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draft-vasseur-mpls-ospf-pcsd-discovery-00.txt



Hi,

NAME OF I-D:

OSPF Path Computation Server discovery

SUMMARY

This draft proposes an OSPF extension for a router to announce its
Path Computation Server capability used in the context of MPLS
Traffic Engineering. This draft defines a new opaque LSA called PCSD
(Path Computation Server Discovery). The PCSD LSA has a variable
length and is made of a set of TLVs.

RELATED DOCUMENTS:
None

WHERE DOES IT FIT IN THE PICTURE OF THE SUB-IP WORK:

This document specifies OSPF extensions in support of MPLS Traffic
Engineering. It relates to the work on off-load computation of
Traffic Engineering Label Switch Path covered by CCAMP.

This document fits into CCAMP WG.

WHY IS IT TARGETED AT THIS WG

This addresses specific items of the CCAMP WG charter.

From the CCAMP WG Charter:
"- Define signalling protocols and measurement protocols such that they support multiple physical path and tunnel technologies (e.g. O-O and O-E-O optical switches, ATM and Frame Relay switches, MPLS, GRE) using input from technology-specific working groups such as MPLS, IPO, etc.
- Define signalling and measurement protocols that are independent of each other. This allows applications other than the signalling protocol to use the measurement protocol; it also allows the signalling protocol to use knowledge obtained by means other than the measurement protocol.
..."

JUSTIFICATION
The draft directly addresses items of the charter.

Many thanks in advance.

Best regards.

JP.
Internet draft draft-vasseur-mpls-ospf-pcsd-discovery-00.txt  June 2002 

Network Working Group                                        JP Vasseur 
Internet Draft                                             Peter Psenak 
Document: draft-vasseur-mpls-ospf-pcsd-discovery-    Cisco Systems, Inc 
00.txt                                              
 
IETF Internet Draft                                      
Expires: December, 2002                             
                                                              June 2002 
 
 
                                     
                 OSPF Path Computation Server discovery 
    
    
                                     
               draft-vasseur-mpls-ospf-pcsd-discovery-00.txt 
 
    
 
Status of this Memo 
    
   This document is an Internet-Draft and is in full conformance with 
   all provisions of Section 10 of RFC2026. Internet-Drafts are 
   Working documents of the Internet Engineering Task Force (IETF), its 
   areas, and its working groups.  Note that other groups may also 
   distribute working documents as Internet-Drafts. 
    
   Internet-Drafts are draft documents valid for a maximum of six 
   months and may be updated, replaced, or obsoleted by other documents 
   at any time. It is inappropriate to use Internet-Drafts as reference 
   material or to cite them other than as "work in progress." 
    
   The list of current Internet-Drafts can be accessed at 
   http://www.ietf.org/ietf/1id-abstracts.txt. 
   The list of Internet-Draft Shadow Directories can be accessed at 
   http://www.ietf.org/shadow.html. 
 
    
Abstract 
    
   This draft proposes an OSPF extension for a router to announce its 
   Path Computation Server capability used in the context of MPLS 
   Traffic Engineering. This draft defines a new opaque LSA called PCSD 
   (Path Computation Server Discovery). The PCSD LSA has a variable 
   length and is made of a set of TLVs.  
    
    
1. Where does this draft fit in the picture of the Sub-IP work 
    
   This document specifies OSPF extensions in support of MPLS Traffic 
   Engineering. It relates to the work on off-load computation of 
   Traffic Engineering Label Switch Path covered by CCAMP.  
    
    
  
Vasseur and Psenak                                                   1 








Internet draft draft-vasseur-ospf-pcsd-discovery-00.txt       June 2002 
 
 
 
2. Terminology 
    
   Terminology used in this draft 
    
   LSR: Label Switch Router 
    
   PCS: Path Computation Server (may be an LSR (ABR, ASBR, ...) or a 
   dedicated path computation server (typically a UNIX machine) not 
   forwarding packet. 
    
   PCC: Path Computation Client (any head-end LSR) requesting a path 
   computation to the Path Computation Server. 
    
