RFC 5441

A Backward-Recursive PCE-Based Computation (BRPC) Procedure to Compute Shortest Constrained Inter-Domain Traffic Engineering Label Switched Paths

📅 published April 2009, from ietf

1. Introduction ✨

📜 Part 1 of 4 (more parts coming, bestie!)

Okay so, before we dive in, here's the title block tea ☕. This is RFC 5441 💖, published in April 2009 in the Network Working Group series, and it's a Standards Track doc. The title is "A Backward-Recursive PCE-Based Computation (BRPC) Procedure to Compute Shortest Constrained Inter-Domain Traffic Engineering Label Switched Paths" 🦋. The editor is JP. Vasseur, Ed. from Cisco Systems, Inc, and the co-authors are R. Zhang (BT Infonet), N. Bitar (Verizon), and JL. Le Roux (France Telecom). The header doesn't list anything it obsoletes or updates, so there's no drama there 🙈.

Now the actual intro. The requirements for inter-area and inter-AS MPLS Traffic Engineering (TE) were developed by the Traffic Engineering Working Group (TE WG) and stated in [RFC4105] and [RFC4216], respectively 🌸. The framework for inter-domain Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) lives in [RFC4726] 🧚.

Next up is [RFC5152] 💅. It defines a technique for setting up an inter-domain Generalized MPLS (GMPLS) TE Label Switched Path (LSP) where the path gets computed during the signaling process, one domain at a time, by the entry boundary node of each domain. (Each node that triggers the computation of a section of an inter-domain TE LSP path is always along the path of that TE LSP.) This technique hits some of the requirements in [RFC4105] and [RFC4216], but not all of them 😭. Specifically, it can't guarantee that you'll find an optimal (shortest) inter-domain constrained path, and it can't be efficiently used to compute a set of inter-domain diversely routed TE LSPs. Not ideal, bestie.

The Path Computation Element (PCE) architecture is defined in [RFC4655] 👑. The goal of this document is to describe a PCE-based path computation procedure that computes optimal inter-domain constrained (G)MPLS TE LSPs 🔥.

Quick clarification, because "optimal" is doing a lot of work here 🙃. A globally optimal TE LSP placement usually means a set of TE LSPs whose placements optimize network resources against some objective function (for example, a placement that reduces the maximum or average network load while still satisfying the TE LSP constraints). In this document, though, an optimal inter-domain constrained TE LSP is defined as the shortest path that satisfies the set of required constraints, the one you'd get if there were no multiple domains at all (basically, a totally flat IGP network between the source and destination of the TE LSP) ✨. Heads up: this only works if you use consistent metric schemes in each domain (see Section 13) 💜.

1.1. 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 RFC 2119 [RFC2119] 🎀.

2. Terminology

Okay, the glossary time, and I'm going to be so real with you, these matter 🧠.

  • ABR: Area Border Routers. Routers used to connect two IGP areas (areas in OSPF or levels in IS-IS).
  • ASBR: Autonomous System Border Router. Router used to connect together ASes of the same or different service providers via one or more inter-AS links.
  • Boundary Node (BN): a boundary node is either an ABR in the context of inter-area Traffic Engineering or an ASBR in the context of inter-AS Traffic Engineering.
  • Entry BN of domain(n): a BN connecting domain(n-1) to domain(n) along a determined sequence of domains.
  • Exit BN of domain(n): a BN connecting domain(n) to domain(n+1) along a determined sequence of domains.
  • Inter-area TE LSP: A TE LSP that crosses an IGP area boundary.
  • Inter-AS TE LSP: A TE LSP that crosses an AS boundary.
  • LSP: Label Switched Path.
  • 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.
  • PCE(i) is a PCE with the scope of domain(i).
  • TED: Traffic Engineering Database.
  • VSPT: Virtual Shortest Path Tree.

The notion of contiguous, stitched, and nested TE LSPs is defined in [RFC4726] and won't be repeated here 🌈.

