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IDR Working Group                                         R. Raszuk, Ed.
Internet-Draft                                             K. Patel, Ed.
Intended status: Standards Track                           Cisco Systems
Expires: September 25, 2010                               March 24, 2010

                         Transport Instance BGP


   BGP4 protocol is a well established single standard of an inter-
   domain routing and non-routing information distribution today.  For
   many applications it is also the protocol of choice to disseminate
   various application based information intra-domain.  It's popularity
   and it's wide use has been effectively provided by it's reliable
   transport, session protection as well as loop free build in

   It has been observed in both intra-domain as well as inter-domain
   applications that reliable information distribution is an extremely
   desired tool for many services.  Introduction of Multiprotocol
   Extensions to BGP even further attracted various sorts of new
   information to be carried over BGP4.

   The observation proves that amount and nature of information carried
   by BGP increases and diverges from the original goal of
   interconnection for IP Internet Autonomous Systems at a rather fast

   This draft proposes BGP to divide information into two broad
   categories: Internet routing critical and non Internet routing
   critical that would also include information carried by BGP which is
   not related directly to routing.  For the purpose of this document we
   will refer to the latter case as second BGP instance.

   This draft proposes that the current BGP infrastructure will continue
   to be used to disseminate Internet routing related information while
   non routing information or private routing data is recommended to be
   carried by independent transport instance BGP.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that

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   other groups may also distribute working documents as Internet-

   Internet-Drafts are draft documents valid for a maximum of six months
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   The list of current Internet-Drafts can be accessed at

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   This Internet-Draft will expire on September 25, 2010.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Contributors . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Today's operation  . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Related work . . . . . . . . . . . . . . . . . . . . . . . . .  6
   5.  Transport Instance Proposal  . . . . . . . . . . . . . . . . .  6
     5.1.  Router's resource separation . . . . . . . . . . . . . . .  7
     5.2.  Protocol changes . . . . . . . . . . . . . . . . . . . . .  7
     5.3.  AFI/SAFI numbering . . . . . . . . . . . . . . . . . . . .  7
     5.4.  BGP Identifier & BGP peering address . . . . . . . . . . .  8
     5.5.  IP Precedence  . . . . . . . . . . . . . . . . . . . . . .  8
   6.  Summary of benefits  . . . . . . . . . . . . . . . . . . . . .  9
   7.  Applications . . . . . . . . . . . . . . . . . . . . . . . . .  9
   8.  Security considerations  . . . . . . . . . . . . . . . . . . . 10
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   10. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 11
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 11
     11.2. Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12

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1.  Contributors

   The below is the list of contributors to this document:

      Bruno Decraene, France Telecom, 38 rue du General Leclerc, Issy
      Moulineaux cedex 9, France, Email:

      Jakob Heitz, Ericsson, 100 Headquarters Dr., San Jose, CA 95134,
      US Email: jheitz@redback.com

      Thomas D. Nadeau, BT, 81 Newgate Street, London, EC1A 7AJ, United
      Kingdom, Email: tom.nadeau@bt.com

      Jie Dong, Huawei Technologies Co.,Ltd, KuiKe Building, No.9 Xinxi
      Rd., Beijing, Hai-Dian District, 100085, P.R. China, Email:

      Yoshinobu Matsuzaki, Internet Initiative Japan Inc., Jinbocho
      Mitsui Bldg., 1-105 Kanda Jinbo-cho, Tokyo, Chiyoda-ku, Japan,
      Email: maz@iij.ad.jp

2.  Introduction

   BGP4 [RFC4271] protocol is practically a single standard today for
   the distribution of an inter-domain routing information.  Under many
   applications it is also used as the protocol of choice when
   disseminating various application-based information intra-domain.
   It's popularity and it's wide use has been effectively provided by
   it's extensibility, reliable transport, session protection as well as
   built in loop prevention mechanisms.

   It has been observed in both intra-domain as well as inter-domain
   applications that reliable information distribution is an extremely
   desired tool for many applications.  The introduction of
   Multiprotocol extensions to BGP [RFC4760] made it appealing for new
   kinds of information to be carried over BGP4.

   While these extensions have proven to be useful, they however have
   increased the load of information as well as the type of information
   that BGP was originally envisioned to carry.

   This draft proposes BGP to divide information into two broad
   categories: Internet routing critical and non Internet routing
   critical.  The latter would also include information carried by BGP
   which is not related directly to routing.  For the purpose of this
   document we will refer to the latter case as second BGP instance.

