draft-ietf-idr-bgp-optimal-route-reflection-06.txt   draft-ietf-idr-bgp-optimal-route-reflection-07.txt 
IDR Working Group R. Raszuk IDR Working Group R. Raszuk
Internet-Draft NTT I3 Internet-Draft Individual
Intended status: Standards Track C. Cassar Intended status: Standards Track C. Cassar
Expires: July 6, 2014 Cisco Systems Expires: February 1, 2015 Cisco Systems
E. Aman E. Aman
TeliaSonera TeliaSonera
B. Decraene B. Decraene
S. Litkowski S. Litkowski
Orange Orange
January 2, 2014 July 31, 2014
BGP Optimal Route Reflection (BGP-ORR) BGP Optimal Route Reflection (BGP-ORR)
draft-ietf-idr-bgp-optimal-route-reflection-06 draft-ietf-idr-bgp-optimal-route-reflection-07
Abstract Abstract
[RFC4456] asserts that, because the Interior Gateway Protocol (IGP) [RFC4456] asserts that, because the Interior Gateway Protocol (IGP)
cost to a given point in the network will vary across routers, "the cost to a given point in the network will vary across routers, "the
route reflection approach may not yield the same route selection route reflection approach may not yield the same route selection
result as that of the full IBGP mesh approach." One practical result as that of the full IBGP mesh approach." One practical
implication of this assertion is that the deployment of route implication of this assertion is that the deployment of route
reflection may thwart the ability to achieve hot potato routing. Hot reflection may thwart the ability to achieve hot potato routing. Hot
potato routing attempts to direct traffic to the closest AS egress potato routing attempts to direct traffic to the closest AS egress
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 6, 2014. This Internet-Draft will expire on February 1, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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between BGP speakers belonging to the same administrative domain. between BGP speakers belonging to the same administrative domain.
Traditionally route reflectors have been deployed in the forwarding Traditionally route reflectors have been deployed in the forwarding
path and carefully placed on the POP to core boundaries. That model path and carefully placed on the POP to core boundaries. That model
of BGP route reflector placement has started to evolve. The of BGP route reflector placement has started to evolve. The
placement of route reflectors outside the forwarding path was placement of route reflectors outside the forwarding path was
triggered by applications which required traffic to be tunneled from triggered by applications which required traffic to be tunneled from
AS ingress PE to egress PE: for example L3VPN. AS ingress PE to egress PE: for example L3VPN.
This evolving model of intra-domain network design has enabled This evolving model of intra-domain network design has enabled
deployments of centralized route reflectors. Initially this model deployments of centralized route reflectors. Initially this model
was only employed for new address families e.g. L3VPNs, L2VPNs etc was only employed for new address families e.g. L3VPNs, L2VPNs etc
With edge to edge MPLS or IP encapsulation also being used to carry With edge to edge MPLS or IP encapsulation also being used to carry
internet traffic, this model has been gradually extended to other BGP internet traffic, this model has been gradually extended to other BGP
address families including IPv4 and IPv6 Internet routing. This is address families including IPv4 and IPv6 Internet routing. This is
also applicable to new services achieved with BGP as control plane also applicable to new services achieved with BGP as control plane
for example 6PE. for example 6PE.
Such centralized route reflectors can be placed on the POP to core Such centralized route reflectors can be placed on the POP to core
boundaries, but they are often placed in arbitrary locations in the boundaries, but they are often placed in arbitrary locations in the
core of large networks. core of large networks.
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amount of BGP state to all the edge routers. In many networks, the amount of BGP state to all the edge routers. In many networks, the
number of EBGP peers over which full Internet routing information is number of EBGP peers over which full Internet routing information is
received would correlate directly to the number of paths present in received would correlate directly to the number of paths present in
each ASBR. This could easily result in tens of paths for each each ASBR. This could easily result in tens of paths for each
prefix. prefix.
Notwithstanding this drawback, there are a number of reasons for Notwithstanding this drawback, there are a number of reasons for
sending more than just the single best path to the clients. Improved sending more than just the single best path to the clients. Improved
path diversity at the edge is a requirement for fast connectivity path diversity at the edge is a requirement for fast connectivity
restoration, and a requirement for effective BGP level load restoration, and a requirement for effective BGP level load
balancing. Protocol extensions like add-paths balancing.
[I-D.ietf-idr-add-paths] or [RFC6774] diverse-path allow for such
improved path diversity and can be used to address the same problems
addressed by the mechanisms proposed in this draft.
