RFC 6667

LDP 'Typed Wildcard' Forwarding Equivalence Class (FEC) for PWid and Generalized PWid FEC Elements

📅 published July 2012, from ietf

RFC 6667: LDP 'Typed Wildcard' Forwarding Equivalence Class (FEC) for PWid and Generalized PWid FEC Elements 💖

Okay bestie, this is part 1 of 2 🎀 It's an Internet Engineering Task Force (IETF) document, written by K. Raza, S. Boutros, and C. Pignataro from Cisco Systems, and it came out in July 2012. It's a Standards Track document (ISSN 2070-1721), so it's an official Internet standard. The title block doesn't list any Obsoletes or Updates, so it isn't replacing or changing any older RFC 🫶

Abstract ✨

Okay, so the "Typed Wildcard Forwarding Equivalence Class (FEC) Element" is an extension to the Label Distribution Protocol (LDP) 🦋 It's for when you want to request, withdraw, or release every label binding for one FEC Element type all at once. The catch is that a Typed Wildcard FEC Element has to be defined separately for each FEC Element type. This spec defines them for the Pseudowire Identifier (PWid) (0x80) and Generalized PWid (0x81) FEC Element types 💅

Status of This Memo ✨

This is an Internet Standards Track document 💜

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has gotten public review and has been approved for publication by the Internet Engineering Steering Group (IESG). For more on Internet Standards, check out Section 2 of RFC 5741 🌸

You can find out the current status of this document, any errata, and how to send feedback at http://www.rfc-editor.org/info/rfc6667.

Copyright Notice ✨

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 read these carefully, because they describe your rights and restrictions for 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 they come without warranty as described in the Simplified BSD License 🔥

This document may not be modified, and derivative works of it may not be created, except to format it for publication as an RFC or to translate it into languages other than English 🫶

Table of Contents 🧚

1. Introduction ....................................................2
2. Typed Wildcard for PW FEC Elements ..............................3
3. Applicability Statement .........................................4
4. Operation .......................................................4
   4.1. PW Consistency Check .......................................5
   4.2. PW Graceful Shutdown .......................................5
   4.3. Wildcard PW Status .........................................5
   4.4. Typed Wildcard MAC Withdrawal in VPLS ......................6
5. Security Considerations .........................................6
6. Acknowledgments .................................................7
7. References ......................................................7
   7.1. Normative References .......................................7
   7.2. Informative References .....................................7

1. Introduction ✨

Okay, so the Label Distribution Protocol (LDP) [RFC5036] got an extension that defines the general idea of a "Typed Wildcard Forwarding Equivalence Class (FEC) Element" [RFC5918] 🌈 You use it when you want to request, release, or withdraw all label bindings for a given type of FEC Element at once. Same catch as before: a Typed Wildcard FEC Element has to be defined individually for each type of FEC Element 💀

[RFC4447] defines the "PWid FEC Element" and the "Generalized PWid FEC Element", but it doesn't spell out the Typed Wildcard format for them. So this document does 🦋 It specifies the Typed Wildcard FEC Element format for the "PWid FEC Element" and the "Generalized PWid FEC Element". The Typed Wildcard processing for PWid and Generalized PWid FEC Elements works the same way as described in [RFC5918] for any Typed Wildcard FEC Element type ✨

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 [RFC2119] 💜

2. Typed Wildcard for PW FEC Elements 🎀

Here's the format of the Typed Wildcard FEC Element for PWid and Generalized PWid, bestie 👑

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Typed Wcard=0x5| Type=PW FEC   |   Len = 2     |R|   PW type   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    . . .      |
   +-+-+-+-+-+-+-+-+

         Figure 1: Format of Typed Wildcard FEC Element for
                        PW FEC Element Types

Here's what each part means 🌸

Typed Wcard (one octet): this is the Typed Wildcard FEC Element type (0x05), as specified in [RFC5918].
[FEC Element] Type (one octet): this is the PW FEC Element type. It can be:
- PWid: (type 0x80 [RFC4447])
- Generalized PWid: (type 0x81 [RFC4447])
Len [FEC Type Info] (one octet): it's Two. There's extra FEC info to scope the Typed Wildcard 🍓
R bit (Reserved bit): it MUST be set to ZERO on transmit and ignored on receipt 🙈
PW type (15-bits): this is the PW type as specified in [RFC4447]. The field scopes the wildcard FEC operation to limit all PWs of a given type. It MUST be set to "Wildcard" type (0x7FFF), as defined in [IANA-PWE3], when referring to PWs of all types (see Section 4 for its usage) 🦋

[RFC4447] defines the "PW Grouping ID TLV", which can be used for wildcard withdrawal or status messages related to Generalized PWid FECs. When the Typed Wildcard FEC for Generalized PWid FEC element is in use, the "PW Grouping ID TLV" MUST NOT be present in the same message. If it is present anyway, the receiving Label Switching Router (LSR) MUST ignore this TLV silently and process the rest of the message ⭐

3. Applicability Statement 🌈

The Typed Wildcard FEC Elements defined here for the PWid and Generalized PWid FEC Elements give you a finer degree of granularity than the wildcard FEC mechanics defined in [RFC5036] 💅

The PWid FEC Element from [RFC4447] has a Group ID field. It's an arbitrary 32-bit value that represents a group of PWs. It's used to make groups in the PW space, and that can include one single group of all PWs for a given FEC Element type. Grouping lets an LSR send "wildcard" label withdrawals and/or status notification messages for a PW group when there's a physical port failure. [RFC4447] defines the "PW Grouping ID TLV" for the same job on the Generalized PWid FEC Element 🫶

The PWid Typed Wildcard FEC Elements defined in this document help achieve similar functionality to the "Group ID" field or the "PW Grouping ID TLV" for label withdrawal and status notification messages. On top of that, the Typed Wildcard procedures in [RFC5918] give a more generalized and comprehensive solution by allowing:

Typed Wildcard Label Request messages
Label TLVs in label messages to further constrain the wildcard to all FECs of the specified FEC type [and its specific filter] that are also bound to the specified label.

