draft-ietf-idr-rtc-hierarchical-rr-00.txt   draft-ietf-idr-rtc-hierarchical-rr-01.txt 
Network Working Group J. Dong Network Working Group J. Dong
Internet-Draft M. Chen Internet-Draft M. Chen
Intended status: Standards Track Huawei Technologies Intended status: Standards Track Huawei Technologies
Expires: July 2, 2015 R. Raszuk Expires: December 27, 2015 R. Raszuk
Mirantis Inc. Mirantis Inc.
December 29, 2014 June 25, 2015
Extensions to RT-Constrain in Hierarchical Route Reflection Scenarios Extensions to RT-Constrain in Hierarchical Route Reflection Scenarios
draft-ietf-idr-rtc-hierarchical-rr-00 draft-ietf-idr-rtc-hierarchical-rr-01
Abstract Abstract
The Route Target (RT) Constrain mechanism specified in RFC 4684 is The Route Target (RT) Constrain mechanism specified in RFC 4684 is
used to build a route distribution graph in order to restrict the used to build a route distribution graph in order to restrict the
propagation of Virtual Private Network (VPN) routes. In network propagation of Virtual Private Network (VPN) routes. In network
scenarios where hierarchical route reflection (RR) is used, the scenarios where hierarchical route reflection (RR) is used, the
existing RT-Constrain mechanism cannot build a correct route existing RT-Constrain mechanism cannot build a correct route
distribution graph. This document describes the problem scenario and distribution graph. This document describes the problem scenario and
proposes a solution to address the RT-Constrain issue in hierarchical proposes a solution to address the RT-Constrain issue in hierarchical
skipping to change at page 1, line 45 skipping to change at page 1, line 45
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
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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 2, 2015. This Internet-Draft will expire on December 27, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 2 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 2
3. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . 3 3. Potential Solutions . . . . . . . . . . . . . . . . . . . . . 3
3.1. Add-path Based Solution . . . . . . . . . . . . . . . . . 4 3.1. Add-path Based Solution . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 3.2. Disjoint Alternate Path Solution . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
Appendix A. Another Possible Solution . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
The Route Target (RT) Constrain mechanism specified in [RFC4684] is The Route Target (RT) Constrain mechanism specified in [RFC4684] is
used to build a route distribution graph in order to restrict the used to build a route distribution graph in order to restrict the
propagation of Virtual Private Network (VPN) routes. In network propagation of Virtual Private Network (VPN) routes. In network
scenarios where hierarchical route reflection (RR) is used, the scenarios where hierarchical route reflection (RR) is used, the
existing advertisment rules of RT membership information as defined existing advertisment rules of RT membership information as defined
in section 3.2 of [RFC4684] cannot guarantee a correct route in section 3.2 of [RFC4684] cannot guarantee a correct route
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CLUSTER_ID to the CLUSTER_LIST of the path, and according to the CLUSTER_ID to the CLUSTER_LIST of the path, and according to the
rules in Section 3.2 of [RFC4684], it sets the ORIGINATOR_ID to its rules in Section 3.2 of [RFC4684], it sets the ORIGINATOR_ID to its
own router-id, and the NEXT_HOP to the local address for the session. own router-id, and the NEXT_HOP to the local address for the session.
Then RR-1 would advertise this route to both RR-2 and RR-3. On Then RR-1 would advertise this route to both RR-2 and RR-3. On
receipt of the RT-Constrain route from RR-1, RR-2 checks the receipt of the RT-Constrain route from RR-1, RR-2 checks the
CLUSTER_LIST and find its own CLUSTER_ID in the list, so this route CLUSTER_LIST and find its own CLUSTER_ID in the list, so this route
will be ignored by RR-2. As a result, RR-2 will not form the will be ignored by RR-2. As a result, RR-2 will not form the
outbound filter of RT-1 towards RR-1, hence will not advertise VPN outbound filter of RT-1 towards RR-1, hence will not advertise VPN
routes with RT-1 to RR-1. routes with RT-1 to RR-1.
3. Proposed Solution 3. Potential Solutions
This document specifies 2 potential solutions for the RTC issue in
hierarchical RR scenario. In a future revision one solution would be
selected based on the decision of IDR working group.
3.1. Add-path Based Solution 3.1. Add-path Based Solution
During the discussion in the IDR working group, the add-path based This section provides one possible solution which is based on the
solution is proposed. It makes use of the add-path mechanism as add-path mechanism defined in [I-D.ietf-idr-add-paths]. It makes use
defined in [I-D.ietf-idr-add-paths] for RTC route advertisement. The of the add-path mechanism for RTC route advertisement between the
solution is summerized as follows: hierarchical RRs. The solution is summerized as follows:
o The route-reflector clients which themselves are also route- o The route-reflector clients which themselves are also route-
reflectors SHOULD be identified, then BGP add-paths reflectors SHOULD be identified, then BGP add-paths
[I-D.ietf-idr-add-paths] SHOULD be enabled for RT membership NLRI [I-D.ietf-idr-add-paths] SHOULD be enabled for RT membership NLRI
on the BGP sessions between the higher layer RR and the lower on the BGP sessions between the higher layer RR and the lower
layer RRs to ensure that sufficient RT-Constrain routes can be layer RRs to ensure that sufficient RT-Constrain routes can be
advertised by the higher layer RR to the lower layer RRs to pass advertised by the higher layer RR to the lower layer RRs to pass
BGP loop detection. In this case normal BGP path advertisement BGP loop detection. In this case normal BGP path advertisement
rules as defined in [RFC4271] SHOULD be applied. The number of rules as defined in [RFC4271] SHOULD be applied. The number of
RT-Constrain routes to be advertised is a local decision of RT-Constrain routes to be advertised with add-path mechanism is a
operators. local decision of operators. To ensure that sufficient RT-
Constrain routes are advertised to build the distribution graph,
the recommended add-path number is the maximum number of the BGP
client sessions in the same cluster plus 1.
o When advertising an RT membership NLRI to a route-reflector client o When advertising an RT membership NLRI to a route-reflector client
which is not a lower layer RR, the advertisement rule as defined which is not a lower layer RR, the advertisement rule as defined
in section 3.2 of [RFC4684] SHOULD be applied. in section 3.2 of [RFC4684] SHOULD be applied.
