RFC 5089

IS-IS Protocol Extensions for Path Computation Element (PCE) Discovery

📅 published January 2008, from ietf

IS-IS Protocol Extensions for Path Computation Element (PCE) Discovery 🎀

Okay bestie, this is RFC 5089 💅 It's a Standards Track doc from the Network Working Group, dated January 2008. The editors are JL. Le Roux (France Telecom) and JP. Vasseur (Cisco System Inc.), and the other authors are Y. Ikejiri (NTT Communications) and R. Zhang (BT). The title block doesn't list anything it obsoletes or updates, so nothing gets replaced or patched here 🧚

Status of This Memo ✨

This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.

Abstract 🌸

Okay so there are loads of situations where a Path Computation Client (PCC) really wants to find a bunch of Path Computation Elements (PCEs) on its own, automatically, along with info it can use to pick between them 🫶 When the PCE is a Label Switching Router (LSR) in the Interior Gateway Protocol (IGP), or even just a server that's quietly part of the IGP, the simplest and most efficient way to announce PCEs is IGP flooding. So this document defines extensions to the Intermediate System to Intermediate System (IS-IS) routing protocol that advertise PCE Discovery information within an IS-IS area or across the entire IS-IS routing domain. It's giving efficiency, no cap 💜

Table of Contents 🦋

   1. Introduction ....................................................2
   2. Terminology .....................................................4
   3. Overview ........................................................5
      3.1. PCE Discovery Information ..................................5
      3.2. Flooding Scope .............................................5
   4. The IS-IS PCED Sub-TLV ..........................................5
      4.1. PCE-ADDRESS Sub-TLV ........................................6
      4.2. The PATH-SCOPE Sub-TLV .....................................7
      4.3. PCE-DOMAIN Sub-TLV .........................................9
      4.4. NEIG-PCE-DOMAIN Sub-TLV ...................................10
      4.5. PCE-CAP-FLAGS Sub-TLV .....................................10
   5. Elements of Procedure ..........................................11
   6. Backward Compatibility .........................................12
   7. IANA Considerations ............................................12
   8. Security Considerations ........................................12
   9. Manageability Considerations ...................................13
      9.1. Control of Policy and Functions ...........................13
      9.2. Information and Data Model ................................13
      9.3. Liveness Detection and Monitoring .........................13
      9.4. Verify Correct Operations .................................13
      9.5. Requirements on Other Protocols and Functional
           Components ................................................13
      9.6. Impact on Network Operations ..............................14
   10. Acknowledgments ...............................................14
   11. References ....................................................15
      11.1. Normative References .....................................15
      11.2. Informative References ...................................15

1. Introduction 💖

Okay so [RFC4655] is the big-picture doc 🌈 It covers the motivations and architecture for a PCE-based path computation model for Multi-Protocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineered Label Switched Paths (TE LSPs). The model lets the PCE be separated from a Path Computation Client (PCC), which is also called a non co-located PCE, and it lets PCEs cooperate with each other, where one PCE acts as a PCC making requests to the other PCE. All of that depends on a communication protocol between a PCC and a PCE, and also between PCEs. The requirements for that protocol live in [RFC4657], and the protocol itself is defined in [PCEP].

The PCE architecture needs a PCC to know where one or more PCEs are in its domain, and potentially where PCEs in other domains are too, like when you're computing inter-domain TE LSPs 🧚

A network can have a huge number of PCEs, and each one might have totally different capabilities 💅 So it's highly desirable to have a mechanism for automatic and dynamic PCE discovery, which lets PCCs find a set of PCEs along with extra info about each one that the PCC can use for PCE selection. It's also valuable for a PCC to dynamically notice new PCEs, failed PCEs, or any change to PCE information. The detailed requirements for that discovery mechanism are in [RFC4674] 🎀

Note that the PCE selection algorithm a PCC uses is out of the scope of this document 🙈

When PCCs are LSRs taking part in the IGP (OSPF or IS-IS), and PCEs are either LSRs or servers also taking part in the IGP, an effective way to discover PCEs inside an IGP routing domain is to use IGP advertisements. Iconic 👑

This document extends IS-IS [ISO] so that a PCE in an IS-IS routing domain can advertise its location, along with some info that's useful to a PCC for PCE selection, which satisfies the dynamic PCE discovery requirements set out in [RFC4674] ✨

