One document matched: draft-song-l2vpn-vpls-ring-access-00.txt
Network Working Group X. Song
Internet-Draft S. Wu
Intended status: Informational H. Shao
Expires: April 30, 2009 ZTE Corporation
October 27, 2008
VPLS protection switching with ring access
draft-song-l2vpn-vpls-ring-access-00.txt
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Abstract
This document introduces a new method to access VPLS network using
ring techonology . This method can improve VPLS access reliability.
Fast switch can be done within 50 ms after link failure detection.
It not only can be used in normal VPLS, but also can be used in VPLS
PBB network.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. General Terminology . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Dual-homing operation . . . . . . . . . . . . . . . . . . . . 5
4.1. Single CE ring access dual-homing operation . . . . . . . 5
4.2. Dual CE ring dual-homing operation . . . . . . . . . . . . 6
4.3. Multi CE ring multi-homing operation . . . . . . . . . . . 7
4.4. PE operation in the ring . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . . . 10
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1. Introduction
Virtual Private LAN Service (VPLS) is a Layer 2 Virtual Private
Network (VPN) that gives its customers the appearance that their
sites are connected via a Local Area Network (LAN). It is often
required for a Service Provider (SP) to give the customer redundant
connectivity to one or more sites, often called "multi-homing". Ring
access to VPLS will be a good method to implement "multi-homing"
technology .on one hand the access link will be protected more
efficiently ,on the other hand ,ring is used very frequently in the
current Ethernet network ,so deployment of the ring access to VPLS
network is easy.
Section 3 lays out some of the scenarios of ring access multi-homing.
Section 4 describe how to implement the protect switch. Section 5
may someday discuss security considerations.
1.1. General Terminology
Some general terminology is defined here; most is from [RFC4761] or
[RFC4364]. Terminology specific to this memo is introduced as needed
in later sections.
A "Customer Edge" (CE) device, typically located on customer
premises, connects to a "Provider Edge" (PE) device, which is owned
and operated by the SP. A "Provider" (P) device is also owned and
operated by the SP, but has no direct customer connections. A "VPLS
Edge" (VE) device is a PE that offers VPLS services A VPLS domain
represents a bridging domain per customer. A VPLS site is a grouping
of ports on a PE that belong to the same VPLS domain. Sites are
referred to as local or remote depending on whether they are
configured on the PE router in context or on one of the remote PE
routers (network peers).
2. Conventions used in this document
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.
3. Scenarios
The most basic scenario is shown in Figure 1. CE1 is a VPLS CE that
is dual-homed to both PE1 and PE2 for redundant connectivity.
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...............
. . ___ CE2
___ PE1 . /
/ : PE3
__/ : Service :
CE1 __ : Provider PE4
\ : . \___ CE3
\___ PE2 .
. .
...............
Figure 1: Scenario 1
Another extends of dual-homed VPLS module is shown in Figure 2.
...............
. . ___ CE2
CE1 ----- PE1 . /
| : PE3
| : Service :
| : Provider PE4
| : . \___ CE3
CE2 ----- PE2 .
. .
...............
Figure 2: Scenario 2
In Figure 2, PE-CE-CE-PE forms a non-close ring. It is a typical
ring access to VPLS, later the operation of ring will be described.
...............
. . ___ CE2
CE1 ----- PE1 . /
| : PE3
| : Service :
Other User access point : Provider PE4
| : . \___ CE3
CE2 ----- PE2 .
. .
...............
Figure 3: Scenario 3
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...............
. .
CE1 ----- PE1 .
| : . CE4
| : /
| : Service PE4
| : :
CE2 ----- PE2 Provider :
| : PE5
| : . \
| : . CE5
| : .
CE3 ----- PE3 ..............
Figure 4: Scenario 4
4. Dual-homing operation
Before we start discussing ring access to VPLS network, some basic
concept of ring technology must be represented.
