INTERNET-DRAFT                               Danny McPherson
draft-mcpherson-bgp4-experience-00.txt           Keyur Patel
Category                                       Informational
Expires: October 2003                             April 2003


                   Experience with the BGP-4 Protocol
                <draft-mcpherson-bgp4-expereince-00.txt>



Status of this Document

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.


   This document is a product of an individual.  Comments are solicited
   and should be addressed to the author(s).

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.












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                                Abstract


   The purpose of this memo is to document how the requirements for
   advancing a routing protocol from Draft Standard to full Standard
   have been satisfied by Border Gateway Protocol version 4 (BGP-4).

   This report satisfies the requirement for "the second report", as
   described in Section 6.0 of RFC 1264.  In order to fulfill the
   requirement, this report augments RFC 1773 and describes additional
   knowledge and understanding gained in the time between when the
   protocol was made a Draft Standard and when it was submitted for
   Standard.






































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                           Table of Contents


   1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .   4
   2. BGP-4 Overview . . . . . . . . . . . . . . . . . . . . . . . .   4
    2.1. A Border Gateway Protocol . . . . . . . . . . . . . . . . .   4
    2.2. BGP version 2 . . . . . . . . . . . . . . . . . . . . . . .   5
    2.3. BGP version 3 . . . . . . . . . . . . . . . . . . . . . . .   5
    2.4. BGP version 4 . . . . . . . . . . . . . . . . . . . . . . .   6
   3. Management Information Base (MIB). . . . . . . . . . . . . . .   7
   4. Implementations. . . . . . . . . . . . . . . . . . . . . . . .   7
   5. Operational Experience . . . . . . . . . . . . . . . . . . . .   8
   6. Metrics. . . . . . . . . . . . . . . . . . . . . . . . . . . .   9
    6.1. MULTI_EXIT_DISC (MED) . . . . . . . . . . . . . . . . . . .   9
     6.1.1. Sending MEDs to BGP Peers. . . . . . . . . . . . . . . .  10
     6.1.2. MED of Zero Versus No MED. . . . . . . . . . . . . . . .  10
     6.1.3. MEDs and Temporal Route Selection. . . . . . . . . . . .  10
   7. LOCAL_PREF . . . . . . . . . . . . . . . . . . . . . . . . . .  10
   8. Internal BGP In Large Autonomous Systems . . . . . . . . . . .  11
   9. Internet Dynamics. . . . . . . . . . . . . . . . . . . . . . .  12
   10. BGP Routing Information Bases (RIBs). . . . . . . . . . . . .  12
   11. Update Packing. . . . . . . . . . . . . . . . . . . . . . . .  13
   12. Limit Rate Updates. . . . . . . . . . . . . . . . . . . . . .  13
   13. Ordering of Path Attributes . . . . . . . . . . . . . . . . .  14
   14. AS_SET Sorting. . . . . . . . . . . . . . . . . . . . . . . .  14
   15. Control over Version Negotiation. . . . . . . . . . . . . . .  14
   16. Reciept of Non-Transitive Attributes from eBGP
   Peer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  14
   17. Security Considerations . . . . . . . . . . . . . . . . . . .  15
    17.1. TCP MD5 Signature Option . . . . . . . . . . . . . . . . .  15
    17.2. BGP Over IPSEC . . . . . . . . . . . . . . . . . . . . . .  15
    17.3. Miscellaneous. . . . . . . . . . . . . . . . . . . . . . .  16
    17.4. Acknowledgements . . . . . . . . . . . . . . . . . . . . .  16
   18. References. . . . . . . . . . . . . . . . . . . . . . . . . .  17
   19. Authors' Addresses. . . . . . . . . . . . . . . . . . . . . .  18
   20. Full Copyright Statement. . . . . . . . . . . . . . . . . . .  18















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1.  Introduction


   The purpose of this memo is to document how the requirements for
   advancing a routing protocol from Draft Standard to full Standard
   have been satisfied by Border Gateway Protocol version 4 (BGP-4).

