RFC4446]. The Length field specifies the length of the Status Code field in octets (equal to 4). Each bit in the Status Code field can be set individually to indicate more than a single failure at once. Each fault can be cleared by sending an appropriate Notification message in which the respective bit is cleared. The presence of the lowest bit (PW Not Forwarding) acts only as a generic failure indication when there is a link-down event for which none of the other bits apply. The Status TLV is transported to the remote PW peer via the LDP Notification message as described in [RFC5036]. The format of the Notification message for carrying the PW Status is as follows: 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| Notification (0x0001) | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Message ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Status (TLV) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PW Status TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PWid FEC TLV or Generalized ID FEC TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PW Group ID TLV (Optional) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Status TLV status code is set to 0x00000028, "PW status", to indicate that PW status follows. Since this notification does not refer to any particular message, the Message ID field is set to 0. The PW FEC TLV SHOULD NOT include the Interface Parameter Sub-TLVs, as they are ignored in the context of this message. However, the PW FEC TLV MUST include the C-bit, where applicable, as it is part of the FEC. When a PE's Attachment Circuit encounters an error, use of the PW Notification message allows the PE to send a single "wildcard" status message, using a PW FEC TLV with only the Group ID set, to denote this change in status for all affected PW connections. This status message contains either the PW FEC TLV with only the Group ID set, or else it contains the Generalized FEC TLV with only the PW Group ID TLV. As mentioned above, the Group ID field of the PWid FEC Element, or the PW Group ID TLV used with the Generalized PWid FEC Element, can be used to send a status notification for all arbitrary sets of PWs. This procedure is OPTIONAL, and if it is implemented, the LDP Notification message should be as follows: If the PWid FEC Element is used, the PW information length field is set to 0, the PW ID field is not present, and the Interface Parameter Sub-TLVs are not present. If the Generalized FEC Element is used, the AGI, SAII, and TAII are not present, the PW information length field is set to 0, the PW Group ID TLV is included, and the PW Interface Parameters TLV is omitted. For the purpose of this document, this is called the "wildcard PW status notification procedure", and all PEs implementing this design are REQUIRED to accept such a Notification message but are not required to send it.
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + PWid FEC or Generalized PWid FEC + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Interface Parameters | | " | | " | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0|0| Generic Label (0x0200) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|0| PW Status (0x096A) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Status Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ If a PW Status TLV is included in the initial Label Mapping message for a PW, then if the Label Mapping message from the remote PE for that PW does not include a PW Status TLV, or if the remote PE does not support the PW Status TLV, the PW will revert to the label withdraw method of signaling PW status. Note that if the PW Status TLV is not supported by the remote peer, the peer will automatically ignore it, since the I (ignore) bit is set in the TLV. The PW Status TLV, therefore, will not be present in the corresponding FEC advertisement from the remote LDP peer, which results in exactly the above behavior. If the PW Status TLV is not present following the FEC TLV in the initial PW Label Mapping message received by a PE, then the PW Status TLV will not be used, and both PEs supporting the pseudowire will revert to the label withdraw procedure for signaling status changes. If the negotiation process results in the usage of the PW Status TLV, then the actual PW status is determined by the PW Status TLV that was sent within the initial PW Label Mapping message. Subsequent updates of PW status are conveyed through the Notification message.
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub-TLV Type | Length | Variable Length Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Variable Length Value | | " | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Length field is defined as the length of the interface parameter including the Sub-TLV Type and Length field itself. Processing of the interface parameters should continue when unknown interface parameters are encountered, and they MUST be silently ignored. The Interface Parameter Sub-TLV Type values are specified in "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)" [RFC4446]. - Interface MTU sub-TLV type A 2-octet value indicating the MTU in octets. This is the Maximum Transmission Unit, excluding encapsulation overhead, of the egress packet interface that will be transmitting the decapsulated PDU that is received from the MPLS-enabled network. This parameter is applicable only to PWs transporting packets and is REQUIRED for these PW types. If this parameter does not match in both directions of a specific PW, that PW MUST NOT be enabled. - Optional Interface Description string sub-TLV type This arbitrary, and OPTIONAL, interface description string is used to send a human-readable administrative string describing the interface to the remote PE. This parameter is OPTIONAL and is applicable to all PW types. The interface description parameter string length is variable and can be from 0 to 80 octets. Human- readable text MUST be provided in the UTF-8 charset using the Default Language [RFC2277].