   TE LSP: Traffic Engineering Label Switched Path 
    
   Head-end TE LSP: head/source of the TE LSP 
    
   Tail-end TE LSP: tail/destination of the TE LSP 
    
   Intra-area TE LSP: TE LSP whose head-end and tail-end reside in the 
   same area 
    
   Inter-area TE LSP: TE LSP whose head-end and tail-end reside in 
   different areas (the TE LSP spans areas) 
    
   Inter-AS TE LSP: TE LSP whose head-end and tail-end reside in 
   different Autonomous Systems (the TE LSP spans AS) 
    
    
3. Introduction 
    
   This draft specifies a new OSPF opaque LSA called PCSD LSA for the 
   Auto-discovery of one or more Path Computation Server(s). In various 
   situations, an LSR may send a request to a Path Computation Server 
   (PCS) to compute one or more Traffic Engineering LSP paths obeying a 
   set of specified constraints.  
    
   [4] specifies RSVP extensions: 
        - for a PCC to send path computation requests to a PCS to 
        compute TE LSP(s) obeying a set of specified constraints, 
        - for the PCS to provide to the PCC one or more computed paths 
        obeying the set of constraints (or to return an indication 
        mentioning no path obeying the constraints could be found). 
    
   The scope of this document is to define a new OSPF opaque LSA such 
   that a LSR/centralized path computation tool may announce its 
   capability to be a Path Computation Server within an area or an 
   Autonomous System. 
    
   This allows every LSR in the network to automatically discover the 
   Path Computation Server(s), which substantially simplifies the head-

Vasseur et Psenak                                                    2 
 








Internet draft draft-vasseur-ospf-pcsd-discovery-00.txt       June 2002 
 
 
 
   end LSR configuration. Moreover, this allows to detect dynamically 
   any new PCS or that a PCS is no longer active. 
    
    
4. PCSD LSA Packet format 
    
4.1 PCSD LSA Header 
    
   The OSPF PCSD LSA is an opaque LSA (type 10 or type 11). As defined 
   in RFC2370, an opaque LSA header has the following form: 
    
   Header format of the PCSD LSA: 
    
    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 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |            LS age             |     Options   |    10 or 11   | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |Opaque type TBD|               Opaque ID                       | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                      Advertising Router                       | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                      LS Sequence Number                       | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |         LS checksum           |           Length              | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |                                                               | 
   +                                                               + 
   |                      Opaque Information                       | 
   +                                                               + 
   |                                                               | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
    
   The PCSD LSA uses opaque type [TBD by IANA].  
    
   The Opaque ID is used for LSA instantiation and allows a single 
   system to generate multiple PCSD LSA. It has no particular 
   significance. 
    
    
4.2 PCSD LSA payload 
 
   The PCSD LSA payload is made of a set of non ordered TLVs each 
   having the following format:  
    
       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            | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
       |                                                               | 
Vasseur et Psenak                                                    3 
 








Internet draft draft-vasseur-ospf-pcsd-discovery-00.txt       June 2002 
 
 
 
       //                            Value                            //         
       |                                                               | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
   Where  
        Type: identifies the TLV type 
        Length: length of the value field 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 32-bit aligned.  Unrecognized types are ignored.  All 
   types between 32768 and 65535 are reserved for vendor-specific 
   extensions.  All other undefined type codes are reserved for future 
   assignment by IANA. 
    
   A TLV may itself contain one or more sub-TLVs. 
    
   Note that a sub-TLV is similar to a TLV: TLV are carried within an 
   LSA as sub-TLVs are carried within TLVs. Each sub-TLV describes a 
   particular Path Computation Server capability. In the rest of this 
   document both terms will be used interchangeably. 
    
    
4.3 PCSD TLVs format 
    
   This section defines the PCSD TLVs carried within the OSPF PCSD LSA 
   payload.  
    
   The PCSD LSA is made of various non ordered TLVs defined bellow:  
         
   TLV type      Length                Name 
      1            4          Path computation server scope TLV 
      2           variable    Path computation server address TLV 
      3            8          Path computation server capability TLV 
      4            8          AS-domain TLV 
         
   Any non recognized TLV must be silently ignored. 
                 
