GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc5557

Network Working Group Y. Lee Request for Comments: 5557 Huawei Category: Standards Track JL. Le Roux

                                                        France Telecom
                                                               D. King
                                                    Old Dog Consulting
                                                                E. Oki
                                  University of Electro Communications
                                                             July 2009
Path Computation Element Communication Protocol (PCEP) Requirements
and Protocol Extensions in Support of Global Concurrent Optimization

Abstract

 The Path Computation Element Communication Protocol (PCEP) allows
 Path Computation Clients (PCCs) to request path computations from
 Path Computation Elements (PCEs), and lets the PCEs return responses.
 When computing or reoptimizing the routes of a set of Traffic
 Engineering Label Switched Paths (TE LSPs) through a network, it may
 be advantageous to perform bulk path computations in order to avoid
 blocking problems and to achieve more optimal network-wide solutions.
 Such bulk optimization is termed Global Concurrent Optimization
 (GCO).  A GCO is able to simultaneously consider the entire topology
 of the network and the complete set of existing TE LSPs, and their
 respective constraints, and look to optimize or reoptimize the entire
 network to satisfy all constraints for all TE LSPs.  A GCO may also
 be applied to some subset of the TE LSPs in a network.  The GCO
 application is primarily a Network Management System (NMS) solution.
 This document provides application-specific requirements and the PCEP
 extensions in support of GCO applications.

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.

Lee, et al. Standards Track [Page 1] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

Copyright Notice

 Copyright (c) 2009 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents in effect on the date of
 publication of this document (http://trustee.ietf.org/license-info).
 Please review these documents carefully, as they describe your rights
 and restrictions with respect to this document.
 This document may contain material from IETF Documents or IETF
 Contributions published or made publicly available before November
 10, 2008.  The person(s) controlling the copyright in some of this
 material may not have granted the IETF Trust the right to allow
 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified
 outside the IETF Standards Process, and derivative works of it may
 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.

Lee, et al. Standards Track [Page 2] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

Table of Contents

 1. Introduction ....................................................4
 2. Terminology .....................................................6
 3. Applicability of Global Concurrent Optimization (GCO) ...........6
    3.1. Application of the PCE Architecture ........................7
    3.2. Greenfield Optimization ....................................8
         3.2.1. Single-Layer Traffic Engineering ....................8
         3.2.2. Multi-Layer Traffic Engineering .....................8
    3.3. Reoptimization of Existing Networks ........................8
         3.3.1. Reconfiguration of the Virtual Network
                Topology (VNT) ......................................9
         3.3.2. Traffic Migration ...................................9
 4. PCECP Requirements .............................................10
 5. Protocol Extensions for Support of Global Concurrent
    Optimization ...................................................13
    5.1. Global Objective Function (GOF) Specification .............14
    5.2. Indication of Global Concurrent Optimization Requests .....15
    5.3. Request for the Order of TE LSP ...........................15
    5.4. The Order Response ........................................16
    5.5. GLOBAL CONSTRAINTS (GC) Object ............................17
    5.6. Error Indicator ...........................................18
    5.7. NO-PATH Indicator .........................................19
 6. Manageability Considerations ...................................19
    6.1. Control of Function and Policy ............................19
    6.2. Information and Data Models (e.g., MIB Module) ............20
    6.3. Liveness Detection and Monitoring .........................20
    6.4. Verifying Correct Operation ...............................20
    6.5. Requirements on Other Protocols and Functional
         Components ................................................20
    6.6. Impact on Network Operation ...............................20
 7. Security Considerations ........................................21
 8. IANA Considerations ............................................21
    8.1. Request Parameter Bit Flags ...............................21
    8.2. New PCEP TLV ..............................................21
    8.3. New Flag in PCE-CAP-FLAGS Sub-TLV in PCED .................22
    8.4. New PCEP Object ...........................................22
    8.5. New PCEP Error Codes ......................................22
         8.5.1. New Error-Values for Existing Error-Types ..........22
         8.5.2. New Error-Types and Error-Values ...................23
    8.6. New No-Path Reasons .......................................23
 9. References .....................................................23
    9.1. Normative References ......................................23
    9.2. Informative References ....................................24
 10. Acknowledgments ...............................................24
 Appendix A. RBNF Code Fragments ...................................25

Lee, et al. Standards Track [Page 3] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

1. Introduction

 [RFC4655] defines the Path Computation Element (PCE)-based
 architecture and explains how a PCE may compute Label Switched Paths
 (LSPs) in Multiprotocol Label Switching Traffic Engineering (MPLS-TE)
 and Generalized MPLS (GMPLS) networks at the request of Path
 Computation Clients (PCCs).  A PCC is shown to be any network
 component that makes such a request and may be, for instance, a Label
 Switching Router (LSR) or a Network Management System (NMS).  The
 PCE, itself, is shown to be located anywhere within the network, and
 it may be within an LSR, an NMS or Operational Support System (OSS),
 or may be an independent network server.
 The PCE Communication Protocol (PCEP) is the communication protocol
 used between PCC and PCE, and it may also be used between cooperating
 PCEs.  [RFC4657] sets out generic protocol requirements for PCEP.
 Additional application-specific requirements for PCEP are defined in
 separate documents.
 This document provides a set of requirements and PCEP extensions in
 support of concurrent path computation applications.  A concurrent
 path computation is a path computation application where a set of TE
 paths are computed concurrently in order to efficiently utilize
 network resources.  The computation method involved with a concurrent
 path computation is referred to as "global concurrent optimization"
 in this document.  Appropriate computation algorithms to perform this
 type of optimization are out of the scope of this document.
 The Global Concurrent Optimization (GCO) application is primarily an
 NMS or a PCE-Server-based solution.  Owing to complex synchronization
 issues associated with GCO applications, the management-based PCE
 architecture defined in Section 5.5 of [RFC4655] is considered as the
 most suitable usage to support GCO application.  This does not
 preclude other architectural alternatives to support GCO application,
 but they are NOT RECOMMENDED.  For instance, GCO might be enabled by
 distributed LSRs through complex synchronization mechanisms.
 However, this approach might suffer from significant synchronization
 overhead between the PCE and each of the PCCs.  It would likely
 affect the network stability and hence significantly diminish the
 benefits of deploying PCEs.
 The need for global concurrent path computation may also arise when
 network operators need to establish a set of TE LSPs in their network
 planning process.  It is also envisioned that network operators might
 require global concurrent path computation in the event of
 catastrophic network failures, where a set of TE LSPs need to be