length field is set to 0, the PW Group ID TLV is included, the PW Interface Parameters TLV is not present, and the Label TLV is not present. For the purpose of this document, this is called the "wildcard withdraw procedure", and all PEs implementing this design are REQUIRED to accept such withdraw messages but are not required to send it. Note that the PW Group ID TLV only applies to PWs using the Generalized ID FEC Element, while the Group ID only applies to PWid FEC Element. The Interface Parameter Sub-TLVs, or TLV, MUST NOT be present in any LDP PW Label Withdraw or Label Release message. A wildcard Label Release message MUST include only the Group ID or PW Group ID TLV. A Label Release message initiated by a PE router must always include the PW ID.
-ii. If the received Label Mapping message has C=1, and the PW is locally configured such that the use of the control word is preferred, then send a Label Mapping message with C=1; the control word is used. -iii. If the received Label Mapping message has C=1, and the PW is locally configured such that the use of the control word is not preferred or the control word is not supported, then act as if no Label Mapping message for the PW had been received (i.e., proceed to the next paragraph). If a Label Mapping message for the PW has not already been received (or if the received Label Mapping message had C=1 and either local configuration says that the use of the control word is not preferred or the control word is not supported), then send a Label Mapping message in which the C-bit is set to correspond to the locally configured preference for use of the control word. (That is, set C=1 if locally configured to prefer the control word, and set C=0 if locally configured to prefer not to use the control word or if the control word is not supported). The next action depends on what control message is next received for that PW. The possibilities are as follows: -i. A Label Mapping message with the same C-bit value as specified in the Label Mapping message that was sent. PW setup is now complete, and the control word is used if C=1 but is not used if C=0. -ii. A Label Mapping message with C=1, but the Label Mapping message that was sent has C=0. In this case, ignore the received Label Mapping message and continue to wait for the next control message for the PW. -iii. A Label Mapping message with C=0, but the Label Mapping message that was sent has C=1. In this case, send a Label Withdraw message with a "Wrong C-bit" status code, followed by a Label Mapping message that has C=0. PW setup is now complete, and the control word is not used. -iv. A Label Withdraw message with the "Wrong C-bit" status code. Treat as a normal Label Withdraw message, but do not respond. Continue to wait for the next control message for the PW.
If at any time after a Label Mapping message has been received a corresponding Label Withdraw or Release is received, the action taken is the same as for any Label Withdraw or Release messages that might be received at any time. If both endpoints prefer the use of the control word, this procedure will cause it to be used. If either endpoint prefers not to use the control word or does not support the control word, this procedure will cause it not to be used. If one endpoint prefers to use the control word but the other does not, the one that prefers not to use it has no extra protocol to execute; it just waits for a Label Mapping message that has C=0.
Section 7.4.1 ("Label Advertisements").
RFC 5036. The following values have been assigned from said registry: TLV Type Description ===================================== 0x096A PW Status TLV 0x096B PW Interface Parameters TLV 0x096C PW Group ID TLV RFC 5036. The following values have been assigned: Range/Value E Description Reference ------------- ----- ---------------------- --------- 0x00000024 0 Illegal C-Bit [RFC8077] 0x00000025 0 Wrong C-Bit [RFC8077] 0x00000026 0 Incompatible bit-rate [RFC8077] 0x00000027 0 CEP-TDM mis-configuration [RFC8077] 0x00000028 0 PW Status [RFC8077] 0x00000029 0 Unassigned/Unrecognized TAI [RFC8077] 0x0000002A 0 Generic Misconfiguration Error [RFC8077] 0x0000002B 0 Label Withdraw PW Status [RFC8077] Method Not Supported RFC5036].