                 
4.3.1 Path computation server scope TLV 
    
   The path computation server scope TLV specifies the zone for which 
   the path computation server is capable of performing TE LSP path 
   computation. 
    
   The path computation server scope TLV type is 1, its length is 4, and 
   the value is a set of flags: 
    
    
      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 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
Vasseur et Psenak                                                    4 
 








Internet draft draft-vasseur-ospf-pcsd-discovery-00.txt       June 2002 
 
 
 
      |              1                |               4               | 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      |           Reserved            |     Flags     |         |A|I|L| 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
                     
                   Path computation server scope TLV format 
    
    
   Flags: no flags are currently defined. 
    
   Scope 
    
   L (local scope). When set, this flag indicates that the PCS can 
   compute paths for the area the LSP is flooded into (i.e the PCS can 
   compute TE LSP path for intra-area TE LSPs). 
    
   I (inter-area scope). When set, the PCS can perform TE LSP path 
   computation for inter-area TE LSPs (i.e TE LSP whose destination IP 
   address belongs to another area of the head-end LSR) but within the 
   same AS.  
    
   A (multi-domain scope). When set, the PCS can perform path 
   computation for inter-domain TE LSP. In this case, the PCSD LSA must 
   contain one or more AS-domain TLV(s) each describing the domain for 
   which the PCS can compute TE LSPs paths having their destination 
   address in this domain.  
    
   Note that a PCS may set one or more flags. 
    
   See section 4 for a detailed description of the elements of 
   procedure. 
    
    
4.3.2 Path Computation Server address TLV 
    
   The PCS address TLV specifies the IP address to be used to reach the 
   PCS described by this PCSD LSA. This address will typically be a 
   loop-back address, always reachable, provided the router is not 
   isolated. This TLV is required. 
    
   The PCS address TLV type is 2, length is 4 octets for an IPv4 
   address and 16 octets for an IPv6 address, and the value is the PCS 
   IPv4 or IPv6 address. 
    
       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                |      variable (4 or 16)       | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
       |     address-type              |          Reserved             | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
       |                                                               | 
       //                       PCS IP address                        //          
Vasseur et Psenak                                                    5 
 








Internet draft draft-vasseur-ospf-pcsd-discovery-00.txt       June 2002 
 
 
 
       |                                                               | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
                         
                   Path Computation Server address TLV format 
    
   Address-type: 
        1   IPv4 
        2   IPv6 
    
   The Path Computation Server address TLV MUST appear exactly once in 
   the PCSD LSA originated by a router. The only exception is when the 
   PCS has both an IPv4 and IPv6 address; in this case, two path 
   computation server address TLVs might be inserted: one for the IPv4 
   address, one for the IPv6 address. 
    
    
4.3.3 Path Computation Server capability TLV 
    
   The PCS capability TLV is used by the PCS to signal its path 
   computation server capabilities. This TLV is optional. 
    
   The PCS capability TLV type is 3 and the length is 8 octets. 
    
       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 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
       |              3                |             8                 | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
       |                          Reserved                             | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
       |P|M|D|E|G|                Reserved                             |     
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
                        PCS capability TLV format 
    
   P bit 
   The notion of request priority allows a PCC to specify how urgent is 
   the request setting a flag in the REQUEST_ID object of the Path 
   computation request message. See [4] for more details. 
    
   P=1: the PCS takes into account the "request priority" in its 
   scheduling of the various requests. 
   P=0: the PCS does not take the request priority into account 
    
   M bit 
   M=1: the PCS is capable of computing more than one paths obeying a 
   set of specified constraints, provided that they exist. 
   M=0: the PCS cannot compute more than one path obeying a set of 
   specified constraints. 
    
   D bit 
   The PCC may request the PCS to compute N diversely routed paths 
   obeying a set of specified constraints.  
Vasseur et Psenak                                                    6 
 








Internet draft draft-vasseur-ospf-pcsd-discovery-00.txt       June 2002 
 
 
 
   Such N paths may not exist of course depending on the current state 
   of the network. See [4] for more details. 
   D=1: the PCS is capable of computing diversely (link, node, SRLG) 
   routed paths.  
   D=0: the PCS is not capable of computing diversely routed paths. 
   The D bit is relevant if and only if the M bit has been set to 1. It 
   must be set to 0 if the M bit is set to 0. 
    
