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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: draft-ietf-l2vpn-vpls-ldp-mac-opt has been published as RFC 7361 Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Sivabalan 3 Internet-Draft S. Boutros 4 Intended status: Standards Track Cisco Systems, Inc. 5 Expires: August 12, 2014 H. Shah 6 Ciena Corp. 7 S. Aldrin 8 Huawei Technologies. 9 February 08, 2014 11 MAC Address Withdrawal over Static Pseudowire 12 draft-boutros-pwe3-mpls-tp-mac-wd-03.txt 14 Abstract 16 This document specifies a mechanism to signal MAC address withdrawal 17 notification using PW Associated Channel (ACH). Such notification is 18 useful when statically provisioned PWs are deployed in VPLS/H-VPLS 19 environment. 21 Requirements Language 23 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 24 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 25 document are to be interpreted as described in [RFC2119]. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on August 12, 2014. 44 Copyright Notice 46 Copyright (c) 2014 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 62 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 63 3. MAC Withdraw OAM Message . . . . . . . . . . . . . . . . . . 3 64 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 4 65 4.1. Operation of Sender . . . . . . . . . . . . . . . . . . . 5 66 4.2. Operation of Receiver . . . . . . . . . . . . . . . . . . 5 67 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 68 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 69 6.1. Normative References . . . . . . . . . . . . . . . . . . 6 70 6.2. Informative References . . . . . . . . . . . . . . . . . 6 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 73 1. Introduction 75 An LDP-based MAC Address Withdrawal Mechanism is specified in 76 [RFC4762] to remove dynamically learned MAC addresses when the source 77 of those addresses can no longer forward traffic. This is 78 accomplished by sending an LDP Address Withdraw Message with a MAC 79 List TLV containing the MAC addressed to be removed to all other PEs 80 over LDP sessions. When the number of MAC addresses to be removed is 81 large, empty MAC List TLV may be used. [MAC-OPT] describes an 82 optimized MAC withdrawal mechanism which can be used to remove only 83 the set of MAC addresses that need to be re-learned in H-VPLS 84 networks. The solution also provides optimized MAC Withdrawal 85 operations in PBB-VPLS networks. 87 A PW can be signaled via LDP or can be statically provisioned. In 88 the case of static PW, LDP based MAC withdrawal mechanism cannot be 89 used. This is analogous to the problem and solution described in 90 [RFC4762] where PW OAM message has been introduced to carry PW 91 status TLV using in-band PW Associated Channel. In this document, we 92 propose to use PW OAM message to withdraw MAC address(es) learned via 93 static PW. 95 2. Terminology 97 The following terminologies are used in this document: 99 ACK: Acknowledgement for MAC withdraw message. 101 LDP: Label Distribution Protocol. 103 MAC: Media Access Control. 105 PE: Provide Edge Node. 107 MPLS: Multi Protocol Label Switching. 109 PW: PseudoWire. 111 PW OAM: PW Operations, Administration and Maintenance. 113 TLV: Type, Length, and Value. 115 VPLS: Virtual Private LAN Services. 117 3. MAC Withdraw OAM Message 119 LDP provides a reliable packet transport for control plackets for 120 dynamic PWs. This can be contrasted with static PWs which rely on 121 re-transmission and acknowledgments (ACK) for reliable OAM packet 122 delivery as described in [RFC6478]. The proposed solution for MAC 123 withdrawal over static PW also relies on re-transmissions and ACKs. 124 However, ACK is mandatory. A given MAC withdrawal notification is 125 sent as a PW OAM message, and the sender keeps re-transmitting the 126 message until it receives an ACK for that message. Once a receiver 127 successfully remove MAC address(es) in response to a MAC address 128 withdraw OAM message, it should not unnecessarily remove MAC 129 address(es) upon getting refresh message(s). To facilitate this, the 130 proposed mechanism uses sequence number, and defines a new TLV to 131 carry the sequence number. 133 The format of the MAC address withdraw OAM message is shown in 134 Figure 1. The PW OAM message header is exactly the same as what is 135 defined in [RFC6478]. Since the MAC withdrawal PW OAM message is not 136 refreshed forever. A MAC address withdraw OAM message MUST contain a 137 "Sequence Number TLV" otherwise the entire message is dropped. It 138 MAY contain MAC Flush Parameter TLVs defined in [MAC-OPT] when 139 static PWs are deployed in H-VPLS and PBB-VPLS scenarios. The first 140 2 bits of the sequence number TLV are reserved and MUST be set to 0 141 on transmit and ignored on receipt. 143 0 1 2 3 144 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 1 145 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 146 |0 0 0 1|Version| Reserved |0xZZ MAC Withdraw OAM Message | 147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 | Reserved | TLV Length |A|R| Flags | 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 |Res| Sequence Number TLV (TBD) | Sequence Number TLV Length | 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 152 | Sequence Number | 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 154 | | 155 | MAC List TLV | 156 ~ MAC Flush Parameter TLV (optional) ~ 157 | | 158 | | 159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 161 Figure 1: MAC Address Withdraw PW OAM Packet Format 163 In this section, MAC List TLV and MAC Flush Parameter TLV are 164 collectively referred to as "MAC TLV(s)". The processing rules of 165 MAC List TLV are governed by [RFC4762], and the corresponding rules 166 of MAC Flush Parameter TLV are governed by [MAC-OPT]. 168 "TLV Length" is the total length of all TLVs in the message, and 169 "Sequence Number TLV Length" is the length of the sequence number 170 field. 