Section 5 of [RFC5036]. Those considerations also apply to the case where LDP is used to set up pseudowires. A pseudowire connects two Attachment Circuits. It is important to make sure that LDP connections are not arbitrarily accepted from anywhere, or else a local Attachment Circuit might get connected to an arbitrary remote Attachment Circuit. Therefore, an incoming LDP session request MUST NOT be accepted unless its IP source address is known to be the source of an "eligible" LDP peer. The set of eligible peers could be preconfigured (either as a list of IP addresses or as a list of address/mask combinations), or it could be discovered dynamically via an auto-discovery protocol that is itself trusted. (Obviously, if the auto-discovery protocol were not trusted, the set of eligible peers it produces could not be trusted.) Even if an LDP connection request appears to come from an eligible peer, its source address may have been spoofed. Therefore, some means of preventing source address spoofing must be in place. For example, if all the eligible peers are in the same network, source address filtering at the border routers of that network could eliminate the possibility of source address spoofing. The LDP MD5 authentication key option, as described in Section 2.9 of [RFC5036], MUST be implemented, and for a greater degree of security, it must be used. This provides integrity and authentication for the LDP messages and eliminates the possibility of source address spoofing. Use of the MD5 option does not provide privacy, but privacy of the LDP control messages is not usually considered important. As the MD5 option relies on the configuration of pre- shared keys, it does not provide much protection against replay attacks. In addition, its reliance on pre-shared keys may make it very difficult to deploy when the set of eligible neighbors is determined by an auto-configuration protocol. When the Generalized PWid FEC Element is used, it is possible that a particular LDP peer may be one of the eligible LDP peers but may not be the right one to connect to the particular Attachment Circuit identified by the particular instance of the Generalized PWid FEC Element. However, given that the peer is known to be one of the eligible peers (as discussed above), this would be the result of a configuration error rather than a security problem. Nevertheless, it may be advisable for a PE to associate each of its local Attachment Circuits with a set of eligible peers rather than have just a single set of eligible peers associated with the PE as a whole.
Section 2.2 of [RFC6410] specifies four requirements that an Internet Standard must meet. This section documents how this document meets those requirements. The pseudowire technology was first deployed in 2001 and has been widely deployed by many carriers. [RFC7079] documents the results of a survey of PW implementations with specific emphasis on control-word usage. [EANTC] documents a public multi-vendor interoperability test of MPLS and Carrier Ethernet equipment, which included testing of Ethernet, ATM, and TDM pseudowires. The errata against [RFC4447] are generally editorial in nature and have been addressed in this document. All features in this specification have been implemented by multiple vendors. No IPR disclosures have been made to the IETF related to this document, to RFCs 4447 or 6723, or to the Internet-Drafts that resulted in RFCs 4447 and 6723. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>. [RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed., "LDP Specification", RFC 5036, DOI 10.17487/RFC5036, October 2007, <http://www.rfc-editor.org/info/rfc5036>. [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, <http://www.rfc-editor.org/info/rfc3032>. [RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)", BCP 116, RFC 4446, DOI 10.17487/RFC4446, April 2006, <http://www.rfc-editor.org/info/rfc4446>.
[RFC7358] Raza, K., Boutros, S., Martini, L., and N. Leymann, "Label Advertisement Discipline for LDP Forwarding Equivalence Classes (FECs)", RFC 7358, DOI 10.17487/RFC7358, October 2014, <http://www.rfc-editor.org/info/rfc7358>. [RFC2277] Alvestrand, H., "IETF Policy on Character Sets and Languages", BCP 18, RFC 2277, DOI 10.17487/RFC2277, January 1998, <http://www.rfc-editor.org/info/rfc2277>. [RFC3985] Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, DOI 10.17487/RFC3985, March 2005, <http://www.rfc-editor.org/info/rfc3985>. [RFC4842] Malis, A., Pate, P., Cohen, R., Ed., and D. Zelig, "Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Circuit Emulation over Packet (CEP)", RFC 4842, DOI 10.17487/RFC4842, April 2007, <http://www.rfc-editor.org/info/rfc4842>. [RFC4553] Vainshtein, A., Ed., and YJ. Stein, Ed., "Structure- Agnostic Time Division Multiplexing (TDM) over Packet (SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006, <http://www.rfc-editor.org/info/rfc4553>. [RFC4619] Martini, L., Ed., Kawa, C., Ed., and A. Malis, Ed., "Encapsulation Methods for Transport of Frame Relay over Multiprotocol Label Switching (MPLS) Networks", RFC 4619, DOI 10.17487/RFC4619, September 2006, <http://www.rfc-editor.org/info/rfc4619>. [RFC4717] Martini, L., Jayakumar, J., Bocci, M., El-Aawar, N., Brayley, J., and G. Koleyni, "Encapsulation Methods for Transport of Asynchronous Transfer Mode (ATM) over MPLS Networks", RFC 4717, DOI 10.17487/RFC4717, December 2006, <http://www.rfc-editor.org/info/rfc4717>. [RFC4618] Martini, L., Rosen, E., Heron, G., and A. Malis, "Encapsulation Methods for Transport of PPP/High-Level Data Link Control (HDLC) over MPLS Networks", RFC 4618, DOI 10.17487/RFC4618, September 2006, <http://www.rfc-editor.org/info/rfc4618>.
