Internet DRAFT - draft-ietf-pce-disco-proto-ospf

draft-ietf-pce-disco-proto-ospf




 


Network Working Group                              J.L. Le Roux (Editor) 
Internet Draft                                            France Telecom 
Intended Status: Standard Track          
Expires: April 2008                                J.P. Vasseur (Editor) 
                                                       Cisco System Inc. 
                                                                         
                                                          Yuichi Ikejiri  
                                                      NTT Communications 
                                                                         
                                                           Raymond Zhang 
                                                              BT Infonet 
                                                                         
                                                            October 2007 
 
 
    
    
  OSPF Protocol Extensions for Path Computation Element (PCE) Discovery 
 
               draft-ietf-pce-disco-proto-ospf-08.txt 
 
 
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Copyright Notice 
 
   Copyright (C) The IETF Trust (2007).  All rights reserved. 
 

 
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Abstract 
    
   There are various circumstances where it is highly desirable for a 
   Path Computation Client (PCC) to be able to dynamically and 
   automatically discover a set of Path Computation Elements (PCEs), 
   along with information that can be used by the PCC for PCE selection. 
   When the PCE is a Label Switching Router (LSR) participating in the 
   Interior Gateway Protocol (IGP), or even a server participating 
   passively in the IGP, a simple and efficient way to announce PCEs 
   consists of using IGP flooding. For that purpose, this document 
   defines extensions to the Open Shortest Path First (OSPF) routing 
   protocol for the advertisement of PCE Discovery information within an 
   OSPF area or within the entire OSPF routing domain.  
 
Conventions used in this document 
 
   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this 
   document are to be interpreted as described in [RFC2119]. 
 
Table of Contents 
    
   1.      Terminology.................................................3 
   2.      Introduction................................................4 
   3.      Overview....................................................5 
   3.1.    PCE Discovery Information...................................5 
   3.2.    Flooding Scope..............................................5 
   4.      The OSPF PCED TLV...........................................6 
   4.1.    PCE-ADDRESS Sub-TLV.........................................7 
   4.2.    PATH-SCOPE Sub-TLV..........................................8 
   4.3.    PCE-DOMAIN Sub-TLV.........................................10 
   4.4.    NEIG-PCE-DOMAIN Sub-TLV....................................11 
   4.5.    PCE-CAP-FLAGS Sub-TLV......................................11 
   5.      Elements of Procedure......................................13 
   6.      Backward Compatibility.....................................13 
   7.      IANA Considerations........................................14 
   7.1.    OSPF TLV...................................................14 
   7.2.    PCE Capability Flags registry..............................14 
   8.      Security Considerations....................................15 
   9.      Manageability Considerations...............................15 
   9.1.    Control of Policy and Functions............................15 
   9.2.    Information and Data Model.................................15 
   9.3.    Liveness Detection and Monitoring..........................15 
   9.4.    Verify Correct Operations..................................16 
   9.5.    Requirements on Other Protocols and Functional 
             Components...............................................16 
   9.6.    Impact on Network Operations...............................16 
   10.     Acknowledgments............................................16 
   11.     References.................................................16 
   11.1.   Normative References.......................................16 
   11.2.   Informative References.....................................17 
   12.     Editor's Addresses.........................................17 
 
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   13.     Contributors' Addresses....................................18 
   14.     Intellectual Property Statement............................18 
    
1. Terminology 
 
      ABR: OSPF Area Border Router.  
    
      AS: Autonomous System. 
       
      IGP: Interior Gateway Protocol. Either of the two routing    
      protocols Open Shortest Path First (OSPF) or Intermediate System   
      to Intermediate System (ISIS). 
    
      Intra-area TE LSP: A TE LSP whose path does not cross an IGP area  
      boundary.  
    
      Intra-AS TE LSP: A TE LSP whose path does not cross an AS    
      boundary.  
    
      Inter-area TE LSP: A TE LSP whose path transits two or more IGP   
      areas. That is a TE LSP that crosses at least one IGP area  
      boundary. 
        
      Inter-AS TE LSP: A TE LSP whose path transits two or more     
      ASes or sub-ASes (BGP confederations). That is a TE LSP that  
      crosses at least one AS boundary. 
    
