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Malloc Working Group                                      Roger Kermode
Internet Engineering Task Force                           Motorola
INTERNET-DRAFT
8 November 1998
Expires 8 May 1999

                Scoped Address Discovery Protocol (SADP)
                      <draft-ietf-mboned-sadp-00.txt>

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 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 material or to
   cite them other than as a "work in progress".

Abstract

   This document defines a protocol, the Scoped Address Discovery
   Protocol (SADP), for discovering the scoped multicast address(es)
   associated with a session at particular scopes within a
   hierarchically nested set of multicast zones. SADP is designed to
   work within the context of Multicast Address Allocation Architecture
   [MAAA] consisting of the MZAP [MZAP], MASC [MASC], and AAP [AAP]
   protocols. It is intended that SADP will provide the necessary
   general services for reliable multicast and searching applications to
   use expanding-zone searches in lieu of the well known, but less
   efficient expanding-ring search.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.














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Contents

   Abstract. . . . . . . . . . . . . . . . . . . . . . . . .    1

   1.  Introduction. . . . . . . . . . . . . . . . . . . . .    3

   2.  Overview. . . . . . . . . . . . . . . . . . . . . . .    4

   3.  Usage . . . . . . . . . . . . . . . . . . . . . . . .    5
     3.1 Session Identifiers . . . . . . . . . . . . . . . .    6
     3.2 Session Member Operation. . . . . . . . . . . . . .    6
     3.3 SADP Server Operation . . . . . . . . . . . . . . .    7

   4.  Packet Formats. . . . . . . . . . . . . . . . . . . .    8
     4.1 SADP Request. . . . . . . . . . . . . . . . . . . .   10
     4.2 SADP Response . . . . . . . . . . . . . . . . . . .   10

   5.  Constants . . . . . . . . . . . . . . . . . . . . . .   11

   6.  Security Considerations . . . . . . . . . . . . . . .   12

   7.  Acknowledgements. . . . . . . . . . . . . . . . . . .   12

   8.  References. . . . . . . . . . . . . . . . . . . . . .   12

   9.  Author's Address. . . . . . . . . . . . . . . . . . .   13

   10. Full Copyright Statement. . . . . . . . . . . . . . .   13























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1. Introduction

   Administrative scoping [RFC2365] provide a useful means for limiting
   the spread of IP multicast traffic acros the Internet. Unlike Time-
   To-Live (TTL) scoping, administrative scoping provides the means to
   ensure that, for a given scope and ignoring packet loss, the same set
   of nodes will receive a message, regardless of which node sent the
   message. Thus, the use of administrative scoping greatly simplifies
   the design of multicast protocols that require localization, since
   the non-reception of sent packets is solely due to loss and not
   design.

   The Multicast Zone Announcement Protocol (MZAP) [MZAP] will provide
   applications with the means for discovering the various scopes that
   are locally visible at each point in the Internet. In addition, MZAP
   will also provide the means for determining and announcing which
   scope zones completely encapsulate others. This additional ability
   will allow scope zones to be arranged into hierarchies which
   applications can then used expanding zone searches instead of less
   efficient and more problematic expanding-ring (TTL) searches. One
   example of how expanding-zone searches provide increased localization
   can be found in the Scoped Hybrid Automatic Repear reQuest with
   Forward Error Correction (SHARQFEC) reliable multicast protocol
   [SHARQFEC].

   While expanding-ring searches use one multicast address and
   increasing TTLs, expanding-zone searches involve changing the
   multicast addresses for each attempt at a different scope. SADP
   builds upon the Multicast Address Allocation Architecture [MAAA] by
   adding a new service that allows applications to discover the
   relevant multicast address(es) associated with a session at each
   level in a hierarchy of scope zones.  SADP does not provide the means
   to allocate an address should one not be present for a session in a
   particular zone. In this case the application should use the Address
   Allocation Protocol (AAP) [AAP] to allocate a new address for the
   scope, which can then be announced to other application instances
   within the scope.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].