[RFC4448] Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron, "Encapsulation Methods for Transport of Ethernet over MPLS Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006, <http://www.rfc-editor.org/info/rfc4448>. [RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, DOI 10.17487/RFC4447, April 2006, <http://www.rfc-editor.org/info/rfc4447>. [RFC6410] Housley, R., Crocker, D., and E. Burger, "Reducing the Standards Track to Two Maturity Levels", BCP 9, RFC 6410, DOI 10.17487/RFC6410, October 2011, <http://www.rfc-editor.org/info/rfc6410>. [RFC6723] Jin, L., Ed., Key, R., Ed., Delord, S., Nadeau, T., and S. Boutros, "Update of the Pseudowire Control-Word Negotiation Mechanism", RFC 6723, DOI 10.17487/RFC6723, September 2012, <http://www.rfc-editor.org/info/rfc6723>. [RFC7079] Del Regno, N., Ed., and A. Malis, Ed., "The Pseudowire (PW) and Virtual Circuit Connectivity Verification (VCCV) Implementation Survey Results", RFC 7079, DOI 10.17487/RFC7079, November 2013, <http://www.rfc-editor.org/info/rfc7079>. [ANSI] American National Standards Institute, "Telecommunications - Synchronous Optical Network (SONET) - Basic Description Including Multiplex Structures, Rates, and Formats", ANSI T1.105, October 1995. [ITUG] International Telecommunications Union, "Network node interface for the synchronous digital hierarchy (SDH)", ITU-T Recommendation G.707, May 1996. [EANTC] European Advanced Networking Test Center, "MPLS and Carrier Ethernet: Service - Connect - Transport. Public Multi-Vendor Interoperability Test", February 2009. RFC 6723, whose work has been incorporated in this document: Lizhong Jin, Raymond Key, Simon Delord, Tom Nadeau, and Sami Boutros.
RFC 4447. They are listed here in recognition of their work on that document. Nasser El-Aawar Level 3 Communications, LLC. 1025 Eldorado Blvd. Broomfield, CO 80021 United States of America Email: email@example.com Eric C. Rosen Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA 01719 United States of America Email: firstname.lastname@example.org Dan Tappan Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA 01719 United States of America Email: email@example.com Toby Smith Google 6425 Penn Ave. #700 Pittsburgh, PA 15206 United States of America Email: firstname.lastname@example.org Dimitri Vlachos Riverbed Technology Email: email@example.com
Jayakumar Jayakumar Cisco Systems Inc. 3800 Zanker Road, MS-SJ02/2 San Jose, CA 95134 United States of America Email: firstname.lastname@example.org Alex Hamilton, Cisco Systems Inc. 485 East Tasman Drive, MS-SJC07/3 San Jose, CA 95134 United States of America Email: email@example.com Steve Vogelsang ECI Telecom Omega Corporate Center 1300 Omega Drive Pittsburgh, PA 15205 United States of America Email: firstname.lastname@example.org John Shirron ECI Telecom Omega Corporate Center 1300 Omega Drive Pittsburgh, PA 15205 United States of America Email: email@example.com Andrew G. Malis Verizon 60 Sylvan Rd. Waltham, MA 02451 United States of America Email: firstname.lastname@example.org
Vinai Sirkay Reliance Infocomm Dhirubai Ambani Knowledge City Navi Mumbai 400 709 India Email: email@example.com Vasile Radoaca Nortel Networks 600 Technology Park Billerica MA 01821 United States of America Email: firstname.lastname@example.org Chris Liljenstolpe 149 Santa Monica Way San Francisco, CA 94127 United States of America Email: email@example.com Dave Cooper Global Crossing 960 Hamlin Court Sunnyvale, CA 94089 United States of America Email: firstname.lastname@example.org Kireeti Kompella Juniper Networks 1194 N. Mathilda Ave Sunnyvale, CA 94089 United States of America Email: email@example.com