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Versions: 00 01 02 03 draft-ietf-pce-monitoring

Networking Working Group                                JP. Vasseur, Ed.
Internet-Draft                                        Cisco Systems, Inc
Intended status: Standards Track                             JL. Le Roux
Expires: November 12, 2007                                France Telecom
                                                              Y. Ikejiri
                                          NTT Communications Corporation
                                                            May 11, 2007


      A set of monitoring tools for Path Computation Element based
                              Architecture
                  draft-vasseur-pce-monitoring-03.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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   This Internet-Draft will expire on November 12, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   A Path Computation Element (PCE) based architecture has been
   specified for the computation of Traffic Engineering (TE) Label
   Switched Paths (LSPs) in Multiprotocol Label Switching (MPLS) and
   Generalized MPLS (GMPLS) networks in the context of single or



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   multiple domains (where a domain is referred to as a collection of
   network elements within a common sphere of address management or path
   computational responsibility such as IGP areas and Autonomous
   Systems).  In PCE-based environments it is thus critical to monitor
   the state of the path computation chain for troubleshooting and
   performance monitoring purposes: liveness of each element (PCE)
   involved in the PCE chain, detection of potential resource contention
   states, statistics in term of path computation times are examples of
   such metrics of interest.  This document specifies procedures and
   extensions to the Path Computation Element Protocol (PCEP) in order
   to gather such information.

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].


































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Table of Contents

   1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Path Computation Monitoring messages . . . . . . . . . . . . .  5
     3.1.  Path Computation Monitoring Request message (PCMonReq) . .  6
     3.2.  Path Monitoring Reply message (PCMonRep) . . . . . . . . .  8
   4.  Path Computation Monitoring Objects  . . . . . . . . . . . . .  9
     4.1.  MONITORING Object  . . . . . . . . . . . . . . . . . . . .  9
     4.2.  PCE-ID Object  . . . . . . . . . . . . . . . . . . . . . . 11
     4.3.  PROC-TIME Object . . . . . . . . . . . . . . . . . . . . . 12
     4.4.  CONGESTION Object  . . . . . . . . . . . . . . . . . . . . 14
     4.5.  TIMESTAMP Object . . . . . . . . . . . . . . . . . . . . . 15
   5.  Multi-destination monitoring . . . . . . . . . . . . . . . . . 15
   6.  Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
   7.  Elements of procedure  . . . . . . . . . . . . . . . . . . . . 15
   8.  Manageability Considerations . . . . . . . . . . . . . . . . . 16
   9.  To be considered in a further revision of this document  . . . 16
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 18
     13.2. Informative References . . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
   Intellectual Property and Copyright Statements . . . . . . . . . . 20

























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1.  Terminology

   AS: Autonomous System.

   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.

   TE LSP: Traffic Engineering Label Switched Path.

   TED: Traffic Engineering Database.


2.  Introduction

   The Path Computation Element (PCE) based architecture has been
   specified in [RFC4655] for the computation of Traffic Engineering
   (TE) Label Switched Paths (LSPs) in Multiprotocol Label Switching
   (MPLS) and Generalized MPLS (GMPLS) networks in the context of single
   or multiple domains where a domain is referred to as a collection of
   network elements within a common sphere of address management or path
   computational responsibility such as IGP areas and Autonomous
   Systems.

   In PCE-based environments, it is critical to monitor the state of the
   path computation chain for troubeshooting and performance monitoring
   purposes: liveness of each element (PCE) involved in the PCE chain,
   detection of potential resource contention states, statistics in term
   of path computation times are examples of such metrics of interest.
   This document specifies procedures and extensions to the Path
   Computation Element Protocol (PCEP) ([I-D.ietf-pce-pcep]) in order to
   monitor the path computation chain and gather various performance
   metrics.

   As discussed in [RFC4655], a TE LSP may be computed by one PCE
   (referred to as single PCE path computation) or several PCEs
   (referred to as multiple PCE path computation).  In the former case,
   the PCC may be able to use IGP extensions to check the liveness of
   the PCE (see [I-D.ietf-pce-disco-proto-ospf] and
   [I-D.ietf-pce-disco-proto-isis]) or PCEP using Keepalive messages.
   In contrast, when multiple PCEs are involved in the path computation
   chain an example of which is the BRPC procedure defined in
   [I-D.ietf-pce-brpc], the PCC's visibility may be limited to the first



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   PCE involved in the path computation chain.  Thus, it is critical to
   define mechanisms in order to monitor the state of the path
   computation chain.