3. General Assumptions

For the rest of this doc, we're making a set of assumptions that are common to inter-area and inter-AS MPLS TE 🫶:

  • Each IGP area or Autonomous System (AS) is assumed to be Traffic Engineering enabled.
  • No topology or resource information is distributed between domains (as mandated per [RFC4105] and [RFC4216]), which is critical to preserve IGP/BGP scalability and confidentiality 🔒.
  • While certain constraints like bandwidth can be used across different domains, other TE constraints (such as resource affinity, color, metric, etc. [RFC2702]) could be translated at domain boundaries. If required, it is assumed that, at the domain boundary nodes, there will exist some sort of local mapping based on policy agreement, in order to translate such constraints across domain boundaries during the inter-PCE communication process 🦋.
  • Each AS can be made of several IGP areas. The path computation procedure described in this document applies to the case of a single AS made of multiple IGP areas, multiple ASes made of a single IGP area, or any combination of the above. For the sake of simplicity, each AS will be considered to be made of a single area in this document. The case of an inter-AS TE LSP spanning multiple ASes, where some of those ASes are themselves made of multiple IGP areas, can be easily derived from this case by applying the BRPC procedure described in this document, recursively 🍓.
  • The domain path (the set of domains traversed to reach the destination domain) is either administratively predetermined or discovered by some means that is outside of the scope of this document 💜.

4. BRPC Procedure ✨

Okay so the BRPC procedure is a multiple-PCE path computation technique, described in [RFC4655] 💅. One possible setup is hosting the PCE function on boundary nodes (like ABRs or ASBRs), but BRPC doesn't make that mandatory 🧚.

The BRPC procedure runs on communication between cooperating PCEs 🫶. The PCC sends a PCReq to a PCE in its own domain. That request gets passed from PCE to PCE, domain by domain, until it reaches the PCE responsible for the domain with the LSP destination 🎀. The destination-domain PCE builds a tree of potential paths to the destination, called the Virtual Shortest Path Tree - VSPT ✨, and sends it back to the previous PCE in a PCRep. Every PCE along the way adds to the VSPT and passes it back, until the source-domain PCE uses the VSPT to pick an end-to-end path and sends that to the PCC 👑.

BRPC makes no assumption about what kind of inter-domain TE LSP it is. It could be contiguous, nested, or stitched, and it doesn't care 💅.

It also makes no assumption about the path computation algorithm a PCE uses 🌈. That could be any flavor of Constrained Shortest Path First (CSPF), or an algorithm built on linear programming for multi-constraint optimization problems 🧠.

4.1. Domain Path Selection

The PCE-based BRPC procedure is for computing an optimal constrained inter-domain TE LSP 🦋. The sequence of domains to traverse is either set up ahead of time by admins or discovered some other way that's outside the scope of this document 🗺️. The PCC MAY indicate the domain sequence using the Include Route Object (IRO) defined in [RFC5440], so that every PCE can see it 👀. Also, a sequence of PCEs MAY be enforced by policy on the PCC, and that constraint can ride along in the PCEP path computation request (as defined in [PCE-MONITOR]) 💜.

BRPC guarantees the optimal path across one specific sequence of domains, and that sequence counts as an extra constraint 🔒. If you've got an arbitrary set of meshed domains, you can run BRPC across each domain set to get the optimal constrained path between the TE LSP's source and destination 🕸️. It also works across just a subset of the domain sequences, and then you pick the best path among those 🏆.

4.2. Mode of Operation

Definition of VSPT(i)

In each domain i, here's the setup 🧩:

  • There is a set of X-en(i) entry BNs, noted BN-en(k,i), where BN-en(k,i) is the kth entry BN of domain(i).
  • There is a set of X-ex(i) exit BNs, noted BN-ex(k,i), where BN-ex(k,i) is the kth exit BN of domain(i).

VSPT(i) is the MP2P (multipoint-to-point) tree that PCE(i) returns to PCE(i-1) 🌳:

                        Root (TE LSP destination)
                        /         |            \
                  BN-en(1,i)   BN-en(2,i) ... BN-en(j,i).

                   where [X-en(i)] is the number of
                entry BNs in domain i and j<= [X-en(i)]

Figure 1: MP2P Tree

Each link of VSPT(i) is the shortest constrained path between BN-en(j,i) and the TE LSP destination, and it has to satisfy the set of required constraints for the TE LSP (bandwidth, affinities, etc.) 💅. These are the path segments that get you from BN-en(j,i) to the TE LSP destination 🛤️.

PCE(i) only looks at the entry BNs of domain(i), meaning only the BNs that give connectivity from domain(i-1) 🚪. So the set BN-en(k,i) is made only of those BNs that connect domain (i-1) to domain(i). Some BNs might also get excluded because of policy constraints, whether that's local policy or policy signaled in the path computation request 🙅‍♀️.