D1----D2-----D3----D4
From the Scenario above, D1-D4 is a simple non-close ring. When D1
and D4 access to one VPLS network, it seems that it is a close ring.
One device of ring is selected to be master node. In normal
operation, the master node must block one side link for all non-
control Ethernet frames belonging to the given Domain, thereby
avoiding a loop in the ring. If some link is detected failure, the
master node will receive a link failure message, and then it unblocks
the blocked link and allows Ethernet data frames to pass through that
link.
Later some Scenario of ring access to VPLS will be discussed.
4.1. Single CE ring access dual-homing operation
Figure 1 shows a basic module of dual-homing VPLS system. PE1-CE1-
PE2 can be regarded a simple ring.
In the normal state, CE1 is a master node, CE1-PE1 is set in
"forwarding" state and CE1-PE2 is in "blocking" state. And then
traffic of CE1 only can flow to PE1, PE1 sends it to PE3. In the
other direction, PE1 receives the traffic from PE3 and then sends to
CE1.PE2 also maybe can receive the traffic from PE3, but because the
CE-PE2 is blocked, so the traffic can not arrive CE1.
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If PE1-CE1 link is detected failure (the method of detection is
outside the scope of this document).CE1 will be notified the failure
and set CE1-PE2 "forwarding" state.
Supposed that the traffic is bidirectional, traffic of CE1 finds PE1-
CE1 is link failure, so floods itself to PE2, and then PE2 sent it to
PE3. In the process of PE2 and PE3, MAC will be updated. In the
other direction, traffic will flow through the updated path PE3-PE2-
CE1.
Supposed that the traffic is unidirectional the traffic from CE1 to
PE3 is the same as bidirectional. But the traffic from PE3 to CE1
can not switch to PE3-PE2-CE1 without MAC update of the other
direction so the switch must rely on the PE MAC withdrawn massage.
All above can make the traffic recover quickly when link failure.
But there is a disadvantage . CE1 is the only access between user
and VPLS network. If CE1 device is disabled, the traffic will be
totally cut down.
4.2. Dual CE ring dual-homing operation
Figure 2 is a module of dual CE dual-homing VPLS system. PE1-CE1-
CE2-PE2 can be regarded a ring.
This module can relax the disadvantage of single CE ring dual-homing
module. Because there are many accesses between users and VPLS
network, the network layout can split the user to different CE.
In the normal state CE1 is selected a master node. CE1-PE1 is set in
"forwarding" state, CE1-CE2 in "blocking" state, CE2-PE2 "forwarding"
state. Then traffic of CE1 only can flow to PE1 . PE1 sends it to
PE3. Traffic of CE2 only can flow to PE2.PE2 sends it to PE3. In
the other direction, PE1 receives the traffic from PE3 and then sends
it to CE1. PE2 also can receives the traffic from PE3 and sends it
to CE2.
If PE1-CE1 link is detected failure (the method of detection is
outside the scope of this document), CE1 will be notified and then
set CE1-CE2 in "forwarding" state.
Supposed that the traffic is bidirectional, traffic of CE1 finds PE1-
CE1 is link failure, so floods itself. Because CE1-CE2 is in
"forwarding" state, CE2 can receive the traffic, then CE2 send it to
PE2 and PE2 send it to PE3. In the process of PE2 and PE3, MAC will
be updated. In the other direction, traffic will flow through the
updated path PE3-PE2-CE2-CE1.
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Supposed that the traffic is unidirectional, the traffic from CE1 to
PE3 is the same as bidirectional. But the traffic from PE3 to CE1
can't switch to PE3-PE2-CE1 without MAC update of the other
direction. So the switch must rely on the PE MAC withdrawn massage.
Figure3 is also a module of dual CE ring dual-homing. In this module
the access point between user and VPLS network are more.
