Network Working Group H. Chen
Internet-Draft China Telecom
Intended status: Standards Track Z. Hu
Expires: September 11, 2019 H. Chen
Huawei Technologies
March 10, 2019
SRv6 Proxy Forwarding
draft-chen-rtgwg-srv6-midpoint-protection-00
Abstract
The endpoints of a SRv6 path are given by a SRv6 Policy. When an
endpoint node fails, we need bypass this failed endpoint node and
forward the packets to the failed node's next endpoint node.
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 11, 2019.
Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Endpoint Node Protection for Segment List . . . . . . . . . . 3
2.1. Transit Node as PLR . . . . . . . . . . . . . . . . . . . 3
2.2. Endpoint Node as PLR . . . . . . . . . . . . . . . . . . 3
2.3. Endpoint x Node as PLR . . . . . . . . . . . . . . . . . 4
2.4. Endpoint t Node as PLR . . . . . . . . . . . . . . . . . 5
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
"Segment Routing Proxy Forwarding" for IPv4 is defined in
[I-D.hu-spring-segment-routing-proxy-forwarding]. It provides the
protections for the middle endpoints of a SR path. This document
specifies the proxy forwarding for SRv6, which supports the
protections for the middle endpoints of a SRv6 path.
The endpoints of a SRv6 path are given by a SRv6 Policy. When an
endpoint node fails, we need bypass this failed endpoint node and
forward the packets to the failed node's next endpoint node. On the
PLR (i.e., the previous hop node of the failed endpoint node), it
performs the bypass protection as follows if NH = SRH and SL != 0.
If the outbound interface fails and the failed endpoint node (FN for
short) is directly connected to the PLR, then the PLR forwards the
packets through a bypass to the FN's next endpoint node. If it is
not directly connected, the normal Ti-LFA is executed.
If it is a FIB miss, the PLR forwards the packets through a bypass to
the FN's next endpoint node. There is no need to check if the failed
endpoint node is directly connected to the PLR.
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2. Endpoint Node Protection for Segment List
2.1. Transit Node as PLR
When the PLR is a transit node, it provides fast protection against
the endpoint node failure as follows after looking up the FIB.
IF the primary outbound interface used to forward the packet failed
IF NH = SRH && SL != 0, and
the failed endpoint is directly connected to the PLR THEN
SL--; update the IPv6 DA with SRH[SL];
FIB lookup on the updated DA;
forward the packet according to the matched entry;
ELSE
forward the packet according to the backup nexthop;
ELSE // there is no FIB entry for forwarding the packet
IF NH = SRH && SL != 0 THEN
SL--; update the IPv6 DA with SRH[SL];
FIB lookup on the updated DA;
forward the packet according to the matched entry;
ELSE
drop the packet;
Figure 1: PLR transit
2.2. Endpoint Node as PLR
When a node N receives a packet, if the destination address (DA) of
the packet is a local END SID, then node N is an endpoint node.
When the PLR is an endpoint node, it provides fast protections for
the failure through executing the following procedure after looking
up the FIB for the updated DA.
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IF the primary outbound interface used to forward the packet failed
IF NH = SRH && SL != 0, and
the failed endpoint is directly connected to the PLR THEN
SL--; update the IPv6 DA with SRH[SL];
FIB lookup on the updated DA;
forward the packet according to the matched entry;
ELSE
forward the packet according to the backup nexthop;
ELSE // there is no FIB entry for forwarding the packet
IF NH = SRH && SL != 0 THEN
SL--; update the IPv6 DA with SRH[SL];
FIB lookup on the updated DA;
forward the packet according to the matched entry;
ELSE
drop the packet;
//ELSE
// forward accordingly to the matched entry;
Figure 2: PLR endpoint
2.3. Endpoint x Node as PLR
An endpoint node with cross-connect (End.X for short) is an endpoint
node with an array of layer 3 adjacencies.
When a node N receives a packet, if the destination address (DA) of
the packet is a local END.X SID, then node N as PLR provides fast
protections for the failure through executing the following procedure
after updating DA.