   The aim of this document is to specify PCEP extensions in order to
   gather various state metrics along the path computation chain.  In
   this document we call a "state metric" a metric that characterizes a
   PCE state.  For example, such metric can have a form of a bolean (PCE
   is alive or not, PCE is congested or not) or a performance metric
   (path computation time at each PCE).

   PCE state metrics collection can be gathered in two different
   contexts: in band or out of band.  By "In band" we refer to the
   situation whereby a PCC requests to gather metrics in the context of
   a path computation request.  For example, a PCC may send a path
   computation request to a PCE and may want to know the processing time
   of that request in addition to the computed path.  Conversely, if the
   request is "out of band", PCE state metric collection is performed as
   a standalone request (e.g. check the liveness of a specific PCE
   chain, collect the average processing time computed over the last 5mn
   period on one or more PCE(s)").

   In this document we define two monitoring request types: general and
   specific.  A general monitoring request relates to the collection of
   a PCE state metric(s) that is not coupled to a particular path
   computation request (e.g. average CPU load on a PCE).  Conversely, a
   specific monitoring request relates to a particular path computation
   request (processing time to complete the path computation for a TE
   LSP).


3.  Path Computation Monitoring messages

   As defined in [I-D.ietf-pce-pcep], a PCEP message consists of a
   common header followed by a variable length body made of a set of
   objects that can either be mandatory or optional.  As a reminder, an
   object is said to be mandatory in a PCEP message when the object must
   be included for the message to be considered as valid.  The P flag
   (defined in [I-D.ietf-pce-pcep]) is located in the common header of
   each PCEP object and can be set by a PCEP peer to enforce a PCE to
   take into account the related information during the path
   computation.  Because the P flag exclusively relates to a path
   computation request, it MUST be cleared in the two PCEP messages
   (PCEMonReq and PCMonRep message) defined in this document.

   For each PCEP message type a set of rules is defined that specify the
   set of objects that the message can carry.  We use the Backus-Naur
   Form (BNF) to specify such rules.  Square brackets refer to optional



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   sub-sequences.  An implementation MUST form the PCEP messages using
   the object ordering specified in this document.

   In this document we define two PCEP messages referred to as the Path
   Computation Monitoring request (PCMonReq) and Path Computation
   Monitoring Reply (PCMonRep) messages so as to handle "out of band"
   monitoring request.  The aim of the PCMonReq message sent by a PCC to
   a PCE is to gather one or more PCE state metrics on a set of PCEs
   involved in a path computation chain.  The PCMonRep message sent by a
   PCE to a PCC is used to provide such data.

3.1.  Path Computation Monitoring Request message (PCMonReq)

   The Message-Type field of the PCEP common header for the PCMonReq
   message is set to 8 (To be confirmed by IANA).

   There is one mandatory object that MUST be included within a PCMonReq
   message: the Monitoring object (see section Section 4.1).  If the
   Monitoring object is missing, the receiving PCE MUST send an error
   message to the sender.  Other objects are optional.































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   The format of a PCMonReq message is as follows:
   <PCMonReq Message>::= <Common Header>
                         <MONITORING>
                         [<pce-list>]
                         [<svec-list>]
                         [<request-list>]
   where:

   <svec-list>::=<SVEC>
                 [<OF>]
                 [<svec-list>]

   <request-list>::=<request>[<request-list>]

   <request>::= <RP>
                <END-POINTS>
                [<LSPA>]
                [<BANDWIDTH>]
                [<metric-list>]
                [<RRO>]
                [<IRO>]
                [<LOAD-BALANCING>]
                [<XRO>]

   <metric-list>::=<METRIC>[<metric-list>]

   <pce-list>::=<PCE-ID>[<pce-list>]

   The SVEC, RP, END-POINTS, LSPA, BANDWIDTH, METRIC, ERO, IRO and LOAD-
   BALANCING objects are defined in [I-D.ietf-pce-pcep].  The XRO object
   is defined in [I-D.oki-pce-pcep-xro] and the OF object is defined in
   [I-D.leroux-pce-of].

