Internet DRAFT - draft-boutros-pwe3-mpls-tp-mac-wd
draft-boutros-pwe3-mpls-tp-mac-wd
Network Working Group Siva Sivabalan (Ed.)
Internet Draft Sami Boutros (Ed.)
Intended status: Standards Track Luca Martini
Expires: April 15, 2012
Cisco Systems, Inc.
October 15, 2011
MAC Address Withdrawal over Static Pseudowire
draft-boutros-pwe3-mpls-tp-mac-wd-02.txt
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Abstract
This document specifies a mechanism to signal MAC address withdrawal
notification using PW Associated Channel (ACH). Such notification is
useful when statically provisioned PWs are deployed in VPLS/H-VPLS
environment.
This document is a product of a joint Internet Engineering Task
Force(IETF) / International Telecommunication Union
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Telecommunication Standardization Sector (ITU-T) effort to include
an MPLS Transport Profile within the IETF MPLS and PWE3
architectures to support the capabilities and functionalities of a
packet transport network.
Table of Contents
1. Introduction...................................................2
2. Terminology....................................................3
3. MAC Withdraw OAM Message.......................................3
4. Operation......................................................5
4.1.1. Operation of Sender..................................5
4.1.2. Operation of Receiver................................5
5. Security Considerations........................................5
6. IANA Considerations............................................5
7. References.....................................................6
7.1. Normative References......................................6
7.2. Informative References....................................6
Author's Addresses................................................7
Full Copyright Statement..........................................7
Intellectual Property Statement...................................8
1. Introduction
An LDP-based MAC Address Withdrawal Mechanism is specified in
RFC4762 [2] to remove dynamically learned MAC addresses when the
source of those addresses can no longer forward traffic. This is
accomplished by sending an LDP Address Withdraw Message with a MAC
List TLV containing the MAC addressed to be removed to all other PEs
over LDP sessions. When the number of MAC addresses to be removed is
large, empty MAC List TLV may be used. [3] describes an optimized MAC
withdrawal mechanism which can be used to remove only the set of MAC
addresses that need to be re-learned in H-VPLS networks. The solution
also provides optimized MAC Withdrawal operations in PBB-VPLS
networks.
A PW can be signaled via LDP or can be statically provisioned. In the
case of static PW, LDP based MAC withdrawal mechanism cannot be used.
This is analogous to the problem and solution described in [4] where
PW OAM message has been introduced to carry PW status TLV using in-
band PW Associated Channel. In this document, we propose to use PW
OAM message to withdraw MAC address(es) learned via static PW.
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This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunication Union Telecommunication
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and PWE3 architectures to support the
capabilities and functionalities of a packet transport network.
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 [1].
2. Terminology
ACK: Acknowledgement.
LDP: Label Distribution Protocol.
MAC: Media Access Control
MPLS: Multi Protocol Label Switching.
OAM: MPLS Operations, Administration and Maintenance.
PE: Provide Edge Node.
PW: PseudoWire.
TLV: Type, Length, and Value.
VPLS: Virtual Private LAN Services.
3. MAC Withdraw OAM Message
LDP provides a reliable packet transport for control plackets for
dynamic PWs. This can be contrasted with static PWs which rely on re-
transmission and acknowledgments (ACK) for reliable OAM packet
delivery as described in [4]. The proposed solution for MAC
withdrawal over static PW also relies on re-transmissions and ACKs.
However, ACK is mandatory. A given MAC withdrawal notification is
sent as a PW OAM message, and the sender keeps re-transmitting the
message until it receives an ACK for that message. Once a receiver
successfully remove MAC address(es) in response to a MAC address
withdraw OAM message, it should not unnecessarily remove MAC
address(es) upon getting refresh message(s). To facilitate this, the
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proposed mechanism uses sequence number, and defines a new TLV to
carry the sequence number.
The format of the MAC address withdraw OAM message is shown in Figure
1. The PW OAM message header is exactly the same as what is defined
in [4]. Since the MAC withdrawal PW OAM message is not refreshed for
ever, the "Refresh Timer" field in the message header is not used. A
MAC address withdraw OAM message MUST contain a "Sequence Number TLV"
otherwise the entire message is dropped. It may contain MAC Flush
Parameter TLVs defined in [3] when static PWs are deployed in H-VPLS
and PBB-VPLS scenarios. The sequence number TLV has U (Unknown) and F
(Forward) bits set to 1 and 0 respectively so that if a receiver does
not recognize the TLV, it drops the whole message.
In this section, MAC List TLV and MAC Flush Parameter TLV are
collectively referred to as "MAC TLV(s)". The processing rules of MAC
List TLV is governed by [2], and the corresponding rules of MAC Flush
Parameter TLV are governed by [3].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | 0xZZ PW OAM Message |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACH TLV Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Refresh Timer | TLV Length |A| Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|U|F| Sequence Number TLV (TBD) | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| MAC List TLV |
~ MAC Flush Parameter TLV (optional) ~
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: MAC Address Withdraw PW OAM Packet Format.
An ACK for MAC withdraw OAM message is the same as the one shown in
Figure 1 except that:
. A-bit is set.
. It does not include MAC TLV(s).
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. It must include the Sequence Number TLV.
4. Operation
This section describes how the initial MAC withdraw OAM messages
are sent and retransmitted, as well as how the messages are processed
and retransmitted messages are identified.
4.1.1. Operation of Sender
Each PW is associated with a counter to keep track of the sequence
number of the transmitted MAC withdrawal messages. Whenever a node
sends a new set of MAC TLVs, it increments the transmitted sequence
number counter, and include the new sequence number in the message.
The sender expects an ACK from the receiver within a time interval
which we call "Retransmit Time" which can be either a default or
configured value. If the ACK arrives within the Retransmit Time, the
sender assumes that the message transmission is successful.
Otherwise, it retransmits the message with the same sequence number
as the original message.
4.1.2. Operation of Receiver
Each PW is associated with a counter to keep track of the sequence
number of the MAC withdrawal message received last. Whenever a MAC
withdrawal message is received, and if the sequence number on the
message is greater than the receive counter, the MAC address(es)
contained in the MAC TLV(s) is/are removed, and the receive counter
is incremented. The receiver sends an ACK whose sequence number is
the same as the received message.
If the sequence number in the received message is smaller than or
equal to the receive counter, the MAC TLV(s) is/are not processed.
However, an ACK whose sequence number is the same as the received
message is sent.
5. Security Considerations
This document does not introduce any additional security constraints.
6. IANA Considerations
IANA needs to assign the type value for Sequence Number TLV.
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7. References
7.1. Normative References
[1] Bradner. S, "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March, 1997.
7.2. Informative References
[2] Mark Lassere, et. al, "Virtual Private LAN Service (LAN) Using
Label Distribution Protocol (LDP) Signaling", RFC4762, January
2007.
[3] Pranjal Kumar Dutta, et. al, "LDP Extensions for Optimized MAC
Address Withdrawal in H-VPLS", draft-ietf-l2vpn-vpls-ldp-mac-
opt-02.txt (work in progress), July 2010.
[4] Luca Martini, et. al, "Pseudowire Status for Static
Pseudowires", draft-ietf-pwe3-static-pw-status-00.txt (work in
progress), February 2010.
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Author's Addresses
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario, K2K 3E8
Canada
Email: msiva@cisco.com
Sami Boutros
Cisco Systems, Inc.
3750 Cisco Way
San Jose, California 95134
USA
Email: sboutros@cisco.com
Luca Martini
Cisco Systems, Inc.
9155 East Nichols Avenue, Suite 400
Englewood, CO, 80112
United States
Email: lmartini@cisco.com
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