





Network Working Group                                         M. Laubach
Request for Comments: 1754                                   Com21, Inc.
Category: Informational                                     January 1995


                      IP over ATM Working Group's
         Recommendations for the ATM Forum's Multiprotocol BOF
                               Version 1

Status of this Memo

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

1.  Abstract

   This document represents an initial list of requirements submitted to
   the ATM Forum's Multiprotocol BOF for the operation of IP over ATM
   networks as determined by the IETF IP over ATM Working Group and
   other working groups. This RFC is issued for the benefit of community
   members.  The information contained in this document is accurate as
   of the date of publication, but is subject to change.  Subsequent
   RFCs will reflect such changes.

   The content of this memo was submitted by the IETF Liaison to the ATM
   Forum as contribution number 94-0954 in the ATM Forum's documentation
   process on 14 September 1994.

2.  Notice

   This contribution has been prepared to assist the ATM Forum.  This
   document is offered to the Forum as a basis for discussion between
   the ATM Forum Multiprotocol BOF and the IETF.  The statements are
   subject to change in form and content after further study and
   discussion.  Specifically, the IETF reserves reserves the right to
   add to, amend or modify the statements contained herein.

3.  Introduction

   The following is the charter statement from the Internet Engineering
   Task Force's (IETF) IP over ATM Working Group (IPATM WG).  It is
   being reproduced here for the benefit of those in the ATM Forum who
   may not be familiar with it:

   "The IP over ATM Working Group will focus on the issues involved in
   running internetworking protocols over Asynchronous Transfer Mode
   (ATM) networks.  The final goal for the Working Group is to produce



Laubach                                                         [Page 1]

RFC 1754         IPATM WG ATM Forum Recommendations V1      January 1995


   standards for the TCP/IP protocol suite and recommendations which
   could be used by other internetworking protocol standards (e.g., ISO
   CLNP and IEEE 802.2 Bridging).

   The Working Group will initially develop experimental protocols for
   encapsulation, multicasting, addressing, address resolution, call set
   up, and network management to allow the operation of internetwork
   protocols over an ATM network.  The Working Group may later submit
   these protocols for IETF standardization.

   The Working Group will not develop physical layer standards for ATM.
   These are well covered in other standards groups and do not need to
   be addressed in this Group.

   The Working Group will develop models of ATM internetworking
   architectures.  This will be used to guide the development of
   specific IP over ATM protocols.

   The Working Group will also develop and maintain a list of technical
   unknowns that relate to internetworking over ATM.  These will be used
   to direct future work of the Working Group or be submitted to other
   standards or research groups as appropriate.

   The Working Group will coordinate its work with other relevant
   standards bodies (e.g., ANSI T1S1.5) to insure that it does not
   duplicate their work and that its work meshes well with other
   activities in this area.  The Working Group will select among ATM
   protocol options (e.g., selection of an adaptation layer) and make
   recommendations to the ATM standards bodies regarding the
   requirements for internetworking over ATM where the current ATM
   standards do not meet the needs of internetworking."

   Historically, a large number of IETF IPATM WG participants are
   employees of companies who are principal members of the ATM Forum.
   Requirements between the two organizations have been communicated
   informally by these participants.  With the establishment of the ATM
   Forum's Multiprotocol BOF activities, it has become prudent now to
   document IETF requirements in a more formal fashion.

   At the July 1994 meeting of the IETF in Toronto, Canada, a request
   was presented to the IP over ATM Working Group by the ATM Forum
   Liaison, Drew Perkins, for the working group to prepare a list of
   requirements as input to the ATM Forum's Multiprotocol BOF
   activities.  This document is a response to that request.







Laubach                                                         [Page 2]

RFC 1754         IPATM WG ATM Forum Recommendations V1      January 1995


4.  List of Requirements for Consideration

4.1  Standardization & Logistics

      - Formal communications between the IETF and the ATM Forum
        should be made via IETF <> ATM Forum Liaison(s), specific
        written communications (such as this document), and/or
        presentations made at official IETF or ATM Forum meetings.

      - IETF standards define how the TCP/IP protocol suite is defined,
        deployed, and carried over specific network technologies,
        including ATM networks [1][2][8].

      - Any formal communications that affect the IETF standards
        or processes must be made publicly available as the IETF is
        a public international standards body.  Ideally, such
        communications should be written as Internet Drafts [1], the
        IETF's equivalent to incoming contributions.

      - We invite and encourage ATM Forum members to participate in
        the IETF standards process.  See [1], [2], and [8] for
        information on how to participate.

4.2  IPv4 Encapsulation

      - RFC 1483 [3] and RFC 1577 [4] define how IP is encapsulated
        and carried over ATM networks.  The IPATM WG requests that any
        ATM Forum Multiprotocol work support these standards as
        specified, and that any future changes to them be made via the
        IETF standards process.

4.3 Routing

      - RFC 1577 defines the default Logical IP Subnet (LIS) model.

      - The IETF Routing over Large Clouds Working Group is developing
        the Next Hop Resolution Protocol, which allows the incremental
        optimization of routing (and subnets) by routing datagrams
        over preferential ATM paths [9].

      - The IETF IP over ATM Working Group will be working on the
        next generation IP over ATM standards after RFC 1577 moves
        from draft to proposed status.  Requirements to the ATM
        Forum will be forthcoming.

      - ATM signaling should give an indication of connection
        over LAN or WAN and include feedback of time vs byte
        charging.



Laubach                                                         [Page 3]

RFC 1754         IPATM WG ATM Forum Recommendations V1      January 1995


4.4  Security

      - ATM signaling should support a user information element
        that is used to convey security and authentication information
        between IP members and applications.  The IETF IPATM WG would
        like to define the IP specific content of this IE.

