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Internet-Draft                                   Tomohiro Otani (Editor) 
Intended status: Informational                    Kenichi Ogaki (Editor) 
Expires: May 2008                                          KDDI R&D Labs 
                                                     Daniel King(Editor) 
                                                           Aria Networks 
                                                                         
                                                        November 19 2007 
 
 
       Considering Generalized Multiprotocol Label Switching Traffic 
              Engineering Attributes During Path Computation 
 
         Document: draft-otani-ccamp-gmpls-cspf-constraints-07.txt 
    
    
Status of this Memo 
 
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Copyright Notice  
    
   Copyright (C) The IETF Trust (2007). All Rights Reserved. 
    
Abstract 
    
   This document provides guidelines for the consideration of 
   Generalized Multiprotocol Label Switching (GMPLS) Traffic-Engineering 
   (TE) attributes for computation of routes for Label Switched Paths 
   (LSPs) in a GMPLS network. 
        This document summarizes how GMPLS TE attributes on ingress 
   links, transit links, and egress links may be treated as path 
   computation constraints to determine the route of a GMPLS Label 
   Switched Path (LSP). 
    
     
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Table of Contents 
    
Status of this Memo..................................................1 
Abstract.............................................................1 
1. Introduction......................................................3 
2. Problem Statements................................................3 
3. Assumed Network Model.............................................4 
4. Path Computation Considerations...................................6 
5. Security consideration...........................................13 
6. Acknowledgements.................................................14 
7. Intellectual Property Considerations.............................14 
8. IANA Considerations..............................................15 
9. References.......................................................15 


































     
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1. Introduction 
    
   A network is, in general, controlled and managed taking into account 
   various attributes of the underlying technologies of the physical and 
   logical links and nodes. In a network operated using Generalized 
   Multiprotocol Label Switching (GMPLS) protocols, many of these 
   Traffic Engineering (TE) attributes are advertised using routing 
   protocols [RFC3945], [RFC4202].  
    
        To establish a GMPLS Label Switched Path (LSP) it is necessary 
   to compute a route or path for that LSP either hop-by-hop or by the 
   pre-calculation of part or all of the path. In order that the route 
   selected is capable of satisfying the requirements of the user or 
   application that will use the LSP the computation must be constrained 
   by a set of LSP-specific requirements and the TE attributes 
   advertised within the network. Further, considerations of technology 
   and node or link capabilities may also provide restrictions to the 
   feasibility of LSP establishment on certain routes, and this can be 
   deduced from the TE attributes advertised within the network and used 
   by the path computation algorithms to select only viable routes. 
    
        In a mixed, integrated network (for example, one containing 
   optical switches and packet routers) these constraints may vary and 
   are understood differently for different equipment and different LSPs. 
   This document provides guidelines to facilitate path computation for 
   GMPLS LSPs by summarizing how GMPLS TE attributes on ingress links, 
   transit links, and egress links may be treated as path computation 
   constraints to determine the route of a GMPLS Label Switched Path 
   (LSP).  
    
2. Problem Statements 
    
   A GMPLS network is assumed to be composed of different switching 
   capabilities for nodes and different encoding types for TE links. 
   Such a GMPLS network is usually deployed by adopting multiple vendors 
   and each vendor usually has each constraint for a CSPF path 
   calculation and then a problem appears that a signaling message 
   including a calculated route at an ingress node may be rejected at a 
   transit node and the path creation may fail because of the difference 
   of the constraint for a CSPF path calculation between these nodes. 
    
   In an example network as shown in Figure 1, when ingress Router1 
   calculates a path to egress Router2 without considering the encoding 
   type for transit TE links and sends path message to PXC1, PXC1 
   returns path error message to Router1 because PXC1 cannot 
   crossconnect from ethernet encoding link to sonet/sdh encoding link. 
   In this case, if ingress Router1 can calculate with the exact match 
   for all the links through the ingress node to the egress node, the 
   path can be established. 
    
     
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     Router1--(Ethernet)--PXC1--(SONET/SDH)--PXC2--(Ethernet)--Router2 
    
   *(): Encoding type 
                          Figure 1: example network1 
    
 
   On the other hand, when a network includes optical switching nodes 
   such as ROADMs which have a link with the encoding type of lambda 
   between nodes as shown in Figure2 and ingress Router1 calculate with 
   the exact match through all the links, the path calculation will fail. 
   In this environment, even if the encoding type of ingress and egress 
   links is different from transit links, the path should be established. 
   Therefore, constraints for various cases of path calculation must be 
   clearly defined. 
    