   This report satisfies the requirement for "the second report", as
   described in Section 6.0 of RFC 1264.  In order to fulfill the
   requirement, this report augments RFC 1773 and describes additional
   knowledge and understanding gained in the time between when the
   protocol was made a Draft Standard and when it was submitted for
   Standard.



2.  BGP-4 Overview


   BGP is an inter-autonomous system routing protocol designed for
   TCP/IP internets.  The primary function of BGP is to exchange network
   reachability information with other BGP systems.  This information is
   sufficient to construct a graph of loop-free AS connectivity and some
   policy decisions at the AS level may be enforced.

   The initial version of the BGP protocol was published in RFC 1105.
   Since then BGP Versions 2, 3, and 4 have been developed and are
   specified in [RFC 1163], [RFC 1267], and [RFC 1771], respectively.
   Changes since BGP-4 went to Draft Standard [RFC 1771] are listed in
   Appendix N of [BGP4].



2.1.  A Border Gateway Protocol


   BGP [RFC 1105]

   Appendix D of [BGP4] Comparison with 1105:

    o Changes to FSM to accommdate BSD 4.3 TCP UI.
    o Notion of Up/Down/Horizontal relations have been removed.
    o Message format changes:
      - Hold Timer removed from BGP Header and added to OPEN Message
      - Version field removed from BGP Header and added to OPEN Message
      - Link Type field removed from OPEN Message
      - OPEN CONFIRM message deprecated and replaced with implicit
        confirmation provided by KEEPALIVE message.



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      - UPDATE Message format changed.  New fields were added to
        support multiple path attributes.
      - The Marker field was expanded and its role broadened to
        support authentication



2.2.  BGP version 2


   BGPv2 [RFC 1163]

   Appendix C of [BGP4] Comparison with RFC 1163

    o BGP Identifier introduced to deal with collision detection.
    o Removed restriction that border router of NEXT_HOP path attribute
      had to be part of same AS.
    o Optimized and simplified exchange of information about reachable
      routes.

   BGP version 2 removed from the protocol the concept of "up", "down",
   and "horizontal" relations between autonomous systems that were
   present in version 1.  BGP version 2 introduced the concept of path
   attributes.  In addition, BGP version 2 clarified parts of the
   protocol that were "under-specified".



2.3.  BGP version 3


   BGPv3 [RFC 1267]

   Appendix B of [BGP4] Comparison with RFC 1267:

    o Set of destination via single IP prefix.  Concept of
      network classes, or subnetting is foreign to BGP-4.
      To accommodate these capabilities BGP-4 changes the
      semantics and encoding associated with the AS_PATH attribute.
      New text has been added to define semantics associated with
      IP Prefixes.  These abilities allow BGP to support the
      proposed supernetting scheme [RFC 1518] (BGP4 Draft reference
      to [9] needs to be fixed).
    o LOCAL_PREF intrduced to facilitate route selection procedures.
    o INTER_AS_METRIC renamed to MULTI_EXIT_DISC
    o ATOMIC_AGGREGATE introduced to ensure that certain aggregates
      are not deaggregated.
    o Introduced AGGREGATOR.



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    o Holdtimer neogtiation per-connection for symmetry.  Lower value
      used.  Hold Times of zero now supported.

   BGP version 3 lifted some of the restrictions on the use of the
   NEXT_HOP path attribute, and added the BGP Identifier field to the
   BGP OPEN message.  It also clarifies the procedure for distributing
   BGP routes between the BGP speakers within an autonomous system.