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2. Overview

   Administrative scoping affords the ability to create network
   partitions or zones in which multicast traffic addressed to one of a
   block of addresses assigned to that zone will be limited to that
   zone. The boundary of the zone is enforced by Zone Border Routers
   (ZBRs) that reside at the edges of the zone. ZBRs must be carefully
   configured so that traffic addressed within the zone does not pass
   outside the zone.  This can be a non trivial task, and hence the
   Multicast Zone Announcement Protocol (MZAP) [MZAP], which is used to
   announce the existence of zones, also provides the mechanisms to
   detect ZBR misconfigurations.

                     . . . . . . . . .   +B+------>
                    .                 . /
                   .                   *
                   .             <---+A*--------+C+--->
                    .                + .
                     .              /  .
                      .  Zone X <---  .
                       . . . . . . ...

  A, B, C - Routers  * - border interface    + - interface  . - border

          Figure 1: Admin scope zone border example

   Zones may be of different sizes and can also overlap. In addition to
   the services of zone announcement and fault detection, MZAP also
   provides mechanisms for determining and announcing the existence of
   zones that nest inside others as shown in Figure 2.

      +-----------+       +-----------+      +-------------+
      | zone a    |       | zone c    |      | zone e      |
      |   +------+|       |    +------+      |    . . . . .|..
      |   |zone b||       |    |zone d|      |    : zone f | :
      |   +------+|       |    |      |      |    :        | :
      +-----------+       +----+------+      +-------------+ :
                                                  :. . . . ..:

    (a) "Contained"    (b) "Common Border"  (c) "Overlap"
         zone b nests       zone d nests         zones e and f
         inside zone a      inside zone c        do not nest

               Figure 2: Zone nesting examples

   This feature allows admin scope zones to be arranged in a hierarchy
   as shown in Figure 3. The ability to nest admin scope zones in
   hierarchies like that shown in Figure 3 is useful since it affords



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   localization through expanding-zone searches. For example, consider a
   distributed application with session members distributed evenly
   through out zone a. A session member in zone e, would perform a
   search by multicasting a query within zone e, and if unsuccessful,
   expand the scope to search in zone b, and eventually zone a if so
   needed.

         . . . . . . . . . . . . . . . . ..
        .             zone a               .      Zone Boundaries
       .                                    .      . = zone  a
      .  ______________       ______________ .     - = zones b,c
      . /    zone b    \     /   zone c     \ .    # = zones d,e,f, & g
      .|                |   |                |.
      .|  ####    ####  |   |  ####    ####  |.
      .| #zone#  #zone# |   | #zone#  #zone# |.
       .\ # d #  # e  # |   | # f  #  #  g # /.
        .\ ###    #### /     \ ####    #### /.
         .\___________/       \____________/.
          . . . . . . . . . . . . . . . . ..

            Figure 3 : Zone Nesting Hierarchy example

   In order for expanding-zone searches to be feasible, session members
   must be able to determine two things:

   o which zones are involved in the hierarchy for a particular session.

   o what address(es) are to be used for communicating with other
     session members within the zones involved in the hierarchy.

   SADP affords the ability to discover this information by using a
   single multicast group at each scope [SADP-RELATIVE-GROUP] for
   communication between SADP servers and the members of various
   sessions. New members to a session use the channels provided by the
   addresses to query existing SADP servers and session members as to
   which specific zones are valid and which zones to use. Since there is
   only one multicast address used per zone for this purpose, members of
   a particular session will ignore traffic intended for members of
   another session.

3. Usage

   In this section we summarize how session members can use SADP to
   determine which admin zones are used by the session's hierarchy and
   also the address(es) within these zones that are used by the current
   session members should such addresses exist.





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3.1 Session Identifiers

   Each session that uses admin scoping will use a Globally Unique
   Session Identifier (GUSID) that will distinguish it from all other
   sessions. This GUSID will consists of a 128bit integer that is
   allocated dynamically using the process described in [UUID]. The
   GUSID will be allocated by the session creator and will be used to
   associate traffic with a particular session regardless of which
   multicast scoped address the traffic is sent to.