Step 1: First, the PCC has to figure out which PCE can serve its path computation request. It can do that with local configuration or through IGP discovery (see [RFC5088] and [RFC5089]) 🔍. The request then gets relayed until it reaches a PCE(n) where the TE LSP destination lives in domain(n) 🎯. At every step, the next PCE can be statically configured or dynamically discovered through IGP/BGP extensions 🪄. If no next PCE can be found, or the next-hop PCE of choice is unavailable, the procedure stops and a path computation error comes back (see Section 9) 💀. If PCE(i-1) finds multiple PCEs for the adjacent domain(i), PCE(i) may pick a subset of them based on local policies or heuristics 🎲. How PCEs get selected is outside the scope of this document.

Step 2: PCE(n) computes VSPT(n), the tree made of the list of shortest constrained paths between every BN-en(j,n) and the TE LSP destination. It uses a suitable path computation algorithm (e.g., CSPF) and sends the computed VSPT(n) back to PCE(n-1) 🌟.

Step i: For i=n-1 to 2, PCE(i) computes VSPT(i), the tree of shortest constrained paths between each BN-en(j,i) and the TE LSP destination 🧠. It does this by combining its own TED with the information in VSPT(i+1) 🤝.

In the case of inter-AS TE LSP computation, this also means adding the inter-AS TE links that connect domain(i) to domain(i+1) 🔗.

Step n: Finally, PCE(1) computes the end-to-end shortest constrained path from source to destination, and returns that path to the requesting PCC in a PCRep message, as defined in [RFC5440] 🎉.

Each branch of the VSPT (path) can come back in one of two forms 🌿. It can be an explicit path, where every hop along the path segment is listed. Or it can be a loose path, where only the BN is specified. Loose paths keep confidentiality intact, along with the respective cost 🤐. In the loose case, different techniques can retrieve the computed explicit paths on a per-domain basis during signaling, thanks to path keys as described in [PATH-KEY] 🗝️.

A PCE that can compute the requested path for more than one consecutive domain on the path SHOULD do that computation for all of those domains before passing the PCRep to the previous PCE in the sequence 📦.

BRPC guarantees finding the optimal (shortest) constrained inter-domain TE LSP across a set of defined domains to traverse 💯. Other variants of the BRPC procedure that rely on the same principles are also possible 🦄.

Also, when there are Equal Cost Multi-Path (ECMP) paths, more than one path could be returned to the requesting PCC 👯‍♀️.

5. PCEP Protocol Extensions 🧩

The BRPC procedure needs a new flag in the RP object carried within the PCReq message (defined in [RFC5440]). That flag says the PCC wants the shortest paths that satisfy the constraints, running from the destination back to the set of entry boundary nodes 🎯. That set of paths forms the downstream VSPT, as specified in Section 4.2 🌳.

Here's the new flag of the RP object 🚩:

VSPT Flag

Bit Number      Name Flag
   25           VSPT

When it's set, the VSPT Flag tells you the PCC is requesting an inter-domain TE LSP computation using the BRPC procedure defined in this document 💖.

Because path segments computed by a downstream PCE in the context of BRPC MUST be provided along with their respective path costs, the C flag of the METRIC object carried within the PCReq message MUST be set 📏. It's up to the requester to set the O bit of the RP object however it wants 🤷‍♀️.

6. VSPT Encoding 🎀

The VSPT comes back inside a PCRep message 💌. The encoding is a non-ordered list of Explicit Route Objects (EROs), where each ERO represents a path segment from a BN to the destination named in the END-POINT object of the corresponding PCReq message 🧁.

Example:

   <---- area 1 ----><---- area 0 -----><------ area 2 ------>
                                       ABR1-A-B-+
                                        |       |
                                       ABR2-----D
                                        |       |
                                       ABR3--C--+

Figure 2: An Example of VSPT Encoding Using a Set of EROs

In the simple example shown in Figure 2, say a constrained path exists between each ABR and the destination D 🗺️. Then the VSPT computed by a PCE serving area 2 is this non-ordered set of EROs 🫧:

  • ERO1: ABR1(TE Router ID)-A(Interface IP address)-B(Interface IP address)-D(TE Router ID)
  • ERO2: ABR2(TE Router ID)-D(TE Router ID)
  • ERO3: ABR3(TE Router ID)-C(interface IP address)-D(TE Router ID)

The PCReq message, PCRep message, PCEP END-POINT object, and ERO object are all defined in [RFC5440] 📚.

For inter-AS TE LSP path computation, BRPC needs to know the traffic engineering attributes of the inter-AS TE links 🔎. How the PCE actually gets that info is outside the scope of BRPC, which follows the PCE architecture defined in [RFC4655] 🏛️.