2.4.  BGP version 4


   BGP v4 [RFC 1771] [BGP4]

   Appendix A of [BGP4] Comparison with RFC 1771:

    o Changes to reflect use of the TCP MD5 Signature Option,
      Route Reflectors, AS Confederations for BGP and BGP Route
      Refresh.
    o Clarified use of BGP Identifier in AGGREGATOR Attribute
    o Procedures for imposing upper bound of prefixes a speaker will
      accept from a peer.
    o Ability to include more than one instance of it's own AS in the
      AS_PATH attribute for the purpose of inter-AS traffic engineering.
    o Clarified various types of NEXT_HOPS
    o Claried use of ATOMIC_AGGREGATE attribute
    o Discussed relationship be BGP NEXT_HOP attribute and immediate
      next hop.
    o Clarified tie-breaking procedures
    o Clarified route advertisement frequency text.
    o Deprecated Optional Parameter Type 1 (Authentication Information)
    o UPDATE Message Error subcode 7 (AS Routing Loop) deprecated.
    o Use of Marker field for authentication has been deprecated.


   BGP version 4 redefines the (previously defined class-based) network
   layer reachability portion of the updates to specify prefixes of
   arbitrary length in order to represent multiple classful networks in
   a single entry as discussed in [RFC 1519].  BGP version 4 has also
   modified the AS_PATH attribute so that sets of autonomous systems, as
   well as individual ASs may be described.  BGP version 4 has
   redescribed the INTER-AS METRIC attribute as the MULTI_EXIT_DISC and
   added new LOCAL_PREF and AGGREGATOR attributes.

   BGP version 4 defines procedures for imposing an upper bound on the
   number of prefixes that a BGP speaker may accept from its peer. BGP
   version 4 has modifed the AS_PATH attribute to have an ability to



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   include more than one instance of its own AS for the purpose of
   inter-AS traffic engineering.

   BGP version 4 deprecates the use of OPTIONAL PARAMETER Type 1
   (Authentication Information). BGP version 4 also depecates the use of
   UPDATE MESSAGE Error subcode 7 (AS Routing Loop).

   BGP version 4 provides clarifications on use of BGP Identifier in the
   AGGREGATOR attribute and use of the ATOMIC_AGGREGATOR attribute.  BGP
   version 4 also provides clarifications on various types of NEXT_HOPs,
   BGP tie-breaking procedures and frequency of route announcements in
   BGP.

   Possible applications of BGP in the Internet are documented in [RFC
   1772].

   The BGP protocol was developed by the IDR Working Group of the
   Internet Engineering Task Force. This Working Group had a mailing
   list, idr@merit.edu, where discussions of protocol features and
   operation are held. The IDR Working Group meets regularly during the
   Internet Engineering Task Force meetings.  Reports of these meetings
   are published in the IETF's Proceedings.




3.  Management Information Base (MIB)


   The BGP-4 Management Information Base (MIB) has been published [BGP-
   MIB].  The MIB was updated from previous versions documented in [RFC
   1657] and [RFC 1269], respectively.

   Apart from a few system variables, the BGP MIB is broken into two
   tables: the BGP Peer Table and the BGP Received Path Attribute Table.

   The Peer Table reflects information about BGP peer connections, such
   as their state and current activity. The Received Path Attribute
   Table contains all attributes received from all peers before local
   routing policy has been applied. The actual attributes used in
   determining a route are a subset of the received attribute table.



4.  Implementations


   There are numerous independent interoperable implementations of BGP



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   currently available.  Although the previous version of this report
   provided an overview of the implementations currently used in the
   operational Internet, at this time it has been suggested that a
   separate BGP Implementation Report [BGP-IMPL] be generated.

   It should be noted that implementation experience with Cisco's BGP-4
   implementation was documented as part of [RFC 1656].

   For all additional implementation information please reference [BGP-
   IMPL].



5.  Operational Experience


   This section discusses operational experience with BGP and BGP-4.