 
             Router1                                          Router3 
                \                                              / 
                 \                                            / 
               (Ethernet)                              (Ethernet) 
                   \                                        / 
                    \                                      / 
                    ROADM1--(Lambda)--ROADM2--(Lambda)--ROADM3 
                    /                                      \ 
                   /                                        \ 
               (SONET/SDH)                             (SONET/SDH) 
                 /                                            \ 
                /                                              \ 
             Router2                                          Router4 
    
                          Figure 2: example network2 
 
    
3. Assumed Network Model 
    
   3.1 GMPLS TE Attributes Consideration for Path Calculation 
    
   For path computation to establish GMPLS LSPs correctly, various GMPLS 
   attributes [RFC4202], [RFC4203] of links as well as nodes, as 
   indicated below, must be taken into account in a GMPLS network 
   environment in addition to TE attributes of packet based network 
   [RFC3630]. 
    
        (1) Encoding-type: Synchronous Optical Network 
        (SONET)/Synchronous Digital Hierarchy (SDH), Lambda, Ethernet, 
        etc. 
        (2) Switching capability: Time Division Multiplex (TDM), Lambda, 
        Fiber, etc. 
        (3) Bandwidth: OC-192, OC-48, GbE, 10GbE, etc. 
     
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   These logical attributes have a very tight relationship with 
   underlying physical technologies such as SONET/SDH, Optical Transport 
   Network (OTN) or Ethernet in terms of links, and all-optical switches, 
   SONET/SDH-basis digital cross connect or electrical-basis optical 
   switches in terms of nodes.  Therefore, the GMPLS LSPs must satisfy 
   logical constrains as well as corresponding physical constraints. 
   These constraints are sometimes differently understood among 
   different layers, and a logically computed GMPLS LSP may violate the 
   physical constraints, therefore, a consistent guideline to solve this 
   issue should be formulated. 
    
    
   3.2 Considered Network Model 
    
   Figure 3 depicts a typical GMPLS network, consisting of an ingress 
   link, a transit link as well as an egress link, to investigate a 
   consistent guideline for GMPLS path computation. Each link at each 
   interface has its own switching capability, encoding type and 
   bandwidth. 
   The consideration here is based on a single domain GMPLS network, but 
   the analysis maybe applicable to an inter-domain GMPLS networks. 
    
             Ingress             Transit             Egress             
   +-----+   link1-2   +-----+   link2-3   +-----+   link3-4   +-----+  
   |Node1|------------>|Node2|------------>|Node3|------------>|Node4|  
   |     |<------------|     |<------------|     |<------------|     |  
   +-----+   link2-1   +-----+   link3-2   +-----+   link4-3   +-----+  
 
                       Figure 3: GMPLS Network Model 
    
    
   For the simplicity of the analysis in path consideration, the below 
   basic assumptions are made when the LSP is created. 
    
       (1) Switching capabilities (SC) of outgoing links from the 
           ingress and egress nodes (link1-2 and link4-3 in Figure 1)  
           must be consistent with each other. 
       (2) SC of all transit links including incoming links to the 
           ingress and egress nodes (link2-1 and link3-4) should be 
           consistent with switching type of a LSP to be created. 
       (3) Encoding-types of all transit links should be consistent 
           with encoding type of a LSP to be created. 
        
  A GMPLS network maybe a multi-layer network, which is composed of 
  multiple nodes with different switching capabilities and interface 
  encoding types. Therefore, a hierarchical structure may be considered 
  in path computation. In such a case, the combination between the 
  switching type and encoding type of a desired LSP, and those of all 
  transit links described as the table in following section may be 
     
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  acceptable. One of advertised multiple interface switching capability 
  descriptors for the same link [RFC4202] should be also appropriately 
  chosen as the attribute for the link. 
        
   Bandwidth of each TE link is maximum LSP bandwidth in interface 
   switching capability descriptor at the priority for a desired LSP 
   [RFC4203], and encoding-types of incoming and outgoing links on the 
   same interface (for example, link1-2 and link2-1) should be 
   consistent with each other. 
    
   In case that the network is comprised of numbered links and 
   unnumbered links [RFC3477], an ingress node, who is able to support 
   numbered links and unnumbered links may choose both links being part 
   of the same desired LSP. 
    