That said, a straightforward solution is letting the ASBRs flood TE information about the inter-ASBR links, even though no IGP TE is enabled over those links (there's no IGP adjacency over inter-ASBR links) 🌊. This gives a domain's PCE full TE visibility all the way up to the set of entry ASBRs in the downstream domain 👀. The IGP extensions defined in [RFC5316] and [RFC5392] cover this 💜.

8. Usage in Conjunction with Per-Domain Path Computation 🤝

BRPC can compute path segments alongside other path computation techniques, like the per-domain path computation technique defined in [RFC5152], to build the end-to-end path 🧩. But when you do that, end-to-end path optimality can't be guaranteed anymore 😭.

9. BRPC Procedure Completion Failure 💀

If BRPC can't finish because a PCE along the domain doesn't recognize the procedure (the VSPT flag of the RP object), then, as stated in [RFC5440], that PCE sends a PCErr message to the upstream PCE with Error-Type=4 (Not supported object), Error-value=4 (Unsupported parameter) 🙈. The PCE may include the parent object (the RP object), up to and including (but no further than) the unknown or unsupported parameter. When the unknown or unsupported parameter is a bit flag (the VSPT flag), the included RP object should contain the whole bit flag field, with all bits after the parameter at issue set to zero. After that, the PCE cancels the corresponding path computation request without any further notification 🛑.

If BRPC can't finish because a PCE along the domain path recognizes the procedure but doesn't support it, that PCE MUST return a PCErr message to the upstream PCE with an Error-Type of "BRPC procedure completion failure" 🚨.

The PCErr message MUST be relayed to the requesting PCC 📨.

PCEP-ERROR objects report PCEP protocol errors. They're characterized by an Error-Type, which specifies the type of error, and an Error-value, which gives extra info about that error type 🗂️. Both the Error-Type and the Error-value are managed by IANA 🏷️.

A new Error-Type relating to the BRPC procedure is defined here 🌸:

  Error-Type       Meaning
      13           BRPC procedure completion failure
                   Error-value
                     1: BRPC procedure not supported by one or more PCEs
                        along the domain path

10. Applicability ✨

Okay so, as we covered in Section 3, the requirements for inter-area and inter-AS MPLS Traffic Engineering were written up by the Traffic Engineering Working Group (TE WG). They live in [RFC4105] and [RFC4216], respectively. 💅 Both docs basically say the same thing: they want a solution that can find an optimal (shortest) constrained inter-domain TE LSP, and also a set of diverse inter-domain TE LSPs. Main character energy 🦋

10.1. Diverse End-to-End Path Computation

PCEP (see [RFC5440]) lets a PCC ask for a set of diverse TE LSPs by setting the SVEC object's flags L, N, or S. L asks for link diversity, N asks for node diversity, and S asks for SRLG (Shared Risk Link Group) diversity. 🎀 These requests MUST be taken into account by each PCE along the path computation chain during the VSPT computation. In BRPC land, you can get a set of diversely routed TE LSPs between two LSRs because a single PCE computes the path segments of the VSPT all at once. ✨ BRPC can also handle diverse paths under different objective functions, like minimizing the sum of the costs of the N diverse paths, and so on.

Now compare that to the 2-step approach 🙄. You compute the first path, then remove the network elements that path used (if that doesn't break confidentiality preservation), then compute the second path. The problem is that you can't guarantee you'll find a solution, even when one exists. 💀 Even if you do find one, it might not be the most optimal one for something like minimizing the sum of the paths' costs or bounding the path delays of both paths. And yes, it's worth flagging that the 2-step approach is usually slower in terms of signaling delays, because you have to set up two serialized TE LSPs. Not it. 🙅‍♀️

10.2. Path Optimality

BRPC guarantees that the optimal (shortest) constrained inter-domain path will always be found, subject to policy constraints. 👑 But here's the tea: if local path computation techniques are used (like building stitched or nested TE LSPs), or if a domain has more than one BN-en or more than one BN-ex, optimality is only guaranteed after some network change happens inside the domain, and only if you completely re-run the BRPC procedure. 😭

11. Reoptimization of an Inter-Domain TE LSP ✨

Reoptimizing an existing inter-domain TE LSP path was explicitly listed as a requirement in [RFC4105] and [RFC4216], so it's a whole thing. 🌸 For a TE LSP reoptimization request, the reoptimization procedure defined in [RFC5440] applies when the path in use is available on the head-end. That path gets included in the path computation request, so the PCEs involved can avoid double bandwidth accounting. Smart, right? 🧠

