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Versions: 00 draft-ietf-idr-performance-routing

Network Working Group                                             X. Xu
Internet Draft                                                    H. Ni
Category: Standard Track                                         Huawei

                                                                 Y. Fan
                                                          China Telecom


Expires: June 2014                                    December 10, 2013


                  Performance-based BGP Routing Mechanism

                     draft-xu-idr-performce-routing-00

Abstract

   Network performance, especially network latency is widely recognized
   as one of major obstacles in adopting public cloud services (e.g.,
   cloud desktop service), especially in the scenario where the network
   paths between cloud end-users and cloud data centers traverse more
   than one Autonomous System (AS). However, the current Border Gateway
   Protocol (BGP) specification [RFC4271] doesn't use network
   performance metrics (e.g., network latency) in the route selection
   decisions. This document describes a performance-based BGP routing
   mechanism in which network latency metric is taken as one of the
   route selection criteria.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 10, 2014.







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Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with
   respect to this document.  Code Components extracted from this
   document must include Simplified BSD License text as described in
   Section 4.e of the Trust Legal Provisions and are provided without
   warranty as described in the Simplified BSD License.

Conventions used in this document

   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].

Table of Contents


   1. Introduction ................................................ 3
   2. Terminology ................................................. 3
   3. Performance Route Advertisement ............................. 4
   4. Capability Advertisement .................................... 5
   5. Performance Route Selection ................................. 5
   6. Deployment Considerations ................................... 6
   7. Security Considerations ..................................... 6
   8. IANA Considerations ......................................... 6
   9. Acknowledgements ............................................ 6
   10. References ................................................. 6
      10.1. Normative References .................................. 6
      10.2. Informative References ................................ 7
   Authors' Addresses ............................................. 7












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1. Introduction

   Network performance, especially network latency is widely recognized
   as one of major obstacles in adopting public cloud services (e.g.,
   cloud desktop service), especially in the scenario where the network
   paths between cloud users and cloud data centers traverse more than
   one Autonomous System (AS). However, the current Border Gateway
   Protocol (BGP) specification [RFC4271] doesn't use network
   performance metrics (e.g., network latency) in the route selection
   decisions. As such, the best route selected based upon the existing
   BGP route selection criteria may not be the best from the user
   experience perspective.

   This document describes a performance-based BGP routing mechanism in
   which network performance metrics are conveyed as additional path
   attributes of the Network Layer Reachability Information (NLRI) and
   used in the route selection decisions. So far it's only the network
   latency metric that would be used in the performance-based route
   selection decisions. Whether or not other network performance
   metrics (e.g., latency variation metric) should be considered as
   well would be discussed in a future version of this draft. To make
   the performance routing paradigm and the vanilla routing paradigm
   coexist, performance routes SHOULD be exchanged as labeled routes as
   per [RFC3107] while using a specified Subsequent Address Family
   Identifier (SAFI).

   Service providers deploying such mechanism in their networks could
   provide performance routing service as a value-added service to
   those users who are sensitive to network latency, while continually
   offering vanilla routing service to other users as before.

2. Terminology

   This memo makes use of the terms defined in [RFC4271].

   Network latency: indicates the amount of time it takes for a packet
   to traverse a given network path. Provided a packet was forwarded
   along a path which contains multiple links and routers, the network
   latency would be the sum of the transmission latency of each link
   (i.e., link latency), plus the sum of the internal delay occurred
   within each router (i.e., router latency) which includes queuing
   latency and processing latency. The sum of the link latency is also
   known as the cumulative link latency. In today's service provider
   networks which usually span across a wide geographical area, the
   cumulative link latency becomes the major part of the network
   latency since the total of the internal latency happened within each



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   high-capacity router seems trivial compared to the cumulative link
   latency. In other words, the cumulative link latency could
   approximately represent the network latency in the above networks.
   Furthermore, since the link latency is more stable than the router
   latency, such approximate network latency represented by the
   cumulative link latency is more stable. Therefore, if there was a
   way to calculate the cumulative link latency of a given network path,
   it is strongly RECOMMENDED to use such cumulative link latency to
   approximately represent the network latency. Otherwise, the network
   latency would have to be measured frequently by some means (e.g.,
   PING).

