Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track M. Boucadair
Expires: August 30, 2015 C. Jacquenet
France Telecom
N. So
Vinci Systems
Y. Shen
Juniper
U. Chunduri
Ericsson
H. Ni
Huawei
Y. Fan
China Telecom
L. Contreras
Telefonica I+D
February 26, 2015
Performance-based BGP Routing Mechanism
draft-ietf-idr-performance-routing-01
Abstract
The current BGP specification doesn't use network performance metrics
(e.g., network latency) in the route selection decision process.
This document describes a performance-based BGP routing mechanism in
which network latency metric is taken as one of the route selection
criteria. This routing mechanism is useful for those server
providers with global reach to deliver low-latency network
connectivity services to their customers.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 30, 2015.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Performance Route Advertisement . . . . . . . . . . . . . . . 4
4. Capability Advertisement . . . . . . . . . . . . . . . . . . 5
5. Performance Route Selection . . . . . . . . . . . . . . . . . 5
6. Deployment Considerations . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Network latency is widely recognized as one of major obstacles in
migrating business applications to the cloud since cloud-based
applications usually have very clearly defined and stringent network
latency requirements. Service providers with global reach aim at
delivering low-latency network connectivity services to their cloud
service customers as a competitive advantage. Sometimes, the network
connectivity may travel across more than one Autonomous System (AS)
under their administration. However, the BGP [RFC4271] which is used
for path selection across ASes doesn't use network latency in the
route selection process. As such, the best route selected based upon
the existing BGP route selection criteria may not be the best from
the customer experience perspective.
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This document describes a performance-based BGP routing paradigm in
which network latency metric is disseminated via a new TLV of the
AIGP attribute [RFC7311] and that metric is used as an input to the
route selection process. This mechanism is useful for those server
providers with global reach, which usually own more than one AS, to
deliver low-latency network connectivity services to their customers.
Furthermore, in order to be backward compatible with existing BGP
implementations and have no impact on the stability of the overall
routing system, it's expected that the performance routing paradigm
could coexist with the vanilla routing paradigm. As such, service
providers could thus provide low-latency routing services while still
offering the vanilla routing services depending on customers'
requirements.
For the sake of simplicity, this document considers only one network
performance metric that's the network latency metric. The support of
multiple network performance metrics is out of scope of this
document. In addition, this document focuses exclusively on BGP
matters and therefore all those BGP-irrelevant matters such as the
mechanisms for measuring network latency are outside the scope of
this document.
A variant of this performance-based BGP routing is implemented (see
http://www.ist-mescal.org/roadmap/qbgp-demo.avi).
1.1. Requirements Language
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].
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 [RFC2679]. 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
high-capacity router seems trivial compared to the cumulative link
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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 or other measurement tools).
3. Performance Route Advertisement
Performance (i.e., low latency) routes SHOULD be exchanged between
BGP peers by means of a specific Subsequent Address Family Identifier
(SAFI) of TBD (see IANA Section) and also be carried as labeled
routes as per [RFC3107]. In other word, performance routes can then
be looked as specific labeled routes which are associated with
network latency metric.
A BGP speaker SHOULD NOT advertise performance routes to a particular
BGP peer unless that peer indicates, through BGP capability
advertisement (see Section 4), that it can process update messages
with that specific SAFI field.
Network latency metric is attached to the performance routes via a
new TLV of the AIGP attribute, referred to as NETWORK_LATENCY TLV.
The value of this TLV 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 TLV is
TBD (see IANA Section), 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. Note that the NETWORK_LATENCY TLV MUST NOT co-exisit
with the AIGP TLV within the same AIGP attribute.
A BGP speaker SHOULD be configurable to enable or disable the
origination of performance routes. If enabled, a local latency value
for a given to-be-originated performance route MUST be configured to
the BGP speaker so that it can be filled to the NETWORK_LATENCY TLV
of that performance route.
A BGP speaker that is enabled to process NETWORK_LATENCY, but it was
not provisioned with the local latency value SHOULD remove the
NETWORK_LATENCY attribute when it advertises the corresponding route
downstream.