12. Path Computation Failure 💔

If a PCE needs to relay a path computation request to a downstream PCE, following the BRPC procedure defined in this document, and no such PCE is available, the PCE MUST send a negative path computation reply to the requester. That reply uses a PCReq message as specified in [RFC5440] and contains a NO-PATH object. In that case, the NO-PATH object MUST carry a NO-PATH-VECTOR TLV (defined in [RFC5440]) with the newly defined bit named "BRPC path computation chain unavailable" set. 🎀

Here's the bit:

   Bit number     Name Flag
      28           BRPC path computation chain unavailable

13. Metric Normalization 🍓

For inter-area TE, the same IGP/TE metric scheme is usually used across all the IGP areas. It might be based on link speed, propagation delay, or some other combo of link attributes. 🌈 So the proposed mechanisms always compute the shortest path across multiple areas that obeys the required constraints for a specified objective function. Inter-AS TE is a different story. For the path computation to actually mean something, metric normalization between ASes may be needed. 🧐

One idea to avoid changing the IGP metrics is for service providers to agree on a TE metric normalization scheme and use the TE metric for TE LSP path computation. If you do that, the use of the TE metric must be requested in the PCEP path computation request, using the METRIC object (defined in [RFC5440]). 🔥

14. Manageability Considerations 🧚

This section follows the guidance of [PCE-MANAGE]. Let's get organized! 📋

14.1. Control of Function and Policy

The only configurable item is whether a PCE supports the BRPC procedure. A PCE MAY have its support of the BRPC procedure controlled by a policy module. That module decides the conditions under which a PCE should take part in the BRPC procedure, like where requests come from or how many requests per second are allowed. 🛡️ If BRPC isn't supported or allowed on a PCE, that PCE MUST send a PCErr message as specified in Section 9. Bye bye, request. 👋

14.2. Information and Data Models

A BRPC MIB module will be specified in a separate document. 📚

14.3. Liveness Detection and Monitoring

BRPC is a multiple-PCE path computation technique, which means a whole set of PCEs is involved in the path computation chain. If that chain isn't working, there are two possible reasons: at least one PCE doesn't support the BRPC procedure, or one of the PCEs that needs to be in the chain isn't available. Procedures for reporting those failures are defined in Sections 9 and 12, respectively. 🔍 There's also a built-in diagnostic tool for checking the availability and performance of a PCE chain, defined in [PCE-MONITOR]. Helpful! 🫶

14.4. Verifying Correct Operation

You can check that BRPC is working correctly by monitoring a set of parameters. 📊 A BRPC implementation SHOULD provide the following parameters:

  • Number of successful BRPC procedure completions on a per-PCE-peer basis
  • Number of BRPC procedure completion failures because the VSPT flag was not recognized (on a per-PCE-peer basis)
  • Number of BRPC procedure completion failures because the BRPC procedure was not supported (on a per-PCE-peer basis)

14.5. Requirements on Other Protocols and Functional Components

The BRPC procedure doesn't put any new requirements on other protocols. 🙌 That said, BRPC relies on PCEP, so there's a dependency between the two. That means BRPC naturally uses the management functions already developed for PCEP. Efficient! 💜

14.6. Impact on Network Operation

BRPC doesn't have any significant impact on network operation. 😌 It's a multiple-PCE path computation scheme as defined in [RFC4655], and it doesn't look any different from any other path computation request.

14.7. Path Computation Chain Monitoring

[PCE-MONITOR] specifies a set of mechanisms for gathering PCE state metrics. Since BRPC is a multiple-PCE path computation technique, those mechanisms could be really useful here. You could use them to check the liveness of the path computation chain, locate a faulty component, monitor overall performance, and so on. 🕵️‍♀️✨

15. IANA Considerations 🗂️

15.1. New Flag of the RP Object

This document defines a new flag of the RP object (specified in [RFC5440]). IANA keeps track of RP object flags in the "RP Object Flag Field" sub-registry of the "Path Computation Element Protocol (PCEP) Numbers" registry. 💖

IANA has allocated the following value:

       Bit      Description              Reference
       25       VSPT                     This document

15.2. New Error-Type and Error-Value

IANA maintains a registry of Error-Types and Error-values for PCEP messages. It's called the "PCEP-ERROR Object Error Types and Values" sub-registry of the "Path Computation Element Protocol (PCEP) Numbers" registry. 📝

A new Error-value is defined for the Error-Type "Not supported object" (type 4):

