Network Working Group S. Sivabalan Internet-Draft S. Boutros Intended status: Standards Track L. Martini Expires: April 22, 2013 N. McGill Cisco Systems, Inc. October 19, 2012 MAC Address Withdrawal over Static Pseudowire draft-boutros-l2vpn-mpls-tp-mac-wd-01.txt 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. 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 [RFC2119]. 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 22, 2013. Copyright Notice Copyright (c) 2012 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 Sivabalan, et al. Expires April 22, 2013 [Page 1] Internet-Draft MAC Address Withdrawal October 2012 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. MAC Withdraw OAM Message . . . . . . . . . . . . . . . . . . . 4 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. Operation of Sender . . . . . . . . . . . . . . . . . . . . 5 4.2. Operation of Receiver . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Sivabalan, et al. Expires April 22, 2013 [Page 2] Internet-Draft MAC Address Withdrawal October 2012 1. Introduction An LDP-based MAC Address Withdrawal Mechanism is specified in [RFC4762] 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. [MAC-OPT] 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 [RFC4762] 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. 2. Terminology The following terms are defined in this document: ACK: Acknowledgement for MAC withdraw message. LDP: Label Distribution Protocol. MAC: Media Access Control. PE: Provide Edge Node. MPLS: Multi Protocol Label Switching. PW: PseudoWire. PW OAM: PW Operations, Administration and Maintenance. TLV: Type, Length, and Value. VPLS: Virtual Private LAN Services. Sivabalan, et al. Expires April 22, 2013 [Page 3] Internet-Draft MAC Address Withdrawal October 2012 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 [RFC6478]. 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 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 [RFC6478]. Since the MAC withdrawal PW OAM message is not refreshed forever. 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 [MAC-OPT] when static PWs are deployed in H-VPLS and PBB-VPLS scenarios. The first 2 bits of the sequence number TLV are reserved and MUST be set to 0 on transmit and ignored on receipt. 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 MAC Withdraw OAM Message | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | TLV Length |A| Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Res| Sequence Number TLV (TBD) | Sequence Number TLV Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | MAC List TLV | ~ MAC Flush Parameter TLV (optional) ~ | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: MAC Address Withdraw PW OAM Packet Format In this section, MAC List TLV and MAC Flush Parameter TLV are collectively referred to as "MAC TLV(s)". The processing rules of Sivabalan, et al. Expires April 22, 2013 [Page 4] Internet-Draft MAC Address Withdrawal October 2012 MAC List TLV are governed by [RFC4762], and the corresponding rules of MAC Flush Parameter TLV are governed by [MAC-OPT]. "TLV Length" is the total length of all TLVs in the message, and "Sequence Number TLV Length" is the length of the sequence number field. A single bit (called A-bit) is set to indicate if a MAC withdraw message is for ACK. Also, ACK does not include MAC TLV(s). Only half of the sequence number space is used. Modular arithmetic is used to detect wrapping of sequence number. When sequence number wraps, all MAC addresses are flushed and the sequence number is reset. 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. 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. 4.2. Operation of Receiver Each PW is associated with a register 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 value in the register, the MAC address(es) contained in the MAC TLV(s) is/are removed, and the register is updated with the received sequence number. The receiver sends an ACK whose sequence number is the same as that in the received message. If the sequence number in the received message is smaller than or Sivabalan, et al. Expires April 22, 2013 [Page 5] Internet-Draft MAC Address Withdrawal October 2012 equal to the value in the register, the MAC TLV(s) is/are not processed. However, an ACK whose sequence number is the same as that in the received message is sent. As mentioned above, since only half of the sequence number space is used, the receiver MUST use modular arithmetic to detect wrapping of the sequence number. 5. Security Considerations This document does not introduce any additional security constraints. 6. IANA Considerations The proposed mechanism requests IANA to a assign new channel type (recommended value 0x0028) from the registry named "Pseudowire Associated Channel Types". The description of the new channel type is "Pseudowire MAC Withdraw OAM Channel". IANA needs to create a new registry for Pseudowire Associated Channel TLVs, and create an entry for "Sequence Number TLV". The recommended value is 0x0001. 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 7.2. Informative References [MAC-OPT] Pranjal, P., Balus, F., and G. Calvignac, "LDP Extensions for Optimized MAC Address Withdrawal in H-VPLS", draft-ietf-l2vpn-vpls-ldp-mac-opt-07.txt (work in progress), 2012. [RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service (VPLS) Using Label Distribution Protocol (LDP) Signaling", RFC 4762, January 2007. [RFC6478] Martini, L., Swallow, G., Heron, G., and M. Bocci, "Pseudowire Status for Static Pseudowires", RFC 6478, May 2012. Sivabalan, et al. Expires April 22, 2013 [Page 6] Internet-Draft MAC Address Withdrawal October 2012 Authors' Addresses Siva Sivabalan Cisco Systems, Inc. 2000 Innovation Drive Kanata, Ontario K2K 3E8 Canada Email: msiva@cisco.com Sami Boutros Cisco Systems, Inc. 170 West Tasman Dr. San Jose, CA 95134 USA Email: sboutros@cisco.com Luca Martini Cisco Systems, Inc. 170 West Tasman Dr. San Jose, CA 95134 USA Email: lmartini@cisco.com Neil McGill Cisco Systems, Inc. 7100-9 Kit Creek Road, PO Box 14987 RESEARCH TRIANGLE PARK, NC 27709-4987 USA Email: nmcgill@cisco.com Sivabalan, et al. Expires April 22, 2013 [Page 7]