With the above advertisement rule, RR-1 in figure 1 SHOULD advertise With the above advertisement rule, RR-1 in figure 1 SHOULD advertise
to RR-2 the RT-Constrain routes received from both RR-2 and RR-3, to RR-2 the RT-Constrain routes received from both RR-2 and RR-3,
then the RTC route from RR-3 will pass the BGP loop detection on RR- then the RTC route from RR-3 will pass the BGP loop detection on RR-
2, thus the route distribution graph can be set up correctly. 2, thus the route distribution graph can be set up correctly.
3.2. Disjoint Alternate Path Solution
This section specifies another possible solution which proposes some
modification to the intra-AS advertisement rule of RTC route.
Since the advertisement of RT-Constrain route is to set up a route
distribution graph and not to guide the data packet forwarding,
actually all the available RT-Constrain routes should be considered
in setting up the route distribution graph, not just the best one.
Thus the following advertisment rule for RT membership information is
proposed to replace the rule i and ii in section 3.2 of [RFC4684]:
o When advertising an RT membership NLRI to a route-reflector peer
(either client or non-client), if the best path as selected by the
path selection procedure described in Section 9.1 of [RFC4271] is
the path received from this peer, and there are alternative paths
received from other peers, then the most disjoint alternative
route SHOULD be advertised to this peer. The most disjoint
alternative path is the path whose CLUSTER_LIST and ORIGINATOR_ID
attributes are diverse from the attributes of the best path.
With the above advertisement rule, RR-1 in figure 1 would advertise
to RR-2 the RT-Constrain route received from RR-3, which is the most
disjoint alternative route compared with the best route received from
RR-2. In this way, RR-2 will not discard the RT-constrain route
received from RR-1, and the route distribution graph can be set up
correctly.
4. IANA Considerations 4. IANA Considerations
This document makes no request of IANA. This document makes no request of IANA.
5. Security Considerations 5. Security Considerations
This document does not change the security properties of BGP based This document does not change the security properties of BGP based
VPNs and [RFC4684]. VPNs and [RFC4684].
6. Acknowledgements 6. Acknowledgements
The authors would like to thank Yaqun Xiao for the discussion about The authors would like to thank Yaqun Xiao for the discussion of RT-
RT-Constrain in hierarchical RR scenario. Many people have made Constrain issue in hierarchical RR scenario. Many people have made
valuable comments and suggestions, including Susan Hares, Jeffrey valuable comments and suggestions, including Susan Hares, Jeffrey
Haas, Stephane Litkowski, Vitkovsky Adam, Xiaohu Xu, Uttaro James, Haas, Stephane Litkowski, Vitkovsky Adam, Xiaohu Xu, Uttaro James,
Shyam Sethuram and Saikat Ray. Shyam Sethuram, Saikat Ray and Bruno Decraene.
7. Normative References 7. References
[I-D.ietf-idr-add-paths] 7.1. Normative References
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.
[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.
[RFC4684] Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk, [RFC4684] Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
R., Patel, K., and J. Guichard, "Constrained Route R., Patel, K., and J. Guichard, "Constrained Route
Distribution for Border Gateway Protocol/MultiProtocol Distribution for Border Gateway Protocol/MultiProtocol
Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
Private Networks (VPNs)", RFC 4684, November 2006. Private Networks (VPNs)", RFC 4684, November 2006.
Appendix A. Another Possible Solution 7.2. Informative References
This section provides another possible solution which was discussed
among authors and IDR participants.
Since the advertisement of RT-Constrain route is to set up a route
distribution graph and not to guide the data packet forwarding,
actually all the available RT-Constrain routes should be considered
in setting up the route distribution graph, not just the best one.
Thus the following advertisment rule for RT membership information is
proposed to replace the rule i and ii in section 3.2 [RFC4684]:
o When advertising an RT membership NLRI to a route-reflector peer
(either client or non-client), if the best path as selected by the
path selection procedure described in Section 9.1 of [RFC4271] is
the path received from this peer, and there are alternative paths
received from other peers, then the most disjoint alternative
route SHOULD be advertised to this peer. The most disjoint
alternative path is the path whose CLUSTER_LIST and ORIGINATOR_ID
attributes are diverse from the attributes of the best path.
With the above advertisement rule, RR-1 in figure 1 would advertise [I-D.ietf-idr-add-paths]
to RR-2 the RT-Constrain route received from RR-3, although the best Walton, D., Retana, A., Chen, E., and J. Scudder,
route is received from RR-2. Thus RR-2 will not discard the RT- "Advertisement of Multiple Paths in BGP", draft-ietf-idr-
constrain route received from RR-1, and the route distribution graph add-paths-10 (work in progress), October 2014.
can be set up correctly.
Authors' Addresses Authors' Addresses
Jie Dong Jie Dong
Huawei Technologies Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd. Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095 Beijing 100095
China China
Email: jie.dong@huawei.com Email: jie.dong@huawei.com
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