Lee, et al. Standards Track [Page 4] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

 optimally rerouted.  The nature of this work promotes the use of such
 systems for off-line processing.  Online application of this work
 should only be considered with proven empirical validation.
 As new TE LSPs are added or removed from the network over time, the
 global network resources become fragmented and the existing placement
 of TE LSPs within the network no longer provides optimal use of the
 available capacity.  A global concurrent path computation is able to
 simultaneously consider the entire topology of the network and the
 complete set of existing TE LSPs and their respective constraints,
 and is able to look to reoptimize the entire network to satisfy all
 constraints for all TE LSPs.  Alternatively, the application may
 consider a subset of the TE LSPs and/or a subset of the network
 topology.  Note that other preemption can also help reduce the
 fragmentation issues.
 While GCO is applicable to any simultaneous request for multiple TE
 LSPs (for example, a request for end-to-end protection), it is NOT
 RECOMMENDED that global concurrent reoptimization would be applied in
 a network (such as an MPLS-TE network) that contains a very large
 number of very low bandwidth or zero bandwidth TE LSPs since the
 large scope of the problem and the small benefit of concurrent
 reoptimization relative to single TE LSP reoptimization is unlikely
 to make the process worthwhile.  Further, applying global concurrent
 reoptimization in a network with a high rate of change of TE LSPs
 (churn) is NOT RECOMMENDED because of the likelihood that TE LSPs
 would change before they could be globally reoptimized.  Global
 reoptimization is more applicable to stable networks such as
 transport networks or those with long-term TE LSP tunnels.
 The main focus of this document is to highlight the PCC-PCE
 communication needs in support of a concurrent path computation
 application and to define protocol extensions to meet those needs.
 The PCC-PCE requirements addressed herein are specific to the context
 where the PCE is a specialized PCE that is capable of performing
 computations in support of GCO.  Discovery of such capabilities might
 be desirable and could be achieved through extensions to the PCE
 discovery mechanisms [RFC4674], [RFC5088], [RFC5089]; but, that is
 out of the scope of this document.
 It is to be noted that Backward Recursive Path Computation (BRPC)
 [RFC5441] is a multi-PCE path computation technique used to compute a
 shortest constrained inter-domain path, whereas this ID specifies a
 technique where a set of path computation requests are bundled and
 sent to a PCE with the objective of "optimizing" the set of computed
 paths.

Lee, et al. Standards Track [Page 5] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

2. Terminology

 Most of the terminology used in this document is explained in
 [RFC4655].  A few key terms are repeated here for clarity.
 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.
 TED: Traffic Engineering Database.  The TED contains the topology and
 resource information of the domain.  The TED may be fed by IGP
 extensions or potentially by other means.
 PCECP: The PCE Communication Protocol.  PCECP is the generic abstract
 idea of a protocol that is used to communicate path computation
 requests from a PCC to a PCE and to return computed paths from the
 PCE to the PCC.  The PCECP can also be used between cooperating PCEs.
 PCEP: The PCE communication Protocol.  PCEP is the actual protocol
 that implements the PCECP idea.
 GCO: Global Concurrent Optimization.  A concurrent path computation
 application where a set of TE paths are computed concurrently in
 order to optimize network resources.  A GCO path computation is able
 to simultaneously consider the entire topology of the network and the
 complete set of existing TE LSPs, and their respective constraints,
 and look to optimize or reoptimize the entire network to satisfy all
 constraints for all TE LSPs.  A GCO path computation can also provide
 an optimal way to migrate from an existing set of TE LSPs to a
 reoptimized set (Morphing Problem).
 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].
 These terms are used to specify requirements in this document.

3. Applicability of Global Concurrent Optimization (GCO)

 This section discusses the PCE architecture to which GCO is applied.
 It also discusses various application scenarios for which global
 concurrent path computation may be applied.