   The PCMonReq message is used to gather various PCE state metrics
   along a path computation chain.  The path computation chain may be
   determined by the PCC (in the form of a series of a series of PCE-ID
   objects defined in Section 4.2.) or may alternatively be determined
   by the path computation procedure.  For example, if the BRPC
   procedure ([I-D.ietf-pce-brpc]) is used to compute an inter-domain TE
   LSP, the PCE chain may be determined dynamically.  In that case, the
   PCC sends a PCMonReq message that contains the PCEP objects that
   charaterize the TE LSP attributes along with the monitoring objects
   (see Section 4.1) that list the set of metric(s) of interest.

   Several PCE state metrics may be requested that are specified by a
   set of objects defined in Section 4.  Note that this set of objects
   is by all means not limitative and may be extended in further
   revision of this document.



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   For the sake of illustraion, consider the three following examples:

   Example 1: PCC1 requests to check the path computation chain should a
   path computation be requested for a specific TE LSP named T1.  A
   PCMonReq message is sent that contains a MONITORING object specifying
   a path computation check, along with the appropriate set of objects
   (e.g.  RP, END-POINTS, ...) that would be included in a PCReq message
   for T1.

   Example 2: PCC1 requests a path computation for a TE LSP and also
   request to gather the processing time along the path computation
   chain selected for the computation of T1.  A PCReq message is sent
   that also contains a MONITORING object that specifies the performance
   metric of interest.  The PCRep message also comprises a PROC-TIME
   object defined in section Section 4.1 that reports the computed
   metrics.

   Example 3: PCC2 requests to gather performance metrics along the
   specific path computation chain <pce1, pce2, pce3, pce7>.  A PCMonreq
   message is sent to PCE1 that contains a set of PCE-ID objects that
   identify PCE1, PCE2, PCE3 and PCE7 respectively.

3.2.  Path Monitoring Reply message (PCMonRep)

   The PCMonRep message is used to provide PCE state metrics back to the
   requester for "out of band" monitoring requests.  The Message-Type
   field of the PCEP common header for the PCMonRep message is set to 9
   (To be confirmed by IANA).

   There is one mandatory object that MUST be included within a PCMonRep
   message: the Monitoring object (see Section 4.1).  If the Monitoring
   object is missing, the receiving PCE MUST send an error message to
   the requesting PCC.  Other objects are optional.


















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   The format of a PCReq message is as follows:
   <PCMonRep Message>::= <Common Header>
                         <MONITORING>
                         [<RP>]
                         [<metric-pce-list>]

   where:

   <metric-pce-list>::=<metric-pce>[<metric-pce-list>]

   <metric-pce>::=[<PCE-ID>]
                  [<PROC-TIME>]
                  [<TIME-STAMP>]
                  [<CONGESTION>]


4.  Path Computation Monitoring Objects

   The PCEP objects defined in the document are compliant with the PCEP
   object format defined in [I-D.ietf-pce-pcep], with the P flag and the
   I flag cleared since these flags are exclusively related to path
   computation request.

   Several objects are defined in this section that can be carried
   within the PCEP PCReq or PCRep messages defined in
   [I-D.ietf-pce-pcep] in case of "in band" monitoring requests.  In
   case of "out of band" monitoring requests, the objects defined in
   this section are carried within PCMonReq and PCMonRep messages.
   Conversely, if the PCC requests the computation of the TE LSP in
   addition to gathering PCE state metrics (i.e.  "In band" requests),
   these objects are carried within PCReq and PCRep messages.

4.1.  MONITORING Object

   The MONITORING object MUST be present within PCMonReq and PCMonRep
   messages ("out of band" monitoring requests) and MAY be carried
   within PCERep and PCReq messages ("in band" monitoring requests).
   There MUST be exactly once instance of the MONITORING object: if more
   than one instance of the MONITORING object is present, the recipient
   MUST only process the first instance and ignore other instances.  The
   MONITORING object is used to specify the set of requested PCE state
   metrics.

   The MONITORING Object-Class is to be assigned by IANA (recommended
   value=19)

   The MONITORING Object-Type is to be assigned by IANA (recommended
   value=1)



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   The format of the MONITORING object body 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Reserved    |              Flags              |I|C|P|G|L|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     monitoring-id-number                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                      Optional TLV(s)                        //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Flags: 18 bits

   The following flags are currently defined:

   L (Liveness) - 1 bit: when set, this indicates that the state metric
   of interest is the PCE's liveness and thus the PCE MUST include a
   PCE-ID object in the corresponding reply.

   G (General) - 1 bit: when set, this indicates that the monitoring
   request is a general monitoring request.  When the requested
   performance metric is specific, the G bit MUST be cleared.