    
4. Path Computation Considerations 
 
        In this section, we consider GMPLS constraints to be satisfied 
   in different cases of link attributes. When a LSP indicated in below 
   tables is created, the path computation must choose the route so as 
   to satisfy switching capability, encoding type and bandwidth at the 
   ingress link, transiting links and the egress link indicated in 
   columns next to the created LSP, considering underlying physical 
   constraints. Here, almost cases of GMPLS path computation 
   consideration are summarized in this document, however, some cases 
   will be added in a future version. 
    
    
   (1) TDM-Switch Capable 
    
          Table 1: Desired GMPLS Attributes in the Case of TDM-SC 
    
   +-------------+---------+------------+---------+------------------+ 
   |LSP attribute|Ingress  |Transit     |Egress   |Remarks           | 
   +---+---------+---------+------------+---------+------------------+ 
   |   |         |TDM      |            |TDM      |                  | 
   |   |         +---------+            +---------+                  | 
   |SC*|TDM      |L2SC     |TDM         |L2SC     |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |PSC      |            |PSC      |                  | 
   +---+---------+---------+------------+---------+                  | 
   |   |SONET/SDH|SONET/SDH|SONET/SDH   |SONET/SDH|Specified in G.691| 
   |   +---------+---------+------------+---------+                  | 
   |Enc|Ethernet |Ethernet |SONET/SDH   |Ethernet |Specified in IEEE | 
   |   |         |         |or Ethernet |         |                  | 
   |   +---------+---------+------------+---------+                  | 
   |   |OTN*     |OTN      |OTN         |OTN      |                  | 
   +---+---------+---------+------------+---------+                  | 
   |BW*|X        |<=bw*    |<=bw        |<=bw     |                  | 
     
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   +---+---------+---------+------------+---------+------------------+ 
    
   *SC in LSP means a desired switching type of LSP. 
   *OTN interfaces are equivalent to digital wrapper technology in this 
   document. 
   * BW is the desired bandwidth of the LSP 
   * bw is the bandwidth available on the link 
 
   In this case, since the interface with TDM SC supports sub-rate 
   switching, BW X can be equal to or less than bw of ingress, transit 
   and egress links, and must be larger than the minimum LSP bandwidth 
   in the interface switching capability descriptor. Sub-rate switching 
   is unsuited for a hierarchical LSP, because the lower-layer link 
   usually has larger granular bandwidth than that layer except PSC-x, 
   for example a TDM LSP with the desired bandwidth of OC-12 should not 
   use a lambda switching capable link with the bandwidth of OC-48 as a 
   transit link. In such a case, a lambda LSP as a forwarding adjacency 
   (FA) LSP is created on the lower (lambda) layer in advance, then the 
   FA-LSP [LSP-HIER] may be advertised as a TDM SC link. 
    
    
   (2) Lambda Switch Capable (LSC) 
    
        Table 2.1: The Case of End-Point(Ingress/Egress) Link Attributes 
                          without Lambda Encoding 
    
   +-------------+---------+------------+---------+------------------+ 
   |LSP attribute|Ingress  |Transit     |Egress   |Remarks           | 
   +---+---------+---------+------------+---------+------------------+ 
   |   |         |LSC      |            |LSC      |                  | 
   |   |         +---------+            +---------+                  | 
   |SC |LSC      |TDM      |LSC         |TDM      |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |L2SC     |            |L2SC     |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |PSC      |            |PSC      |                  | 
   +---+---------+---------+------------+---------+[RFC4202]         | 
   |   |SONET/SDH|SONET/SDH|SONET/SDH   |SONET/SDH|section 3.6, 3.9  | 
   |   |         |         |or lambda   |         |Specified in G.691| 
   |   +---------+---------+------------+---------+                  | 
   |Enc|Ethernet |Ethernet |Ethernet    |Ethernet |Specified in IEEE | 
   |   |         |         |or lambda   |         |                  | 
   |   +---------+---------+------------+---------+                  | 
   |   |OTN      |OTN      |OTN         |OTN      |Specified in G.709| 
   |   |         |         |or lambda   |         |                  | 
   |---+---------+---------+------------+---------+                  | 
   |BW |X        |=bw      |=bw         |=bw      |                  | 
   |   |         |         |or *<=bw    |         |                  | 
   +---+---------+---------+------------+---------+------------------+ 

     
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   If an interface supports only a specific bit-rate and format such as 
   SONET/SDH or Ethernet encoding, BW X must be equal to bw so as to 
   match bit-rate and its framing. 
    
   *In the case of an interface with a lambda encoding and a transparent 
   to bit-rate and framing, BW X must be equal to or less than bw. 
    