      LSA: Link State Advertisement. 
 
      LSR: Label Switching Router. 
 
      PCC: Path Computation Client. Any client application requesting a  
      path computation to be performed by a Path Computation Element.  
 
      PCE: Path Computation Element. An entity (component, application,  
      or network node) that is capable of computing a network path or  
      route based on a network graph, and applying computational  
      constraints. 
    
      PCE-Domain: In a PCE context this refers to any collection of 
      network elements within a common sphere of address management or 
      path computational responsibility (referred to as a "domain" in 
      [RFC4655]). Examples of PCE-Domains include IGP areas and ASes. 
      This should be distinguished from an OSPF routing domain. 
 
      PCEP: Path Computation Element Protocol. 
    
      TE LSP: Traffic Engineered Label Switched Path. 
    



 
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2. Introduction 
 
   [RFC4655] describes the motivations and architecture for a Path 
   Computation Element (PCE)-based  
   path computation model for Multi-Protocol Label Switching (MPLS) and 
   Generalized MPLS (GMPLS) Traffic Engineered Label Switched Paths (TE 
   LSPs). The model allows for the separation of the PCE from a Path 
   Computation Client (PCC) (also referred to as a non co-located PCE) 
   and allows for cooperation between PCEs (where one PCE acts as a PCC 
   to make requests of the other PCE). This relies on a communication 
   protocol between PCC and PCE, and also between PCEs. The requirements 
   for such a communication protocol can be found in [RFC4657], and the 
   communication protocol is defined in [PCEP]. 
          
   The PCE architecture requires that a PCC be aware of the location of 
   one or more PCEs in its domain, and also, potentially, of PCEs in 
   other domains, e.g., in the case of inter-domain TE LSP computation.  
    
   A network may contain a large number of PCEs, each with potentially 
   distinct capabilities. In such a context it is highly desirable to 
   have a mechanism for automatic and dynamic PCE discovery that allows 
   PCCs to automatically discover a set of PCEs along with additional 
   information about each PCE that may be used by a PCC to perform PCE 
   selection. Additionally, it is valuable for a PCC to dynamically 
   detect new PCEs, failed PCEs, or any modification to the PCE 
   information. Detailed requirements for such a PCE discovery mechanism 
   are provided in [RFC4674]. 
    
   Note that the PCE selection algorithm applied by a PCC is out of the 
   scope of this document. 
    
   When PCCs are LSRs participating in the IGP (OSPF or IS-IS), and PCEs 
   are either LSRs or servers also participating in the IGP, an 
   effective mechanism for PCE discovery within an IGP routing domain 
   consists of utilizing IGP advertisements. 
    
   This document defines extensions to OSPFv2 [RFC2328] and OSPFv3 
   [RFC2740] to allow a PCE in an OSPF routing domain to advertise its 
   location along with some information useful to a PCC for PCE 
   selection so as to satisfy dynamic PCE discovery requirements set 
   forth in [RFC4674]. 
    
   Generic capability advertisement mechanisms for OSPF are defined in 
   [OSPF-CAP]. These allow a router to advertise its capabilities within 
   an OSPF area or an entire OSPF routing domain. This document 
   leverages this generic capability advertisement mechanism to fully 
   satisfy the dynamic PCE discovery requirements.  
    
   This document defines a new TLV (named the PCE Discovery (PCED) TLV) 
   to be carried within the OSPF Router Information LSA ([OSPF-CAP]). 
 

 
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   The PCE information advertised is detailed in Section 3. Protocol 
   extensions and procedures are defined in Sections 4 and 5. 
    
   The OSPF extensions defined in this document allow for PCE discovery 
   within an OSPF routing domain. Solutions for PCE discovery across AS 
   boundaries are beyond the scope of this document, and for further 
   study. 
 