Lee, et al. Standards Track [Page 6] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

3.1. Application of the PCE Architecture

 Figure 1 shows the PCE-based network architecture as defined in
 [RFC4655] to which GCO application is applied.  It must be observed
 that the PCC is not necessarily an LSR [RFC4655].  The GCO
 application is primarily an NMS-based solution in which an NMS plays
 the function of the PCC.  Although Figure 1 shows the PCE as remote
 from the NMS, it might be collocated with the NMS.  Note that in the
 collocated case, there is no need for a standard communication
 protocol; this can rely on internal APIs.
  1. ———-

Application | —– |

                  Request             |  | TED |  |
                     |                |   -----   |
                     v                |     |     |
               ------------- Request/ |     v     |
              |     PCC     | Response|   -----   |
              | (NMS/Server)|<--------+> | PCE |  |
              |             |         |   -----   |
               -------------           -----------
             Service |
             Request |
                     v
                ----------  Signaling   ----------
               | Head-End | Protocol   | Adjacent |
               |  Node    |<---------->|   Node   |
                ----------              ----------
                       Figure 1: PCE-Based Architecture for
                          Global Concurrent Optimization
 Upon receipt of an application request (e.g., a traffic demand matrix
 is provided to the NMS by the operator's network planning procedure),
 the NMS requests a global concurrent path computation from the PCE.
 The PCE then computes the requested paths concurrently applying some
 algorithms.  Various algorithms and computation techniques have been
 proposed to perform this function.  Specification of such algorithms
 or techniques is outside the scope of this document.
 When the requested path computation completes, the PCE sends the
 resulting paths back to the NMS.  The NMS then supplies the head-end
 LSRs with a fully computed explicit path for each TE LSP that needs
 to be established.

Lee, et al. Standards Track [Page 7] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

3.2. Greenfield Optimization

 Greenfield optimization is a special case of GCO application when
 there are no TE LSPs already set up in the network.  The need for
 greenfield optimization arises when the network planner wants to make
 use of a computation server to plan the TE LSPs that will be
 provisioned in the network.  Note that greenfield operation is a
 one-time optimization.  When network conditions change due to failure
 or other changes, then the reoptimization mode of operation will kick
 in.
 When a new TE network needs to be provisioned from a greenfield
 perspective, a set of TE LSPs needs to be created based on traffic
 demand, network topology, service constraints, and network resources.
 In this scenario, the ability to perform concurrent computation is
 desirable, or required, to utilize network resources in an optimal
 manner and avoid blocking.

3.2.1. Single-Layer Traffic Engineering

 Greenfield optimization can be applied when layer-specific TE LSPs
 need to be created from a greenfield perspective.  For example, an
 MPLS-TE network can be planned based on Layer 3 specific traffic
 demands, the network topology, and available network resources.
 Greenfield optimization for single-layer traffic engineering can be
 applied to optical transport networks such as Synchronous Digital
 Hierarchy/Synchronous Optical Network (SDH/SONET), Ethernet
 Transport, Wavelength Division Multiplexing (WDM), etc.

3.2.2. Multi-Layer Traffic Engineering

 Greenfield optimization is not limited to single-layer traffic
 engineering.  It can also be applied to multi-layer traffic
 engineering [PCE-MLN].  The network resources and topology (of both
 the client and server layers) can be considered simultaneously in
 setting up a set of TE LSPs that traverse the layer boundary.

3.3. Reoptimization of Existing Networks

 The need for global concurrent path computation may arise in existing
 networks.  When an existing TE LSP network experiences sub-optimal
 use of its resources, the need for reoptimization or reconfiguration
 may arise.  The scope of reoptimization and reconfiguration may vary
 depending on particular situations.  The scope of reoptimization may
 be limited to bandwidth modification to an existing TE LSP.  However,
 it could well be that a set of TE LSPs may need to be reoptimized
 concurrently.  In an extreme case, the TE LSPs may need to be
 globally reoptimized.

Lee, et al. Standards Track [Page 8] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

 In loaded networks, with large size TE LSPs, a sequential
 reoptimization may not produce substantial improvements in terms of
 overall network optimization.  Sequential reoptimization refers to a
 path computation method that computes the reoptimized path of one TE
 LSP at a time without giving any consideration to the other TE LSPs
 that need to be reoptimized in the network.  The potential for
 network-wide gains from reoptimization of TE LSPs sequentially is
 dependent upon the network usage and size of the TE LSPs being
 optimized.  However, the key point remains: computing the reoptimized
 path of one TE LSP at a time without giving any consideration to the
 other TE LSPs in the network could result in sub-optimal use of
 network resources.  This may be far more visible in an optical
 network with a low ratio of potential TE LSPs per link, and far less
 visible in packet networks with micro-flow TE LSPs.
 With regards to applicability of GCO in the event of catastrophic
 failures, there may be a real benefit in computing the paths of the
 TE LSPs as a set rather than computing new paths from the head-end
 LSRs in a distributed manner.  Distributed jittering is a technique
 that could prevent race condition (i.e., competing for the same
 resource from different head-end LSRs) with a distributed
 computation.  GCO provides an alternative way that could also prevent
 race condition in a centralized manner.  However, a centralized
 system will typically suffer from a slower response time than a
 distributed system.

3.3.1. Reconfiguration of the Virtual Network Topology (VNT)

 Reconfiguration of the VNT [RFC5212] [PCE-MLN] is a typical
 application scenario where global concurrent path computation may be
 applicable.  Triggers for VNT reconfiguration, such as traffic demand
 changes, network failures, and topological configuration changes may
 require a set of existing TE LSPs to be re-computed.

