VBR would be a provisioned
   service to a site, but we expect to discuss this with the WG]


   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.  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 accomodate varied sites' needs. The principle is that IP over ATM
   service may be provided by different sites by different types of pro-
   cured 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 provisioned.  We want to
   fill in the table parameters to offer 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 documents.  Amendments to
   this set of tables will be iterated in WG discussion.



















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   3.3.1.  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.


   3.3.2.  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.  (WG agreed to this in San Jose.)


   3.3.3.  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 catergory.
   The figure below shows the allowable ATC values.









Maher, Mankin                                                   [Page 6]


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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          |
          -------------------------------------------------------------


   3.3.4.  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. [WG needs to decide on this. Is there any benefit in using these
   or do they just make signalling more complex?)


   3.3.4.1.  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]).


   3.4.  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



Maher, Mankin                                                   [Page 7]


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

      - Forward/Backward ABR Initital 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).


   3.5.  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
   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 requiered that they all forward the
   signalling.



   3.6.  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)   |
          ----------------------------------------------------------


   4.  Security Considerations

   The ATM Forum has established an ATM Security sub-working group for
   the purpose of defining seurity 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.


   5.  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]

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", 1996 Work in Progress.

   [UNI94] ATM Forum, "ATM User-Network Interface Specification Version
       3.1", (Englewood Cliffs, NJ: Prentice Hall, 1994)

   [TMGT96] ATM Forum, "ATM Forum Traffic Management Specification Ver-
       sion 4.0", 1996, Work in Progress.

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





Maher, Mankin                                                   [Page 9]


INTERNET-DRAFT      IP over ATM Signalling - UNI 4.0 Update    June 1996


   [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
   maher@isi.edu

   Allison Mankin
   mankin@isi.edu

   4350 N. Fairfax Drive, Suite 620
   Arlington VA 22203
   703-807-0133












Maher, Mankin                                                  [Page 10]


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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               (send IP MTU value)
          bkw_max_sdu_size_ident         129
          bkw_max_sdu_size               (recv IP MTU value)
          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)
          spare                            0
          tagging_bkw                      1   (on)
          tagging_fwd                      1   (on)
          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          nrt-vbr  (
          susceptibility_to_clipping       0        (not susceptible to clipping)
          spare                            0
          user_plane_configuration         0        (point_to_point)


        bb_low_layer_information



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          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 12]


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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       |               |               |
      +--------------------------------------------------------------------+






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      +--------------------------------------------------------------------+
      |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 14]


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      +--------------------------------------------------------------------+
      |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 15]


INTERNET-DRAFT      IP over ATM Signalling - UNI 4.0 Update    June 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 16]


INTERNET-DRAFT      IP over ATM Signalling - UNI 4.0 Update    June 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 17]


INTERNET-DRAFT      IP over ATM Signalling - UNI 4.0 Update    June 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 18]


INTERNET-DRAFT      IP over ATM Signalling - UNI 4.0 Update    June 1996


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

      ^ = (note 5).

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













































Maher, Mankin                                                  [Page 19]