3.2 Session Member Operation

   Several predefined administrative scopes already exist [RFC2365]:

   o Link Local: Traffic is only carried across one physical link.

   o Local:      Traffic is restricted to a specific network region.

   o Global:     The entire multicast enabled network.

   By definition Link Local zones nest inside Local zone which in turn
   nests inside the Global zone. Other zones may exist between the local
   and global scopes. These zones are constructed by the union of two or
   more local zones and are announced to routers within their confines
   using MZAP [MZAP].

   The general algorithm that new members to a session should use to
   determine which zones and addresses are involved in the hierarchy for
   a particular session is as follows:

   1) Determine the GUSID, largest zone, and addresses for the largest
      zone for the session. (this task is beyond the scope of this
      document, but can be assumed to involve some kind of out-of-band
      communication.)

   2) Starting with the SADP group [SADP-RELATIVE-GROUP] for the
      local scope, issue a SADP Request (SADP_REQ) message
      containing the GUSID address.

   3) Wait for a response on the SADP [SADP-RELATIVE-GROUP] address
      for at least [SADP-REQ-TIMEOUT] seconds. If no response is
      heard increase the scope to the next largest zone and repeat step
      2. In cases where there are two non-nesting zones larger than the
      current try one zone and then the other, should the first zone not
      result in a reply.

   4) Continue steps 2) and 3) until the largest zone has been queried
      or a response has been heard.



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   In cases where the scope must be increased in order to find a session
   member that can reply, the new session member MAY decide to add
   levels to the hierarchy in order to increase localization for future
   session members. New session members that decide to take this step
   will use the existing addresses as discovered using SADP and request
   new ones using AAP [AAP].

   SADP servers and existing session members, upon hearing an SADP_REQ
   message from a new session member will issue an SADP Response
   (SADP_RESP) after waiting for a random amount of time (T) that is
   calculated as follows:

     Choose a random value X from a  uniform random interval [0:1]
     Let C = 256
     Set T = [SADP-SUPPRESSION-INTERVAL] log( C*X + 1) / log(C)

   Should a member receive a SADP_RESP before its timer it expires it
   SHALL suppress its own response. This method ensures that close to
   one session member will respond.

3.2 SADP Server Operation

   Were SADP to be deployed in a wide scale session with the members of
   various sessions to use SADP between each other it would quickly
   cause catastrophic congestion. The reason for this is that whenever a
   new node joined a sparsely populated session with a large maximum
   scope, it would inevitably end up sending SADP_REQs to every scope up
   until the largest scope. Thus the highly likely occurrence of having
   a global and continental scope zones combined with numerous sparse
   sessions (probably on the order of 10,000 to 100,000) would quickly
   cause SADP_REQ flooding at the continental scope.

   To address this shortcoming SADP allows, and in fact encourages, the
   deployment of SADP servers. These servers subscribe to the [SADP-
   RELATIVE-GROUP] for each zone they are in and cache the SADP_RESP
   messages they receive at each scope. Having cached and merged the
   responses for sessions at various scopes, they can then respond to
   SADP_REQs heard at lower scopes using the information heard at the
   larger scope(s). Should a SADP server hear a SADP_REQ at some
   intermediate scope it MUST NOT announce address information for
   scopes smaller than one on which the SADP_REQ was received.

   The effect of allowing larger-scoped information to be announced at
   lower scopes by SADP servers significantly reduces the number of
   scopes a new session will have to query. New session members now need
   only expand the scope until a SADP server is found. This is a marked
   improvement over the case where no SADP servers exist and the search
   must continue until an existing session member is found.