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When distributing a performance route learnt from a BGP peer, if this
BGP speaker has set itself as the NEXT_HOP of such route, the value
of the NETWORK_LATENCY TLV SHOULD be increased by adding the network
latency from itself to the previous NEXT_HOP of such route.
Otherwise, the NETWORK_LATENCY TLV of such route MUST NOT be
modified.
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 reflect the network latency of that TE
LSP path, rather than the IGP shortest path. In the case where the
latency to the NEXT HOP could not be obtained due to some reason(s),
that latency SHOULD be set to 0xFFFFFFFF by default.
To keep performance routes stable enough, a BGP speaker SHOULD use a
configurable threshold for network latency fluctuation to avoid
sending any update which would otherwise be triggered 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.
A BGP speaker that implements the Performance Routing Capability MUST
support the BGP Labeled Route Capability, as defined in [RFC3107]. A
BGP speaker that advertises the Performance Routing Capability to a
peer using BGP Capabilities advertisement [RFC5492] does not have to
advertise the BGP Labeled Route Capability to that peer.
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 TLV SHOULD be increased by adding the network
latency from the BGP speaker to the NEXT_HOP of that route.
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The Loc-RIB of the performance routing paradigm is independent from
that of the vanilla routing paradigm. Accordingly, the routing table
of the performance routing paradigm is independent from that of the
vanilla routing paradigm. Whether the performance routing paradigm
or the vanilla routing paradigm would be applied to a given packet is
a local policy issue which is outside the scope of this document.
6. Deployment Considerations
This section is not normative.
Enabling the performance-based BGP routing at large (i.e., among
domains that do not belong to the same administrative entity) may be
conditioned by other administrative settlement considerations that
are out of scope of this document. Nevertheless, this document does
not require nor exclude activating the proposed route selection
scheme between domains that are managed by distinct administrative
entities.
The main deployment case targeted by this specification is where
involved domains are managed by the same administrative entity.
Concretely, this performance-based BGP routing mechanism can
advantageously be enabled in a multi-domain environment, where all
the involved domains are operated by the same administrative entity
so that the processing of the low latency routes can be consistent
throughout the domains. Besides security considerations that may
arise (and which are further discussed in Section 9), there is indeed
a need to consistently enforce a low-latency-based BGP routing policy
within a set of domains that belong to the same administrative
entity. This is motivated by the processing of traffic which is of
very different nature and which may have different QoS requirements.
Moreover, the combined use of BGP-inferred low latency information
with traffic engineering tools that would lead to the computation and
the establishment of traffic-engineered LSP paths between "low
latency"-enabled BGP peers based upon the manipulation of the
Unidirectional Link delay sub-TLV
[I-D.ietf-isis-te-metric-extensions]
[I-D.ietf-ospf-te-metric-extensions] would contribute to guarantee
the overall consistency of the low latency information within each
domain.
In network environments where router reflectors are deployed but
next-hop-self is disabled on them, route reflectors usually reflect
those received routes which are optimal (i.e., lowest latency) from
their perspectives but may not be optimal from the receivers'
perspectives. Some existing solutions as described in
[I-D.ietf-idr-add-paths], [I-D.ietf-idr-bgp-optimal-route-reflection]
and [RFC6774] can be used to address this issue.
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From a network provider perspective, the ability to manipulate low
latency routes may lead to different, presumably service-specific
designs. In particular, there is a need to assess the impact of
using such capability on the overall performance of the BGP peers
from a route computation and selection procedure as a function of the
tie-breaking operation. A typical use case would consist in
selecting low latency routes for traffic that for example pertains to
the VoIP, or whose nature demands the selection of the lowest latency
route in the Adj-RIB-Out database of the corresponding BGP peers.
Typically, live broadcasting services or some e-health services could
certainly take advantage of such capability. It is out of scope of
this document to exhaustively elaborate on such service-specific
designs that are obviously deployment-specific.