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IF the layer-3 adjacency interface is down THEN
FIB lookup on the updated DA;
IF the primary interface used to forward the packet failed THEN
IF NH = SRH && SL != 0, and
the failed endpoint is directly connected to the PLR THEN
SL--; update the IPv6 DA with SRH[SL];
FIB lookup on the updated DA;
forward the packet according to the matched entry;
ELSE
forward the packet according to the backup nexthop;
ELSE // there is no FIB entry for forwarding the packet
IF NH = SRH && SL != 0 THEN
SL--; update the IPv6 DA with SRH[SL];
FIB lookup on the updated DA;
forward the packet according to the matched entry;
ELSE
drop the packet;
//ELSE
// forward accordingly to the matched entry;
Figure 3: PLR endpoint cross-connect
2.4. Endpoint t Node as PLR
An endpoint node with specific IPv6 table (End.T for short) is an
endpoint node with specific IPv6 table lookup function.
When a node N receives a packet, if the destination address (DA) of
the packet is a local END.T SID, then node N as PLR provides fast
protections for the failure through executing the following procedure
after looking up the next segment in IPv6 table T associated with the
SID.
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IF the primary interface used to forward the packet failed THEN
IF NH = SRH && SL != 0, and
the failed endpoint is directly connected to the PLR THEN
SL--; update the IPv6 DA with SRH[SL];
lookup the next segment in IPv6 table T associated with the SID;
forward the packet according to the matched entry;
ELSE
forward the packet according to the backup nexthop;
ELSE // there is no FIB entry for forwarding the packet
IF NH = SRH && SL != 0 THEN
SL--; update the IPv6 DA with SRH[SL];
lookup the next segment in IPv6 table T associated with the SID;
forward the packet according to the matched entry;
ELSE
drop the packet;
//ELSE
// forward accordingly to the matched entry;
Figure 4: PLR endpoint table
3. IANA Considerations
TBD
4. Security Considerations
TBD
5. Acknowledgements
TBD
6. References
6.1. Normative References
[I-D.bashandy-isis-srv6-extensions]
Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and
Z. Hu, "IS-IS Extensions to Support Routing over IPv6
Dataplane", draft-bashandy-isis-srv6-extensions-05 (work
in progress), March 2019.
[I-D.hu-spring-segment-routing-proxy-forwarding]
Hu, Z., Chen, H., Yao, J., and C. Bowers, "Segment Routing
Proxy Forwarding", draft-hu-spring-segment-routing-proxy-
forwarding-01 (work in progress), March 2019.
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[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., and B. Decraene, "IS-IS Extensions for
Segment Routing", draft-ietf-isis-segment-routing-
extensions-22 (work in progress), December 2018.
[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-27 (work in progress), December 2018.
[I-D.li-ospf-ospfv3-srv6-extensions]
Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak,
"OSPFv3 Extensions for SRv6", draft-li-ospf-
ospfv3-srv6-extensions-03 (work in progress), March 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding
Scope Link State PDUs (LSPs)", RFC 7356,
DOI 10.17487/RFC7356, September 2014,
<https://www.rfc-editor.org/info/rfc7356>.
6.2. Informative References
[I-D.bashandy-rtgwg-segment-routing-ti-lfa]
Bashandy, A., Filsfils, C., Decraene, B., Litkowski, S.,
Francois, P., daniel.voyer@bell.ca, d., Clad, F., and P.
Camarillo, "Topology Independent Fast Reroute using
Segment Routing", draft-bashandy-rtgwg-segment-routing-ti-
lfa-05 (work in progress), October 2018.
[I-D.hegde-spring-node-protection-for-sr-te-paths]
Hegde, S., Bowers, C., Litkowski, S., Xu, X., and F. Xu,
"Node Protection for SR-TE Paths", draft-hegde-spring-
node-protection-for-sr-te-paths-04 (work in progress),
October 2018.
[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d.,
bogdanov@google.com, b., and P. Mattes, "Segment Routing
Policy Architecture", draft-ietf-spring-segment-routing-
policy-02 (work in progress), October 2018.
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[I-D.sivabalan-pce-binding-label-sid]
Sivabalan, S., Filsfils, C., Tantsura, J., Hardwick, J.,
Previdi, S., and C. Li, "Carrying Binding Label/Segment-ID
in PCE-based Networks.", draft-sivabalan-pce-binding-
label-sid-06 (work in progress), February 2019.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field", RFC 5462, DOI 10.17487/RFC5462, February
2009, <https://www.rfc-editor.org/info/rfc5462>.
Authors' Addresses
Huanan Chen
China Telecom
109, West Zhongshan Road, Tianhe District
Guangzhou 510000
China
Email: chenhn8.gd@chinatelecom.cn
Zhibo Hu
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: huzhibo@huawei.com
Huaimo Chen
Huawei Technologies
Boston, MA
USA
Email: Huaimo.chen@huawei.com
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