[Pce] FW: I-D Action:draft-ietf-pce-brpc-08.txt
JP Vasseur <jvasseur@cisco.com> Wed, 02 April 2008 21:13 UTC
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Date: Wed, 02 Apr 2008 17:12:55 -0400
From: JP Vasseur <jvasseur@cisco.com>
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Subject: [Pce] FW: I-D Action:draft-ietf-pce-brpc-08.txt
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Hi, This new revision takes into account the comments received during Last Call: 1) Editorial changes, clarifications, updated references, ... 2) Text added: The BRPC procedure relies on communication between cooperating PCEs. In particular, the PCC sends a PCReq to a PCE in its domain. The request is forwarded between PCEs, domain-by-domain until the PCE responsible for the domain containing the LSP destination is reached. The PCE in the destination domain creates a tree of potential paths to the destination (the Virtual Shortest Path Tree - VSPT) and passes this back to the previous PCE in a PCRep. Each PCE in turn adds to the VSPT and passes it back until the PCE in the source domain uses the VSPT to select an end-to-end path that it sends to the PCC. Main changes are: 3) Section 4 OLD 4. BRPC Procedure The BRPC procedure is a Multiple-PCE path computation technique as described in [RFC4655]. A possible model consists of hosting the PCE function on boundary nodes (e.g., ABR or ASBR) but this is not mandated by the BRPC procedure. The BRPC procedure does not make any assumption with regards to the nature of the inter-domain TE LSP that could be contiguous, nested or stitched. Furthermore, no assumption is made on the actual path computation algorithm in use by a PCE (e.g., it can be any variant of CSPF or an algorithm based on linear-programming to solve multi-constraints optimization problems). NEW: 4. BRPC Procedure The BRPC procedure is a Multiple-PCE path computation technique as described in [RFC4655]. A possible model consists of hosting the PCE function on boundary nodes (e.g., ABR or ASBR) but this is not mandated by the BRPC procedure. The BRPC procedure relies on communication between cooperating PCEs. In particular, the PCC sends a PCReq to a PCE in its domain. The request is forwarded between PCEs, domain-by-domain until the PCE responsible for the domain containing the LSP destination is reached. The PCE in the destination domain creates a tree of potential paths to the destination (the Virtual Shortest Path Tree - VSPT) and passes this back to the previous PCE in a PCRep. Each PCE in turn adds to the VSPT and passes it back until the PCE in the source domain uses the VSPT to select an end-to-end path that it sends to the PCC. The BRPC procedure does not make any assumption with regards to the nature of the inter-domain TE LSP that could be contiguous, nested or stitched. Furthermore, no assumption is made on the actual path computation algorithm in use by a PCE (e.g., it can be any variant of CSPF or an algorithm based on linear-programming to solve multi-constraint optimization problems). 3) Section 9 OLD: 9. BRPC procedure completion failure If the BRPC procedure cannot be completed because a PCE along the domain path does not support the procedure, a PCErr message MUST be returned to the upstream PCE with a Error-Type "BRPC procedure completion failure". The PCErr message MUST be relayed to the requesting PCC. PCEP-ERROR objects are used to report a PCEP protocol error and are characterized by an Error-Type which specifies the type of error and an Error-value that provides additional information about the error type. Both the Error-Type and the Error-Value are managed by IANA. A new Error-Type is defined that relates to the BRPC procedure. Error-type Meaning 13 BRPC procedure completion failure Error-value 1: BRPC procedure not supported by one or more PCEs along the domain path NEW: 9. BRPC Procedure Completion Failure If the BRPC procedure cannot be completed because a PCE along the domain does not recognize the procedure (VSPT flag of the RP object), as stated in [I-D.ietf-pce-pcep], the PCE sends a PCErr message to the upstream PCE with an Error-Type=4 (not supported object), Error- value-4 (Unsupported paramater). The PCE may include the parent object (RP object) up to and including (but no further than) the unknown or unsupported parameter. In this case where the unknown or unsupported parameter is a