Internet DRAFT - draft-wang-bess-evpn-frr-label
draft-wang-bess-evpn-frr-label
BESS Working Group H. Wang
Internet-Draft Huawei Technologies
Intended status: Standards Track D. Eastlake
Expires: January 13, 2022 Futurewei Technologies
T. Zhu
Huawei Technologies
July 12, 2021
EVPN ELAN FRR Loop Prevent label
draft-wang-bess-evpn-frr-label-01
Abstract
This document describes how to use Fast Re-Route (FRR) labels avoid
traffic loop in CE failures when deploying FRR protection in EVPN
scenarios.
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 13, 2022.
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document authors. All rights reserved.
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Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. FRR Label Extended Community . . . . . . . . . . . . . . . . 3
3. The Control Plane Process . . . . . . . . . . . . . . . . . . 4
4. The Data Plane Process . . . . . . . . . . . . . . . . . . . 4
5. Other considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
9. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
In the EVPN active-active scenario, to solve the failure of a CE
access channel to one PE, we can deploy Fast Re-Route (FRR)
protection mode to achieve fast convergence. All active PEs can be
deployed with FRR. When a link failure occurs on the CE connection
to the PE, traffic can be rapidly FRR to another PE to improve the
switching performance. However, if the CE device fails, both the two
PEs sense that their CE link is faulty at the same time. They will
each perform fast switching according to the FRR. Then the traffic
will loop between the dual PEs.
If one PE detects a failure and withdraw the ES-AD route, the other
PE, after receiving the withdrawal of the ES-AD route, deletes the
FRR path to the PE, and the loop is eliminated. The time until the
loop is eliminated may be short, but during this time, the loop will
cause traffic congestion between the dual-homing PEs.
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+-----+
| CE2 |
+-----+
|
+-----+
| EVI1|
| PE3 |
+-----+
/ \
/ \
/ \
/ \
/ \
+-----+ +-----+
| PE1 | | PE2 |
| EVI1|-------------| EVI1|
+-----+ +-----+
\ /
\ /
ESI1 ESI1
\ Trunk /
+\-----/+
| \ / |
+---+---+
|
+-----+
| CE1 |
+-----+
Figure 1: Basic networking of the EVPN all-active scenario
2. FRR Label Extended Community
The FRR Label Extended Community is a new transitive Extended
Community having a Type field value of 0x06 and the Sub-Type TBD. It
may be advertised along with MAC/IP Advertisement routes and Ethernet
A-D per EVI routes.
The FRR Label Extended Community is encoded as an 8-octet value, as
follows:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=0x06 | Sub-Type=TBD | Flags(1 octet)| Reserved=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved=0 | FRR Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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3. The Control Plane Process
If we enable the FRR LABEL function for an instance, then when the PE
advertises the MAC-IP route or Ethernet A-D per EVI route of the
instance, it also carries an FRR Label Extended Community attribute.
When another PE on the dual-homed side receives the MAC-IP route or
the EVI-AD route, and uses the Label in the FRR Label Extended
Community attribute as the label for the Edge FRR path. The single-
homing-side PE receives the MAC-IP route or Ethernet A-D per EVI
route advertised by the PE will ignores the FRR Label Extended
Community attribute.
Because the FRR Label Extended Community attribute is an optional
transitve attribute, if there are RR devices or ASBR devices in the
network, the attributes can be transparently transmitted and
processed by the final PE device.
Taking Figure 1 as an example, the EVI1 of PE2 enables the FRR LABEL
function, and PE2 applies for a new label. PE2 advertises the MAC-IP
route and the Ethernet A-D per EVI route carries the label through
the FRR Label Extended Community attribute. Because CE1 is dual-
homed to PE1 and PE2, PE1 learns the MAC address of CE1 from the data
plane. Therefore, when PE1 receives the MAC-IP route or Ethernet A-D
per EVI route from PE2, it can generate the MAC address learned from
CE1 to form an edge FRR entry and the label filled in the FRR entry
is the FRR label.
For PE3, even if CE1 is dual-homed to PE1 and PE2 in single-active
mode, PE3 form FRR does not use the FRR label.
The feature is available for EVPN ELAN service , EVPN VPWS and EVPN
L3VPN service.
4. The Data Plane Process
The PE receives the traffic from the network side and finds the
corresponding bridge-domain according to the Label. If the Label is
a normal EVI label, the MAC address is normally queried. If the
local outbound interface of the MAC fails, the FRR of the MAC is
further protected. If the Label is an FRR label, the MAC address
continues to be queried normally. If the local outbound interface of
the MAC fails, the FRR of the MAC is no longer protected.
Taking Figure 1 as an example. CE2 send traffic to CE1, traffic
arrived PE3 will encapsulate PE2 's EVI label and send to PE1.
Traffic arrived at PE1 and use the EVI label to lookup MAC table, but
find the out-interface is failed. PE1 will do MAC FRR for that and
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encapsulate the FRR label, which is advertised by PE2. Traffic
arrived at PE2 and use the FRR label to lookup MAC table. The
traffic will send to CE1 according to the MAC infomation. When the
MAC's out-interface is failed, the traffic will dropped to avoid
traffic loop.
5. Other considerations
The solution of this document is not only applicable to the EVPN
scenario. The traditional L3VPN can also use this solution to
achieve rapid loop breaking.
6. IANA Considerations
IANA is requested to assign a new type of FRR label extended
community with value TBD.
7. Security Considerations
TBD
8. Acknowledgements
9. Normative References
[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>.
Authors' Addresses
Haibo Wang
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing 100095
China
Email: rainsword.wang@huawei.com
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Donald E. Eastlake
Futurewei Technologies
2386 Panoramic Circle
Apopka FL 32703
USA
Phone: +1-508-333-2270
Email: d3e3e3@gmail.com
Tong Zhu
Huawei Technologies
101 software Avenue, Yuhua District
Nanjing 210012
China
Email: zhu.tong@huawei.com
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