   P (Processing Time) - 1 bit: the P bit of the MONITORING object
   carried in a PCMonReq or a PCReq message is set to indicate that the
   processing times is a metric of interest, in which case a PROC-TIME
   object MUST be inserted in the corresponding PCMonRep or PCRep
   message.  The P bit MUST always be set in a PCMonRep message if also
   set in the corresponding PCMonReq message.

   C (Congestion) - 1 bit: The C bit of the MONITORING object carried in
   a PCMonReq or a PCReq message is set to indicate that the congestion
   status is a metric of interest, in which case a CONGESTION object
   MUST be inserted in the corresponding PCMonRep or PCRep message.  The
   C bit MUST always be set in a PCMonRep message if also set in the
   corresponding PCMonReq message.

   I (Incomplete) - 1 bit: the I bit MUST be set by a PCE that supports
   the PCMonReq message, which does not trigger any policy violation but
   that cannot provide the set of requested performance metrics for
   unspecified reasons.

   Monitoring-id-number (32 bits).  The monitoring-id-number value
   combined with the source IP address of the PCC and the PCE address
   uniquely identify the monitoring request context.  The monitoring-id-



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   number MUST be incremented each time a new monitoring is sent to a
   PCE.  The value 0x0000000 is considered as invalid.  If no reply to a
   monitoring request is received from the PCE, and the PCC wishes to
   resend its path computation monitoring request, the same monitoring-
   id-number MUST be used.  Conversely, different monitoring-id-number
   MUST be used for different requests sent to a PCE.  The same
   monitoring-id-number may be used for path computation monitoring
   requests sent to different PCEs.  The path computation monitoring
   reply is unambiguously identified by the IP source address of the
   replying PCE.

   Unassigned bits are considered as reserved and MUST be set to zero on
   transmission.

   No optional TLVs are currently defined.

4.2.  PCE-ID Object

   The PCE-ID Object is used to specify a PCE's IP address.

   A set of PCE-ID objects may be inserted within a PCReq or a PCMonReq
   message to specify the PCE for which PCE state metrics are requested
   and in a PCMonRep or a PCRep message to record the IP address of the
   PCE reporting PCE state metrics or that was involved in the path
   computation chain.

   Two PCE-ID objects (for IPv4 and IPv6) are defined.  PCE-ID Object-
   Class is to be assigned by IANA (recommended value=20) PCE-ID Object-
   Type is to be assigned by IANA (recommended value=1 for IPv4 and 2
   for IPv6)

   The format of the PCE-ID Object is as follows:



















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   The format of the PCE-ID object body for IPv4 and IPv6 are 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           IPv4 Address                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                           IPv6 Address                        |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   The PCE-ID object body has a fixed length of 4 octets for IPv4 and 16
   octets for IPv6.

   A PCE MUST use the same IP address as the address used in the PCE-
   ADDRESS sub-TLV defined in [I-D.ietf-pce-disco-proto-ospf] and
   [I-D.ietf-pce-disco-proto-isis] should a dynamic discovery mechanism
   be used for PCE discovery.

4.3.  PROC-TIME Object

   The PROC-TIME object MUST be present within a PCMonRep or a PCRep
   message if the P bit of the MONITORING object carried within the
   corresponding PCMonReq or PCReq message is set.  The PROC-TIME object
   is used to report various processing time related metrics.

   1) Case of general monitoring requests

   A PCC may request processing time metrics for general monitoring
   requests (e.g. the PCC may want to know the minimum, maximum and
   average processing times on a particular PCE).  In this case, general
   requests can only be made by using PCMonReq/PCMonRep messages.  The
   processing-time field (as explained below) is exclusively used for
   specific monitoring requests and MUST be cleared for general
   monitoring requests.  The algorithm(s) used by a PCE to compute the
   Min, Average, Max and Variance of the processing times are out of the
   scope of this document (A PCE may decide to compute the minimum
   processing time over a period of times, for the last N path
   computation requests, ...).

   2) Case of specific monitoring requests




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   In the case of a specific request, the algorithm(s) used by a PCE to
   compute the Procesing-time metrics are out of the scope of this
   document but a flag is specified that is used to indicate to the
   requester whether the processing time value was estimated or
   computed.  The PCE may either (1) estimate the processing time
   without performing an actual path computation or (2) effectively
   perform the computation to report the processing time.  In the former
   case, the E bit of the PROC-TIME object MUST be set.  The G bit MUST
   be cleared and the Min-processing-time, Max-processing-time, Average-
   processing-time and Variance-processing-time MUST be set to
   0x00000000.