    
    
    
    
 
 
        Table 2.2: The Case of End-Point(Ingress/Egress) Link Attributes 
                           with Lambda Encoding 
    
   +-------------+---------+------------+---------+------------------+ 
   |LSP attribute|Ingress  |Transit     |Egress   |Remarks           | 
   +---+---------+---------+------------+---------+------------------+ 
   |   |         |LSC      |            |LSC      |                  | 
   |   |         +---------+            +---------+                  | 
   |SC |LSC      |TDM      |LSC         |TDM      |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |L2SC     |            |L2SC     |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |PSC      |            |PSC      |                  | 
   +---+---------+---------+------------+---------+                  | 
   |   |lambda   |         |lambda      |         |[RFC4202]         | 
   |   +---------+         +------------+         |section 3.7, 3.10 | 
   |Enc|SONET/SDH|         |SONET/SDH   |         |Specified in G.691| 
   |   |         |         |or lambda   |         |                  | 
   |   +---------+lambda   +------------+lambda   |                  | 
   |   |Ethernet |         |Ethernet    |         |Specified in IEEE | 
   |   |         |         |or lambda   |         |                  | 
   |   +---------+         +------------+         |                  | 
   |   |OTN      |         |OTN         |         |Specified in G.709| 
   |   |         |         |or lambda   |         |                  | 
   +---+---------+---------+------------+---------+                  | 
   |BW |X        |<=bw     |=bw         |<=bw     |                  | 
   |   |         |         |or *<=bw    |         |                  | 
   +---+---------+---------+------------+---------+------------------+ 
    
   If an interface supports only a specific bit-rate and format such as 
   SONET/SDH or Ethernet encoding, BW X must be equal to bw so as to 
   match bit-rate and its framing. 
    
   *In the case of an interface with a lambda encoding and a transparent 
   to bit-rate and framing, BW X must be equal to or less than bw. 
    
    
     
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           Table 2.3: The Case of One End-Point (Ingress/Egress) Link 
                      Attribute with Lambda Encoding 
    
   +-------------+---------+------------+---------+------------------+ 
   |LSP attribute|Ingress  |Transit     |Egress   |Remarks           | 
   +---+---------+---------+------------+---------+------------------+ 
   |   |         |LSC      |            |LSC      |                  | 
   |   |         +---------+            +---------+                  | 
   |SC |LSC      |TDM      |LSC         |TDM      |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |L2SC     |            |L2SC     |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |PSC      |            |PSC      |                  | 
   +---+---------+---------+------------+---------+[RFC4202]         | 
   |   |SONET/SDH|         |SONET/SDH   |SONET/SDH|section 3.6, 3.9  | 
   |   |         |         |or lambda   |         |Specified in G.691| 
   |   +---------+         +------------+---------+                  | 
   |Enc|Ethernet |lambda   |Ethernet    |Ethernet |Specified in IEEE | 
   |   |         |         |or lambda   |         |                  | 
   |   +---------+         +------------+---------+                  | 
   |   |OTN      |         |OTN         |OTN      |Specified in G.709| 
   |   |         |         |or lambda   |         |                  | 
   +---+---------+---------+------------+---------+                  | 
   |BW |X        |<=bw     |=bw         |=bw      |                  | 
   |   |         |         |or *<=bw    |         |                  | 
   +---+---------+---------+------------+---------+------------------+ 
    
   The case of ingress link with the specific encoding and egress link 
   with lambda encoding also follows the same manner. 
    
   If an interface supports only a specific bit-rate and format such as 
   SONET/SDH or Ethernet encoding, BW X must be equal to bw so as to 
   match bit-rate and its framing. 
    
   *In the case of an interface with a lambda encoding and a transparent 
   to bit-rate and framing, BW X must be equal to or less than bw. 
    
     
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   (3) Fiber Switch Capable (FSC) 
    
     Table 3.1: The Case of End-Point(Ingress/Egress) Link Attributes 
                     without Lambda or Fiber Encoding 
    
