< draft-chen-spring-anycast-sid-frr-00.txt   draft-chen-spring-anycast-sid-frr-01.txt >
Networking Working Group Ran. Chen Networking Working Group Ran. Chen
Internet-Draft Shaofu. Peng Internet-Draft Shaofu. Peng
Intended status: Standards Track Jie. Han Intended status: Standards Track Jie. Han
Expires: March 1, 2019 ZTE Corporation Expires: January 6, 2020 ZTE Corporation
August 28, 2018 July 5, 2019
Anycast-SID FRR in SR Anycast-SID FRR in SR
draft-chen-spring-anycast-sid-frr-00 draft-chen-spring-anycast-sid-frr-01
Abstract Abstract
This document specifies the fast redundancy protection mechanism, This document specifies the fast redundancy protection mechanism,
aimed at providing protection of the links and domain boundary nodes aimed at providing protection of the links and domain boundary nodes
for network that use segment routing. for network that use segment routing.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 1, line 33 skipping to change at page 1, line 33
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Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 2 2. Conventions used in this document . . . . . . . . . . . . . . 2
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Problem statement . . . . . . . . . . . . . . . . . . . . . . 2
4. Anycast-SID FRR Solution . . . . . . . . . . . . . . . . . . 2 4. Proposal . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1. Domain boundary nodes protection . . . . . . . . . . . . 2 4.1. Domain boundary nodes protection . . . . . . . . . . . . 3
4.2. Links and nodes protection in Inter-Area scenario . . . . 4 4.2. example . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. Normative references . . . . . . . . . . . . . . . . . . . . 4 7. Normative references . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction 1. Introduction
This document extends the use of Anycast-SID FRR to provide links and This document extends the use of Anycast-SID FRR to provide links and
domain boundary nodes that use segment routing. domain boundary nodes that use segment routing.
2. Conventions used in this document 2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119. document are to be interpreted as described in RFC2119.
3. Motivation 3. Problem statement
The procedures specified in this document, in combination with +----------------------------+ +---------------+ +------------------+
[I-D.ietf-spring-segment-routing] provide the fast redundancy | SID:20 SID:30 | | | | SID:60 |
protection. | A2-----A3--Link311-GW11------C1------GW21------A6 |
| / \ / | |\ / \ /| | \ |
| / \ / LinkL | \ / \ / | | \ |
|SID:10/ \/ Adj-SID 3| | \ / \ / | | \ SID:80 |
| A1 /\ SID:100 \ / SID:200 A8 |
| \ / \ | | / \ / \ | | / |
| \ / \ | | / \ / \ | | / |
| \/ \ | |/ \ / \| | / |
| A4--------A5---------GW12------C2------GW22-------A7 |
| SID:40 SID:50 | | | | SID:70 |
+----------------------------+ +---------------+ +------------------+
The procedures specified in this document aims at providing Figure 1
protection of the links and domain boundary nodes for network that
use segment routing
4. Anycast-SID FRR Solution The figure above describes a network example with two groups of the
domain boundary nodes. The GW11 and GW12 are in the same anycast
group. They are all configured with the same anycast prefix and the
same prefix-sid 100, in addition, GW11 has node-sid 110 and GW12 has
node-sid 120. Suppose that the metric of link between two anycast
node is large while other links' metirc are small. From A1/A2/A3
perspective, GW11 is an active anycast node and GW12 is a standby,
from A4/A5 perspective, GW12 is active an anycast node , andGW11 is a
standby.
On the A3 node, it can select the primary or backup TI-LFA
FRR[I-D.ietf-rtgwg-segment-routing-ti-lfa] forwarding path (to
destination node GW12) which not through the active anycast node GW11
as the backup path to anycast-sid 100. In this example it will
select the direct next-hop A2 which is the primary path to
destination node GW12.
Supposed that an SID list is {100, 200, 80} which represents the SR-
TE path from A1 to A8.
Time1: the active anycast node GW11 DOWN.