   When the processing time is requested in addition to a path
   computation (case where the MONITORING object is carried within a
   PCReq message), the PROC-TIME object always report the actual
   processing time for that request and thus the E bits MUST be cleared.

   The PROC-TIME Object-Class is to be assigned by IANA (recommended
   value=21)

   The PROC-TIME Object-Type is to be assigned by IANA (recommended
   value=1)

   The format of the PROC-TIME object body 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Reserved                |           Flags               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Processing-time                   |E|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Min-processing-time                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Max-processing-time                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Average-processing time                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Variance-processing-time                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Flags: 18 bits - No Flags are currently defined:

   E (Estimated) - 1 bit: when set, this indicates that the reported
   metric value is based on estimated processing time as opposed to
   actual computation(s).

   Current-processing-time: This field indicates in milliseconds the



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   processing time for the path computation of interest characterized in
   the corresponding PCMonReq message.

   Min-processing-time: This field indicates in milliseconds the minimum
   processing time.

   Max-processing-time: This field indicates in milliseconds the maximum
   processing time.

   Average-processing-time: This field indicates in milliseconds the
   average processing time.

   Variance-processing-time: This field indicates in milliseconds the
   variance of the processing times.

   Unassigned bits are considered as reserved and MUST be set to zero on
   transmission.

   More granularity may be introduced in further revision of this
   document to get a monitoring metric for a general request of a
   particular class (e.g. all PCReq of priority X).

4.4.  CONGESTION Object

   The CONGESTIION object MUST be present within a PCMonRep or a PCRep
   message if the C bit of the MONITORING object carried within the
   corresponding PCMonReq or PCReq message is set.  The CONGESTION
   object is used to report a PCE processing congestion state.  The
   CONGESTION Object-Class is to be assigned by IANA (recommended
   value=22) The CONGESTION Object-Type is to be assigned by IANA
   (recommended value=1)

   The format of the CONGESTION object body 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |C|        Reserved             |    Congestion Duration        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   C (Congestion) - 1 bit: when set, this indicates that PCE is
   congested, in which case the congestion duration may be non nul.
   When cleared this indicates that the PCE is not congested.
   Congestion duration - 16 bits: This field indicates in seconds the
   estimated congestion duration.






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4.5.  TIMESTAMP Object

   A TIMESTAMP object will be specified in a further revision of this
   document that could be used to indicate when a PCMonReq message has
   been received by a PCE and when the PCMonReq message has been relayed
   to the next-hop PCE or the time at which a PCMonRep message has been
   sent to the requester.


5.  Multi-destination monitoring

   In a further revision of this document, a new object will be
   specified allowing a PCC or a user to gather PCE state metrics for a
   set of destinations using a single PCMonReq message.  For example,
   using a single PCMonreq message originated by a PCC, PCE state
   metrics for the set of path computation chains involved in the
   computation of a set of TE LSPs will be gathered.  Such set of
   destinations could be specified in the form of a subnets.


6.  Policy

   The receipt of a PCMonReq message may trigger a policy violation on
   some PCE in which case the PCE MUST send a PCErr message with Error-
   Type=5 and Error-value=3 (To be Confirmed by IANA).


7.  Elements of procedure

   I bit processing: as indicated in section Section 4.1, the I bit MUST
   be set by a PCE that supports the PCMonReq message, which does not
   trigger any policy violation but that cannot provide the set of
   required performance metrics for unspecified reasons.  Once set, the
   I bit MUST NOT be changed by a receiving PCE.

   Reception of a PCMonReq message: upon receiving a PCMonReq message:

   1) If the PCE does not support the PCMonReq message, the PCE MUST
   send a PCErr message with Error-type=14 and Error-value=1.

   2) If the PCE supports the PCMonReq message but the request is
   prohibited by policy, the PCE MUST send a PCErr message with Error-
   Type=5 and Error-value=3.

   3) If the PCE supports the PCMonReq and the monitoring request is not
   prohibited by policy, the receiving PCE MUST first determine whether
   it is the last PCE of the path computation chain.  If the PCE is not
   the last element of the path computation chain, the PCMonReq message



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   is relayed to the next hop PCE: such next-hop may either be specified
   by means of a PCE-ID object present in the PCMonReq message or
   dynamically determined by means of a procedure outside of the scope
   of this document.  Conversely, if the PCE is the last PCE of the path
   computation chain, the PCE originates a PCMonRep message that
   contains the requested objects according to the set of requested PCE
   states metrics listed in the MONITORING object carried in the
   corresponding PCMonReq message.