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   This draft proposes that the current BGP infrastructure will continue
   to be used to disseminate Internet routing related information while
   non Internet routing information or private routing data are
   recommended to be carried by independent transport instance BGP.

   For all currently defined and deployed AFI/SAFIs the mapping on which
   plane of BGP (routing or transport) such information may be carried
   is left to the choice of the implementation flexibility and the
   operator's decision.  For all subsequent new AFI/SAFIs it is
   RECOMMENDED that implementations would have them supported on both
   instances and that authors of new specifications provide a guidance
   on which BGP plane they should be carried.  It is expected that both
   instances while running independently from each other will be
   executed from the same bgp code base.

   Authors would like to also observe that the idea of separation
   routing from non routing related information to be carried over
   routing protocol is not only limited to BGP.  As example one could
   notice proposed OSPF Transport Instance document
   [I-D.acee-ospf-transport-instance] where the idea of safely reusing
   reliable flooding has been recently proposed.  We do admit that it
   has also been some form of inspiration for this proposal.

   Another point of view in favor of BGP instance separation is the
   aspect of service protection.  One could see BGP process responsible
   for global routing due to it's global nature much more exposed to
   control plane errors and attacks then potentially private only BGP
   instance contained to one or few ASes, possibly under common
   administration.  In the same way one could also observe that by fully
   separating global Internet BGP from any local BGP based services the
   Internet itself can be fully isolated from any issues caused by local
   service provider's services.

3.  Today's operation

   In today's networks BGP4 operates per BGP specification [RFC4271].
   This model of operation has proven to have number of disadvantages
   when it comes to concurrent support of multiple applications when
   amount of transported number of entries is already non trivial, when
   is not bounded by application architecture and when it is
   continuously growing.

   There are many examples where major router vendors recommend to
   separate route reflectors into disjoined clusters so Internet routes
   are not affected by L3VPN routes and vice-versa.  To put things into
   right perspective one needs to observe that local per box scaling
   numbers have already reached millions of VPN routes.  Such scaling

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   provides real challenge for CPU as well as addressable memory space
   in 32-bit operating systems when all of such applications use single
   instance of BGP.

   Another common complain is that by default all address families are
   carried today over single TCP session and any major protocol error or
   local system failure may results in full BGP instance reset affecting
   all applications carried between such pair of BGP speakers.

4.  Related work

   To address the session separation without forcing users to manually
   bound each session or group of session to a different BGP peering
   address Multisession BGP [I-D.scudder-bgp-multisession] solution has
   been proposed.  It is our opinion that Multisession BGP is an
   excellent tool to automatically bound selected group of applications
   to different TCP BGP sessions.  But this is only limited to session

   All BGP OPEN messages would still end up going to the same BGP TCP
   port number 179.  Furthermore, all the incoming sessions are handled
   by the same BGP process.  Even in distributed BGP systems today
   single speaker is still tasked to handle all address families
   exchanged with a set of peers it is serving.

   Multisession is an excellent way to easily separate different address
   families and bound them to different TCP sessions within each BGP
   instance.  Such separation would be done at the micro level (session
   level) while separation of BGP instances could be seen as macro level
   division (BGP process/thread, memory space, internal queuing and
   buffering etc ...).

5.  Transport Instance Proposal

   In order to minimize impact between different classes of applications
   carried today or to be carried by BGP in the future to those of
   critical nature for Internet connectivity, this draft proposes to run
   two separate instances of BGP one for each of them.

   The separation of concurrent, but not necessarily congruent BGP
   instances will be complete.  It will include both the router side and
   network side.

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5.1.  Router's resource separation

   There are many ways in modern router's operating systems to separate
   threads or processes running under single operating system from each

   We will leave the details to the implementation, but it is assumed
   that any implementation which complies with this document will allow
   to differentiate the amount of control plane CPU processing time
   allowed for specific BGP instance in it's scheduler's prioritization.
   It is recommended that prioritization of one instance over another in
   terms of CPU processing will be left to the local operator's
   decision.  The proposed separation may also very much allow to run
   each BGP instance on separate core of multi core CPU or different RP
   where applicable.

   It is also observed that such instance isolation will allow to use
   memory separation as well as different LC/RP communication channels/
   queues resulting in even greater instance isolation and minimizing
   any potential impact between one another.