3. Overview 
 
 
3.1. PCE Discovery Information 
    
   The PCE discovery information is composed of: 
 
   - The PCE location: an IPv4 and/or IPv6 address that is used to reach    
     the PCE. It is RECOMMENDED to use an address that is always     
     reachable if there is any connectivity to the PCE; 
    
   - The PCE path computation scope (i.e., intra-area, inter-area,  
     inter-AS, or inter-layer); 
    
   - The set of one or more PCE-Domain(s) into which the PCE has   
     visibility and for which the PCE can compute paths; 
 
   - The set of zero, one or more neighbor PCE-Domain(s) toward which  
     the PCE can compute paths; 
 
   - A set of communication capabilities (e.g., support for request  
     prioritization) and path computation-specific capabilities    
     (e.g., supported constraints).  
    
   PCE discovery information is by nature fairly static and does not 
   change with PCE activity. Changes in PCE discovery information may 
   occur as a result of PCE configuration updates, PCE 
   deployment/activation, PCE deactivation/suppression, or PCE failure. 
   Hence, this information is not expected to change frequently. 
 
    
3.2. Flooding Scope 
 
   The flooding scope for PCE information advertised through OSPF can be 
   limited to one or more OSPF areas the PCE belongs to, or can be 
   extended across the entire OSPF routing domain.  
    
   Note that some PCEs may belong to multiple areas, in which case the 
   flooding scope may comprise these areas. This could be the case for 
   an ABR, for instance, advertising its PCE information within the 
   backbone area and/or a subset of its attached IGP area(s). 
    
    
    
 
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4. The OSPF PCED TLV  
    
   The OSPF PCE Discovery TLV (PCED TLV) contains non-ordered set of 
   sub-TLVs.  
    
   The format of the OSPF PCED TLV and its sub-TLVs is identical to the 
   TLV format used by the Traffic Engineering Extensions to OSPF 
   [RFC3630]. That is, the TLV is composed of 2 octets for the type, 2 
   octets specifying the TLV length, and a value field. The Length field 
   defines the length of the value portion in octets.  
    
   The TLV is padded to four-octet alignment; padding is not included in 
   the Length field (so a three octet value would have a length of 
   three, but the total size of the TLV would be eight octets). Nested 
   TLVs are also four-octet aligned. Unrecognized types are ignored.   
 
   The OSPF PCED TLV has the following format:  
    
                        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            | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
   |                                                               |  
   //                            sub-TLVs                          //          
   |                                                               |  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    
              
         Type     To be defined by IANA (suggested value=5) 
         Length   Variable 
         Value    This comprises one or more sub-TLVs  
 
   Five sub-TLVs are defined:                   
         Sub-TLV type  Length               Name   
               1      variable     PCE-ADDRESS sub-TLV   
               2         4         PATH-SCOPE sub-TLV 
               3         4         PCE-DOMAIN sub-TLV 
               4         4        NEIG-PCE-DOMAIN sub-TLV 
               5      variable     PCE-CAP-FLAGS sub-TLV 
               
   The PCE-ADDRESS and PATH-SCOPE sub-TLVs MUST always be present within 
   the PCED TLV. 
    
   The PCE-DOMAIN and NEIG-PCE-DOMAIN sub-TLVs are optional. They MAY be 
   present in the PCED TLV to facilitate selection of inter-domain PCEs. 
    
   The PCE-CAP-FLAGS sub-TLV is optional and MAY be present in the PCED 
   TLV to facilitate the PCE selection process. 
    
 
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   Malformed PCED TLVs or sub-TLVs not explicitly described in this 
   document MUST cause the LSA to be treated as malformed according to 
   the normal procedures of OSPF. 
    
   Any unrecognized sub-TLV MUST be silently ignored. 
 
   The PCED TLV is carried within an OSPF Router Information LSA  
   defined in [OSPF-CAP]. 
    
   No additional sub-TLVs will be added to the PCED TLV in the future. 
   If a future application requires the advertisement of additional PCE 
   information in OSPF, this will not be carried in the Router 
   Information LSA. 
 
   The following sub-sections describe the sub-TLVs which may be carried 
   within the PCED sub-TLV. 
 
4.1. PCE-ADDRESS Sub-TLV  
    
   The PCE-ADDRESS sub-TLV specifies an IP address that can be  
   used to reach the PCE. It is RECOMMENDED to make use of an address      
   that is always reachable, provided that the PCE is alive and 
   reachable. 
 
