Internet DRAFT - draft-xu-bess-evpn-vpls-multihoming
draft-xu-bess-evpn-vpls-multihoming
Network Working Group J. Xu
Internet-Draft T,. Zhu
Intended status: Standards Track Huawei Technologies
Expires: 18 February 2024 17 August 2023
EVPN VPLS multihoming based on BD
draft-xu-bess-evpn-vpls-multihoming-00
Abstract
EVPN VPLS supports multi-homing to implement redundancy between PEs,
including single-active and all-active redundancy [RFC7432]. The
redundancy function on the access side needs to be implemented in
another mode, which is described in this document.
Status of This Memo
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This Internet-Draft will expire on 18 February 2024.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language and Terminology . . . . . . . . . . . . 2
3. Scenario Description . . . . . . . . . . . . . . . . . . . . 2
4. Solution Description . . . . . . . . . . . . . . . . . . . . 3
5. IANA considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
This document provides a multihoming single-active solution based on
BD. In an existing EVPN VPLS multi-homing scenario, a CE is multi-
homed to multiple PEs. When multiple devices (eg. BNGs) are multi-
homed to PEs, the multi-homing function based on BD must be supported
to implement redundancy among the devices.
2. Requirements Language and Terminology
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 [RFC2119].
* DF, NDF and BDF - Designated Forwarder, Non-Designated Forwarder
and Backup Designated Forwarder.
* DF Alg - refers to Designated Forwarder Election Algorithm. This
is sometimes shortened to “Alg” in this document.
* ES, vES and ESI - Ethernet Segment, virtual Ethernet Segment and
Ethernet Segment Identifier.
* BD - Broadcast Domain. An EVI may be comprised of one (VLAN-Based
or VLAN Bundle services) or multiple (VLAN-Aware Bundle services)
Broadcast Domains.
* BNG - Broadband Network Gateway.
* UPE - User facing-Provider Edge.
3. Scenario Description
BNG1, BNG2, and BNG3 belong to the same BD and are multi-homed to PE1
and PE2 as access devices. BNG (Broadband Network Gateway) is the
access point for subscribers, through which they connect to the
broadband network. Only one of the BNGs is selected when connecting.
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+---------------------+
| USER ACCESS NETWORK |
+---------------------+
+-------+ +-----+
| BNG1 |-----| |
+-------+ | PE1 |
+-------+ | | +-----+
| BNG2 |-----| |----| |
+-------+ +-----+ | |
| UPE |----SUBSCRIBER
+-------+ +-----+ | |
| BNG3 |-----| PE2 |----| |
+-------+ +-----+ +-----+
Figure 1
4. Solution Description
In Figure 1, PE1 and PE2 procedures are as follow:
a. The PEs must assign the same ESI to the BD to which BNG1, BNG2,
and BNG3 belong. DF election is performed based on the Ethernet
Segment route corresponding to the ESI. Assume that PE1 is the
Designated Forwarder PE and PE2 is the NDF PE.
b. The subscriber access packet is sent to the UPE, and the UPE
broadcasts the packet to PE1 and PE2.
* PE2 drops the packet because it is not the designated forwarder.
* PE1 will forward that packet to BNG1 and BNG2.
* BNG1 and BNG2 reply packets to the UPE. If the UPE receives
packets from BNG1 first, the UPE establishes a session with BNG1
and the subscriber goes online successfully.
c. When the link between BNG1 and PE1 fails, subscriber go offline
due to timeout. The subscriber retransmits an online packet. The
packet is sent to BNG2 through PE1. BNG2 replies with a packet.
Then the subscriber goes online successfully.
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d. When the link between BNG2 and PE1 fails again, all access
devices in the BD on PE1 fail. In this case, the Ethernet Segment
route corresponding to the ESI of the BD is withdrawn and the DF
election is performed again. PE2 is elected as the designated
forwarder. After that, when the subscriber goes online, the access
packet is sent to BNG3 through PE2. BNG3 replies with a packet,
indicating that the subscriber goes online successfully.
e. When the link between BNG1 or BNG2 and PE1 recovers, the non-
revertive capability of Highest-Preference DF Alg
[I-D.ietf-bess-evpn-pref-df] can be used for DF. In this way, the DF
PE remains unchanged, preventing subscriber from going offline.
5. IANA considerations
None.
6. Security Considerations
This document raises no new security issues for EVPN.
7. References
[I-D.ietf-bess-evpn-pref-df]
Rabadan, J., Sathappan, S., Lin, W., Drake, J., and A.
Sajassi, "Preference-based EVPN DF Election", Work in
Progress, Internet-Draft, draft-ietf-bess-evpn-pref-df-11,
6 July 2023, <https://datatracker.ietf.org/doc/html/draft-
ietf-bess-evpn-pref-df-11>.
[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>.
Authors' Addresses
Jianyong Xu
Huawei Technologies
No.101 Software Avenue, Yuhuatai District
Nanjing
210012
China
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Email: xujianyong1@huawei.com
Tong Zhu
Huawei Technologies
No.101 Software Avenue, Yuhuatai District.
Nanjing
210012
China
Email: zhu.tong@huawei.com
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