4.5  Broadcast and Multicast

      - The IPATM WG is currently discussing models of how best to map
        IP multicast facilities onto ATM facilities.  While this work is
        preliminary, the IETF does support the ATM Forum's currently
        planned multicasting enhancements, such as leaf-initiated joins
        and support of multiple multicast congestion management
        policies.  A further list of requirements will be presented at a
        later time.

4.6  Signaling and Addressing

      - The IPATM WG is currently producing a specification for using
        UNI 3.0 and 3.1 signaling to support RFCs 1483 and 1577.  This
        specification will be published as an informational reference
        for UNI 3.0 signaling, and as a proposed standard for UNI 3.1
        signaling following UNI 3.1's ratification and official
        publication.

      - IPv6 packets will include a Flow ID field intended to support
        service classes in some way. Until the semantics of this field
        are fully defined it is hard to say much, but presumably a soft
        mapping between this and the VC to be used is desirable.  A
        further list of requirements will be presented at a later time.

      - IPv6 addresses will be 16 bytes and there will likely be a
        defined embedding of them inside 20-byte NSAP format. There will
        also likely be a mapping of US-GOSIP-like NSAPs into IPv6
        addresses (deleting the unuseful bytes), but that is still
        controversial in the IPv6 discussions.  A further list of
        requirements will be presented at a later time.













Laubach                                                         [Page 4]

RFC 1754         IPATM WG ATM Forum Recommendations V1      January 1995


4.7  Quality of Service, Performance, and Traffic Management

      - ATM should support extremely bursty applications with
        significant elasticity in their bandwidth demands.

      - ATM should support elastic applications as defined in
        RFC-1633 [7] very efficiently.  That means enable high
        bottleneck utilization while keeping delay reasonably bounded
        (i.e., doubling delay wouldn't be terrible for elastic apps).
        This should not be at the expense of delay sensitive classes
        of service.

      - ATM should provide a a class of service which strives to
        cooperate with existing TCP congestion avoidance, thereby
        explicitly providing support not only for directly ATM-attached
        and -aware endstations, but also for endstations on LANs (or
        using LAN Emulation) that are using current TCP implementations
        and interconnected via ATM-attached bridges and routers.

      - Predictive QoS should be supported in addition to guaranteed QoS
        to support applications which are somewhat tolerant of delay
        variation and low levels of loss.

      - IP uses both point-to-point and point-to-multipoint (future)
        connections.  To satisfy IP's needs an ABR-like service
        would need to be applicable to both types of connections [6].

      - No specification of minimum or maximum bandwidths by the ATM
        end-systems [6].

      - As simple as possible [6].

      - Full line-rate transmission over otherwise-idle links [6].

      - When end-to-end delay through the network is less than 1 second,
        the cell loss for AAL5 frames over an ABR-like service should be
        on the order of 3 in 10**8 cells for 1500 byte frames, or 3 in
        10**9 cells for 18 Kbyte frames [6].

5.  Security Considerations

   Security issues raised in this memo will be addressed by the IETF IP
   over ATM Working Group and presented in subsequent updates to this
   memo.







Laubach                                                         [Page 5]

RFC 1754         IPATM WG ATM Forum Recommendations V1      January 1995


6.  Acknowledgement

   The basis of this memo is a summary of comments made on the email
   discussion list of the IP over ATM Working Group.  The contribution
   was reviewed by Drew Perkins and Andy Malis as a sanity check before
   submission to the ATM Forum.

7.  References

   [1]  IETF Secretariat and G. Malkin, "The Tao of the IETF - A Guide
        for New Attendees of the Internet Engineering Task Force",
        FYI 17, RFC 1718, CNRI, Xylogics, Inc., November 1994.

   [2]  Internet Architecture Board, and Internet Engineering Steering
        Group, "The Internet Standards Process -- Revision 2", RFC 1602,
        IAB, IESG, March 1994.

   [3]  Heinanen, J., "Multiprotocol Encapsulation over ATM Adaptation
        Layer 5", RFC 1483, Telecom Finland, July 1993.

   [4]  Laubach, M., "Classical IP and ARP over ATM", RFC 1577,
        Hewlett-Packard Laboratories, January 1994.

   [5]  Deering, S., "Host Extensions for IP Multicasting", STD 5,
        RFC 1112, Stanford University, August 1989.

   [6]  McCloghrie, K., "Lan-Emulation's Needs for Traffic Management",
        ATM-Forum/94-0533, ATM Forum, June 1994.

   [7]  Braden, R., Clark, D., and S. Shenker, "Integrated Services
        in the Internet Architecture: an Overview", RFC 1633,
        USC/Information Sciences Institute, MIT, Xerox PARC, June 1994.

   [8]  Postel, J., Editor, "Internet Official Protocol Standards",
        STD 1, RFC 1720, USC/Information Sciences Institute, July 1994.

   [9]  Malis, A., "Routing Over Large Clouds Liaison to the ATM Forum
        Multiprotocol BOF", ATM-Forum/94-0766, ATM Forum,
        September 1994.












Laubach                                                         [Page 6]

RFC 1754         IPATM WG ATM Forum Recommendations V1      January 1995


8.  IETF <> ATM Forum Liaison

   Drew Perkins
   FORE Systems, Inc.
   174 Thornhill Road
   Warrendale, PA 15086
   Phone: (412) 772-6527
   Fax:   (412) 772-6500
   Email: ddp@fore.com

9.  Author's Address

   Mark Laubach
   Com21, Inc.
   2113 Landings Drive
   Mountain View, CA 94043

   Phone: (415) 254-5882
   Fax:   (415) 254-5883
   EMail: laubach@com21.com































Laubach                                                         [Page 7]