This document lets you use the Typed Wildcard PW FEC Element in any LDP message that specifies a FEC TLV as a mandatory or optional parameter of the message 🎀 Along with LDP label messages, that also covers notification messages (containing PW Status) and Address Withdraw messages (for MAC address withdrawal [RFC4762]) in the context of LDP PW signaling. When a Typed Wildcard PW FEC Element is used in an Address Withdraw message for Virtual Private LAN Service (VPLS) Media Access Control (MAC) address withdrawal, the MAC List TLV MUST contain an empty list 🔥

Part 1 ends here, bestie! Part 2 picks up with Section 4 (Operation) 🦋💖

4.4. Typed Wildcard MAC Withdrawal in VPLS ✨

Okay so [RFC4762] is the pseudowire-based way to build Virtual Private LAN Service (VPLS) 🌸, and Section 6.2 of RFC 4762 is where the MAC Withdrawal stuff lives 💅. Those procedures use the LDP Address Withdraw message, which carries the FEC TLV (with the PW FEC element for the VPLS instance) and the MAC List TLV (listing the addresses to be withdrawn). RFC 4762 also lets you wildcard MAC address withdrawal for a given VPLS instance 🦋.

Here's the thing: a PE LSR can withdraw all MAC addresses for one VPLS instance by sending an Address Withdraw message with that VPLS instance's PW FEC element in a FEC TLV, plus a MAC List TLV with an empty list of addresses 🧚. But if there's more than one VPLS instance on the same PE LSR node, the PE LSR has to send separate Address Withdraw messages whenever it wants to withdraw MAC addresses for all or a subset of those instances, say after a global failure or a config change 😭. Per-PW (VPLS instance) MAC Withdraw messages can get a bit much in a large-scale network, so it's giving scalability concerns 🙈.

This is where the good stuff comes in ✨. As stated in Section 3, this document lets you use the Typed Wildcard PW FEC in Address Withdraw messages for VPLS MAC Withdrawal 🎀. The Typed Wildcard PW FEC widens the scope of MAC withdrawal past a single VPLS instance, so a PE node can wildcard withdraw all MAC addresses for:

all VPLS instances; or
all VPLS instances corresponding to a given PW type.

Iconic, honestly 👑.

5. Security Considerations 🔐

Okay, security time, and I need you to take this seriously bestie 💀. No new security considerations beyond the ones already covered by [RFC5036], [RFC4447], [RFC4762], [RFC5918], and [RFC5920] apply to the use of the PW Typed Wildcard FEC Element types described in this document 🫶. So if you're already following those specs, you're in the clear for this one, but don't skip them, periodt 🔥.

6. Acknowledgments 💜

The authors gave a big shoutout to Eric Rosen, Reshad Rahman, Siva Sivabalan, and Zafar Ali for reviewing the doc and dropping valuable comments 🌈. They also gave credit to Daniel Cohn for suggesting the Typed Wildcard PW FEC for VPLS MAC withdrawal 🍓.

This document was prepared using 2-Word-v2.0 template.dot. 📝

7. References 📚

7.1. Normative References

[RFC5036]   Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
            "LDP Specification", RFC 5036, October 2007.

[RFC5918]   Asati, R., Minei, I., and B. Thomas, "Label Distribution
            Protocol (LDP) 'Typed Wildcard' Forward Equivalence Class
            (FEC)", RFC 5918, August 2010.

[RFC5919]   Asati, R., Mohapatra, P., Chen, E., and B. Thomas,
            "Signaling LDP Label Advertisement Completion", RFC 5919,
            August 2010.

[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, April 2006.

[RFC4762]   Lasserre, M., Ed., and V. Kompella, Ed., "Virtual Private
            LAN Service (VPLS) Using Label Distribution Protocol
            (LDP) Signaling", RFC 4762, January 2007.

            [RFC2119]   Bradner, S., "Key words for use in RFCs to
            Indicate Requirement Levels", BCP 14, RFC 2119, March
            1997.

7.2. Informative References

[RFC5920]   Fang, L., Ed., "Security Framework for MPLS and GMPLS
            Networks", RFC 5920, July 2010.

[IANA-PWE3] Internet Assigned Numbers Authority, "Pseudo Wires Name
            Spaces (PWE3)",
            http://www.iana.org/assignments/pwe3-parameters, May
            2011.

Authors' Addresses 📮

Kamran Raza
Cisco Systems, Inc.
2000 Innovation Drive
Ottawa ON K2K-3E8
Canada
EMail: skraza@cisco.com

Sami Boutros
Cisco Systems, Inc.
3750 Cisco Way
San Jose, CA 95134
USA
EMail: sboutros@cisco.com

Carlos Pignataro
Cisco Systems, Inc.
7200 Kit Creek Road
Research Triangle Park, NC 27709-4987
USA
EMail: cpignata@cisco.com

📦 where this page comes from

ietf: rfc6667 2012-07
💖 girlified by claude-haiku-5-5 on 2026-10-17: a language model's rewrite of the original, under its terms