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               Scope b Boundary
      Scope a        :  Scope a and Scope b
     _________       :      ____________                _____________
    /         \      :     /            \              /             \
    |Source at| _____:___\ |SADP Server | /___________ | New Session |
    |Scope a  | SADP_RESP/ | Scopes a,b | \ SADP_REQ   | Member      |
    \_________/      :     \____________/ ___________\ | Scopes a,b  |
                     :                      SADP_RESP/ \_____________/
                     :

         Figure 4 : SADP Server acting as proxy session member

4. Packet Formats

   All SADP messages are sent over UDP, with a destination port of
   [SADP-PORT]. THe common SADP message header (which follows the UDP
   header), is shown below,

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Version    |     PTYPE     |NumScop|AddrFam|    NameLen    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Message Origin                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Session ID (Hi)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Session ID (Mid Hi)                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Session ID (Mid Lo)                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Session ID (Lo)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Session Name                         |
   +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |     Padding (if needed)       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Authentication Block
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Version: 8 bits
      The version defined in this document is version 0.

   Packet Type (PTYPE): 8 bits
      The packet types defined in this document are:
         0: SADP Request
         1: SADP Response




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   Number of Scope Entries (NumScop) : 4 bits
      The number of scope entries present within a SADP_RESP message.
      This field should be set to zero for SADP_REQ messages.

   Address Family (AddrFam): 4 bits
      This indicates the format of the following packet.  The following
      values are defined by this document:
          0: IPv4
          1: IPv6

   Message Origin: 32 bits (IPv4) or 128 bits (IPv6)
      This gives the IP address of the interface that originated the
      message.

   Session ID Address: 128 bits
      This 128 bit number uniquely identifies a session.

   Name Len:
      The length, in bytes, of the Session Name field.

   Session Name: multiple of 8 bits
      The Zone Name is an ISO 10646 character string in UTF-8 encoding
      [RFC2279] indicating the name given to the session (e.g.:
      ``42ndIETF-Chicago''). It should be relatively short and MUST be
      less than 256 bytes in length. All the session members SHOULD be
      configured to give the same Session Name, or a zero length string
      MAY be given.  A zero length string is taken to mean that another
      session member is expected to be configured with the session
      name. Having ALL the members of a session announce zero length
      names should be considered an error.

   Padding (if needed):
      The SADP header is padded with null bytes until it is 4-byte
      aligned.

   Authentication Block:
      The Authentication Block provides information which can be used
      to confirm that the sender of the SADP message is a valid member
      of the session. Session Members that cannot confirm that the
      sender of an SADP Request Message MAY ignore it, while new
      session members that receiver an SADP Response Message MUST
      ignore it. (the format of the authentication block is to be
      decided)








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4.1 SADP Request

   SADP Request (SADP_REQ) Messages have PTYPE=0, and are sent by new
   session members that wish to learn which administrative scopes and
   multicast addresses to use within a particular session. SADP_REQ
   Messages are sent according to the algorithm described in 3.2.

4.2 SADP Response

   The SADP Response (SADP_RESP) Message has PTYPE=1, and is sent in
   response to a SADP_REQ Message. It contains the list of address that
   are to be used by a session within each scope. Session members that
   transmit SADP Response Messages MUST NOT include zone and address
   information for scopes known to be smaller that of the address upon
   which the triggering SADP Request Message was received.

   The format for a SADP Response Message is shown below:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                              MSADP Header
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |  MBZ  | SCOP  |  NumSessAddr  |            MBZ                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Zone Start Address 1                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Zone Stop Address 1                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Zone 1 Session Address 1                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                             . . . . . . .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Zone 1 Session Address K                  |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |  MBZ  | SCOP  |  NumSessAddr  |            MBZ                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Zone Start Address N                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Zone Stop Address N                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Zone N Session Address 1                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                             . . . . . . .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Zone N Session Address L                  |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+




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   SCOP : 4 bits
       The SCOP value associated with the zone as defined in RFC 1884
       [RFC1884] for IPv6 and RFC 2365 [RFC2365] for IPv4.

   NumSessAddr : 8 bits
       The number of session address per scope zone that are included.
       Addresses will be listed in ascending order. The correspondence
       between address and channel function is the responsibility of
       the session application.

   MBZ :
       Must Be Zero, these bits must be set to zero, but may be used
       for other functions later revision of the protocol.