3.3.2. Traffic Migration

 When migrating from one set of TE LSPs to a reoptimized set of TE
 LSPs, it is important that the traffic be moved without causing
 disruption.  Various techniques exist in MPLS and GMPLS, such as
 make-before-break [RFC3209], to establish the new TE LSPs before
 tearing down the old TE LSPs.  When multiple TE LSP routes are
 changed according to the computed results, some of the TE LSPs may be
 disrupted due to the resource constraints.  In other words, it may
 prove to be impossible to perform a direct migration from the old TE
 LSPs to the new optimal TE LSPs without disrupting traffic because
 there are insufficient network resources to support both sets of TE
 LSPs when make-before-break is used.  However, a PCE may be able to
 determine a sequence of make-before-break replacement of individual

Lee, et al. Standards Track [Page 9] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

 TE LSPs or small sets of TE LSPs so that the full set of TE LSPs can
 be migrated without any disruption.  This scenario assumes that the
 bandwidth of existing TE LSP is kept during the migration, which is
 required in optical networks.  In packet networks, this assumption
 can be relaxed as the bandwidth of temporary TE LSPs during migration
 can be zeroed.
 It may be the case that the reoptimization is radical.  This could
 mean that it is not possible to apply make-before-break in any order
 to migrate from the old TE LSPs to the new TE LSPs.  In this case, a
 migration strategy is required that may necessitate TE LSPs being
 rerouted using make-before-break onto temporary paths in order to
 make space for the full reoptimization.  A PCE might indicate the
 order in which reoptimized TE LSPs must be established and take over
 from the old TE LSPs, and it may indicate a series of different
 temporary paths that must be used.  Alternatively, the PCE might
 perform the global reoptimization as a series of sub-reoptimizations
 by reoptimizing subsets of the total set of TE LSPs.
 The benefit of this multi-step rerouting includes minimization of
 traffic disruption and optimization gain.  However, this approach may
 imply some transient packets desequencing, jitter, as well as control
 plane stress.
 Note also that during reoptimization, traffic disruption may be
 allowed for some TE LSPs carrying low priority services (e.g.,
 Internet traffic) and not allowed for some TE LSPs carrying mission
 critical services (e.g., voice traffic).

4. PCECP Requirements

 This section provides the PCECP requirements to support global
 concurrent path computation applications.  The requirements specified
 here should be regarded as application-specific requirements and are
 justifiable based on the extensibility clause found in Section 6.1.14
 of [RFC4657]:
    The PCECP MUST support the requirements specified in the
    application-specific requirements documents.  The PCECP MUST also
    allow extensions as more PCE applications will be introduced in
    the future.
 It is also to be noted that some of the requirements discussed in
 this section have already been discussed in the PCECP requirement
 document [RFC4657].  For example, Section 5.1.16 in [RFC4657]
 provides a list of generic constraints while Section 5.1.17 in
 [RFC4657] provides a list of generic objective functions that MUST be
 supported by the PCECP.  While using such generic requirements as the

Lee, et al. Standards Track [Page 10] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

 baseline, this section provides application-specific requirements in
 the context of global concurrent path computation and in a more
 detailed level than the generic requirements.
 The PCEP SHOULD support the following capabilities either via
 creation of new objects and/or modification of existing objects where
 applicable.
 o  An indicator to convey that the request is for a global concurrent
    path computation.  This indicator is necessary to ensure
    consistency in applying global objectives and global constraints
    in all path computations.  Note: This requirement is covered by
    "synchronized path computation" in [RFC4655] and [RFC4657].
    However, an explicit indicator to request a global concurrent
    optimization is a new requirement.
 o  A Global Objective Function (GOF) field in which to specify the
    global objective function.  The global objective function is the
    overarching objective function to which all individual path
    computation requests are subjected in order to find a globally
    optimal solution.  Note that this requirement is covered by
    "synchronized objective functions" in Section 5.1.7 [RFC4657] and
    that [RFC5541] defined three global objective functions as
    follows.  A list of available global objective functions SHOULD
    include the following objective functions at the minimum and
    SHOULD be expandable for future addition:
  • Minimize aggregate Bandwidth Consumption (MBC)
  • Minimize the load of the Most Loaded Link (MLL)
  • Minimize Cumulative Cost of a set of paths (MCC)
 o  A Global Constraints (GC) field in which to specify the list of
    global constraints to which all the requested path computations
    should be subjected.  This list SHOULD include the following
    constraints at the minimum and SHOULD be expandable for future
    addition:
  • Maximum link utilization value – This value indicates the

highest possible link utilization percentage set for each link.

       (Note: to avoid floating point numbers, the values should be
       integer values.)
  • Minimum link utilization value – This value indicates the

lowest possible link utilization percentage set for each link.

       (Note: same as above.)

Lee, et al. Standards Track [Page 11] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

  • Overbooking factor – The overbooking factor allows the

reserved bandwidth to be overbooked on each link beyond its

       physical capacity limit.
  • Maximum number of hops for all the TE LSPs – This is the

largest number of hops that any TE LSP can have. Note that

       this constraint can also be provided on a per-TE-LSP basis (as
       requested in [RFC4657] and defined in [RFC5440]).
  • Exclusion of links/nodes in all TE LSP path computation (i.e.,

all TE LSPs should not include the specified links/nodes in

       their paths).  Note that this constraint can also be provided
       on a per-TE-LSP basis (as requested in [RFC4657] and defined in
       [RFC5440]).
  • An indication should be available in a path computation

response that further reoptimization may only become available

       once existing traffic has been moved to the new TE LSPs.
 o  A Global Concurrent Vector (GCV) field in which to specify all the
    individual path computation requests that are subject to
    concurrent path computation and subject to the global objective
    function and all of the global constraints.  Note that this
    requirement is entirely fulfilled by the SVEC object in the PCEP
    specification [RFC5440].  Since the SVEC object as defined in
    [RFC5440] allows identifying a set of concurrent path requests,
    the SVEC can be reused to specify all the individual concurrent
    path requests for a global concurrent optimization.
 o  An indicator field in which to indicate the outcome of the
    request.  When the PCE cannot find a feasible solution with the
    initial request, the reason for failure SHOULD be indicated.  This
    requirement is partially covered by [RFC4657], but not in this
    level of detail.  The following indicators SHOULD be supported at
    the minimum:
  • no feasible solution found. Note that this is already covered

in [RFC5440].