5.2.  Protocol changes

   The proposed here Transport Instance BGP does not require any changes
   to BGP4 protocol mechanism, state machine, error handling or
   operation.  The exact same procedures and semantics apply in the same
   way for routing instance as well as transport instance BGP.  The
   operational advantage in the instance separation is the ability to
   apply different Hold Time interval in each instance fitting to the
   operator's needs.

   The only protocol change proposed in this document is the new TCP
   port number Transport Instance BGP will be waiting on for BGP OPEN
   Messages.  Such new port number is to be allocated by IANA.

5.3.  AFI/SAFI numbering

   With the introduction of MP-BGP extension to BGP [RFC4760] protocol
   has been enhanced with the ability to carry different sets of
   information each separated by it's own AFI/SAFI value as listed in
   IANA's Subsequent Address Family Identifiers (SAFI) registry.

   For Transport Instance BGP authors decided not to create a new IANA
   registry which would specify new SAFI pool.  Instead we recommend
   that single AFI/SAFI pool to be used by both BGP instances.

   The main motivation for this choice is to prevent any confusion on
   which SAFIs are allowed to be transported over which BGP instance as

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   well as to allow for customer configuration choice based on the
   actual network needs and amount of information carried in each
   address family.

   Another valid reason for single SAFI pool and no SAFI bonding to any
   particular BGP instance is the easy migration requirement from one
   instance to the other in smooth and not service impacting fashion.
   In order to perform such migration between instances operator will be
   free to run during a migration window given address family on both
   instances and when the target instance already populates the
   application database with the data terminate the originally deployed
   distribution of such information.  Such process is bi-directional ie.
   rollback can be also supported gracefully.

5.4.  BGP Identifier & BGP peering address

   When running both independent instances on the same platform question
   arises on the recommended choice for BGP Identifier
   [I-D.ietf-idr-bgp-identifier] as well as BGP peering address to be

   It needs to be observed that since via different BGP OPEN TCP port
   number and then different session ports if only implementation allows
   there is no requirement this specification would enforce to make any
   of those different between both instances.

   Never the less this draft would like to encourage that such freedom
   of choice is given to the network administrator and that any dual
   instance BGP implementation should accommodate it.

   Another advantage of sharing the same peering address of BGP sessions
   between instances is that in the event of operator's choice to use
   fast failure detection tools like BFD [I-D.ietf-bfd-base] the same
   event can be passed to both instances without any additional need to
   run two parallel and independent BFD sessions.

5.5.  IP Precedence

   On the network side all today's BGP messages are send with IP
   precedence value of Internetwork Control of 110000, which is used for
   high-priority routing traffic.

   Transport Instance BGP SHOULD use as default the same IP precedence,
   but implementations MAY allow configuring a different one to reflect
   the real purpose of the new BGP instance.

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6.  Summary of benefits

   Below is a combined list of main benefits provided by Transport
   Instance BGP:

      Mutual isolation and independence from protocol or process
      failures caused by any instance.

      Independence in: CPU usage, memory space and internal router

      Different port for BGP OPEN messages allowing the same BGP
      router_id or peering address sharing between instances.

      Different and fully isolated TCP sessions between instances.  Each
      instance may still benefit from multisessions BGP proposal within
      each instance.

      Possibility of different IP precedence BGP message marking for
      more fair and accurate PHB treatment.

      Open platform for carrying non Internet routing information or
      easy migration path with minimized risk to current BGP
      infrastructure in new emerging Internet architecture's
      hierarchical model.

   The technique here is quite general.  If, in the future, it is found
   that there is a clearly definable need for yet more separate
   transports, additional RFCs can be written defining the applicability
   and the TCP/SCTP port number to be used.

7.  Applications

   As examples one may notice that carrying router names for easy
   operational enhancement, carrying free form ADVISORY
   [I-D.scholl-idr-advisory] Messages or adding flexibility to auto
   discover IBGP peers [I-D.raszuk-idr-ibgp-auto-mesh] fit nicely into
   Transport Instance BGP.

   Another group of potential candidates for Transport Instance BGP
   could be any type of auto discovery mechanism for other applications.
   For example: L2VPN/VPLS or MVPN Auto Discovery
   [I-D.ietf-l3vpn-2547bis-mcast] are possible candidates.

   Along the same lines a service provider may also choose to use
   Transport Instance BGP to distribute information about L3VPN route
   targets as described in RFC4684 [RFC4684].