172 A single bit (called A-bit) is set to indicate if a MAC withdraw 173 message is for ACK. Also, ACK does not include MAC TLV(s). 175 Only half of the sequence number space is used. Modular arithmetic 176 is used to detect wrapping of sequence number. When sequence number 177 wraps, all MAC addresses are flushed and the sequence number is 178 reset. 180 A single bit (called R-bit) is set to indicate if the sender is 181 requesting reset of the sequence numbers. The sender sets this bit 182 when the Pseudowire is restarted and has no local record of send and 183 expected receive sequence number. 185 4. Operation 187 This section describes how the initial MAC withdraw OAM messages are 188 sent and retransmitted, as well as how the messages are processed and 189 retransmitted messages are identified. 191 4.1. Operation of Sender 193 Each PW is associated with a counter to keep track of the sequence 194 number of the transmitted MAC withdrawal messages. Whenever a node 195 sends a new set of MAC TLVs, it increments the transmitted sequence 196 number counter, and include the new sequence number in the message. 197 The transmit sequence number is initialized to 1 at the onset. 199 The sender expects an ACK from the receiver within a time interval 200 which we call "Retransmit Time" which can be either a default (1 201 second) or configured value. If the ACK does not arrive within the 202 Retransmit Time, the sender retransmits the message with the same 203 sequence number as the original message. The retransmission is 204 ceased anytime when ACK is received or after three retries. This 205 avoids unended retransmissions in the absence of acknowledgements. 206 In addition, if during the period of retransmission, if a need to 207 send a new MAC withdraw message with updated sequence number arises 208 then retransmission of the older unacknowledged withdraw message is 209 suspended and retransmit time for the new sequence number is 210 initiated. In essence, sender engages in retrasmission logic only 211 for the latest send withdraw message for a given PW. 213 In the event that a Pseudowire was deleted and re-added or the router 214 is restarted with configuration, the local node may lose information 215 about the send sequence number of previous incarnation. This becomes 216 problematic for the remote peer as it will continue to ignore the 217 received MAC withdraw messages with lower sequence numbers. In such 218 cases, it is desirable to reset the sequence numbers at both ends of 219 the Pseudowire. The 'R' reset bit is set in the first MAC withdraw 220 to notify the remote peer to reset the send and receive sequence 221 numbers. The 'R' bit must be cleared in subsequent MAC withdraw 222 messages after the acknowledgement is received 224 4.2. Operation of Receiver 226 Each PW is associated with a register to keep track of the sequence 227 number of the MAC withdrawal message received last. Whenever a MAC 228 withdrawal message is received, and if the sequence number on the 229 message is greater than the value in the register, the MAC 230 address(es) contained in the MAC TLV(s) is/are removed, and the 231 register is updated with the received sequence number. The receiver 232 sends an ACK whose sequence number is the same as that in the 233 received message. 235 If the sequence number in the received message is smaller than or 236 equal to the value in the register, the MAC TLV(s) is/are not 237 processed. However, an ACK with the received sequence number MUST be 238 sent as a response. The receiver processes the ACK message as an 239 acknowledgement for all the MAC withdraw messages sent up to the 240 sequence number present in the ACK message and terminates 241 retransmission. 243 As mentioned above, since only half of the sequence number space is 244 used, the receiver MUST use modular arithmetic to detect wrapping of 245 the sequence number. 247 A MAC withdraw message with 'R' bit set MUST be processed by 248 resetting the send and receive sequence number first. The rest of 249 MAC withdraw message processing is performed as described above. The 250 acknowledgement is sent with 'R' bit cleared. 252 5. IANA Considerations 254 The proposed mechanism requests IANA to a assign new channel type 255 (recommended value 0x0028) from the registry named "Pseudowire 256 Associated Channel Types". The description of the new channel type 257 is "Pseudowire MAC Withdraw OAM Channel". 259 IANA needs to create a new registry for Pseudowire Associated Channel 260 TLVs, and create an entry for "Sequence Number TLV". The recommended 261 value is 0x0001. 263 6. References 265 6.1. Normative References 267 [MAC-OPT] Dutta, P., Balus, F., Stokes, O., and G. Calvinac, "LDP 268 Extensions for Optimized MAC Address Withdrawal in 269 H-VPLS", draft-ietf-l2vpn-vpls-ldp-mac-opt-10.txt (work in 270 progress), January 2014. 272 [RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service 273 (VPLS) Using Label Distribution Protocol (LDP) Signaling", 274 RFC 4762, January 2007. 276 [RFC6478] Martini, L., Swallow, G., Heron, G., and M. Bocci, 277 "Pseudowire Status for Static Pseudowires", RFC 6478, May 278 2012. 280 6.2. Informative References 282 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 283 Requirement Levels", BCP 14, RFC 2119, March 1997. 285 Authors' Addresses 287 Siva Sivabalan 288 Cisco Systems, Inc. 289 2000 Innovation Drive 290 Kanata, Ontario K2K 3E8 291 Canada 293 Email: msiva@cisco.com 295 Sami Boutros 296 Cisco Systems, Inc. 297 170 West Tasman Dr. 298 San Jose, CA 95134 299 US 301 Email: sboutros@cisco.com 303 Himanshu Shah 304 Ciena Corp. 305 3939 North First Street 306 San Jose, CA 95134 307 US 309 Email: hshah@ciena.com 311 Sam Aldrin 312 Huawei Technologies. 313 2330 Central Express Way 314 Santa Clara, CA 95051 315 US 317 Email: aldrin.ietf@gmail.com