   Reception of a PCMonRep message: upon receiving a PCMonRep message,
   the PCE processes the request, adds the relevant objects to the
   PCMonRep message and forwards the PCMonRep message to the upstream
   requesting PCE or PCC.

   Special case of Multi-destination monitoring: monitoring request
   related to more than one destinations may involve a set of path
   computation chains.  In that case, a PCE sends each copy of the
   PCMonReq message to each downstream PCE of each path computation
   chain.


8.  Manageability Considerations

   To be addressed in a further revision of this document.


9.  To be considered in a further revision of this document

   It might be desirable to modify the format of the PCMonReq and
   PCMonRep messages to support the bundling of multiple performance
   metrics collection for a set of TE LSPs.


10.  IANA Considerations

   Two new PCEP (specified in [I-D.ietf-pce-pcep]) messages are defined
   in this document:

   Value    Meaning
     8      Path Computation Monitoring Request (PCMonReq)
     9      Path Computation Monitoring Reply (PCMonRep)

   The following new PCEP objects are defined in this document.








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   Object-Class      Name

          19         MONITORING
                     Object-Type
                        1

          20         PCE-ID
                     Object-Type
                      1: IPv4 addresses
                      2: IPv6 addresses

          21         PROC-TIME
                     Object-Type
                        1

          22         CONGESTION
                     Object-Type
                        1

   A new Error type for the PCErr message (see [I-D.ietf-pce-pcep]) is
   defined in this document (Error-Type and Error-value to be assigned
   by IANA).

    Error-type          Meaning
        14              Performance Monitoring not supported
                         Error-value
                             1: Monitoring message not supported by one
                                of PCEs along the domain path
                             2: MONITORING object missing in a PCMonReq
                                message

   A new Error-value for the PCErr message Error-types=4 (see
   [I-D.ietf-pce-pcep]) is defined in this document (Error-Type and
   Error-value to be assigned by IANA).

    Error-type        Meaning
       5              Performance Monitoring Policy violation
                            3: Monitoring message supported but rejected
                               due to policy violation


11.  Security Considerations

   To be addressed in a further revision of this document.







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12.  Acknowledgements

   The authors would like to thank Eiji Oki, Mach Chen and Dimitri
   Papadimitriou for their useful comments.


13.  References

13.1.  Normative References

   [I-D.ietf-pce-pcep]
              Roux, J. and J. Vasseur, "Path Computation Element (PCE)
              communication Protocol (PCEP)", draft-ietf-pce-pcep-07
              (work in progress), March 2007.

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

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655, August 2006.

13.2.  Informative References

   [I-D.ietf-pce-brpc]
              Vasseur, J., "A Backward Recursive PCE-based Computation
              (BRPC) procedure to compute  shortest inter-domain Traffic
              Engineering Label Switched Paths", draft-ietf-pce-brpc-04
              (work in progress), March 2007.

   [I-D.ietf-pce-disco-proto-isis]
              Roux, J., "IS-IS protocol extensions for Path Computation
              Element (PCE) Discovery",
              draft-ietf-pce-disco-proto-isis-05 (work in progress),
              May 2007.

   [I-D.ietf-pce-disco-proto-ospf]
              Roux, J., "OSPF protocol extensions for Path Computation
              Element (PCE) Discovery",
              draft-ietf-pce-disco-proto-ospf-05 (work in progress),
              May 2007.

   [I-D.leroux-pce-of]
              Roux, J., "Encoding of Objective Functions in Path
              Computation Element (PCE)  communication and discovery
              protocols", draft-leroux-pce-of-00 (work in progress),
              February 2007.

   [I-D.oki-pce-pcep-xro]



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              Oki, E. and A. Farrel, "Extensions to the Path Computation
              Element Communication Protocol (PCEP) for  Route
              Exclusions", draft-oki-pce-pcep-xro-00 (work in progress),
              January 2007.


Authors' Addresses

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

   Email: jpv@cisco.com


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

   Email: jeanlouis.leroux@orange-ftgroup.com


   Yuichi Ikejiri
   NTT Communications Corporation
   1-1-6, Uchisaiwai-cho, Chiyoda-ku
   Tokyo,   100-8019
   Japan

   Email: : y.ikejiri@ntt.com


















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