Networking Working Group R. Chen
Internet-Draft Y. Wang
Intended status: Standards Track ZTE Corporation
Expires: April 21, 2011 L. Guo
China Telecom
October 18, 2010
LDP Extensions for Optimized MAC Address Withdrawal in VPLS model 3
supporting Qualified learning
draft-chen-l2vpn-vpls-mac-opt-qualified-00
Abstract
This draft defines a method for optimized MAC Address Withdrawal in
VPLS model 3 [RFC4664] supporting qualified learning [RFC4762].
Based on the MAC Address Withdrawal procedures defined in [RFC4762]
and [I-D.ietf-l2vpn-vpls-ldp-mac-opt], some extensions are made to
enable a PE device to remove only the MAC addresses that belong to
MAC address space affected by topology change and need to be
relearned.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 21, 2011.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
Chen, et al. Expires April 21, 2011 [Page 1]
Internet-Draft Optimized MAC Withdrawal in VPLS model 3 October 2010
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Description . . . . . . . . . . . . . . . . . . . . . . 4
4. Optimized MAC Flush Mechanism . . . . . . . . . . . . . . . . . 5
4.1. MAC Address Space TLV . . . . . . . . . . . . . . . . . . . 5
4.2. MAC Address Space TLV Processing Rules . . . . . . . . . . 6
4.3. Optimized MAC Flush Procedures . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
7. Normative references . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Chen, et al. Expires April 21, 2011 [Page 2]
Internet-Draft Optimized MAC Withdrawal in VPLS model 3 October 2010
1. Introduction
[RFC4762] defines a basic MAC Address Withdrawal mechanism to remove
or unlearn MAC addresses for faster convergence on topology change.
It defines MAC List TLV which contains a list of MAC addresses to be
flushed in LDP Address Withdraw Message, and when a MAC List TLV
contains a large number of MAC addresses, it may be preferable to
send a LDP Address Withdraw Message with an empty MAC List.
As per the processing rules in [RFC4762], a PE device on receiving a
MAC Address Withdrawal Message with MAC List TLV removes the
association between the MAC address and the AC or PW over which this
message is received. For a MAC Address Withdraw message with empty
MAC list, a PE removes all MAC addresses associated with the
specified VPLS instance (as indicated in the FEC TLV) except the MAC
addresses learned over the newly activated PW. The PE device further
triggers a MAC Address Withdrawal message to each remote PE devices
connected to it in the VPLS full mesh. The problem is that it will
flush MAC addresses which are not affected due to topology change,
thus leading to unnecessary flooding and relearning.
Draft [I-D.ietf-l2vpn-vpls-ldp-mac-opt] proposes to extend LDP
protocol to support source initiated P2MP signaling, but it involves
very few P2MP PW parameter negotiation Mechanism.
This draft describes the problem and a solution to optimize the MAC
flush procedure in [RFC4762] and [I-D.ietf-l2vpn-vpls-ldp-mac-opt] so
it flushes only the MAC addresses that belong to MAC address space
affected by topology change and need to be relearned in VPLS model 3
supporting Qualified learning.
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 RFC2119.
2.1. Terminology
AC: Attachment Circuit
CE: Customer Edge device
LDP: Label Distribution Protocol
PE: Provider Edge
Chen, et al. Expires April 21, 2011 [Page 3]
Internet-Draft Optimized MAC Withdrawal in VPLS model 3 October 2010
PW: Pseudowire
MTU-s: Multi-Tenant Unit switch
3. Problem Description
VLAN1
VLAN2 VLAN2
CE-2 CE-3
/ /
PE-1 / PE-3 /
+--------+/ +--------+/
| | | |
| -- | PW2 | -- |
VLAN1 | / \ |------------------| / \ |
CE-1 /------| \ s/ | | \S / |
\ primary spoke PW | -- | /------| -- |
\ / +--------+ / +--------+
\ (MTU-s)/ | \ PW3 / PW6|
+--------+/ | \ / |
| | | \ / |
| -- | PW1 | \ / |
| / \ | | H-VPLS Full Mesh Core|
| \S / | | / \ |
| -- | | / \ |
+--------+\ | PW4/ \ |
backup spoke PW | / \ |
\ +--------+ \--------+--------+
\ | | | |
\------| -- | PW5 | -- |
| / \ |------------------| / \ |
| \s / | | \S / |
| -- | | -- |
/+--------+ +--------+
/ PE-2 PE-4
/
CE-4
VLAN1
VLAN2
Figure 1: Dual homed MTU-s in two tier hierarchy H-VPLS
Figure.1 is an example for the dual-homing access topology in VPLS
model 3 supporting qualified learning.