Time2: Anycast FRR take effect in the event of node GW11 has failed,
the flow will be encapsulated with node-sid of GW12 and directed to
next-hop A2.
Time3: route convergence executed, depending on the convergence speed
of the nodes, A3 may regard GW12 as the new originator source of
anycast prefix, so that any flow that match the anycast prefix will
be forwarded to direct next-hop A2 to destination node GW12.
However, A2 may not converge so quickly, it will still regard GW11 as
the originator source of the anycast prefix, its forwarding entry of
anycast-prefix is still to destination GW11 and the next hop is A3.
There is a loop here. So A3 has responsibility to generate a micro-
loop avoided path {GW12, anycast-prefix} to anycast prefix, that is,
it must insert the new originator source to the unloop path.
4. Proposal
4.1. Domain boundary nodes protection 4.1. Domain boundary nodes protection
The solution consists of three parts. The solution consists of three parts.
o Configure the same anycast prefix and associated prefix-sid for o Configure the same anycast prefix and associated prefix-sid for
each domain boundary node that forms redundant protection, then each domain boundary node that forms redundant protection, then
the anycast prefix and associated prefix-sid with Anycast-Group the anycast prefix and associated prefix-sid with Anycast-Group
flag should be advertised to the neighbor node. flag should be advertised to the neighbor node.
o Create the anycast-group forwarding entry (i.e. FRR entry) after o Create the anycast-group forwarding entry (i.e. FRR entry) after
the direct neighbor node of the domain boundary nodes receive the the direct neighbor node of the domain boundary nodes receive the
prefix-sid with Anycast-Group flag advertisement. The anycast- prefix-sid with Anycast-Group flag advertisement. The anycast-
group forwarding entry includes the forwarding information which group forwarding entry includes the forwarding information which
points to each of the domain boundary node , then the forwarding points to each of the domain boundary node, then the forwarding
entry pointing to the main domain boundary (one of the direct entry pointing to the main domain boundary (one of the direct
connected boundary nodes from the PLR) is set to the active state, connected boundary nodes from the PLR) is set to the active state,
and others are set to the backup state. Only the direct neighbor and others are set to the backup state. Only the direct neighbor
of the domain boundary nodes need to set up the anycast-group of the domain boundary nodes need to set up the anycast-group
forwarding entry. forwarding entry. The anycast-group forwarding entry may also be
created on PLR by default, when it received an anycast-prefix
advertisement from two or more originator source.
o if the neighbor node detects the main domain boundary node o if the neighbor node detects the main domain boundary node
failure, the neighbor node immediately activates the backup entry. failure, the neighbor node immediately activates the backup entry.
Note that the backup entry contains the node-sid of the slave Note that the backup entry contains the node-sid of the slave
boundary node, and the packet will be forwarded based on the node- boundary node, and the packet will be forwarded based on the node-
sid, not the anycast prefix-sid again. sid, not the anycast prefix-sid again.
+-----------------------+ +---------------+ +------------------+ 4.2. example
| SID:20 SID:30 | | | | SID:60 |
| A2-----A3------GW11------C1------GW21------A6 |
| / \ / | |\ / \ /| | \ |
| / \ / | | \ / \ / | | \ |
|SID:10/ \ / | | \ / \ / | | \ SID:80 |
| A1 / SID:100 / / SID:200 A8 |
| \ / \ | | / \ / \ | | / |
| \ / \ | | / \ / \ | | / |
| \ / \ | |/ \ / \| | / |
| A4-----A5------GW12------C2------GW22-------A7 |
| SID:40 SID:50 | | | | SID:70 |
+-----------------------+ +---------------+ +------------------+
Figure 1
The figure above describes a network example with two groups of the
domain boundary nodes. The GW11 and GW12 are in the same anycast
group. They are all configured with the same anycast prefix and the
same prefix-sid 100, in addition, GW11 has node-sid 110 and GW12 has
node-sid 120. All these prefix-sid should be advertised to the
Neighbors(e.g, node A3 and A5), and the anycast-group forwarding
entry will be set up by the direct Neighbor node A3 and A5. For
example, the anycast-group forwarding entry created by A3 contains a
master item which points to anycast-sid 100 and a slave item which
points to node-sid 120.