   E bit 
   The PCC may request the PCS the computation of a path obeying a set 
   of constraints one of those constraints being that one or more 
   specified network element object must not be traversed by the LSP (a 
   network element may be a link, an LSR or an Autonomous System). See 
   [4] for more details. 
   E=1: the PCS is capable of computing TE LSP paths excluding some 
   network elements. 
   E=0: the PCS is not capable of computing paths excluding network 
   elements. 
    
   G bit 
   As defined in [4], the PCC may send a request specifying the metric 
   to be used by the PCS when computing the shortest path during the 
   CSPF. 
   G=1: the PCS supports the computation of CSPF with various metrics 
   G=0: the PCS just computes the CSPF based on the TE metric 
    
   Note that for future capability, it may be desirable to introduce 
   new flags or may be new TLV to be carried in the PCSD LSA if the 
   capability needs more than just a single flag to be described. 
    
    
4.3.4 AS-domain TLV 
    
   When the PCS can perform path computation for inter-domain TE LSP, 
   the A bit of the path computation server scope TLV must be set. 
   Moreover, one or more TLVs MUST included within the PCSD TLV, each 
   TLV identifying an AS number. Each TLV will have the following form:     
    
    
       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 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
       |              4                |             4                 | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
       |                           AS Number                           | 
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    
                           AS-domain TLV format 
    
   The AS-domain TLV type is 4, length is 4 octets, and the value is the 
   AS number identifying the AS for which the PCS can compute inter-
   domain TE LSP paths (TE LSP having their destination address in this 
   domain). When coded on two bytes (which is the current defined format 
Vasseur et Psenak                                                    7 
 








Internet draft draft-vasseur-ospf-pcsd-discovery-00.txt       June 2002 
 
 
 
   as the time of writing), the AS Number field must have its left two 
   bytes set to 0. 
    
   The set of AS-domain TLVs specifies a list of ASes (AS1, ... , ASn). 
   This means that the PCS can compute TE LSP path such that the 
   destination address of the TE LSP belong to this set of ASes. 
    
    
5. Elements of procedure 
    
   A router must originate its PCSD opaque LSA whenever its content 
   change or whenever required by the regular OSPF procedure (LSA 
   refresh (every LSRefreshTime, new OSPF adjacency, ...). 
    
   As defined in RFC2370, an opaque LSA has a flooding scope determined 
   by its LSA type: 
        - link-local (type 9),  
        - area-local (type 10)  
        - entire OSPF routing domain (type 11). In this case, the 
        flooding scope is equivalent to the Type 5 LSA flooding scope. 
    
   A PCSD LSA may be generated as a type 10 or 11 depending on the path 
   computation server scope.  
    
   - If the PCS can compute intra-area TE LSP the L bit of the path 
   computation server scope sub-TLV must be set, 
   - If the PCS can compute inter-area TE LSP the I bit of the path 
   computation server scope sub-TLV must be set, 
   - If the PCS can compute inter-AS TE LSP the A bit of the path 
   computation server scope sub-TLV must be set, 
    
   Note: if the PCS can both compute intra and inter-area TE LSP paths, 
   both the L and I bits of the path computation server scope TLV must 
   be set. The flags are not exclusive. 
    
   Type of PCSD opaque LSA 
    
   If a PCS can only compute intra-area TE LSP path computation, it 
   MUST originate a unique PCSD LSA of type 10 with the S, I and A 
   flags of its Path Computation Server scope TLV set as described 
   above. 
    
   If a PCS can only compute inter-area or inter-AS TE LSP path, it 
   MUST originate a unique PCSD LSA of type 11 with the S, I and A 
   flags of its Path Computation Server scope TLV set as described 
   above. 
    
   If a PCS can compute intra-area TE LSP and inter-area or inter-AS TE 
   LSP path, it must originate: 
        - a type 10 PCSD LSA with L=1 and the I and A flags of its Path 
        Computation Server scope TLV set as described above, 

Vasseur et Psenak                                                    8 
 








Internet draft draft-vasseur-ospf-pcsd-discovery-00.txt       June 2002 
 
 
 
        - a type 11 PCSD LSA with L=0 and the I and A flags of its Path 
        Computation Server scope TLV set as described above. 
    