Chen, et al. Expires April 21, 2011 [Page 4]
Internet-Draft Optimized MAC Withdrawal in VPLS model 3 October 2010
There are four VLANs in Figure 1, and each customer VLAN has its own
broadcast domain and MAC address space. CE-1 and CE-3 belong to
VLAN1, CE-2 and CE-4 belong to VLAN2.
CE-1, CE-2, CE-3 and CE-4 connect with MTU-S, PE-1, PE-4 and PE-2
respectively. The MTU-S is dual-homed to PE-1 and PE-2. Only the
primary spoke PW is active at MTU-s, thus PE-1 is acting as the
active device to reach the full mesh in the VPLS instance.
When MTU-s switches to the backup spoke PW and activates it, PE-2
becomes the active device to reach the full mesh core. Traffic
entering the H-VPLS from CE-1 is diverted by the MTU-s to the backup
spoke PW. For faster convergence MTU-s may desire to unlearn or
remove the MAC addresses belonging to VLAN1 and learned from the PW
that terminates at PE-1 MUST be removed. Once the backup PW has been
made active, MTU-s may send a MAC flush message to PE-2.
As per the processing rules defined in [RFC4762], PE-2 flushes all of
the MAC addresses learned in the VPLS from the PWs terminating at
PE-1, PE-3 and PE-4. PE-2 further relays MAC flush messages to PE-1,
PE-3 and PE-4. Same processing rule applies at all those PE devices.
As per the processing rules defined in
[I-D.ietf-l2vpn-vpls-ldp-mac-opt], PE-2 flushes all of the MAC
addresses learned in the VPLS from the PWs terminating at PE-1. In
fact, PE2 need not flush the MAC addresses belong to VLAN2 and
learned over PW1.There are multi-Mac addresses spaces in a single
VPLS, and the affected Mac addresses spaces is only VLAN1. PE-2 only
need flush and relearn MAC addresses belong to VLAN1 and learned over
PW1.
With the number of PE devices in the full-mesh increases, the number
of unaffected MAC addresses flushed in a VPLS instance also
increases, thus leading to unnecessary flooding and relearning.
4. Optimized MAC Flush Mechanism
4.1. MAC Address Space TLV
This draft proposes a MAC Address Space TLV to be used with LDP
Address Withdraw Message. The MAC Address Space TLV carries a list
of MAC addresses Spaces which are affected due to topology change.
When a PE receives a LDP Address Withdraw message with a MAC Address
Space TLV, then the PE only flushes the suspect MAC addresses belong
to the MAC Address Space elements.
The new MAC Address Space TLV format is as follows:
Chen, et al. Expires April 21, 2011 [Page 5]
Internet-Draft Optimized MAC Withdrawal in VPLS model 3 October 2010
0 1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| MAC Address Space TLV(TBD)| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC address space #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC address space #2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC address space #n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: MAC Address Space TLV format
U bit: Unknown bit. This bit MUST be set to 1. If the MAC address
Space format is not understood, then it MUST be ignored.
F bit: Forward bit. This bit MUST be set to 0. Since the LDP
mechanism used here is targeted, the TLV MUST NOT be forwarded.
Type: Type field. This identifies the TLV type as MAC Address Space
TLV.
Length: Length field. This field specifies the total length in
octets of value in MAC Address Space TLV.
MAC Address Space: This identifies the MAC addresses Space which are
affected due to topology change.
4.2. MAC Address Space TLV Processing Rules
If a PE device receives a MAC Address Withdraw with MAC Address Space
TLV and empty MAC list, it SHOULD remove all the MAC addresses
associated with the MAC Address Spaces (specified by the MAC Address
Space TLV) in a VPLS instance, except the MAC addresses learned over
the PW associated with this signaling session over which the message
was received.