Generic capability advertisement mechanisms for IS-IS are defined in [RFC4971]. They let a router advertise its capabilities within an IS-IS area or an entire IS-IS routing domain. This document uses that generic mechanism to fully satisfy the dynamic PCE discovery requirements 🦋

This document defines a new sub-TLV, named the PCE Discovery (PCED) sub-TLV, which gets carried inside the IS-IS Router Capability TLV ([RFC4971]) 🍓

The PCE information being advertised is detailed in Section 3. The protocol extensions and procedures are defined in Sections 4 and 5 🌸

The IS-IS extensions in this document allow PCE discovery within an IS-IS routing domain. Solutions for PCE discovery across AS boundaries are beyond the scope of this document and are left for further study 😭

This document defines a set of sub-TLVs that nest inside each other. When the nesting degree is 2 (a TLV carried within another TLV), the TLV carried within a TLV is called a sub-TLV. Strictly speaking, when the nesting degree is 3, a sub-sub-TLV is carried within a sub-TLV that is itself carried within a TLV. For the sake of terminology simplicity, a TLV carried within another TLV is called a sub-TLV regardless of the degree of nesting 🫶

2. Terminology 🧚

ABR: IS-IS Area Border Router.

AS: Autonomous System.

IGP: Interior Gateway Protocol. Either of the two routing protocols, Open Shortest Path First (OSPF) or Intermediate System to Intermediate system (IS-IS).

Intra-area TE LSP: A TE LSP whose path does not cross an IGP area boundary.

Intra-AS TE LSP: A TE LSP whose path does not cross an AS boundary.

Inter-area TE LSP: A TE LSP whose path transits two or more IGP areas. That is, a TE LSP that crosses at least one IGP area boundary.

Inter-AS TE LSP: A TE LSP whose path transits two or more ASes or sub-ASes (BGP confederations). That is, a TE LSP that crosses at least one AS boundary.

IS-IS LSP: Link State PDU.

LSR: Label Switching Router.

PCC: Path Computation Client. Any client application requesting a path computation to be performed by a Path Computation Element.

PCE: Path Computation Element. An entity (component, application, or network node) that is capable of computing a network path or route based on a network graph and applying computational constraints.

PCED: PCE Discovery.

PCE-Domain: In a PCE context, this refers to any collection of network elements within a common sphere of address management or path computational responsibility (referred to as a "domain" in [RFC4655]). Examples of PCE-Domains include IGP areas and ASes. This should be distinguished from an IS-IS routing domain as defined by [ISO].

PCEP: Path Computation Element communication Protocol.

TE LSP: Traffic Engineered Label Switched Path.

TLV: Type-Length-Variable data encoding.

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]. 🌈

3. Overview 🌟

3.1. PCE Discovery Information 💜

The PCE discovery information is made up of:

The PCE location: an IPv4 and/or IPv6 address that is used to reach the PCE. It is RECOMMENDED to use an address that is always reachable if there is any connectivity to the PCE;
The PCE path computation scope (i.e., intra-layer, inter-area, inter-AS, or inter-layer);
The set of one or more PCE-Domain(s) into which the PCE has visibility and for which the PCE can compute paths;
The set of zero, one, or more neighbor PCE-Domain(s) toward which the PCE can compute paths;
A set of communication capabilities (e.g., support for request prioritization) and path computation-specific capabilities (e.g., supported constraints).

PCE discovery information is, by nature, pretty static and doesn't change with PCE activity 🥹 Changes can happen because of PCE configuration updates, PCE deployment or activation, PCE deactivation or suppression, or PCE failure. So this info isn't expected to change often 🍓

3.2. Flooding Scope 🦋

The flooding scope for PCE information advertised through IS-IS can be a single L1 area, an L1 area and the L2 sub-domain, or the entire IS-IS routing domain 🌸

4. The IS-IS PCED Sub-TLV ✨

okay so the IS-IS PCED sub-TLV is basically a bag of sub-TLVs, and the order doesn't matter 🧚💖

It uses the same TLV shape as the Traffic Engineering Extensions to IS-IS [RFC3784] 🎀. That means 1 octet for the type, 1 octet for the length, and then a value field. The Length field tells you how many octets are in the value part.