3. Performance Route Advertisement

   Performance routes SHOULD be exchanged between BGP peers by using a
   specified Subsequent Address Family Identifier (SAFI) of TBD.
   Meanwhile, these routes SHOULD be carried as labeled routes as per
   [RFC3107]. A BGP speaker SHOULD NOT advertise performance routes to
   a particular BGP peer unless that peer indicates, through BGP
   capability advertisement, that it can process update messages with
   the specified SAFI field.

   Network latency metric is attached to the performance routes as one
   additional path attribute, referred to as NETWORK_LATENCY path
   attribute, which is a well-known mandatory attribute. This attribute
   indicates the network latency in microseconds from the BGP speaker
   depicted by the NEXT_HOP path attribute to the address depicted by
   the NLRI prefix. The type code of this attribute is TBD, and the
   value field is 4 octets in length. In some abnormal cases, if the
   cumulative link latency exceeds the maximum value of 0xFFFFFFFF, the
   value field SHOULD be set to 0xFFFFFFFF.

   When distributing a selected performance route learnt from one BGP
   peer to another, unless this BGP speaker has set itself as the
   NEXT_HOP of such route, the NETWORK_LATENCY path attribute of such
   route MUST NOT be modified. Otherwise when setting itself as the
   NEXT_HOP of such route, this BGP speaker SHOULD increase the value
   of the NETWORK_LATENCY path attribute by adding the network latency
   value from itself to the previous NEXT_HOP of such route. It's
   strongly RECOMMENDED to use the cumulative link latency from this
   BGP speaker to the NEXT_HOP to represent the network latency between
   them if possible. Otherwise, the measured network latency between
   them can be used instead. It's strongly RECOMMENDED that the type of
   network latency SHOULD be kept consistent across all these AS's
   (i.e., either cumulative link latency or measured network latency,
   choose one).




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   As for how to obtain the network latency to a given BGP NEXT_HOP is
   outside the scope of this document. However, note that the path
   latency to the NEXT HOP SHOULD approximately represent the network
   latency of the exact forwarding path towards the NEXT_HOP. For
   example, if a BGP speaker uses a Traffic-Engineering (TE) Label
   Switching Path (LSP) from itself to the NEXT_HOP, rather than the
   shortest path calculated by Interior Gateway Protocol (IGP), the
   latency to the NEXT HOP SHOULD approximately reflect the network
   latency of that TE LSP path, rather than an IGP shortest path.

   To keep performance routes stable enough, a BGP speaker SHOULD use a
   configurable threshold of network latency fluctuation to suppress
   any update which would otherwise be triggered just by a minor
   network latency fluctuation below that threshold.

4. Capability Advertisement

   A BGP speaker that uses multiprotocol extensions to advertise
   performance routes SHOULD use the Capabilities Optional Parameter,
   as defined in [RFC5492], to inform its peers about this capability.
   The MP_EXT Capability Code, as defined in [RFC4760], is used to
   advertise the (AFI, SAFI) pairs available on a particular connection.

5. Performance Route Selection

   Performance route selection only requires the following modification
   to the tie-breaking procedures of the BGP route selection decision
   (phase 2) described in [RFC4271]: network latency metric comparison
   SHOULD be executed just ahead of the AS-Path Length comparison step.