  • memory overflow.
  • PCE too busy. Note that this is already covered in [RFC5440].
  • PCE not capable of concurrent reoptimization.
  • no migration path available.
  • administrative privileges do not allow global reoptimization.

Lee, et al. Standards Track [Page 12] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

 o  In order to minimize disruption associated with bulk path
    provisioning, the following requirements MUST be supported:
  • The request message MUST allow requesting the PCE to provide

the order in which TE LSPs should be reoptimized (i.e., the

       migration path) in order to minimize traffic disruption during
       the migration.  That is, the request message MUST allow
       indicating to the PCE that the set of paths that will be
       provided in the response message (PCRep) has to be ordered.
  • In response to the "ordering" request from the PCC, the PCE

MUST be able to indicate in the response message (PCRep) the

       order in which TE LSPs should be reoptimized so as to minimize
       traffic disruption.  It should indicate for each request the
       order in which the old TE LSP should be removed and the order
       in which the new TE LSP should be setup.  If the removal order
       is lower than the setup order, this means that make-before-
       break cannot be done for this request.  It MAY also be
       desirable to have the PCE indicate whether ordering is in fact
       required or not.
  • During a migration, it may not be possible to do a make-before-

break for all existing TE LSPs. The request message MUST allow

       indicating for each request whether make-before-break is
       required (e.g., voice traffic) or break-before-make is
       acceptable (e.g., Internet traffic).  The response message must
       allow indicating TE LSPs for which make-before-break
       reoptimization is not possible (this will be deduced from the
       TE LSP setup and deletion orders).

5. Protocol Extensions for Support of Global Concurrent Optimization

 This section provides protocol extensions for support of global
 concurrent optimization.  Protocol extensions discussed in this
 section are built on [RFC5440].
 The format of a PCReq message after incorporating new requirements
 for support of global concurrent optimization is as follows.  The
 message format uses Reduced Backus-Naur Format as defined in
 [RFC5511].  Please see Appendix A for a full set of RBNF fragments
 defined in this document and the necessary code license.
 <PCReq Message> ::= <Common Header>
                     [<svec-list>]
                     <request-list>

Lee, et al. Standards Track [Page 13] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

 The <svec-list> is changed as follows:
 <svec-list> ::= <SVEC>
                 [<OF>]
                 [<GC>]
                 [<XRO>]
                 [<svec-list>]
 Note that three optional objects are added, following the SVEC
 object:  the OF (Objective Function) object, which is defined in
 [RFC5541], the GC (Global Constraints) object, which is defined in
 this document (Section 5.5), as well as the eXclude Route Object
 (XRO), which is defined in [RFC5521].  The placement of the OF object
 (in which the global objective function is specified) in the SVEC-
 list is defined in [RFC5541].  Details of this change will be
 discussed in the following sections.
 Note also that when the XRO is global to an SVEC, and F-bit is set,
 it SHOULD be allowed to specify multiple Record Route Objects in the
 PCReq message.

5.1. Global Objective Function (GOF) Specification

 The global objective function can be specified in the PCEP Objective
 Function (OF) object, defined in [RFC5541].  The OF object includes a
 16-bit Objective Function identifier.  As discussed in [RFC5541],
 Objective Function identifier code points are managed by IANA.
 Three global objective functions defined in [RFC5541] are used in the
 context of GCO.
    Function
    Code       Description
     4         Minimize aggregate Bandwidth Consumption (MBC)
     5         Minimize the load of the Most Loaded Link (MLL)*
     6         Minimize the Cumulative Cost of a set of paths (MCC)
  • Note: This can be achieved by the following objective function:

minimize max over all links {A(i)/C(i)} where C(i) is the link

   capacity for link i, and A(i) is the total bandwidth allocated on
   link i.

Lee, et al. Standards Track [Page 14] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

5.2. Indication of Global Concurrent Optimization Requests

 All the path requests in this application should be indicated so that
 the global objective function and all of the global constraints are
 applied to each of the requested path computation.  This can be
 indicated implicitly by placing the GCO related objects (OF, GC, or
 XRO) after the SVEC object.  That is, if any of these objects follows
 the SVEC object in the PCReq message, all of the requested path
 computations specified in the SVEC object are subject to OF, GC, or
 XRO.

5.3. Request for the Order of TE LSP

 In order to minimize disruption associated with bulk path
 provisioning, the PCC may indicate to the PCE that the response MUST
 be ordered.  That is, the PCE has to include the order in which TE
 LSPs MUST be moved so as to minimize traffic disruption.  To support
 such indication a new flag, the D flag, is defined in the RP object
 as follows:
 D-bit (orDer - 1 bit): when set, in a PCReq message, the requesting
 PCC requires the PCE to specify in the PCRep message the order in
 which this particular path request is to be provisioned relative to
 other requests.
 To support the determination of whether make-before-break
 optimization is required, a new flag, the M flag, is defined in the
 RP object as follows.
 M-bit (Make-before-break - 1 bit): when set, this indicates that a
 make-before-break reoptimization is required for this request.
 When the M-bit is not set, this implies that a break-before-make
 reoptimization is allowed for this request.  Note that the M-bit can
 be set only if the R (Reoptimization) flag is set.
 Two new bit flags are defined to be carried in the Flags field in the
 RP object.
 Bit 21 (M-bit): When set, make-before-break is required.
 Bit 22 (D-bit): When set, report of the request order is required.