    
   Example 
    
   <-----------------AS1-----------------> 
    
   <---area 1--><----area 0-----><-area 2-> 
    
   R1---------ABR1*------------ABR3*-----|                 ------------ 
    |           |                |       |                 |          | 
    |     S1    |      S2        |     ASBR1*--eBGP--ASBR2-|    AS2   | 
    |           |                |       |                 |          | 
   R2---------ABR2*------------ABR4------|                 ------------ 
    
    
   The areas contents are not detailed. 
    
   Assumptions: 
   - area 1 and area 2 are regular areas 
   - the * indicates a Path computation server capability 
   - ABR1 is a PCS for area 1 only 
   - ABR2 is a PCS for intra and inter-area TE LSP path computation in 
   area 0 and 1 
   - ABR3 is a PCS for only inter-area TE LSP path computation in areas 
   0 and 2 
   - S1 is a PCS for area 1 only 
   - S2 is a PCS for the whole AS 
   - ASBR1 is a PCS for inter-AS TE LSP only whose destination resides 
   in AS2 (not for intra or inter-area area TE LSPs). 
    
   In the example above: 
   - S1 originates a type 10 PCSD LSA with: 
        o The L bit of the path computation server scope TLV set, 
        o The I and A bits of the path computation server scope TLV 
        cleared. 
    
   - ABR1 originates in area 1 a type 10 PCSD LSA with: 
        o The L bit of the path computation server scope TLV set, 
        o The I and A bits of the path computation server scope TLV 
        cleared, 
    
   - ABR2 originates: 
        - in both area 0 and 1 a type 10 PCSD LSA with: 
                o The L and I bits of the path computation server scope 
                TLV set, 
                o The A bit of the path computation server scope TLV  
                cleared, 
        - a type 11 PCSD LSA with: 
                o The L bit of the path computation server scope TLV 
                cleared,  
Vasseur et Psenak                                                    9 
 








Internet draft draft-vasseur-ospf-pcsd-discovery-00.txt       June 2002 
 
 
 
                o The I bit of the path computation server scope TLV 
                set, 
                o The A bit of the path computation server scope TLV  
                cleared, 
    
   - ABR3 originates a type 11 PCSD LSA with: 
        o The L bit of the path computation server scope TLV cleared, 
        o The I bit of the path computation server scope TLV set, 
        o The A bit of the path computation server scope TLV  cleared, 
    
   - S2 originates: 
        - in area 0 a type 10 PCSD LSA with: 
                o The L and I bits of the path computation server scope 
                TLV set, 
                o The A bit of the path computation server scope TLV  
                cleared, 
        - a type 11 PCSD LSA with: 
                o The L bit of the path computation server scope TLV 
                cleared,  
                o The I bit of the path computation server scope TLV 
                set, 
                o The A bit of the path computation server scope TLV  
                cleared, 
    
   - ASBR1 originates a type 11 PCSD LSA with: 
        o The L bit of the path computation server scope TLV cleared, 
        o The I bit of the path computation server scope TLV cleared, 
        o The A bit of the path computation server scope TLV set, 
        o One AS-domain TLV within the PCSD TLV with AS number = AS2 
    
   The receipt of a new PCSD LSA never triggers an SPF calculation. 
    
   When an LSR or a dedicated path computation server is newly 
   configured as a PCS, the corresponding PCSD LSA must be immediately 
   flooded. 
    
   When a PCS capability changes, the corresponding PCSD LSA must be 
   immediately flooded. 
    
   When an LSR or a dedicated path computation server looses its path 
   computation server capability, the corresponding PCSD LSA must be 
   immediately flooded with LS age = MaxAge. 
    
    
5. Interoperability with routers non supporting this capability 
    
   There is no interoperability issue as a router non-supporting the 
   OSPF PCSD opaque LSA should just silently discard any received OSPF 
   PCSD LSA as specified in RFC2370. 
    