   The PCE-ADDRESS sub-TLV is mandatory; it MUST be present within the 
   PCED TLV. It MAY appear twice, when the PCE has both an IPv4 and IPv6 
   address. It MUST NOT appear more than once for the same address type. 
   If it appears more than once, only the first occurrence is processed 
   and any others MUST be ignored. 
 
   The format of the PCE-ADDRESS sub-TLV is as follows: 
        
                            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 = 1         |             Length            | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
       |     address-type              |          Reserved             |  
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
       |                                                               |  
       //                       PCE IP Address                        // 
       |                                                               |  
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
                             
                            PCE-ADDRESS sub-TLV format  
        
         Type     1 
         Length   8 (IPv4) or 20 (IPv6) 
    
         Address-type:  
 
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                       1   IPv4  
                       2   IPv6  
    
         Reserved: SHOULD be set to zero on transmission and MUST be   
         ignored on receipt. 
    
         PCE IP Address: The IP address to be used to reach the PCE.  
                          
       
4.2. PATH-SCOPE Sub-TLV 
 
   The PATH-SCOPE sub-TLV indicates the PCE path computation scope, 
   which refers to the PCE's ability to compute or take part in the 
   computation of paths for intra-area, inter-area, inter-AS, or inter-
   layer_TE LSPs.  
    
   The PATH-SCOPE sub-TLV is mandatory; it MUST be present within the 
   PCED TLV. There MUST be exactly one instance of the PATH-SCOPE sub-
   TLV within each PCED TLV. If it appears more than once, only the 
   first occurrence is processed and any others MUST be ignored. 
 
   The PATH-SCOPE sub-TLV contains a set of bit-flags indicating the 
   supported path scopes, and four fields indicating PCE preferences. 
    
   The PATH-SCOPE sub-TLV has the following format:  
      
                        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 = 2         |             Length            | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
   |0|1|2|3|4|5|   Reserved        |PrefL|PrefR|PrefS|PrefY| Res   |              
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
    
              
         Type     2 
         Length   4 
         Value    This comprises a 2-octet flag field where each bit  
                  represents a supported path scope, as well as four  
                  preference fields used to specify PCE preferences.    
          
         The following bits are defined: 
 
         Bit      Path Scope 
 
          0      L bit:  Can compute intra-area paths 
          1      R bit:  Can act as PCE for inter-area TE LSP  
                         computation 
          2      Rd bit: Can act as a default PCE for inter-area TE LSP  
                         computation        
          3      S bit:  Can act as PCE for inter-AS TE LSP computation 
          4      Sd bit: Can act as a default PCE for inter-AS TE LSP   
 
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                         computation       
          5      Y bit:  Can compute or take part into the computation    
                         of paths across layers. 
 
          PrefL field: PCE's preference for intra-area TE LSPs  
          computation. 
    
          PrefR field: PCE's preference for inter-area TE LSPs  
          computation. 
    
          PrefS field: PCE's preference for inter-AS TE LSPs  
          computation. 
    
          PrefY field: PCE's preference for inter-layer TE LSPs  
          computation. 
    
          Res: Reserved for future use. 
 
   The L, R, S, and Y bits are set when the PCE can act as a PCE for 
   intra-area, inter-area, inter-AS, or inter-layer TE LSPs computation 
   respectively. These bits are non-exclusive. 
    
   When set, the Rd bit indicates that the PCE can act as a default PCE 
   for inter-area TE LSPs computation (that is, the PCE can compute a 
   path toward any neighbor area). Similarly, when set, the Sd bit 
   indicates that the PCE can act as a default PCE for inter-AS TE LSP 
   computation (the PCE can compute a path toward any neighbor AS).  
    
   When the Rd and Sd bit are set the PCED TLV MUST NOT contain a NEIG-
   PCE-DOMAIN sub-TLV (see Section 4.1.4). 
    
   When the R bit is clear, the Rd bit SHOULD be clear on transmission 
   and MUST be ignore on receipt. When the S bit is clear, the Sd bit 
   SHOULD be clear on transmission and MUST be ignored on receipt. 
    