   Zone X Start Address : 32 bits (IPv4) or 128 bits (IPv6)
       The smallest address for the block of multicast addresses
       associated with a zone. If a zone X is valid for the range
       239.128.0.0 to 239.128.255.255, this field will be set to
       239.128.0.0.

   Zone X Stop Address : 32 bits (IPv4) or 128 bits (IPv6)
       The largest address for the block of multicast addresses
       associated with a zone. If a zone X is valid for the range
       239.128.0.0 to 239.128.255.255, this field will be set to
       239.128.255.255.

   Zone X Session Address Y : 32 bits (IPv4) or 128 bits (IPv6)
       Up to Y address may be included for a zone address entry, where
       Y is equal to the NumSessAddr value for entry X.

5. Constants

   [SADP-RELATIVE-GROUP]: The relative group with each scope zone, to
   which session members send SADP Requests and Responses. All sessions
   that use administratively scoped multicast MUST subscribe to this
   address.

   [SADP-REQ-TIMEOUT]: The time after which a session member that sends
   SADP Request should wait before concluding that no session members
   are present at the current scope. Default value is 3 seconds.

   [SADP-SUPPRESSION-INTERVAL]: The interval over which a session member
   chooses a random delay before responding to SADP Request. Default
   value 2 seconds.







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6. Security Considerations

   SADP employs distributed mechanisms to allow new session members to
   learn of the existence of session-specific admin scoped multicast
   address. This fact lay SADP open to attack by malicious hosts that
   could potentially mis-inform new session members of incorrect
   addresses, thereby affecting a man-in-the-middle attack.

   To prevent attacks of this nature by non-session members from
   occurring all SADP messages are signed by the sender. However, this
   measure does not prevent malicious hosts from joining a session and
   then performing the same attack. Hence, SADP's security depends upon
   a suitable gating process for new-member admittance combined with (as
   yet to be determined) mechanisms that allow spoofed SADP messages to
   be identified for removal before processing.


7. Acknowledgments

   The Author would like to acknowledge Mark Handley and Dave Thaler for
   the helpful discussions and feedback which helped shape and refine
   this document.

8. References

   [AAP]      Handley, M., "The Address Allocation Protocol", Internet
              Draft, August 1998.

   [MAAA]     Handley, M., Thaler, D., and D. Estrin, "The Internet
              Multicast Address Allocation Architecture", Internet
              Draft, December 1997.

   [MZAP]     Handley, M., Thaler, D., "Multicast-Scope Zone
              Announcement Protocol (MZAP)",
              draft-ietf-mboned-mzap-02.txt, Internet-Draft, August,
              1998.

   [RFC1884]  Hinden, R., Deering, S., "IP Version 6 Addressing
              Architecture", RFC 1884, December 1995.

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

   [RFC2279]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", RFC 2279, January 1998.

   [RFC2365]  Meyer, D., "Administratively Scoped IP Multicast", BCP,
              RFC 2365, July 1998.



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   [SHARQFEC] Kermode, R., "Scoped Hybrid Automatic Repeat reQuest with
              Forward Error Correction (SHARQFEC)", ACM SIGCOMM98,
              Vancouver Canada, September 1998.

   [UUID]     Leach, J., Salz, R., "UUIDs and GUIDs",
              draft-leach-uuids-guids-01.txt, Internet-Draft, February,
              1998.


9. Author's Address

   Roger Kermode
   Motorola
   Chicago Corporate Research Laboratories
   1301 East Algonquiin Rd, MS IL02-2712
   Schaumburg, IL 60196

   Phone: (847) 538 4587
   Email: ark008@email.mot.com


10. Full Copyright Statement

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it or
   assist in its implementation may be prepared, copied, published and
   distributed, in whole or in part, without restriction of any kind,
   provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works. However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of developing
   Internet standards in which case the procedures for copyrights defined
   in the Internet languages other than English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT
   NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN
   WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."





Kermode                                                        [Page 13]


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