   BGP has been used in the production environment since 1989, BGP-4
   since 1993.  Production use of BGP includes utilization of all
   significant features of the protocol.  The present production
   environment, where BGP is used as the inter-autonomous system routing
   protocol, is highly heterogeneous.  In terms of the link bandwidth it
   varies from 64 Kbs to 10 Gbs.  In terms of the actual routes that run
   BGP it ranges from a relatively slow performance PC/RT to a very high
   performance RISC-based CPUs, and includes both the special purpose
   routers and the general purpose workstations running various UNIX
   derivatives and other operating systems.

   In terms of the actual topologies it varies from a very sparse to
   quite dense.  Full-mesh IBGP topologies have been largely mitigated
   by BGP Route Reflection [RFC 2796], Autonomous System Confederations
   for BGP [RFC 3065], or some combination of the two, in many networks.

   At the time of this writing BGP-4 is used as an inter-autonomous
   system routing protocol between ALL Internet-attached autonomous
   systems, with nearly 15k active autonomous systems in the global
   Internet routing table.

   BGP is used both for the exchange of routing information between a
   transit and a stub autonomous system, and for the exchange of routing
   information between multiple transit autonomous systems.  There is no
   protocol distinction between sites historically considered
   "backbones" versus "regional" networks.

   Within transit networks, BGP is typically used as the exclusive
   carrier of exterior routing information.




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   The full set of exterior routes that is carried by BGP is well over
   115,000 aggregate entries, representing several times that number of
   connected networks.  The number of active paths in some service
   provider core routers has exceeded 2 million.  Native AS_PATH lengths
   are as long as 10 for some routes, and "padded" path lengths of 25 or
   more ASs exist.



6.  Metrics


   This section discusses different metrics used within the BGP
   protocol. BGP has a seperate metric parameter for IBGP and EBGP. This
   allows policy based metrics to overwrite the distance based metrics;
   allowing each autonomous systems to define their independent policies
   in Intra-AS as well as Inter-AS. BGP Multi Exit Discriminator (MED)
   is used as a metric by EBGP peers while BGP Local Preference is used
   by IBGP peers.



6.1.  MULTI_EXIT_DISC (MED)


   BGP version 4 re-defined the old INTER-AS metric as a MULTI_EXIT_
   DISC (MED).  This value may be used in the tie-breaking process when
   selecting a preferred path to a given address space, and provides BGP
   speakers with the capability to convey to a peer AS the optimal entry
   point into the local AS.

   Although the MED was meant to only be used when comparing paths
   received from different external peers in the same AS, many
   implementations provide the capability to compare MEDs between
   different ASs as well.

   The MED was purposely designed to be a "weak" metric that would only
   be used late in the best-path decision process.  The BGP working
   group was concerned that any metric specified by a remote operator
   would only affect routing in a local AS if no other preference was
   specified.  A paramount goal of the design of the MED was ensure that
   peers could not "shed" or "absorb" traffic for networks that they
   advertise.








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6.1.1.  Sending MEDs to BGP Peers


   [BGP4] allows MEDs received from any EBGP peers by a BGP speaker to
   be passed to its IBGP peers.  Although advertising MEDs to IBGP peers
   is not a required behavior, it is a common default. MEDs received
   from EBGP peers by a BGP speaker MUST NOT be sent to other EBGP
   peers.



6.1.2.  MED of Zero Versus No MED


   An implementation MUST provide a mechanism that allows for MED to be
   removed.  Previously, implementations did not consider a missing MED
   value to be the same as a MED of zero.  No MED value should now be
   equal to a value of zero.



6.1.3.  MEDs and Temporal Route Selection


   Some implementations have hooks to apply temporal behavior in MED-
   based best path selection.  That is, all other things being equal up
   to MED consideration, preference would be applied to the "oldest"
   path, without preferring the lower MED value.  The reasoning for this
   is that "older" paths are presumably more stable, and thus more
   preferable.  However, temporal behavior in route slection results in
   non-deterministic behavior, and as such, is often undesirable.