7. IANA Considerations
A new BGP Capability Code for the Performance Routing Capability, a
new SAFI specific for performance routing and a new type code for
NETWORK_LATENCY TLV of the AIGP attribute are required to be
allocated by IANA.
8. Security Considerations
In addition to the considerations discussed in [RFC4271], the
following items should be considered as well:
a. Tweaking the value of the NETWORK_LATENCY by an illegitimate
party may influence the route selection results. Therefore, the
Performance Routing Capability negotiation between BGP peers
which belong to different administration domains MUST be disabled
by default. Furthermore, a BGP speaker MUST discard all
performance routes received from the BGP peer for which the
Performance Routing Capability negotiation has been disabled.
b. Frequent updates of the NETWORK_LATENCY TLV may have a severe
impact on the stability of the routing system. Such practice
SHOULD be avoided by setting a reasonable threshold for network
latency fluctuation.
9. Acknowledgements
Thanks to Joel Halpern, Alvaro Retana, Jim Uttaro, Robert Raszuk,
Eric Rosen, Bruno Decraene, Qing Zeng, Jie Dong, Mach Chen, Saikat
Ray, Wes George, Jeff Haas, John Scudder, Stephane Litkowski and
Sriganesh Kini for their valuable comments on this document. Special
thanks should be given to Jim Uttaro and Eric Rosen for their
proposal of using a new TLV of the AIGP attribute to convey the
network latency metric.
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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.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
[RFC7311] Mohapatra, P., Fernando, R., Rosen, E., and J. Uttaro,
"The Accumulated IGP Metric Attribute for BGP", RFC 7311,
August 2014.
10.2. Informative References
[I-D.ietf-idr-add-paths]
Walton, D., Retana, A., Chen, E., and J. Scudder,
"Advertisement of Multiple Paths in BGP", draft-ietf-idr-
add-paths-10 (work in progress), October 2014.
[I-D.ietf-idr-bgp-optimal-route-reflection]
Raszuk, R., Cassar, C., Aman, E., Decraene, B., and S.
Litkowski, "BGP Optimal Route Reflection (BGP-ORR)",
draft-ietf-idr-bgp-optimal-route-reflection-08 (work in
progress), October 2014.
[I-D.ietf-isis-te-metric-extensions]
Previdi, S., Giacalone, S., Ward, D., Drake, J., Atlas,
A., Filsfils, C., and W. Wu, "IS-IS Traffic Engineering
(TE) Metric Extensions", draft-ietf-isis-te-metric-
extensions-04 (work in progress), October 2014.
[I-D.ietf-ospf-te-metric-extensions]
Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
Previdi, "OSPF Traffic Engineering (TE) Metric
Extensions", draft-ietf-ospf-te-metric-extensions-11 (work
in progress), January 2015.
[RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Delay Metric for IPPM", RFC 2679, September 1999.
[RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in
BGP-4", RFC 3107, May 2001.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
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[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760, January
2007.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
[RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement
with BGP-4", RFC 5492, February 2009.
[RFC6774] Raszuk, R., Fernando, R., Patel, K., McPherson, D., and K.
Kumaki, "Distribution of Diverse BGP Paths", RFC 6774,
November 2012.
Authors' Addresses
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
Mohamed Boucadair
France Telecom
Email: mohamed.boucadair@orange.com
Christian Jacquenet
France Telecom
Email: christian.jacquenet@orange.com
Ning So
Vinci Systems
Email: ning.so@vinci-systems.com
Yimin Shen
Juniper
Email: yshen@juniper.net
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Uma Chunduri
Ericsson
Email: uma.chunduri@ericsson.com
Hui Ni
Huawei
Email: nihui@huawei.com
Yongbing Fan
China Telecom
Email: fanyb@gsta.com
Luis M. Contreras
Telefonica I+D
Ronda de la Comunicacion, s/n
Sur-3 building, 3rd floor
Madrid, 28050
Spain
Email: luismiguel.contrerasmurillo@telefonica.com
URI: http://people.tid.es/LuisM.Contreras/
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