When A3 detects GW11 failure, it immediately diverting traffic from
GW11 to A4 (e.g. the best next-hop to node-sid 120) according to the
anycast-group forwarding entry.
It is an implementation choice for data-plane whether the slave item In figure 1, considering that the GW11 DOWN,then
only points to node-sid 120 for cascade table lookup, or integrates
the forwarding information of node-sid 120 (such as a single next-
hop, a TI-LFA FRR index for cascade table lookup, or an ECMP index
for cascade table lookup).
Note that the anycast-group FRR described in this document could co- Time1:GW11 DOWN.
exist with other FRR solutions, such as LFA/RLFA/TI-LFA. The
anycast-group FRR solution needn't complex alternate path
computation, it just reuses the forwarding information which points
to the slave boundary node.
4.2. Links and nodes protection in Inter-Area scenario Time2: Primary or backup TI-LFA
[I-D.ietf-rtgwg-segment-routing-ti-lfa]provides protection in the
event of GW11 has failed on the A3 node.
TBD. Time3: When A3 detects GW11 failure, and the anycast-sid 100 is the
top Label in the label stack.The anycast-sid 100 is swapped with the
node-sid 120 (node-sid of the GW12) according to the anycast-group
forwarding entry. Pachets is forwarded to next-hop A2.
5. Security Considerations 5. Security Considerations
TBD. TBD.
6. Acknowledgements 6. Acknowledgements
TBD. TBD.
7. Normative references 7. Normative references
[I-D.ietf-isis-segment-routing-extensions] [I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A., Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura, Gredler, H., and B. Decraene, "IS-IS Extensions for
"IS-IS Extensions for Segment Routing", draft-ietf-isis- Segment Routing", draft-ietf-isis-segment-routing-
segment-routing-extensions-19 (work in progress), July extensions-25 (work in progress), May 2019.
2018.
[I-D.ietf-ospf-ospfv3-segment-routing-extensions]
Psenak, P., Filsfils, C., Previdi, S., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3
Extensions for Segment Routing", draft-ietf-ospf-ospfv3-
segment-routing-extensions-15 (work in progress), August
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-25 (work in progress), April 2018.
[I-D.ietf-spring-segment-routing] [I-D.ietf-rtgwg-segment-routing-ti-lfa]
Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B., Litkowski, S., Bashandy, A., Filsfils, C., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing Francois, P., daniel.voyer@bell.ca, d., Clad, F., and P.
Architecture", draft-ietf-spring-segment-routing-15 (work Camarillo, "Topology Independent Fast Reroute using
in progress), January 2018. Segment Routing", draft-ietf-rtgwg-segment-routing-ti-
lfa-01 (work in progress), March 2019.
[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, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001, DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>. <https://www.rfc-editor.org/info/rfc3031>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
Authors' Addresses Authors' Addresses
Ran Chen Ran Chen
ZTE Corporation ZTE Corporation
No.50 Software Avenue,Yuhuatai District
Nanjing, Jiangsu Province 210012
China
Phone: +86 025 88014636
Email: chen.ran@zte.com.cn Email: chen.ran@zte.com.cn
Shaofu Peng Shaofu Peng
ZTE Corporation ZTE Corporation
No.68 Zijinghua Road,Yuhuatai District
Nanjing, Jiangsu Province 210012
China
Email: peng.shaofu@zte.com.cn Email: peng.shaofu@zte.com.cn
Jie Han Jie Han
ZTE Corporation ZTE Corporation
No.68 Zijinghua Road,Yuhuatai District
Nanjing, Jiangsu Province 210012 Email: han.jie@zte.com.cn
China
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