   Error-Type     Meaning and error values                 Reference
      4           Not supported object

                  Error-value=4: Unsupported parameter     This document

This document also defines a brand new Error-Type, as follows:

   Error-Type     Meaning                                  Reference
     13           BRPC procedure completion failure        This document

                  Error-value=1: BRPC procedure not        This document
                  supported by one or more PCEs along
                  the domain path

15.3. New Flag of the NO-PATH-VECTOR TLV

A new flag of the NO-PATH-VECTOR TLV defined in [RFC5440]) is specified in this document. 🦋

IANA maintains a registry of flags for the NO-PATH-VECTOR TLV in the "NO-PATH-VECTOR TLV Flag Field" sub-registry of the "Path Computation Element Protocol (PCEP) Numbers" registry.

IANA has allocated the following allocation value:

      Bit number  Meaning                  Reference
         4        BRPC path computation    This document
                  chain unavailable

16. Security Considerations 🚨

Okay, serious moment, bestie. 🥺 The BRPC procedure relies on PCEP, so it's exposed to the potential attacks listed in Section 10 of [RFC5440]. On top of the security mechanisms described in [RFC5440] for spoofing, snooping, falsification, and denial of service, an implementation MAY support a policy module. That module governs the conditions under which a PCE should take part in the BRPC procedure. 🔐

The BRPC procedure does not increase the information exchanged between ASes, and it preserves topology confidentiality, in compliance with [RFC4105] and [RFC4216]. Topology stays private, periodt. 🤫

17. Acknowledgments 🫶

The authors want to thank Arthi Ayyangar, Dimitri Papadimitriou, Siva Sivabalan, Meral Shirazipour, and Mach Chen for their useful comments. A special thanks goes to Adrian Farrel for his useful comments and suggestions. 🌟

18. References 📚

18.1. Normative References

  • [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
  • [RFC5440] Vasseur, J., Ed. and J. Roux, Ed., "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, April 2009.

18.2. Informative References ✨

okay bestie, these are the informative refs 🦋 they're not required to implement, but they're the background reading that explains where a lot of this came from 📚

  • [PATH-KEY] Bradford, R., Vasseur, J., and A. Farrel, "Preserving Topology Confidentiality in Inter-Domain Path Computation Using a Key-Based Mechanism", Work in Progress, November 2008.
  • [PCE-MANAGE] Farrel, A., "Inclusion of Manageability Sections in PCE Working Group Drafts", Work in Progress, January 2009.
  • [PCE-MONITOR] Vasseur, J., Roux, J., and Y. Ikejiri, "A set of monitoring tools for Path Computation Element based Architecture", Work in Progress, November 2008.
  • [RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J. McManus, "Requirements for Traffic Engineering Over MPLS", RFC 2702, September 1999.
  • [RFC4105] Le Roux, J., Vasseur, J., and J. Boyle, "Requirements for Inter-Area MPLS Traffic Engineering", RFC 4105, June 2005.
  • [RFC4216] Zhang, R. and J. Vasseur, "MPLS Inter-Autonomous System (AS) Traffic Engineering (TE) Requirements", RFC 4216, November 2005.
  • [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, August 2006.
  • [RFC4726] Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for Inter-Domain Multiprotocol Label Switching Traffic Engineering", RFC 4726, November 2006.
  • [RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "OSPF Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5088, January 2008.
  • [RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "IS-IS Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5089, January 2008.
  • [RFC5152] Vasseur, JP., Ayyangar, A., and R. Zhang, "A Per-Domain Path Computation Method for Establishing Inter-Domain Traffic Engineering (TE) Label Switched Paths (LSPs)", RFC 5152, February 2008.
  • [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering", RFC 5316, December 2008.
  • [RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering", RFC 5392, January 2009.

Authors' Addresses 💌

The squad behind this doc, with their contact details 🫶

JP Vasseur (editor)
Cisco Systems, Inc
1414 Massachusetts Avenue
Boxborough, MA  01719
USA

EMail: jpv@cisco.com


Raymond Zhang
BT Infonet
2160 E. Grand Ave.
El Segundo, CA  90025
USA

EMail: raymond.zhang@bt.com


Nabil Bitar
Verizon
117 West Street
Waltham, MA  02451
USA

EMail: nabil.n.bitar@verizon.com


JL Le Roux
France Telecom
2, Avenue Pierre-Marzin
Lannion,   22307
FRANCE

EMail: jeanlouis.leroux@orange-ftgroup.com
📦 where this page comes from