   The PrefL, PrefR, PrefS, and PrefY fields are each three bits long 
   and allow the PCE to specify a preference for each computation scope, 
   where 7 reflects the highest preference. Such preferences can be used 
   for weighted load balancing of path computation requests. An operator 
   may decide to configure a preference for each computation scope at 
   each PCE so as to balance the path computation load among them. The 
   algorithms used by a PCC to load balance its path computation 
   requests according to such PCE preferences is out of the scope of 
   this document and is a matter for local or network-wide policy. The 
   same or different preferences may be used for each scope. For 
   instance, an operator that wants a PCE capable of both inter-area and 
   inter-AS computation to be prefered for use for inter-AS computations 
   may configure PrefS higher than PrefR.  
    
   When the L, R, S, or Y bits are cleared, the PrefL, PrefR, PrefS, and 
   PrefY fields SHOULD respectively be set to 0 on transmission and MUST 
   be ignored on receipt.  
 
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   Both reserved fields SHOULD be set to zero on transmission and MUST  
   be ignored on receipt. 
 
4.3. PCE-DOMAIN Sub-TLV 
    
   The PCE-DOMAIN sub-TLV specifies a PCE-Domain (area or AS) where the 
   PCE has topology visibility and through which the PCE can compute 
   paths.  
 
   The PCE-DOMAIN sub-TLV SHOULD be present when PCE-Domains for which 
   the PCE can operate cannot be inferred by other IGP information, for 
   instance when the PCE is inter-domain capable (i.e., when the R bit 
   or S bit is set) and the flooding scope is the entire routing domain 
   (see Section 5 for a discussion of how the flooding scope is set and 
   interpreted). 
    
   A PCED TLV may include multiple PCE-DOMAIN sub-TLVs when the PCE has 
   visibility into multiple PCE-Domains. 
 
   The PCE-DOMAIN sub-TLV has the following format:  
    
                            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=3           |             Length            | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
       |     Domain-type               |          Reserved             |  
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
       |                       Domain ID                               | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
                             
                            PCE-DOMAIN sub-TLV format  
        
         Type     3 
         Length   8 
    
         Two domain-type values are defined:  
                       1   OSPF Area ID 
                       2   AS Number 
    
         Domain ID: With the domain-type set to 1, this indicates the 32     
         bit Area ID of an area where the PCE has visibility and can  
         compute paths. With domain-type set to 2, this indicates an AS  
         number of an AS where the PCE has visibility and can compute  
         paths. When the AS number is coded in two octets, the AS Number 
         field MUST have its first two octets set to 0. 
.        
 
 
                
 
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4.4. NEIG-PCE-DOMAIN Sub-TLV 
    
   The NEIG-PCE-DOMAIN sub-TLV specifies a neighbor PCE-domain (area or 
   AS) toward which a PCE can compute paths. It means that the PCE can 
   take part in the computation of inter-domain TE LSPs with paths that 
   transit this neighbor PCE-domain.  
 
   A PCED sub-TLV may include several NEIG-PCE-DOMAIN sub-TLVs when the 
   PCE can compute paths towards several neighbour PCE-domains.  
 
   The NEIG-PCE-DOMAIN sub-TLV has the same format as the PCE-DOMAIN 
   sub-TLV: 
 
                            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 = 4         |             Length            | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
       |     Domain-type               |          Reserved             |  
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
       |                           Domain ID                           |   
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
                             
                            NEIG-PCE-DOMAIN sub-TLV format  
        
         Type     4 
         Length   8 
    
         Two domain-type values are defined:  
                       1   OSPF Area ID 
                       2   AS Number 
    
         Domain ID: With the domain-type set to 1, this indicates the 32  
         bit Area ID of a neighbour area toward which the PCE can        
         compute paths. With domain-type set to 2, this indicates the AS   
         number of a neighbor AS toward which the PCE can compute paths.    
         When the AS number is coded in two octets, the AS Number field  
         MUST have its first two octets set to 0. 
 
   The NEIG-PCE-DOMAIN sub-TLV MUST be present at least once with 
   domain-type set to 1 if the R bit is set and the Rd bit is cleared, 
   and MUST be present at least once with domain-type set to 2 if the S 
   bit is set and the Sd bit is cleared. 
 
4.5. PCE-CAP-FLAGS Sub-TLV  
           
   The PCE-CAP-FLAGS sub-TLV is an optional sub-TLV used to indicate PCE 
   capabilities. It MAY be present within the PCED TLV. It MUST NOT be 
   present more than once. If it appears more than once, only the first 
   occurrence is processed and any others MUST be ignored. 
    
 
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   The value field of the PCE-CAP-FLAGS sub-TLV is made up of an array 
   of units of 32 bit-flags numbered from the most significant bit as 
   bit zero, where each bit represents one PCE capability.  
        
   The format of the PCE-CAP-FLAGS sub-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 = 5         |             Length            | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |                                                               | 
     //                 PCE Capability Flags                          // 
      |                                                               | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
 
         Type     5 
         Length   Multiple of 4 octets 
         Value    This contains an array of units of 32 bit flags  
                  numbered from the most significant as bit zero, where  
                  each bit represents one PCE capability.  
 
   IANA is requested to manage the space of the PCE Capability Flags 
    
   The following bits are to be assigned by IANA: 
 
 
     Bit       Capabilities 
 
      0        Path computation with GMPLS link constraints  
      1        Bidirectional path computation  
      2        Diverse path computation  
      3        Load-balanced path computation  
      4        Synchronized path computation  
      5        Support for multiple objective functions  
      6        Support for additive path constraints                           
               (max hop count, etc.) 
      7        Support for request prioritization 
      8        Support for multiple requests per message   
    
     9-31    Reserved for future assignments by IANA. 
    
   These capabilities are defined in [RFC4657]. 
    
   Reserved bits SHOULD be set to zero on transmission and MUST be 
   ignored on receipt. 
 



 
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5. Elements of Procedure 
     
   The PCED TLV is advertised within OSPFv2 Router Information LSAs 
   (Opaque type of 4 and Opaque ID of 0) or OSPFv3 Router Information 
   LSAs (function code of 12) which are defined in [OSPF-CAP].  As such, 
   elements of procedure are inherited from those defined in [OSPF-CAP]. 
    
   In OSPFv2 the flooding scope is controlled by the opaque LSA type (as  
   defined in [RFC2370]) and in OSPFv3 by the S1/S2 bits (as defined in  
   [RFC2740]). If the flooding scope is local to an area then the PCED 
   TLV MUST be carried within an OSPFv2 type 10 router information LSA 
   or an OSPFV3 Router Information LSA with the S1 bit set and the S2 
   bit clear. If the flooding scope is the entire IGP domain then the 
   PCED TLV MUST be carried within an OSPFv2 type 11 Router Information 
   LSA or OSPFv3 Router Information LSA with the S1 bit clear and the S2 
   bit set. When only the L bit of the PATH-SCOPE sub-TLV is set, the 
   flooding scope MUST be area local. 
    
   When the PCE function is deactivated, the OSPF speaker advertising 
   this PCE MUST originate a new Router Information LSA that no longer 
   includes the corresponding PCED TLV, provided there are other TLVs in 
   the LSA. If there are no other TLVs in the LSA, it MUST either send 
   an empty Router Information LSA or purge it by prematurely aging it. 
 
   The PCE address (i.e., the address indicated within the PCE ADDRESS 
   TLV) SHOULD be reachable via some prefixes advertised by OSPF. This 
   allows the detection of a PCE failure to be sped up. When the PCE 
   address is no longer reachable, the PCE node has failed, has been 
   torn down, or there is no longer IP connectivity to the PCE.  
 
   A change in information in the PCED TLV MUST NOT trigger any SPF  
   computation at a receiving router. 
    
   The way PCEs determine the information they advertise is out of the  
   scope of this document. Some information may be configured on the PCE    
   (e.g., address, preferences, scope) and other information may be  
   automatically determined by the PCE (e.g., areas of visibility). 
 
            
6. Backward Compatibility 
    
   The PCED TLV defined in this document does not introduce any 
   interoperability issues.  
    
   A router not supporting the PCED TLV will just silently ignore the 
   TLV as specified in [OSPF-CAP].  
 
 
 
 
 
 
 
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7. IANA Considerations 
 
7.1. OSPF TLV 
    
   IANA has defined a registry for TLVs carried in the Router 
   Information LSA defined in [OSPF-CAP]. IANA is requested to assign a 
   new TLV code-point for the PCED TLV carried within the Router 
   Information LSA. 
 
   Value      TLV Name                      Reference 
   -----     --------                       ---------- 
     5         PCED                       (this document)               
     
 
7.2. PCE Capability Flags registry 
    
   This document provides new capability bit flags, which are present  
   in the PCE-CAP-FLAGS TLV referenced in section 4.1.5. 
    
   The IANA is requested to create a new top-level OSPF registry, the 
   "PCE Capability Flags" registry, and to manage the space of PCE 
   capability bit flags numbering them in the usual IETF notation 
   starting at zero and continuing at least through 31, with the most 
   significant bit as bit zero. 
 
   New bit numbers may be allocated only by an IETF Consensus action. 
    
   Each bit should be tracked with the following qualities: 
    
   - Bit number      
   - Capability Description 
   - Defining RFC     
       
   Several bits are defined in this document. Here are the suggested 
   values: 
 
     Bit       Capability Description     
 
      0        Path computation with GMPLS link constraints 
      1        Bidirectional path computation  
      2        Diverse path computation 
      3        Load-balanced path computation 
      4        Synchronized paths computation 
      5        Support for multiple objective functions 
      6        Support for additive path constraints                            
               (max hop count, etc.) 
      7        Support for request prioritization 
      8        Support for multiple requests per message       
 
 
 
 
 
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8. Security Considerations 
 
   This document defines OSPF extensions for PCE discovery within an 
   administrative domain. Hence the security of the PCE discovery relies 
   on the security of OSPF. 
 
   Mechanisms defined to ensure authenticity and integrity of OSPF LSAs 
   [RFC2154], and their TLVs, can be used to secure the PCE Discovery 
   information as well. 
    
   OSPF provides no encryption mechanism for protecting the privacy of 
   LSAs, and in particular the privacy of the PCE discovery information.  
 
9. Manageability Considerations 
    
   Manageability considerations for PCE Discovery are addressed in 
   Section 4.10 of [RFC4674]. 
    
9.1. Control of Policy and Functions 
    
   Requirements for the configuration of PCE discovery parameters on 
   PCCs and PCEs are discussed in Section 4.10.1 of [RFC4674]. 
    
   In particular, a PCE implementation SHOULD allow the following 
   parameters to be configured on the PCE: 
        - The PCE IPv4/IPv6 address(es) (see Section 4.1) 
        - The PCE Scope, including the inter-domain functions (inter- 
          area, inter-AS, inter-layer), the preferences, and whether the  
          PCE can act as default PCE (see Section 4.2) 
        - The PCE domains (see Section 4.3) 
        - The neighbour PCE domains (see Section 4.4) 
        - The PCE capabilities (see Section 4.5) 
    
9.2. Information and Data Model 
    
   A MIB module for PCE Discovery is defined in [PCED-MIB]. 
    
9.3. Liveness Detection and Monitoring 
    
   PCE Discovery Protocol liveness detection relies upon OSPF liveness 
   detection. OSPF already includes a liveness detection mechanism 
   (Hello protocol), and PCE discovery does not require additional 
   capabilities. 
    
   Procedures defined in Section 5 allow a PCC to detect when a PCE has 
   been deactivated, or is no longer reachable. 
 
 
 
 
 
 
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9.4. Verify Correct Operations  
    
   The correlation of information advertised against information 
   received can be achieved by comparing the information in the PCED TLV 
   received by the PCC with that stored at the PCE  using the PCED MIB 
   [PCED-MIB].  The number of dropped, corrupt, and rejected information 
   elements are available through the PCED MIB. 
    
9.5. Requirements on Other Protocols and Functional Components 
 
   The OSPF extensions defined in this document do not imply any  
   requirement on other protocols. 
 
9.6. Impact on Network Operations 
 
   Frequent changes in PCE information advertised in the PCED TLV, may 
   have a significant impact on OSPF and might destabilize the operation 
   of the network by causing the PCCs to swap between PCEs.  
    
   As discussed in Section 4.10.4 of [RFC4674], it MUST be possible to 
   apply at least the following controls: 
    
      - Configurable limit on the rate of announcement of changed 
        parameters at a PCE. 
      - Control of the impact on PCCs such as through rate-limiting                  
        the processing of PCED TLVs. 
      - Configurable control of triggers that cause a PCC to swap to 
        another PCE. 
    
10. Acknowledgments 
 
   We would like to thank Lucy Wong, Adrian Farrel, Les Ginsberg, Mike 
   Shand, and Lou Berger for their useful comments and suggestions. 
    
   We would also like to thank Dave Ward, Lars Eggert, Sam Hartman, and 
   Tim Polk for their comments during the final stages of publication. 
 
11. References 
    
11.1. Normative References 
    
   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate 
   Requirement Levels", BCP 14, RFC 2119, March 1997. 
 
   [RFC2328] Moy, J., "OSPF Version 2", RFC 2328, April 1998. 
    
   [RFC2740] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", 
   RFC 2740, December 1999. 
 
   [RFC2370] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370, July 
   1998. 
    
 
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   [RFC3630] Katz, D., Yeung, D., Kompella, K., "Traffic Engineering 
   Extensions to OSPF Version 2", RFC 3630, September 2003. 
    
   [OSPF-CAP] Lindem, A., Shen, N., Aggarwal, R., Shaffer, S., Vasseur, 
   J.P., "Extensions to OSPF for advertising Optional Router 
   Capabilities", draft-ietf-ospf-cap, work in progress. 
    
   [RFC2154] Murphy, S., Badger, M., and B. Wellington, "OSPF with 
   Digital Signatures", RFC 2154, June 1997. 
 
11.2. Informative References 
 
   [RFC4657] Ash, J., Le Roux, J.L., "PCE Communication Protocol Generic 
   Requirements", RFC4657, September 2006. 
    
   [PCEP] Vasseur, Le Roux, et al., "Path Computation Element (PCE) 
   communication Protocol (PCEP) - Version 1", draft-ietf-pce-pcep, work 
   in progress. 
    
   [PCED-MIB] Stephan, E., "Definitions of Managed Objects for Path 
   Computation Element Discovery", draft-ietf-pce-disc-mib, work in 
   progress. 
    
   [PCED-ISIS] Le Roux, Vasseur, et al. "IS-IS protocol extensions for  
   Path Computation Element (PCE) Discovery", draft-ietf-pce-disco- 
   proto-isis, work in progress. 
    
   [RFC4655] Farrel, A., Vasseur, J.P., Ash, J., "Path Computation 
   Element (PCE)-based Architecture", RFC4655, August 2006. 
    
   [RFC4674] Le Roux, J.L., et al. "Requirements for PCE discovery", 
   RFC4674, October 2006. 
 
12. Editor's Addresses 
     
   Jean-Louis Le Roux (Editor) 
   France Telecom  
   2, avenue Pierre-Marzin  
   22307 Lannion Cedex  
   FRANCE 
   Email: jeanlouis.leroux@orange-ftgroup.com 
     
   Jean-Philippe Vasseur (Editor) 
   Cisco Systems, Inc.  
   1414 Massachusetts avenue  
   Boxborough , MA - 01719  
   USA  
   Email: jpv@cisco.com  
 
 
 
 
 
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13. Contributors' Addresses 
    
   Yuichi Ikejiri                                       
   NTT Communications Corporation                      
   1-1-6, Uchisaiwai-cho, Chiyoda-ku                  
   Tokyo 100-8019    
   JAPAN    
   Email: y.ikejiri@ntt.com   
    
    
   Raymond Zhang 
   BT Infonet 
   2160 E. Grand Ave. 
   El Segundo, CA 90025 
   USA 
   Email: raymond_zhang@bt.infonet.com 
    
  
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   WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE 
   ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS 
   FOR A PARTICULAR PURPOSE. 
 
   Copyright Statement 
    
   Copyright (C) The IETF Trust (2007). This document is subject to the 
   rights, licenses and restrictions contained in BCP 78, and except as 
   set forth therein, the authors retain all their rights. 
    
 
 








































 
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