In practical terms, add/diverse path deployments are expected to In practical terms, add/diverse path deployments are expected to
result in the distribution of 2, 3 or n (where n is a small number) result in the distribution of 2, 3 or n (where n is a small number)
'good' paths rather than all domain external paths. While the route 'good' paths rather than all domain external paths. While the route
reflector chooses one set of n paths and distributes those same n reflector chooses one set of n paths and distributes those same n
paths to all its route reflector clients, those n paths may not be paths to all its route reflector clients, those n paths may not be
the right n paths for all clients. In the context of the problem the right n paths for all clients. In the context of the problem
described above, those n paths will not necessarily include the described above, those n paths will not necessarily include the
closest egress point out of the network for each route reflector closest egress point out of the network for each route reflector
client. The mechanisms proposed in this document are likely to be client. The mechanisms proposed in this document are likely to be
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CLIENT A CLIENT A
POP3 POP3
N - represents the different exit points for a given prefix. POP2 is N - represents the different exit points for a given prefix. POP2 is
a geographically large PoP with two paths; N2 and N3. a geographically large PoP with two paths; N2 and N3.
In a deployment where the centralized RRs tie break on the basis of In a deployment where the centralized RRs tie break on the basis of
their IGP-based view of the network, N1 above would be advertised to their IGP-based view of the network, N1 above would be advertised to
all clients on the basis that it is closest to the RR. Path N4 would all clients on the basis that it is closest to the RR. Path N4 would
be a more appropriate choice for client B. Similarly, N5 would be be a more appropriate choice for client B. Similarly, N5 would be
more appropriate for client A since path N5 is closer to client A more appropriate for client A since path N5 is closer to client A
then path N1. then path N1.
4.2. Proposed solution 4.2. Proposed solution
The proposed solution revolves around the operator establishing the The proposed solution revolves around the operator establishing the
angular position of the route-reflector clients and inter-domain exit angular position of the route-reflector clients and inter-domain exit
points in the network. The route reflector then picks the path to points in the network. The route reflector then picks the path to
advertise to a client based on the client's angular position versus advertise to a client based on the client's angular position versus
the angular position of the inter-domain exit points originating the the angular position of the inter-domain exit points originating the
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IANA is requested to allocate a type code for the Standard BGP IANA is requested to allocate a type code for the Standard BGP
Community to be used for inter cluster propagation of angular Community to be used for inter cluster propagation of angular
position of the clients. position of the clients.
IANA is requested to allocate a new type code from BGP OPEN Optional IANA is requested to allocate a new type code from BGP OPEN Optional
Parameter Types registry to be used for Group_ID propagation. Parameter Types registry to be used for Group_ID propagation.
9. Acknowledgments 9. Acknowledgments
Authors would like to thank Eric Rosen, Clarence Filsfils, Uli Authors would like to thank Eric Rosen, Clarence Filsfils, Uli
Bornhauser Russ White, Jakob Heitz and Mike Shand for their valuable Bornhauser Russ White, Jakob Heitz, Mike Shand and Jon Mitchell for
input. their valuable input.
10. References 10. References
10.1. Normative References 10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006. Protocol 4 (BGP-4)", RFC 4271, January 2006.
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Specific BGP Extended Community", RFC 5668, October 2009. Specific BGP Extended Community", RFC 5668, October 2009.
[RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", RFC [RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework", RFC
5714, January 2010. 5714, January 2010.
[RFC6774] Raszuk, R., Fernando, R., Patel, K., McPherson, D., and K. [RFC6774] Raszuk, R., Fernando, R., Patel, K., McPherson, D., and K.
Kumaki, "Distribution of Diverse BGP Paths", RFC 6774, Kumaki, "Distribution of Diverse BGP Paths", RFC 6774,
November 2012. November 2012.
Authors' Addresses Authors' Addresses
Robert Raszuk Robert Raszuk
NTT I3 Individual
101 S Ellsworth Avenue Suite 350
San Mateo, CA 94401
US
Email: robert@raszuk.net Email: robert@raszuk.net
Christian Cassar Christian Cassar
Cisco Systems Cisco Systems
10 New Square Park 10 New Square Park
Bedfont Lakes, FELTHAM TW14 8HA Bedfont Lakes, FELTHAM TW14 8HA
UK UK
Email: ccassar@cisco.com Email: ccassar@cisco.com
Erik Aman Erik Aman
TeliaSonera TeliaSonera
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