The IS-IS PCED sub-TLV looks like this:

TYPE:   5
LENGTH: Variable
VALUE:  Set of sub-TLVs

There are five sub-TLVs defined 🌈:

Sub-TLV type  Length               Name
    1      variable     PCE-ADDRESS sub-TLV
    2         3         PATH-SCOPE sub-TLV
    3      variable     PCE-DOMAIN sub-TLV
    4      variable     NEIG-PCE-DOMAIN sub-TLV
    5      variable     PCE-CAP-FLAGS sub-TLV

The PCE-ADDRESS and PATH-SCOPE sub-TLVs MUST always be present within the PCED sub-TLV. no exceptions, bestie 😤

The PCE-DOMAIN and NEIG-PCE-DOMAIN sub-TLVs are optional. They MAY be present in the PCED sub-TLV to help with picking inter-domain PCEs 🦋

The PCE-CAP-FLAGS sub-TLV is also optional, and it MAY be present in the PCED sub-TLV to help with the PCE selection process 💅

Any unrecognized sub-TLV MUST be silently ignored 🙈

The PCED sub-TLV rides inside an IS-IS CAPABILITY TLV, which is defined in [RFC4971] 🫶

No additional sub-TLVs will be added to the PCED TLV in the future. If a future application needs to advertise more PCE information in IS-IS, that info will not go in the CAPABILITY TLV. it's giving "new home needed" energy 💀

The sub-sections below walk through each sub-TLV that can show up inside the PCED sub-TLV 🍓

4.1. PCE-ADDRESS Sub-TLV

The PCE-ADDRESS sub-TLV gives an IP address you can use to reach the PCE 📍. It is RECOMMENDED to use an address that is always reachable, as long as the PCE is alive and reachable.

This one is mandatory, so it MUST be present within the PCED sub-TLV 😭. It MAY appear twice, which makes sense when the PCE has both an IPv4 and an IPv6 address 🌸. It MUST NOT appear more than once for the same address type. If it does show up more than once for the same address type, only the first occurrence is processed and any others MUST be ignored. no double dipping 💅

The PCE-ADDRESS sub-TLV looks like this:

TYPE:   1
LENGTH: 5 for an IPv4 address or 17 for an IPv6 address.
VALUE:  This comprises one octet indicating the address-type and 4
        or 16 octets encoding the IPv4 or IPv6 address to be used
        to reach the PCE.

The address-type values are:

1   IPv4
2   IPv6

4.2. The PATH-SCOPE Sub-TLV

The PATH-SCOPE sub-TLV tells everyone what the PCE's path computation scope is 🔥. That means whether it can compute paths for intra-area, inter-area, inter-AS, or inter-layer TE LSPs (or take part in computing them) 👑

This one is mandatory too, so it MUST be present within the PCED sub-TLV. There MUST be exactly one instance of the PATH-SCOPE sub-TLV in each PCED sub-TLV 🎀. If it shows up more than once, only the first occurrence is processed and any others MUST be ignored.

The PATH-SCOPE sub-TLV has a set of bit flags for the supported path scopes, plus four fields for PCE preferences ✨

It looks like this:

TYPE:   2
LENGTH: 3
VALUE:  This comprises a 1-octet flags field where each flag
        represents a supported path scope, followed by a 2-octet
        preferences field indicating PCE preferences.

Here's the flags field layout 🦋:

+-+-+-+-+-+-+-+-+
|0|1|2|3|4|5|Res|
+-+-+-+-+-+-+-+-+

And here's what each bit means:

Bit      Path Scope

0      L bit:  Can compute intra-area paths.
1      R bit:  Can act as PCE for inter-area TE LSP computation.
2      Rd bit: Can act as a default PCE for inter-area TE LSP
               computation.
3      S bit:  Can act as PCE for inter-AS TE LSP computation.
4      Sd bit: Can act as a default PCE for inter-AS TE LSP
               computation.
5      Y bit:  Can act as PCE for inter-layer TE LSP
               computation.
6-7   Reserved for future use.

Now the preferences field 💜:

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PrefL|PrefR|PrefS|PrefY| Res   |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

PrefL field: PCE's preference for intra-area TE LSP computation.
PrefR field: PCE's preference for inter-area TE LSP computation.
PrefS field: PCE's preference for inter-AS TE LSP computation.
Pref-Y field: PCE's preference for inter-layer TE LSP computation.
Res: Reserved for future use.

The L, R, S, and Y bits get set when the PCE can act as a PCE for intra-area, inter-area, inter-AS, or inter-layer TE LSP computation, respectively 🌈. These bits are non-exclusive, so a PCE can have several set at once. 🙌

When the Rd bit is set, the PCE can act as a default PCE for inter-area TE LSP computation. Basically, it can compute a path toward any neighbor area 🧚. Same vibe for the Sd bit: when it's set, the PCE can act as a default PCE for inter-AS TE LSP computation, meaning it can compute a path toward any neighbor AS 💖.