If a PE device receives a MAC Address Withdraw with MAC Address Space
TLV and MAC list TLV, it SHOULD remove the MAC address (specified by
the MAC List TLV) associated with the MAC Address Space (specified by
the MAC Address Space TLV) in a VPLS instance.
If a PE device receives a MAC Address Withdraw with MAC Address Space
TLV and PE-ID TLV, from the specified MAC Address Space which is
Chen, et al. Expires April 21, 2011 [Page 6]
Internet-Draft Optimized MAC Withdrawal in VPLS model 3 October 2010
identified by MAC Address Space TLV GBP[not]it SHOULD remove all the
MAC addresses learned from the PW ,which terminates at the PE
identified by the PE-ID.
If a PE device that doesn't support MAC Address Space TLV, receives a
MAC flush message with this option, it MUST ignore the option and
follow the processing rules as per [RFC4762] and
[I-D.ietf-l2vpn-vpls-ldp-mac-opt].
The scope of a MAC List TLV is the MAC Address Space (specified by
the MAC Address Space TLV) in the VPLS (specified by the FEC TLV in
the MAC Address Withdraw Message).
4.3. Optimized MAC Flush Procedures
This section explains the optimized MAC flush procedure in the
scenario shown in Figure.1.
When the backup PW is activated by MTU-s, it may send MAC Address
Withdraw message to PE-2 with the FEC TLV and the optional PE-ID TLV
and MAC Address Space TLV. The MAC Address Space TLV carries a list
of MAC addresses Space which are affected due to topology change.
Upon receipt of the MAC Address Withdraw message, PE-2 identifies the
VPLS instance that requires MAC Address Withdraw from the FEC element
in the FEC TLV. From the PE-ID TLV, PE-2 identifies the PW in the
VPLS that terminates in PE-1. From the MAC Address Space TLV, PE-2
identifies MAC addresses Space which are affected due to topology
change. PE-2 removes all MAC addresses belong to VLAN1 and learned
over PW1.
PE-2 relays MAC Address Withdraw messages with the received MAC
Address Space TLV and PE-ID to all its peer PE devices. When the
message is received at PE-3/PE-4, MAC addresses belonging to VLAN1
and learned over the PW that terminates at PE1 MUST be removed.
5. IANA Considerations
The type field in the MAC List TLV is defined as 0x406 and is subject
to IANA approval
6. Security Considerations
This section will be added in a future version.
Chen, et al. Expires April 21, 2011 [Page 7]
Internet-Draft Optimized MAC Withdrawal in VPLS model 3 October 2010
7. Normative references
[I-D.ietf-l2vpn-vpls-ldp-mac-opt]
Dutta, P., Balus, F., Calvignac, G., and O. Stokes, "LDP
Extensions for Optimized MAC Address Withdrawal in
H-VPLS", draft-ietf-l2vpn-vpls-ldp-mac-opt-02 (work in
progress), July 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
Heron, "Pseudowire Setup and Maintenance Using the Label
Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4664] Andersson, L. and E. Rosen, "Framework for Layer 2 Virtual
Private Networks (L2VPNs)", RFC 4664, September 2006.
[RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service
(VPLS) Using Label Distribution Protocol (LDP) Signaling",
RFC 4762, January 2007.
[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007.
Authors' Addresses
Ran Chen
ZTE Corporation
4F,RD Building 2,Zijinghua Road
Yuhuatai District,Nanjing 210012
P.R.China
Phone: +86 025 52878135
Email: chen.ran@zte.com.cn
Yubao Wang
ZTE Corporation
4F,RD Building 2,Zijinghua Road
Yuhuatai District,Nanjing 210012
P.R.China
Phone: +86 025 52872130
Email: wang.yubao2@zte.com.cn
Chen, et al. Expires April 21, 2011 [Page 8]
Internet-Draft Optimized MAC Withdrawal in VPLS model 3 October 2010
Liang Guo
China Telecom
26/F,109 Zhongshan Ave
Tianhe District,Guangzhou 510630
P.R.China
Phone: +86 020 38639595
Email: guoliang@gsta.com
Chen, et al. Expires April 21, 2011 [Page 9]