BESS Working Group H. Wang
Internet-Draft D. Eastlake
Intended status: Experimental Huawei Technologies
Expires: April 25, 2019 October 22, 2018
EVPN ELAN FRR Loop Prevent label
draft-wang-bess-evpn-frr-label-00
Abstract
This document describes how to use Fast Re-Route (FRR) labels avoid
loop problems 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
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 April 25, 2019.
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to this document. Code Components extracted from this document must
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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 FRRed 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
cancels 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 both EVPN ELAN service and EVPN VPWS
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.
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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 (Rainsword) Wang
Huawei Technologies
Huawei Bld., No.156 Beiqing Road
Beijing 100085
China
Email: rainsword.wang@huawei.com
Donald Eastlake 3rd
Huawei Technologies
1424 Pro Shop Court
Davenport, FL 33896
USA
Phone: +1-508-333-2270
Email: d3e3e3@gmail.com
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