Lee, et al. Standards Track [Page 15] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

5.4. The Order Response

 The PCE MUST specify the order number in response to the Order
 Request made by the PCC in the PCReq message if so requested by the
 setting of the D-bit in the RP object in the PCReq message.  To
 support such an ordering indication, a new optional TLV, the Order
 TLV, is defined in the RP object.
 The Order TLV is an optional TLV in the RP object, that indicates the
 order in which the old TE LSP must be removed and the new TE LSP must
 be setup during a reoptimization.  It is carried in the PCRep message
 in response to a reoptimization request.
 The Order TLV MUST be included in the RP object in the PCRep message
 if the D-bit is set in the RP object in the PCReq message.
 The format of the Order TLV 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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |              Type             |             Length            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Delete Order                         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                           Setup Order                         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      Figure 2: The Order TLV in the RP Object in the PCRep Message
 Type: 5
 Length: Variable
 Delete Order: 32-bit integer that indicates the order in which the
 old TE LSP should be removed.
 Setup Order: 32-bit integer that indicates the order in which the new
 TE LSP should be setup.
 The delete order SHOULD NOT be equal to the setup order.  If the
 delete order is higher than the setup order, this means that the
 reoptimization can be done in a make-before-break manner, else it
 cannot be done in a make-before-break manner.
 For a new TE LSP, the delete order is not applicable.  The value 0 is
 designated to specify this case.  When the value of the delete order
 is 0, it implies that the resulting TE LSP is a new TE LSP.

Lee, et al. Standards Track [Page 16] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

 To illustrate this, consider a network with two established TE LSPs:
 R1 with path P1, and R2 with path P2.  During a reoptimization, the
 PCE may provide the following ordered reply:
 R1, path P1', remove order 1, setup order 4
 R2, path P2', remove order 3, setup order 2
 This indicates that the NMS should do the following sequence of
 tasks:
 1: Remove path P1
 2: Set up path P2'
 3: Remove path P2
 4: Set up path P1'
 That is, R1 is reoptimized in a break-before-make manner and R2 in a
 make-before-break manner.

5.5. GLOBAL CONSTRAINTS (GC) Object

 The GLOBAL CONSTRAINTS (GC) Object is used in a PCReq message to
 specify the necessary global constraints that should be applied to
 all individual path computations for a global concurrent path
 optimization request.
 GLOBAL-CONSTRAINTS Object-Class is 24.
 Global Constraints Object-Type is 1.
 The format of the GC object body that includes the global constraints
 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 2
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    MH         |    MU         |    mU         |    OB         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    //                         Optional TLV(s)                     //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     Figure 3: GC Body Object Format
 MH (Max Hop: 8 bits): 8-bit integer that indicates the maximum hop
 count for all the TE LSPs.

Lee, et al. Standards Track [Page 17] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

 MU (Max Utilization Percentage: 8 bits) : 8-bit integer that
 indicates the upper-bound utilization percentage by which all links
 should be bound.  Utilization = (Link Capacity - Allocated Bandwidth
 on the Link)/ Link Capacity.  MU is intended to be an integer that
 can only be between 0 and 100.
 mU (minimum Utilization Percentage: 8 bits) : 8-bit integer that
 indicates the lower-bound utilization percentage by which all links
 should be bound.  mU is intended to be an integer that can only be
 between 0 and 100.
 OB (Over Booking factor Percentage: 8 bits) : 8-bit integer that
 indicates the overbooking percentage that allows the reserved
 bandwidth to be overbooked on each link beyond its physical capacity
 limit.  The value, for example, 10% means that 110 Mbps can be
 reserved on a 100 Mbps link.
 The exclusion of the list of nodes/links from a global path
 computation can be done by including the XRO object following the GC
 object in the new SVEC-list definition.
 Optional TLVs may be included within the GC object body to specify
 additional global constraints.  The TLV format and processing is
 consistent with Section 7.1 of RFC 5440.  Any TLVs will be allocated
 from the "PCEP TLV Type Indicators" registry.  Note that no TLVs are
 defined in this document.

5.6. Error Indicator

 To indicate errors associated with the global concurrent path
 optimization request, a new Error-Type (14) and subsequent error-
 values are defined as follows for inclusion in the PCEP-ERROR Object:
 A new Error-Type (15) and subsequent error-values are defined as
 follows:
 Error-Type=15; Error-value=1: if a PCE receives a global concurrent
 path optimization request and the PCE is not capable of processing
 the request due to insufficient memory, the PCE MUST send a PCErr
 message with a PCEP-ERROR Object (Error-Type=15) and an Error-value
 (Error-value=1).  The PCE stops processing the request.  The
 corresponding global concurrent path optimization request MUST be
 cancelled at the PCC.
 Error-Type=15; Error-value=2: if a PCE receives a global concurrent
 path optimization request and the PCE is not capable of global
 concurrent optimization, the PCE MUST send a PCErr message with a
 PCEP-ERROR Object (Error-Type=15) and an Error-value (Error-value=2).