7.  LOCAL_PREF


   The LOCAL_PREF attribute was added so a network operator could easily
   configure a policy that overrode the standard best path determination
   mechanism without independently configuring local preference policy
   on each router.

   One shortcoming in the BGP-4 specification was a suggestion for a
   default value of LOCAL-PREF to be assumed if none was provided.
   Defaults of 0 or the maximum value each have range limitations, so a
   common default would aid in the interoperation of multi-vendor
   routers in the same AS (since LOCAL_PREF is a local administration
   knob, there is no interoperability drawback across AS boundaries).



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   LOCAL_PREF MUST be sent to IBGP Peers.

   LOCAL_PREF Attribute MUST NOT be sent to EBGP Peers. (Handling
   errors)  Spec says Notification with Error Code UPDATE Message Error.

   The common default value for LOCAL_PREF is 100.  No default value is
   defined.

   Another area where more exploration is required is a method whereby
   an originating AS may influence the best path selection process.  For
   example, a dual-connected site may select one AS as a primary transit
   service provider and have one as a backup.


                    /---- transit B ----/\n
        end-customer                     transit A----
                   /---- transit C ----/


   In a topology where the two transit service providers connect to a
   third provider,  the real decision is performed by the third provider
   and there is no mechanism for indicating a preference should the
   third provider wish to respect that preference.

   A general purpose suggestion that has been brought up is the
   possibility of carrying an optional vector corresponding to the AS-
   PATH where each transit AS may indicate a preference value for a
   given route.  Cooperating ASs may then chose traffic based upon
   comparison of "interesting" portions of this vector according to
   routing policy.

   While protecting a given ASs routing policy is of paramount concern,
   avoiding extensive hand configuration of routing policies needs to be
   examined more carefully in future BGP-like protocols.



8.  Internal BGP In Large Autonomous Systems


   While not strictly a protocol issue, one other concern has been
   raised by network operators who need to maintain autonomous systems
   with a large number of peers.  Each speaker peering with an external
   router is responsible for propagating reachability and path
   information to all other transit and border routers within that AS.
   This is typically done by establishing internal BGP connections to
   all transit and border routers in the local AS.




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   In a large AS, this leads to a full mesh of TCP connections (n *
   (n-1)) and some method of configuring and maintaining those
   connections.  BGP does not specify how this information is to be
   propagated,  so alternatives, such as injecting BGP attribute
   information into the local IGP have been suggested.  Also, there is
   effort underway to develop internal BGP "route reflectors" or a
   reliable multicast transport of IBGP information which would reduce
   configuration, memory and CPU requirements of conveying information
   to all other internal BGP peers.

   BGP "Route Reflector" extensions has been defined in RFC 1966 to
   alleviate the the need for "full mesh" IBGP.



9.  Internet Dynamics


   As discussed in [BGP4-ANALYSIS], the driving force in CPU and
   bandwidth utilization is the dynamic nature of routing in the
   Internet.  As the net has grown, the number of route changes per
   second has increased.

   We automatically get some level of damping when more specific NLRI is
   aggregated into larger blocks, however this isn't sufficient.  In
   Appendix F of [BGP4] are descriptions of damping techniques that
   should be applied to advertisements.  In future specifications of
   BGP-like protocols,  damping methods should be considered for
   mandatory inclusion in compliant implementations.

   Route changes are announced using BGP UPDATE messages. The greatest
   overhead in advertising UPDATE messages happens whenever route
   changes to be announced are inefficiently packed.Announcing routing
   changes sharing common attributes in a single BGP UPDATE message
   [13.1] also helps save considerable bandwidth.

   Persistent BGP errors may cause BGP peers to flap persistently if
   peer dampening is not implemented. This would result in significant
   CPU utilization. Implementors may find it useful to implement peer
   dampening to avoid such persistent  peer flapping [BGP4].



10.  BGP Routing Information Bases (RIBs)


   [BGP4] states "Any local policy which results in routes being added
   to an Adj-RIB-Out without also being added to the local BGP speaker's



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   forwarding table, is outside the scope of this document".