CE1 ----- PE1
| :
C1
|
C2
><
CE2 ----- PE2
Figure 5
In figure 5, PE1-CE1-C1-C2-CE2-PE2 is a ring. We set C2 is a master
node. C2 will set one side link (C1-C2) in "forwarding" state and
set the other side of link (C2-CE2) in "blocking " state. The user
data of C2, C1, CE1 will arrive VPLS through PE1.The user data of CE2
will arrive VPLS network through PE2.
If any link between PE1 and PE2 is detected failure, one message will
sent to C2 (master node) and C2 will set C2-CE2 in "forwarding"
state. Supposed that CE1-C1 is detected failure, C2 will open C2-
CE2. The user data of C1, C2, CE2 will arrive VPLS network through
PE2. The data of CE1 arrive VPLS network through PE1. It is shown
in Figure 6.
CE1 ----- PE1
><
C1
|
C2
|
CE2 ----- PE2
Figure 6
4.3. Multi CE ring multi-homing operation
Figure 4 is a module of multi CE ring multi-homing VPLS system. PE1-
CE1-CE2-PE2 can be regarded a ring. CE2-CE3-PE3 is another ring.
The operation of PE1-CE1-CE2-PE2 ring is the same as dual CE ring
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access dual-homing.
In ring CE2-CE3-PE3, We set CE3 a master node of the ring. CE3-PE3
is in "forwarding" state and CE2-CE3 is in "blocking" state in normal
operation. Once CE3-PE3 is detected failure, CE2-CE3 is set
"forwarding". So the data of CE3 will sent to CE2 .CE2 send the
traffic to VPLS network through PE2.
4.4. PE operation in the ring
Chapter 4.1, 4.2, 4.3 describe that middle device of the ring do
switching when some link is detected failure. This chapter will
discuss edge of ring PE do some switching at the moment of link
failure.
In Figure 1, PE2 is the master node. At normal status, CE1-PE2 is
set in "blocking" state. When CE1-PE1 link is detected failure, PE1
send a control message through PW to PE2, then PE2 set CE1-PE2 in
"forwarding" state and send MAC flush message to PE1 and PE3.
Traffic will flood and learn MAC over again.
In figure 2, PE2 is also the master node. At normal status, CE2-PE2
is set in "blocking" state. So CE2 send traffic to CE1 and then CE1
send to PE1. When CE1-PE1 link is detected failure, PE1 sends one
message to PE2, then PE2 sets CE2-PE2 in "forwarding" state and sends
MAC flush message to PE1, PE3. Traffic will flood and then CE1 sent
traffic to CE2, CE2 send it to PE2.
5. Security Considerations
The security considerations in here are the same as the ones
described in [RFC-4762], and there are no additional security aspects
that need to be considered beyond the ones described in [RFC-4762].
6. IANA Considerations
There have been no IANA considerations so far in this document.
7. Acknowledgments
The authors gratefully acknowledge the contributions of Wu Shaoyong,
Shao Hong, Luo Jian.
8. References
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8.1. Normative References
[RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service
(VPLS) Using Label Distribution Protocol (LDP) Signaling",
RFC 4762, January 2007.
8.2. Informative References
[RFC4664] Andersson, L. and E. Rosen, "Framework for Layer 2 Virtual
Private Networks (L2VPNs)", RFC 4664, September 2006.
[RFC4761] Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
(VPLS) Using BGP for Auto-Discovery and Signaling",
RFC 4761, January 2007.
Authors' Addresses
Xiaojuan Song
ZTE Corporation
68 zhijinghua Road
Yuhuatai distinct,Nanjing 210000
P.R.China
Email: song.xiaojuan@zte.com.cn
Shaoyong Wu
ZTE Corporation
68 zhijinghua Road
Yuhuatai distinct,Nanjing 210000
P.R.China
Email: wu.shaoyong@zte.com.cn
Hong Shao
ZTE Corporation
68 zhijinghua Road
Yuhuatai distinct,Nanjing 210000
P.R.China
Email: shao.hong@zte.com.cn
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