When the Rd and Sd bits are both set, the PCED sub-TLV MUST NOT contain a NEIG-PCE-DOMAIN sub-TLV (see Section 4.4) 🙅‍♀️

When the R bit is clear, the Rd bit SHOULD be clear on transmission and MUST be ignored on receipt. When the S bit is clear, the Sd bit SHOULD be clear on transmission and MUST be ignored on receipt. 🫠

The PrefL, PrefR, PrefS, and PrefY fields are each three bits long, which lets the PCE state a preference for each computation scope. 7 is the highest preference 👑. These preferences can be used for weighted load balancing of path computation requests ⚖️. An operator might configure a preference for each scope at each PCE to spread the path computation load around 🍓. How a PCC actually balances its requests based on these PCE preferences is out of scope for this document. That's up to local or network-wide policy 💅. The same or different preferences can be used for each scope.

For example, say an operator has a PCE that can do both inter-area and inter-AS computation, and they want it to be the go-to for inter-AS work. They could set PrefS higher than PrefR 🦋.

When the L, R, S, or Y bits are cleared, the PrefL, PrefR, PrefS, and PrefY fields SHOULD respectively be set to 0 on transmission and MUST be ignored on receipt 🙈.

Both reserved fields SHOULD be set to zero on transmission and MUST be ignored on receipt ✨.

4.3. PCE-DOMAIN Sub-TLV

The PCE-DOMAIN sub-TLV names a PCE-Domain (an area and/or an AS) where the PCE has topology visibility and can compute paths through 🗺️.

The PCE-DOMAIN sub-TLV SHOULD be present when the PCE-Domains a PCE can operate in can't be figured out from other IGP information 🔍. A classic example is when the PCE is inter-domain capable (meaning the R bit or S bit is set) and the flooding scope is the entire routing domain. (Check out Section 5 for how the flooding scope gets set and interpreted 💖.)

A PCED sub-TLV can include multiple PCE-DOMAIN sub-TLVs when the PCE can see multiple PCE-Domains 🌸.

The PCE-DOMAIN sub-TLV looks like this:

TYPE:   3
LENGTH: Variable
VALUE:  This is composed of one octet indicating the domain-type
        (area ID or AS Number) and a variable length IS-IS area ID
        or a 32-bit AS number, identifying a PCE-Domain where the
        PCE has visibility and can compute paths.

Two domain types are defined:

1   Area ID
2   AS Number

The Area ID is the area address as defined in [ISO] 🧩.

When the AS number is coded in two octets, the AS Number field MUST have its first two octets set to 0. 🔢

4.4. NEIG-PCE-DOMAIN Sub-TLV

The NEIG-PCE-DOMAIN sub-TLV names a neighbor PCE-Domain (an area or an AS) that a PCE can compute paths toward 🚀. It basically means the PCE can take part in computing inter-domain TE LSPs whose paths go through that neighbor PCE-Domain 🌈.

A PCED sub-TLV can include several NEIG-PCE-DOMAIN sub-TLVs when the PCE can compute paths toward several neighbor PCE-Domains 💜.

The NEIG-PCE-DOMAIN sub-TLV has the same format as the PCE-DOMAIN sub-TLV:

TYPE:   4
LENGTH: Variable
VALUE:  This comprises one octet indicating the domain-type (area
        ID or AS Number) and a variable length IS-IS area ID or a
        32-bit AS number, identifying a PCE-Domain toward which
        the PCE can compute paths.

Two domain types are defined:

1   Area ID
2   AS Number

The Area ID is the area address as defined in [ISO].

When the AS number is coded in two octets, the AS Number field MUST have its first two octets set to 0.

The NEIG-PCE-DOMAIN sub-TLV MUST be present at least once with domain-type set to 1 if the R bit is set and the Rd bit is cleared. It MUST also be present at least once with domain-type set to 2 if the S bit is set and the Sd bit is cleared 🫶.

4.5. PCE-CAP-FLAGS Sub-TLV

The PCE-CAP-FLAGS sub-TLV is optional, and it's used to show PCE capabilities 💫. It MAY be present within the PCED sub-TLV. It MUST NOT be present more than once. If it does appear more than once, only the first occurrence is processed and any others MUST be ignored 🙅‍♀️.