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   Another class of applications perfectly fitting the separate BGP
   instance model for it's global information distribution authors
   foresee a mapping plane of identifiers to locators in the new
   evolving internet architecture.  As example LISP-ALT
   [I-D.fuller-lisp-alt] or APT [I-D.jen-apt] are already calling to use
   BGP as a mapping plane protocol to simplify initial deployment.
   While it is foreseen that in the future those may migrate to better
   distribution schemes for example LISP-DHT to get enough of initial
   traction and momentum a Transport Instance BGP seems like a very good
   match to the mapping plane requirements.

   One may observe that Service Providers may choose to deploy a new
   instance of BGP to carry their critical services (example L3VPNs)
   over it for full isolation from Internet BGP.  In such application
   they will be able to prioritize such instance according to their
   internal policy and offered services prioritization.

   Last, but not least to recommend to be enabled on transport instance
   BGP is RFC5512 [RFC5512] BGP Encapsulation SAFI and BGP Tunnel
   Encapsulation Attribute.

8.  Security considerations

   Transport Instance BGP proposed in this document does not introduce
   any new security concerns as compared to base BGP4 specification
   [RFC4271].  Also all security work applicable to base routing
   instance BGP does also apply as is to transport instance BGP.

9.  IANA Considerations

   The new TCP port number for Transport Instance BGP are to be
   allocated by IANA from WELL KNOWN PORT NUMBERS registry.

   bgp-ti xxx/tcp BGP Transport Instance

   While routing instance BGP has also been allocated UDP port 179
   authors see no particular reason for UDP port allocation for BGP.

   The new SCTP port number for Transport Instance BGP are to be
   allocated by IANA from WELL KNOWN PORT NUMBERS registry.

   bgp-ti xxx/sctp BGP Transport Instance

   Specification to use BGP over SCTP can be found here

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10.  Acknowledgments

   The authors would like to thank Randy Bush, Tom Scholl and Joel
   Halpern for their valuable comments.

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              January 2007.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

11.2.  Informative References

              Lindem, A., Roy, A., and S. Mirtorabi, "OSPF Transport
              Instance Extensions",
              draft-acee-ospf-transport-instance-03 (work in progress),
              February 2009.

              Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "LISP
              Alternative Topology (LISP+ALT)", draft-fuller-lisp-alt-05
              (work in progress), February 2009.

              Katz, D. and D. Ward, "Bidirectional Forwarding
              Detection", draft-ietf-bfd-base-11 (work in progress),
              January 2010.

              Chen, E. and J. Yuan, "AS-wide Unique BGP Identifier for
              BGP-4", draft-ietf-idr-bgp-identifier-11 (work in
              progress), February 2010.


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              Aggarwal, R., Bandi, S., Cai, Y., Morin, T., Rekhter, Y.,
              Rosen, E., Wijnands, I., and S. Yasukawa, "Multicast in
              MPLS/BGP IP VPNs", draft-ietf-l3vpn-2547bis-mcast-10 (work
              in progress), January 2010.

              Jen, D., Meisel, M., Massey, D., Wang, L., Zhang, B., and
              L. Zhang, "APT: A Practical Transit Mapping Service",
              draft-jen-apt-01 (work in progress), November 2007.

              Raszuk, R., "IBGP Auto Mesh",
              draft-raszuk-idr-ibgp-auto-mesh-00 (work in progress),
              June 2003.

              Scholl, T. and J. Scudder, "BGP Advisory Message",
              draft-scholl-idr-advisory-00 (work in progress),
              March 2009.

              Scudder, J. and C. Appanna, "Multisession BGP",
              draft-scudder-bgp-multisession-00 (work in progress),
              November 2003.

              Fang, K. and F. Cai, "BGP-4 message transport over SCTP",
              draft-zhiyfang-fecai-bgp-over-sctp-00 (work in progress),
              May 2009.

   [RFC4684]  Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
              R., Patel, K., and J. Guichard, "Constrained Route
              Distribution for Border Gateway Protocol/MultiProtocol
              Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
              Private Networks (VPNs)", RFC 4684, November 2006.

   [RFC5512]  Mohapatra, P. and E. Rosen, "The BGP Encapsulation
              Subsequent Address Family Identifier (SAFI) and the BGP
              Tunnel Encapsulation Attribute", RFC 5512, April 2009.

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Authors' Addresses

   Robert Raszuk (editor)
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA  95134

   Email: raszuk@cisco.com

   Keyur Patel (editor)
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA  95134

   Email: keyupate@cisco.com

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