bit flag (VSPT flag), the included RP object should contain the whole bit flag field with all bits after the parameter at issue set to zero. The corresponding path computation request is then cancelled by the PCE without further notification. If the BRPC procedure cannot be completed because a PCE along the domain path recognises but does not support the procedure, it MUST return a PCErr message to the upstream PCE with an Error-Type "BRPC procedure completion failure". The PCErr message MUST be relayed to the requesting PCC. PCEP-ERROR objects are used to report a PCEP protocol error and are characterized by an Error-Type which specifies the type of error and an Error-value that provides additional information about the error type. Both the Error-Type and the Error-Value are managed by IANA. A new Error-Type is defined that relates to the BRPC procedure. Error-type Meaning 13 BRPC procedure completion failure Error-value 1: BRPC procedure not supported by one or more PCEs along the domain path 4) Section 4.14 (to be in-line with the definition of "Verifying Correct Operation" adopted in PCEP). OLD: 14.4. Verifying Correct Operation Verifying the correct operation of BRPC can be done by looking at the TEDs related to the various domains traversed by a TE LSP at the time the BRPC procedure was invoked and verify that the path computed by the BRPC procedure is the expected optimal inter-domain constrained path (the path that would be obtained in the absence of multiple domains). NEW: 14.4. Verifying Correct Operation Verifying the correct operation of BRPC can be performed by monitoring a set of parameters. A BRPC implementation SHOULD provide the following parameters: o Number of successful BRPC Procedure completions on a per PCE peer basis, o Number of BRPC procedure completion failures because the VSPT flag was not recognized (on a per PCE peer basis), o Number of BRPC procedure completetion failures because the BRPC procedure was not supported (on a per PCE peer basis), Thanks. JP. ------ Forwarded Message > From: <Internet-Drafts@ietf.org> > Reply-To: <internet-drafts@ietf.org> > Date: Wed, 2 Apr 2008 14:00:01 -0700 (PDT) > To: <i-d-announce@ietf.org> > Cc: <pce@ietf.org> > Subject: I-D Action:draft-ietf-pce-brpc-08.txt > > A New Internet-Draft is available from the on-line Internet-Drafts > directories. > This draft is a work item of the Path Computation Element Working Group of the > IETF. > > > Title : draft-ietf-pce-brpc-08.txt > Author(s) : J. Vasseur, et al. > Filename : draft-ietf-pce-brpc-08.txt > Pages : 19 > Date : 2008-04-02 > > The ability to compute shortest constrained Traffic Engineering Label > Switched Paths (TE LSPs) in Multiprotocol Label Switching (MPLS) and > Generalized MPLS (GMPLS) networks across multiple domains (where a > domain is a collection of network elements within a common sphere of > address management or path computational responsibility such as an > IGP area or an Autonomous Systems) has been identified as a key > requirement. This document specifies a procedure relying on the use > of multiple Path Computation Elements (PCEs) to compute such inter- > domain shortest constrained paths across a predetermined sequence of > domains, using a backward recursive path computation technique. This > technique preserves confidentiality across domains, which is > sometimes required when domains are managed by different Service > Providers. > > A URL for this Internet-Draft is: > http://www.ietf.org/internet-drafts/draft-ietf-pce-brpc-08.txt > > Internet-Drafts are also available by anonymous FTP at: > ftp://ftp.ietf.org/internet-drafts/ > > Below is the data which will enable a MIME compliant mail reader > implementation to automatically retrieve the ASCII version of the > Internet-Draft. > Content-Type: text/plain > Content-ID: <2008-04-02135711.I-D@ietf.org> > > _______________________________________________ > I-D-Announce mailing list > I-D-Announce@ietf.org > https://www.ietf.org/mailman/listinfo/i-d-announce > Internet-Draft directories: http://www.ietf.org/shadow.html > or ftp://ftp.ietf.org/ietf/1shadow-sites.txt ------ End of Forwarded Message _______________________________________________ Pce mailing list Pce@ietf.org https://www.ietf.org/mailman/listinfo/pce
- [Pce] I-D Action:draft-ietf-pce-brpc-08.txt Internet-Drafts
- [Pce] FW: I-D Action:draft-ietf-pce-brpc-08.txt JP Vasseur