The value field of the PCE-CAP-FLAGS sub-TLV is an array of 32-bit flag units. The bits are numbered starting from the most significant bit, which counts as bit zero, and each bit stands for one PCE capability 🎀.

The PCE-CAP-FLAGS sub-TLV looks like this:

TYPE:   5
LENGTH: Multiple of 4
VALUE:  This contains an array of units of 32-bit flags numbered
        from the most significant as bit zero, where each bit
        represents one PCE capability.

The PCE capability registry is managed by IANA. It's shared with OSPF and defined in [RFC5088] 🌸.

Reserved bits SHOULD be set to zero on transmission and MUST be ignored on receipt 🍓.

5. Elements of Procedure 🎀

okay so the PCED sub-TLV rides inside an IS-IS Router Capability TLV from [RFC4971], which means it borrows all of that RFC's procedures. no need to reinvent the wheel bestie 💅

the flooding scope is controlled by the S flag in the Router Capability TLV (see [RFC4971]). so if the PCED sub-TLV is area local, it MUST be carried in a Router Capability TLV with the S bit cleared. if it's meant for the whole IS-IS routing domain, it MUST be carried in one with the S bit set. ALSO, lowkey important: when only the L bit of the PATH-SCOPE sub-TLV is set, the flooding scope MUST be area local 🧚

an L1L2 node can put a PCED TLV in a Router Capability TLV with the S bit cleared in BOTH its L1 and L2 LSPs. this keeps the flooding restricted to the L1 area and the L2 sub-domain. very neat, very contained 🦋

when the PCE function gets deactivated, the IS-IS speaker advertising it MUST originate a new IS-IS LSP that no longer includes the matching PCED TLV. gone, bye 👋

the PCE address (the one in the PCE-ADDRESS sub-TLV) SHOULD be reachable via some prefixes advertised by IS-IS. not a hard rule, but it's giving "you'll thank yourself later" 🌸

the PCED sub-TLV info about a specific PCE is only considered current and useable when the router advertising it is itself reachable via IS-IS calculated paths, at the level of the LSP where the PCED sub-TLV shows up. no reachability, no trust. period 💀

a change in a PCE's state (activate, deactivate, parameter change) MUST result in a matching change in the PCED sub-TLV that the IS-IS router advertises in its LSP (inserted, removed, or updated). keep it in sync or it's a mess 🫶

how PCEs figure out what to advertise, and how that gets handed over to IS-IS, is out of scope for this doc. some stuff can be configured (like address, preferences, scope) and other stuff the PCE can work out on its own (like areas of visibility). not our problem here ✨

and finally, a change in PCED sub-TLV info MUST NOT trigger any SPF computation at a receiving router. no unnecessary recomputing, we respect the CPU 🧠💖

6. Backward Compatibility 🦋

the PCED sub-TLV in this doc doesn't cause any interoperability issues. it's giving smooth

an IS-IS router that doesn't support the PCED sub-TLV will just silently ignore it, as specified in [RFC4971]. no drama, no crashes, just vibes 🌈

7. IANA Considerations 📋

IANA has a registry for the sub-TLVs carried in the IS-IS Router Capability TLV from [RFC4971]. and they've assigned a brand new sub-TLV codepoint for the PCED sub-TLV, inside the Router Capability TLV. here's the table:

  Value      Sub-TLV                   References
  -----     --------                   ----------
    5       PCED sub-TLV              (this document)

8. Security Considerations 🔐

okay this section is SERIOUS so let's be serious for a sec 😭

this document defines IS-IS extensions for PCE discovery within an administrative domain. which means the security of PCE discovery depends on the security of IS-IS. so if IS-IS is shaky, everything built on it is shaky too 💀

the mechanisms for ensuring authenticity and integrity of IS-IS LSPs and their TLVs, from [RFC3567], can be used to secure the PCED sub-TLV as well. good news 🔒

BUT, the warning: IS-IS provides NO encryption mechanism for protecting the privacy of LSPs. that includes the privacy of the PCE discovery information. so anyone who can read the LSPs can read the PCE info. not private, bestie 🙈

9. Manageability Considerations ⭐

manageability for PCE Discovery is covered in Section 4.10 of [RFC4674]. go read that one too, it's the main character here 📚

9.1. Control of Policy and Functions 🎛️

the requirements for configuring PCE discovery parameters on PCCs and PCEs are discussed in Section 4.10.1 of [RFC4674].

specifically, a PCE implementation SHOULD allow these parameters to be configured on the PCE:

The PCE IPv4/IPv6 address(es) (see Section 4.1).
The PCE Scope, including the inter-domain functions (inter-area, inter-AS, inter-layer), the preferences, and whether the PCE can act as default PCE (see Section 4.2).
The PCE-Domains (see Section 4.3).
The neighbor PCE-Domains (see Section 4.4).
The PCE capabilities (see Section 4.5).