Lee, et al. Standards Track [Page 18] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

 The PCE stops processing the request.  The corresponding global
 concurrent path optimization MUST be cancelled at the PCC.
 To indicate an error associated with policy violation, a new error
 value "global concurrent optimization not allowed" should be added to
 an existing error code for policy violation (Error-Type=5) as defined
 in [RFC5440].
 Error-Type=5; Error-value=5: if a PCE receives a global concurrent
 path optimization request that is not compliant with administrative
 privileges (i.e., the PCE policy does not support global concurrent
 optimization), the PCE sends a PCErr message with a PCEP-ERROR Object
 (Error-Type=5) and an Error-value (Error-value=5).  The PCE stops the
 processing the request.  The corresponding global concurrent path
 computation MUST be cancelled at the PCC.

5.7. NO-PATH Indicator

 To communicate the reason(s) for not being able to find global
 concurrent path computation, the NO-PATH object can be used in the
 PCRep message.  The format of the NO-PATH object body is defined in
 [RFC5440].  The object may contain a NO-PATH-VECTOR TLV to provide
 additional information about why a path computation has failed.
 Two new bit flags are defined to be carried in the Flags field in the
 NO-PATH-VECTOR TLV carried in the NO-PATH Object.
 Bit 6: When set, the PCE indicates that no migration path was found.
 Bit 7: When set, the PCE indicates no feasible solution was found
 that meets all the constraints associated with global concurrent path
 optimization in the PCRep message.

6. Manageability Considerations

 Manageability of global concurrent path computation with PCE must
 address the following considerations:

6.1. Control of Function and Policy

 In addition to the parameters already listed in Section 8.1 of
 [RFC5440], a PCEP implementation SHOULD allow configuring the
 following PCEP session parameters on a PCC:
 o  The ability to send a GCO request.

Lee, et al. Standards Track [Page 19] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

 In addition to the parameters already listed in Section 8.1 of
 [RFC5440], a PCEP implementation SHOULD allow configuring the
 following PCEP session parameters on a PCE:
 o  The support for Global Concurrent Optimization.
 o  The maximum number of synchronized path requests per request
    message.
 o  A set of GCO specific policies (authorized sender, request rate
    limiter, etc.).
 These parameters may be configured as default parameters for any PCEP
 session the PCEP speaker participates in, or may apply to a specific
 session with a given PCEP peer or a specific group of sessions with a
 specific group of PCEP peers.

6.2. Information and Data Models (e.g., MIB Module)

 Extensions to the PCEP MIB module defined in [PCEP-MIB] should be
 defined, so as to cover the GCO information introduced in this
 document.

6.3. Liveness Detection and Monitoring

 Mechanisms defined in this document do not imply any new liveness
 detection and monitoring requirements in addition to those already
 listed in Section 8.3 of [RFC5440].

6.4. Verifying Correct Operation

 Mechanisms defined in this document do not imply any new verification
 requirements in addition to those already listed in Section 8.4 of
 [RFC5440]

6.5. Requirements on Other Protocols and Functional Components

 The PCE Discovery mechanisms ([RFC5088] and [RFC5089]) may be used to
 advertise global concurrent path computation capabilities to PCCs.  A
 new flag (value=9) in PCE-CAP-FLAGs Sub-TLV has been assigned to be
 able to indicate GCO capability.

6.6. Impact on Network Operation

 Mechanisms defined in this document do not imply any new network
 operation requirements in addition to those already listed in Section
 8.6 of [RFC5440].

Lee, et al. Standards Track [Page 20] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

7. Security Considerations

 When global reoptimization is applied to an active network, it could
 be extremely disruptive.  Although the real security and policy
 issues apply at the NMS, if the wrong results are returned to the
 NMS, the wrong actions may be taken in the network.  Therefore, it is
 very important that the operator issuing the commands has sufficient
 authority and is authenticated, and that the computation request is
 subject to appropriate policy.
 The mechanism defined in [RFC5440] to secure a PCEP session can be
 used to secure global concurrent path computation requests/responses.

8. IANA Considerations

 IANA maintains a registry of PCEP parameters.  IANA has made
 allocations from the sub-registries as described in the following
 sections.

8.1. Request Parameter Bit Flags

 As described in Section 5.3, two new bit flags are defined for
 inclusion in the Flags field of the RP object.  IANA has made the
 following allocations from the "RP Object Flag Field" sub-registry.
    Bit      Description                         Reference
    21       Make-before-break (M-bit)           [RFC5557]
    22       Report the request order (D-bit)    [RFC5557]

8.2. New PCEP TLV

 As described in Section 5.4, a new PCEP TLV is defined to indicate
 the setup and delete order of TE LSPs in a GCO.  IANA has made the
 following allocation from the "PCEP TLV Type Indicators" sub-
 registry.
    TLV Type        Meaning                 Reference
    5               Order TLV               [RFC5557]

Lee, et al. Standards Track [Page 21] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

8.3. New Flag in PCE-CAP-FLAGS Sub-TLV in PCED

 As described in Section 6.5, a new PCE-CAP-FLAGS Sub-TLV is defined
 to indicate a GCO capability.  IANA has made the following allocation
 from the "Path Computation Element (PCE) Capability Flags" sub-
 registry, which was created by Section 7.2 of RFC 5088.  It is an
 OSPF registry.
    FLAG            Meaning                                Reference
    9               Global Concurrent Optimization (GCO)   [RFC5557]

8.4. New PCEP Object

 As descried in Section 5.5, a new PCEP object is defined to carry
 global constraints.  IANA has made the following allocation from the
 "PCEP Objects" sub-registry.
    Object  Name                                            Reference
    Class
    24      GLOBAL-CONSTRAINTS                              [RFC5557]
                Object-Type
                1: Global Constraints                       [RFC5557]

8.5. New PCEP Error Codes

 As described in Section 5.6, new PCEP error codes are defined for GCO
 errors.  IANA has made allocations from the "PCEP-ERROR Object Error
 Types and Values" sub-registry as set out in the following sections.