   However, several well-known implementations do not confirm that Loc-
   RIB entries were used to populate the forwarding table before
   installing them in the Adj-RIB-Out.  The most common occurrence of
   this is when routes for a given prefix are presented by more than one
   protocol and the preferences for the BGP learned route is lower than
   that of another protocol.  As such, the route learned via the other
   protocol is used to populate the forwarding table.

   It may be desirable for an implementation to provide a knob that
   permits advertisement of "inactive" BGP routes.

   It may be also desirable for an implementation to provide a knob that
   allows a BGP speaker to advertise BGP routes that were not selected
   by descision process.



11.  Update Packing


   The BGP4 protocol permits advertisement of multiple prefixes with a
   common set of path attributes to be advertised in a single update
   message.  When possible, Update packing is recommended as it reduces
   overhead in receivers in terms of:

    o System overhead due to receipt of fewer Update messages.
    o Overhead for scanning the routing table for BGP Updates to
      its peers and other routing protocols (and the
      redistribution of this information as well).

   The BGP protocol suggests that withdrawal information should be
   packed in the begining of Update message along with information about
   more or less specific reachable routes in a single UPDATE message.
   This would help alleviate excessive route flapping in BGP.



12.  Limit Rate Updates


   The BGP protocol defines different mechanisms to rate limit the
   Updates. The BGP protocol defines MinRouteAdvertisementInterval
   parameter that determines the minimum time that must be elsape
   between the advertisement of routes to a particular destination from
   a single BGP speaker. This value is set on a per BGP peer basis.




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13.  Ordering of Path Attributes


   The BGP protocol suggests that BGP speakers sending multiple prefixes
   per an UPDATE message should sort and order path attributes according
   to Type Codes. This would help their peers to quickly identify sets
   of attributes from different update messages which are semantically
   different.

   Implementers may find it useful to order path attributes according to
   Type Code so that sets of attributes with identical semantics can be
   more quickly identified.



14.  AS_SET Sorting


   AS_SETs are commonly used in BGP route aggregation. They reduce the
   size of AS_PATH information by listing AS numbers only once
   regardless of any number of times it might appear in process of
   aggregation. AS_SETs are usually sorted in increasing order to
   facilitate efficient lookups of AS numbers within them. This
   optimization is entirely optional.



15.  Control over Version Negotiation


   Because pre-BGP-4 route aggregation can't be supported by earlier
   version of BGP, an implementation that supports versions in addition
   to BGP-4 should provide the version support on a per-peer basis.




16.  Reciept of Non-Transitive Attributes from eBGP Peer


   E.g., LOCAL_PREF, RR or confed, etc..

   NEEDS MORE WORK








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17.  Security Considerations


   BGP provides flexible and extendible mechanism for authentication and
   security.  The mechanism allows to support schemes with various
   degree of complexity.  All BGP sessions are authenticated based on
   the BGP Identifier of a peer.  In addition, all BGP sessions are
   authenticated based on the autonomous system number advertised by a
   peer.

   Since BGP runs over TCP and IP, BGP's authentication scheme may be
   augmented by any authentication or security mechanism provided by
   either TCP or IP.




17.1.  TCP MD5 Signature Option


   RFC 2385 defines a way in which the TCP MD5 signature option can be
   used to valid information transmitted between two peers.  This method
   prevents any third party from injecting information (e.g., a TCP RST)
   into the datastream, or modifying the routing information carried
   between two BGP peers.  RFC ???? provides suggestions for choosing
   passwords to be used with MD5.

   TCP MD5 is not ubiquitously deployed at the moment, especially in
   inter- domain scenarios, largely because of key distribution issues.
   Most key distribution mechanisms are considered to be too "heavy" at
   this point.