    
6. Security Considerations 
Vasseur et Psenak                                                   10 
 








Internet draft draft-vasseur-ospf-pcsd-discovery-00.txt       June 2002 
 
 
 
 
   No new security issues are raised in this document. 
    
    
7. Acknowledgments 
    
   The authors would like to thank Abhay Roy, Dan Tappan and Robert 
   Raszuk for their comments. 
    
    
8. References 
    
   [1] Moy, J., "OSPF Version 2", RFC 2328, April 1998. 
    
   [2] Awduche, D., et al, "Requirements for Traffic Engineering Over 
   MPLS," RFC 2702, September 1999. 
    
   [3] Coltun, R., "The OSPF Opaque LSA Option," RFC 2370, July 1998. 
    
   [4] Vasseur et al, "RSVP Path computation request and reply 
   messages ", draft-vasseur-mpls-computation-rsvp-te-03.txt, work in 
   progress. 
    
   [5] Katz, D., Yeung, D., "Traffic Engineering Extensions to OSPF", 
       draft-katz-yeung-ospf-traffic-04.txt 
    
   [6] Smit, H. and T. Li, "ISIS Extensions for Traffic Engineering," 
       draft-ietf-isis-traffic-03.txt, work in progress. 
    
   [7] Kompella, K., and Rekhter, Y., "LSP Hierarchy with MPLS TE", 
   Internet Draft, draft-ietf-mpls-lsp-hierarchy-02.txt, Feb., 2001. 
    
   [8]  Kompella, K., Rekhter, Y., "Signalling Unnumbered Links in RSVP-
   TE", Internet Draft, draft-ietf-mpls-rsvp-unnum-01.txt, February 2001 
    
   [9] Kompella, K., Rekhter, Y., Banerjee, A. et al, "OSPF 
      Extensions in Support of Generalized MPLS", draft-ietf-ccamp-  
      ospf-gmpls-extensions-06.txt (work in progress) 
    
   [10] Ashwood-Smith, P. et al, "Generalized MPLS Signaling - CR-LDP 
   Extensions", Internet Draft, draft-ietf-mpls-generalized-cr-ldp-
   01.txt, February 2001. 
    
   [11] Ashwood-Smith, P. et al, "Generalized MPLS - Signaling 
   Functional Description", Internet Draft, draft-ietf-mpls-generalized-
   signaling-02.txt, 
   February 2001. 
    
   [12] Bradner, S., "Key words for use in RFCs to Indicate Requirement 
   Levels," RFC 2119. 
    

Vasseur et Psenak                                                   11 
 








Internet draft draft-vasseur-ospf-pcsd-discovery-00.txt       June 2002 
 
 
 
   [13] Braden, R. Ed. et al, "Resource ReserVation Protocol-- Version 1 
   Functional Specification", RFC 2205, September 1997. 
    
   [14] Awduche, et al, "RSVP-TE: Extensions to RSVP for LSP Tunnels", 
   RFC 3209, December 2001. 
    
   [15] Berger L., Gan D., Swallow G., Pan P., Tommasi F., Molendini S., 
   "RSVP Refresh Overhead Reduction Extensions", RFC 2961, April 2001. 
    
   [16] Le faucheur, "Use of IGP Metric as a second TE Metric", 
   Internet draft, draft-lefaucheur-te-metric-igp-00.txt. 
    
   [17] Fedyk D., Ghanwani A., Ash J., Vedrenne A. "Multiple Metrics 
   for Traffic Engineering with IS-IS and OSPF", Internet draft,  
   draft-fedyk-isis-ospf-te-metrics-01.txt 
 
    
8. Author's Addresses 
    
      JP Vasseur 
      CISCO Systems, Inc. 
      11, rue Camille Desmoulins 
      92782  Issy les Moulineaux Cedex 9 
      FRANCE 
      Email: jpv@cisco.com 
    
      Peter Psenak 
      CISCO Systems, Inc. 
      Pegasus Parc  
      De Kleetlaan 6A 
      1831, Diegem  
      BELGIUM 
      Email: ppsenak@cisco.com 
    


















Vasseur et Psenak                                                   12