8.5.1. New Error-Values for Existing Error-Types

    Error-
    Type    Meaning                                         Reference
    5       Policy violation
              Error-value=5:                                [RFC5557]
                Global concurrent optimization not allowed

Lee, et al. Standards Track [Page 22] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

8.5.2. New Error-Types and Error-Values

    Error-
    Type    Meaning                                         Reference
    15      Global Concurrent Optimization Error            [RFC5557]
              Error-value=1:
                Insufficient memory                         [RFC5557]
              Error-value=2:
                Global concurrent optimization not supported
                                                            [RFC5557]

8.6. New No-Path Reasons

 IANA has made the following allocations from the "NO-PATH-VECTOR TLV
 Flag Field" sub-registry for bit flags carried in the NO-PATH-VECTOR
 TLV in the PCEP NO-PATH object as described in Section 5.7.
    Bit
    Number          Name                         Reference
    25              No GCO solution found        [RFC5557]
    26              No GCO migration path found  [RFC5557]

9. References

9.1. Normative References

 [RFC5441]  Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux,
            "A Backward-Recursive PCE-Based Computation (BRPC)
            Procedure to Compute Shortest Constrained Inter-Domain
            Traffic Engineering Label Switched Paths", RFC 5441, April
            2009.
 [RFC5541]  Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
            Objective Functions in Path Computation Element
            Communication Protocol (PCEP)", RFC 5541, May 2009.
 [RFC5521]  Oki, E., Takeda, T., and A. Farrel, "Extensions to the
            Path Computation Element Communication Protocol (PCEP) for
            Route Exclusions", RFC 5521, April 2009.
 [RFC5440]  Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path Computation
            Element (PCE) Communication Protocol (PCEP)", RFC 5440,
            March 2009.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.

Lee, et al. Standards Track [Page 23] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

 [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
            and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
            Tunnels", RFC 3209, December 2001.
 [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.
 [RFC5089]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
            Zhang, "IS-IS Protocol Extensions for Path Computation
            Element (PCE) Discovery", RFC 5089, January 2008.

9.2. Informative References

 [PCE-MLN]  Oki, E., Takeda, T., Le Roux, JL., and A. Farrel,
            "Framework for PCE-Based Inter-Layer MPLS and GMPLS
            Traffic Engineering", Work in Progress, March 2009.
 [PCEP-MIB] Koushik, K. and E. Stephan, "PCE communication protocol
            (PCEP) Management Information Base", Work in Progress,
            November 2008.
 [RFC5511]  Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
            Used to Form Encoding Rules in Various Routing Protocol
            Specifications", RFC 5511, April 2009.
 [RFC4655]  Farrel, A., Vasseur, J.-P., 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.
 [RFC5212]  Shiomoto, K., Papadimitriou, D., Le Roux, JL., Vigoureux,
            M., and D. Brungard, "Requirements for GMPLS-Based Multi-
            Region and Multi-Layer Networks (MRN/MLN)", RFC 5212, July
            2008.

10. Acknowledgments

 We would like to thank Jerry Ash, Adrian Farrel, J-P Vasseur, Ning
 So, Lucy Yong, and Fabien Verhaeghe for their useful comments and
 suggestions.

Lee, et al. Standards Track [Page 24] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

Appendix A. RBNF Code Fragments

 Copyright (c) 2009 IETF Trust and the persons identified as authors
 of the code.  All rights reserved.
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions
 are met:
  1. Redistributions of source code must retain the above copyright

notice, this list of conditions and the following disclaimer.

  1. Redistributions in binary form must reproduce the above copyright

notice, this list of conditions and the following disclaimer in the

   documentation and/or other materials provided with the
   distribution.
  1. Neither the name of Internet Society, IETF or IETF Trust, nor the

names of specific contributors, may be used to endorse or promote

   products derived from this software without specific prior written
   permission.
 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT
 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 <PCReq Message> ::= <Common Header>
                     [<svec-list>]
                     <request-list>
 <svec-list> ::= <SVEC>
                 [<OF>]
                 [<GC>]
                 [<XRO>]
                 [<svec-list>]

Lee, et al. Standards Track [Page 25] RFC 5557 PCEP Requirements & Protocol Extensions for GCO July 2009

Authors' Addresses

 Young Lee
 Huawei
 1700 Alma Drive, Suite 100
 Plano, TX  75075
 US
 Phone: +1 972 509 5599 x2240
 Fax:   +1 469 229 5397
 EMail: ylee@huawei.com
 JL Le Roux
 France Telecom
 2, Avenue Pierre-Marzin
 Lannion  22307
 FRANCE
 EMail: jeanlouis.leroux@orange-ftgroup.com
 Daniel King
 Old Dog Consulting
 United Kingdom
 EMail: daniel@olddog.co.uk
 Eiji Oki
 University of Electro-Communications
 1-5-1 Chofugaoka
 Chofu, Tokyo  182-8585
 JAPAN
 EMail: oki@ice.uec.ac.jp

Lee, et al. Standards Track [Page 26]

/data/webs/external/dokuwiki/data/pages/rfc/rfc5557.txt · Last modified: 2009/07/16 22:01 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki