Internet DRAFT - draft-chen-bess-srv6-service-bypass-sid
draft-chen-bess-srv6-service-bypass-sid
Network Working Group H. Chen
Internet-Draft China Telecom
Intended status: Standards Track Y. Gu
Expires: January 14, 2021 H. Wang
Huawei
July 13, 2020
SRv6 SID Bypass Functions
draft-chen-bess-srv6-service-bypass-sid-00
Abstract
This document introduces the SRv6 SID Bypass Functions to enhance
reliability and prevent traffic loop in fast reroute(FRR) scenario.
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
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 14, 2021.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. SRv6 SID Bypass Functions . . . . . . . . . . . . . . . . . . 3
2.1. End.DX2L . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Control Plane Processing . . . . . . . . . . . . . . . . . . 4
4. Data Plane Processing . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
In SRv6 EVPN VPWS all-active scenario, a router or switch (CE1) is
dual-homed to enterprise site (PE1 and PE2). SRv6 EVPN VPWS service
is run between enterprise sites (PE1, PE2, and CPE). When one PE
fails, services can be rapidly switched to the other PE, minimizing
the impact on services.
As shown in Figure 1, deploy fast reroute(FRR) service on PE1 and
PE2. When the AC(attachment circuit) link on PE1 fails, PE1 receives
downlink traffic and can bypass it to the PE2 device for forwarding.
PE2 is also the same. If the AC side links on PE1 and PE2 fail
together, a brief traffic loop between PE1 and PE2 occurs. The
traffic loop will waste the forwarding resources of the equipment and
cause performance pressure. The length of the traffic loop depends
on the convergence of the control plane. That is, PE1 withdraws the
per-EVI Ethernet A-D route advertised to PE2. The FRR backup path on
PE2 is destroyed. PE2 does not send traffic to PE1. In order to
solve the above problem, this document defines the SRv6 SID Bypass
Functions that will be contained in the SRv6 SID Information Sub-TLV
[I-D.ietf-bess-srv6-services], and to be advertised with per-EVI
Ethernet A-D routes.
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+-----+
| CE2 |
+-----+
|
+-----+
|EVPL1| Local/Remote
-------------------| PE3 | Ethernet Tag ID->100/200
| +-----+
| / \
| / \
SRv6 EVPN ELINE / \
| / \
| / \
| +-----+SRv6 Bypass +-----+
--------- | PE1 | Tunnel | PE2 |
L/R Ethernet |EVPL1|-------------|EVPL1| L/R Ethernet
Tag ID->200/100 +-----+ +-----+ Tag ID->200/100
\ /
\ /
ESI1 ESI1
\ Trunk /
+\-----/+
| \ / |
+---+---+
|
+-----+
| CE1 |
+-----+
Figure 1: Basic Networking of the SRv6 EVPN VPWS All-Active Scenario
2. SRv6 SID Bypass Functions
2.1. End.DX2L
The "Endpoint with decapsulation and Layer-2 cross-connect to an
local outgoing L2 interface (OIF) only" (End.DX2L for short) is a
variant of the endpoint behavior. Allocation is expected from IANA
for an End.DX2L function codepoint from the "SRv6 Endpoint Behaviors"
sub-registry.
One of the applications of the End.DX2L behavior is the L2VPN/EVPN
VPWS [RFC7432][RFC8214] use-case.
The End.DX2L SID MUST be the last segment in a SR Policy, and it is
associated with one outgoing interface I.
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When N receives a packet destined to S and S is a local End.DX2L SID,
N does:
S01. When an SRH is processed {
S02. If (Segments Left != 0) {
S03. Send an ICMP Parameter Problem to the Source Address,
Code 0 (Erroneous header field encountered),
Pointer set to the Segments Left field.
Interrupt packet processing and discard the packet.
S04. }
S05. Proceed to process the next header in the packet
S06. }
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an SRv6 End.DX2L SID, the following is
done:
S01. If (Upper-Layer Header type != 143) {
S02. Process as per Section 4.1.1 of [I-D.ietf-spring-srv6-network-programming]
S03. }
S04. Remove the outer IPv6 Header with all its extension headers and forward the Ethernet frame to the OIF I.
S05. If (OIF I is down) {
S06. Interrupt packet processing and discard the packet.
S07. }
3. Control Plane Processing
As shown in Figure 1:
o 1. PE1 advertises per-EVI Ethernet A-D routes to PE2 and PE3.
The route carries the SRv6 Service SID (SID Type=2, End.DX2) sid1
and SRv6 Service Bypass SID sid11 allocated by the EVPL1 service
on PE1.
o 2. The PE2 device receives the per-EVI Ethernet A-D route
advertised by PE1 and finds that it is the same as the Local/
Remote Ethernet Tag ID and ESI1 of its own EVPL1. PE2 considers
it to be a dual-homing relationship with PE1. PE2 uses the SRv6
Service Bypass SID to establish an SRv6 bypass path to PE1. The
tunnel is marked as sid11. The SRv6 Service Bypass SID takes
effect when its EVPL Local/Remote Ethernet Tag ID and ESI are the
same as the per-EVI Ethernet A-D route received.
o 3. The EVPL1 Local/Remote Ethernet Tag ID of the PE3 device
matches PE1. PE3 uses the SRv6 Service SID to establish an EVPN
VPWS service to PE1. The service is marked as sid1. PE3's EVPL1
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Local/Remote Ethernet Tag ID and ESI are different from the per-
EVI Ethernet A-D routes received. PE3 should ignore this
attribute.
o 4. In the same way, PE2 advertises per-EVI Ethernet A-D routes to
PE1 and PE3. The routes carry the SRv6 Service SID sid2 and SRv6
Service Bypass SID sid22 allocated by EVPL1 services on PE2.
o 5. Finally, the primary path from PE1 to CE1 is the local AC port
and the bypass path is the SRv6 tunnel labeled by sid22. The
primary path from PE2 to CE1 is the local AC port and the bypass
path is the SRv6 tunnel labeled by sid11. Paths from PE3 to PE1
and PE2 are marked as sid1 and sid2.
4. Data Plane Processing
This section will describe the processes of the downlink Layer 2
packet forwarding cases.
As shown in Figure 1:
o 1. After receiving a Layer 2 packet sent by the CE2, PE3
encapsulates the packet with the EVPL1 sid1 as the destination
IPv6 of the SRH header, and forwards the packet to PE1.
o 2. After receiving a Layer 2 packet sent by the PE3, PE1 parses
the EVPL1 sid1 of the SRH header and forwards it according to the
function End.DX2 of sid1. When the primary path from PE1 to CE1
fails, PE1 encapsulates the packet with the EVPL1 bypass sid22 as
the destination IPv6 of the SRH header, and forwards the packet to
PE2.
o 3. After receiving a Layer 2 packet sent by the PE1, PE2 parses
the EVPL1 bypass sid22 of the SRH header and forwards it according
to the function End.DX2L of sid22. When the primary path from PE2
to CE1 fails, PE2 discards the packet and successfully breaks the
loop.
o 4. As above, if PE2 receives a Layer 2 packet from PE3, EVPL1
bypass sid11 can also been used to break the loop.
5. IANA Considerations
TBD
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6. Security Considerations
TBD
7. Contributors
The following individuals gave significant contributions to this
document:
Shunwan Zhuang
Huawei Technologies
Email: zhuangshunwan@huawei.com
Chongyang Hu
Huawei Technologies
Email: huchongyang@huawei.com
Bingshe Liu
Huawei Technologies
Email: liubingshe@huawei.com
8. Acknowledgements
The authors would like to thank xxx for the discussion and review of
this document.
9. References
9.1. Normative References
[I-D.ietf-bess-srv6-services]
Dawra, G., Filsfils, C., Raszuk, R., Decraene, B., Zhuang,
S., and J. Rabadan, "SRv6 BGP based Overlay services",
draft-ietf-bess-srv6-services-03 (work in progress), July
2020.
[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 Network Programming",
draft-ietf-spring-srv6-network-programming-16 (work in
progress), June 2020.
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[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>.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <https://www.rfc-editor.org/info/rfc7432>.
[RFC8214] Boutros, S., Sajassi, A., Salam, S., Drake, J., and J.
Rabadan, "Virtual Private Wire Service Support in Ethernet
VPN", RFC 8214, DOI 10.17487/RFC8214, August 2017,
<https://www.rfc-editor.org/info/rfc8214>.
9.2. Informative References
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
Authors' Addresses
Huanan Chen
China Telecom
109, West Zhongshan Road, Tianhe District
Guangzhou 510000
China
Email: chenhuan6@chinatelecom.cn
Yunan Gu
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: guyunan@huawei.com
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Haibo Wang
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: rainsword.wang@huawei.com
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