17.2.  BGP Over IPSEC


   BGP can run over IPSEC, either in a tunnel, or in transport mode,
   where the TCP portion of the IP packet is encrypted.  This not only
   prevents random insertion of information into the data stream between
   two BGP peers, it also prevents an attacker from learning the data
   which is being exchanged between the peers.

   IPSEC does, however, offer several options for exchanging session
   keys, which may be useful on inter-domain configurations.  These
   options are being explored in many deployments, although no
   definitive solution has been reach on the issue of key exchange for
   BGP in IPSEC.



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   It should be noted that since BGP runs over TCP and IP, BGP is
   vulnerable to the same denial of service or authentication attacks
   that are present in any other TCP based protocol.



17.3.  Miscellaneous


   Another issue any routing protocol faces is providing evidence of the
   validity and authority of the routing information carried within the
   routing system.  This is currently the focus of several efforts at
   the moment, including efforts to define the threats which can be used
   against this routing information in BGP [draft-murphy, attack tree],
   and efforts at providing a means to provide validation and authority
   for routing information carried within BGP [SBGP, soBGP and possibly
   ATT stuff].

   Should information as it relates to IRR derived prefix-based filters
   be included here?

   BTSH & RP Queuing...?




17.4.  Acknowledgements


   We would like to thank Paul Traina and Yakov Rekhter for authoring
   previous versions of this document.  We would also like to
   acknowledge Russ White for valuable feedback on this document.



















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18.  References


   [RFC 1105] Lougheed, K., and Rekhter, Y, "Border Gateway Protocol
              BGP", RFC 1105, June 1989.

   [RFC 1163] Lougheed, K., and Rekhter, Y, "Border Gateway Protocol
              BGP", RFC 1105, June 1990.

   [RFC 1264] Hinden, R., "Internet Routing Protocol Standardization
              Criteria", RFC 1264, October 1991.

   [RFC 1267] Lougheed, K., and Rekhter, Y, "Border Gateway Protocol 3
              (BGP-3)", RFC 1105, October 1991.

   [RFC 1519] Fuller, V., Li. T., Yu J., and K. Varadhan, "Classless
              Inter-Domain Routing (CIDR): an Address Assignment and
              Aggregation Strategy", RFC 1519, September 1993.

   [RFC 1656] Traina, P., "BGP-4 Protocol Document Roadmap and
              Implementation Experience", RFC 1656, July 1994.

   [RFC 1771] Rekhter, Y., and T. Li, "A Border Gateway Protocol 4
              (BGP-4)", RFC 1771, March 1995.

   [RFC 1772] Rekhter, Y., and P. Gross, Editors, "Application of the
              Border Gateway Protocol in the Internet", RFC 1772, March
              1995.

   [RFC 1773] Traina, P., "Experience with the BGP-4 protocol", RFC
              1773, March 1995.

   [RFC 2796] Bates, T., Chandra, R., and Chen, E, "Route Reflection -
              An Alternative to Full Mesh IBGP", RFC 2796, April 2000.

   [RFC 3065] Traina, P., McPherson, D., and Scudder, J, "Autonomous
              System Confederations for BGP", RFC 3065, Febuary 2001.

   [RFC 3345] McPherson, D., Gill, V., Walton, D., and Retana, A, "BGP
              Persistent Route Oscillation Condition", RFC 3345,
              August 2002.

   [BGP4-ANALYSIS] Work in Progress.

   [BGP4-IMPL] Work in Progress.

   [BGP4] Rekhter, Y., T. Li., and Hares. S, Editors, "A Border
          Gateway Protocol 4 (BGP-4)", BGP Draft, Work in Progress.



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19.  Authors' Addresses



   Danny McPherson
   Arbor Networks
   Email: danny@arbor.net

   Keyur Patel
   Cisco Systems
   Email: keyupate@cisco.com



20.  Full Copyright Statement

   Copyright (C) The Internet Society (2003). 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 Standards process must be
   followed, or as required to translate it into 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.










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