9.2. Information and Data Model 🗂️

a MIB module for PCE Discovery is defined in [PCED-MIB]. data model moment 🍓

9.3. Liveness Detection and Monitoring 💓

this document specifies the use of IS-IS as a PCE Discovery Protocol. the requirements in [RFC4674] include being able to determine liveness of the PCE Discovery protocol. and guess what? normal IS-IS operation already meets those requirements. iconic, no extra work ✨

9.4. Verify Correct Operations 🔍

you can match up what's advertised with what's received by comparing the info in the PCED sub-TLV the PCC received against what's stored at the PCE, using the PCED MIB [PCED-MIB]. and the number of dropped, corrupt, and rejected information elements are all available through the PCED MIB. detective work, but make it aesthetic 🕵️‍♀️💜

9.5. Requirements on Other Protocols and Functional Components 🧩

the IS-IS extensions in this document don't imply any requirements on other protocols. nothing else has to change, we're good 🫶

9.6. Impact on Network Operations 🌪️

ok this one is important. frequent changes in the PCE info advertised in the PCED sub-TLV can have a big impact on IS-IS, and might destabilize the network by making PCCs keep swapping between PCEs. nobody wants that chaos 😭

as discussed in Section 4.10.4 of [RFC4674], it MUST be possible to apply at least the following controls:

Configurable limit on the rate of announcement of changed parameters at a PCE.
Control of the impact on PCCs, such as through rate-limiting the processing of PCED sub-TLVs.
Configurable control of triggers that cause a PCC to swap to another PCE.

10. Acknowledgments 🙏

big thank you to Lucy Wong, Adrian Farrel, Les Ginsberg, Mike Shand, Lou Berger, David Ward, Ross Callon, and Lisa Dusseault for their useful comments and suggestions. legends, every one of them 👑

11. References 📚

11.1. Normative References 🔗

[ISO] "Intermediate System to Intermediate System Intra-Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service" ISO/IEC 10589:2002 Second Edition.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3567] Li, T. and R. Atkinson, "Intermediate System to Intermediate System (IS-IS) Cryptographic Authentication", RFC 3567, July 2003.
[RFC3784] Smit, H. and T. Li, "Intermediate System to Intermediate System (IS-IS) Extensions for Traffic Engineering (TE)", RFC 3784, June 2004.
[RFC4971] Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed., "Intermediate System to Intermediate System (IS-IS) Extensions for Advertising Router Information", RFC 4971, July 2007.
[RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R. Zhang, "OSPF Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5088, January 2008.

11.2. Informative References 💡

[PCED-MIB] Stephan, E., "Definitions of Managed Objects for Path Computation Element Discovery", Work in Progress, March 2007.
[PCEP] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path Computation Element (PCE) communication Protocol (PCEP) ", Work in Progress, November 2007.
[RFC4655] Farrel, A., Vasseur, JP., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC4657] Ash, J., Ed., and J. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol Generic Requirements", RFC 4657, September 2006.
[RFC4674] Le Roux, J., Ed., "Requirements for Path Computation Element (PCE) Discovery", RFC 4674, October 2006.

Authors' Addresses 🏠

Jean-Louis Le Roux (Editor)
France Telecom
2, avenue Pierre-Marzin
22307 Lannion Cedex
FRANCE
EMail: jeanlouis.leroux@orange-ftgroup.com


Jean-Philippe Vasseur (Editor)
Cisco Systems, Inc.
1414 Massachusetts avenue
Boxborough, MA 01719
USA
EMail: jpv@cisco.com


Yuichi Ikejiri
NTT Communications Corporation
1-1-6, Uchisaiwai-cho, Chiyoda-ku
Tokyo 100-8019
JAPAN
EMail: y.ikejiri@ntt.com


Raymond Zhang
BT
2160 E. Grand Ave.
El Segundo, CA 90025
USA
EMail: raymond.zhang@bt.com

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Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr.

The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org.

📦 where this page comes from

ietf: rfc5089 2008-01
💖 girlified by claude-haiku-5-5 on 2026-10-17: a language model's rewrite of the original, under its terms