   Prior to executing the network latency metric comparison, the value
   of the NETWORK_LATENCY path attribute SHOULD be increased by adding
   the network latency from the BGP speaker to the NEXT_HOP of that
   route. In the case where a router reflector is deployed without
   next-hop-self enabled when reflecting received routes from one IBGP
   peer to other IBGP peer, it's strongly RECOMMENDED to enable such
   route reflector to reflect all received performance routes by using
   some mechanisms such as [ADD-PATH], rather than reflecting only the
   performance route which is the best from its own perspective.
   Otherwise, it may result in a non-optimal choice by its clients
   and/or its IBGP peers.

   The Loc-RIB of performance routing paradigm is independent from that
   of vanilla routing paradigm. Accordingly, the routing table of
   performance routing paradigm is independent from that of the vanilla
   routing paradigm. Whether performance routing paradigm or vanilla




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   routing paradigm would be used for a given packet is a local policy
   issue which is outside the scope of this draft.

6. Deployment Considerations

   It's RECOMMENDED to deploy this performance-based BGP routing
   mechanism across multiple ASs which are within a single
   administrative domain. Whether it is practical to deploy such
   mechanism across AS's of different administrative domains as well is
   a matter of trust and/or policy, which is outside of the scope of
   this document.

   Within each AS, it's RECOMMENTED to deliver a packet from a BGP
   speaker to the BGP NEXT_HOP via tunnels, especially TE LSP tunnels.
   Furthermore, it's strongly RECOMMENDED to use the latency metric
   carried in Unidirectional Link Delay Sub-TLV [OSPF-TE-EXT] [ISIS-TE-
   EXT] if possible, rather than the TE metric [RFC3630] [RFC5305] to
   perform the C-SPF calculation, unless the TE metric has already been
   set to the link latency metric. In this way, it could avoid the need
   for timely measurement of network latency between IBGP peers.

7. Security Considerations

   This extension to BGP does not change the underlying security issues
   inherent in the existing BGP specification [RFC4271].

8. IANA Considerations

   A new BGP Capability Code for the Performance Routing Capability, a
   new SAFI specific for performance routing and a new path attribute
   for NETWORK_LATENCY are required to be allocated by IANA.

9. Acknowledgements

   Thanks to Joel Halpern, Alvaro Retana, Jim Uttaro, Robert Raszuk,
   Eric Rosen, Qing Zeng, Jie Dong and Mach Chen for their valuable
   comments on the initial idea of this document.

10. References

   10.1. Normative References

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






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

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

   10.2. Informative References

   [RFC5492] Chandra, R. and J. Scudder, "Capabilities Advertisement
             with BGP-4", RFC 5492, February 2009.

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

   [RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label
             Information in BGP-4", RFC 3107, May 2001.

   [OSPF-TE-EXT] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
             Previdi, "OSPF Traffic Engineering (TE) Metric
             Extensions", draft-ietf-ospf-te-metric-extensions-02 (work
             in progress), December 2012.

   [ISIS-TE-EXT] Previdi, S., Giacalone, S., Ward, D., Drake, J., Atlas,
             A., and C. Filsfils, "IS-IS Traffic Engineering (TE)
             Metric Extensions", draft-previdi-isis-te-metric-
             extensions-02 (work in progress), October 2012.

   [RFC3630] Katz, D., Kompella, K., Yeung, D., "Traffic
             Engineering (TE) Extensions to OSPF Version 2", RFC 3630,
             September 2003.

   [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
             Engineering", RFC 5305, October 2008.

   [ADD-PATH] D. Walton, A. Retana, E. Chen, J. Scudder, "Advertisement
             of Multiple Paths in BGP", draft-ietf-idr-add-paths-09
             (work in progress), October 2013.

Authors' Addresses

   Xiaohu Xu
   Huawei Technologies,
   Beijing, China
   Phone: +86-10-60610041
   Email: xuxiaohu@huawei.com



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   Hui Ni
   Huawei Technologies,
   Beijing, China
   Phone: +86-10-606100212
   Email: nihui@huawei.com


   Yongbing Fan
   China Telecom
   Guangzhou, China.
   Phone: +86 20 38639121
   Email: fanyb@gsta.com


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