   +---+---------+---------+------------+---------+------------------+ 
   |LSP attribute|Ingress  |Transit     |Egress   |Remarks           | 
   +---+---------+---------+------------+---------+------------------+ 
   |   |         |FSC      |            |FSC      |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |LSC      |            |LSC      |                  | 
   |   |         +---------+            +---------+                  | 
   |SC |FSC      |TDM      |FSC         |TDM      |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |L2SC     |            |L2SC     |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |PSC      |            |PSC      |                  | 
   +---+---------+---------+------------+---------+[RFC4202]         | 
   |Enc|SONET/SDH|SONET/SDH|SONET/SDH   |SONET/SDH|section 3.6, 3.9  | 
   |   |         |         |or lambda   |         |Specified in G.691| 
   |   |         |         |or fiber    |         |                  | 
   |   +---------+---------+------------+---------+                  | 
   |   |Ethernet |Ethernet |Ethernet    |Ethernet |Specified in IEEE | 
   |   |         |         |or lambda   |         |                  | 
   |   |         |         |or fiber    |         |                  | 
   |   +---------+---------+------------+---------+                  | 
   |   |OTN      |OTN      |OTN         |OTN      |Specified in G.709| 
   |   |         |         |or lambda   |         |                  | 
   |   |         |         |or fiber    |         |                  | 
   +---+---------+---------+------------+---------+                  | 
   |BW |X        |=bw      |=bw         |=bw      |                  | 
   |   |         |         |or *<=bw    |         |                  | 
   +---+---------+---------+------------+---------+------------------+ 
    
   If an interface supports only a specific bit-rate and format such as 
   SONET/SDH or Ethernet encoding, BW X must be equal to bw so as to 
   match bit-rate and its framing. 
     
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   *In the case of an interface with a lambda or fiber encoding and a 
   transparent to bit-rate and framing, BW X must be equal to or less 
   than bw. 
    
    
    
    
    
    
    
 
 
   Table 3.2: The Case of End-Point(Ingress/Egress) Link Attributes with 
                         Lambda or Fiber Encoding 
    
   +---+---------+---------+------------+---------+------------------+ 
   |LSP attribute|Ingress  |Transit     |Egress   |Remarks           | 
   +---+---------+---------+------------+---------+------------------+ 
   |   |         |FSC      |            |FSC      |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |LSC      |            |LSC      |                  | 
   |   |         +---------+            +---------+                  | 
   |SC |FSC      |TDM      |FSC         |TDM      |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |L2SC     |            |L2SC     |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |PSC      |            |PSC      |                  | 
   +---+---------+---------+------------+---------+[RFC4202]         | 
   |   |fiber    |fiber    |fiber       |fiber    |section 3.8       | 
   |   +---------+---------+------------+---------+                  | 
   |Enc|lambda   |         |lambda      |         |section 3.7, 3.10 | 
   |   |         |         |or fiber    |         |                  | 
   |   +---------+         +------------+         |section 3.6, 3.9  | 
   |   |SONET/SDH|         |SONET/SDH   |         |Specified in G.691| 
   |   |         |         |or lambda   |         |                  | 
   |   |         |lambda   |or fiber    |lambda   |                  | 
   |   +---------+or fiber +------------+or fiber |                  | 
   |   |Ethernet |         |Ethernet    |         |Specified in IEEE | 
   |   |         |         |or lambda   |         |                  | 
   |   |         |         |or fiber    |         |                  | 
   |   +---------+         +------------+         |                  | 
   |   |OTN      |         |OTN         |         |Specified in G.709| 
   |   |         |         |or lambda   |         |                  | 
   |   |         |         |or fiber    |         |                  | 
   +---+---------+---------+------------+---------+                  | 
   |BW |X        |<=bw     |=bw         |<=bw     |                  | 
   |   |         |         |or *<=bw    |         |                  | 
   +---+---------+---------+------------+---------+------------------+ 
    
     
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   If an interface supports only a specific bit-rate and format such as 
   SONET/SDH or Ethernet encoding, BW X must be equal to bw so as to 
   match bit-rate and its framing. 
    
   *In the case of an interface with a lambda or fiber encoding and a 
   transparent to bit-rate and framing, BW X must be equal to or less 
   than bw.  
    
    
    
    
    
    
   Table 3.3: The Case of One End-Point (Ingress/Egress) Link Attribute 
                       with Lambda or Fiber Encoding 
                                      
   +---+---------+---------+------------+---------+------------------+ 
   |LSP attribute|Ingress  |Transit     |Egress   |Remarks           | 
   +---+---------+---------+------------+---------+------------------+ 
   |   |         |FSC      |            |FSC      |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |LSC      |            |LSC      |                  | 
   |   |         +---------+            +---------+                  | 
   |SC |FSC      |TDM      |FSC         |TDM      |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |L2SC     |            |L2SC     |                  | 
   |   |         +---------+            +---------+                  | 
   |   |         |PSC      |            |PSC      |                  | 
   +---+---------+---------+------------+---------+[RFC4202]         | 
   |Enc|SONET/SDH|         |SONET/SDH   |SONET/SDH|section 3.6, 3.9  | 
   |   |         |         |or lambda   |         |Specified in G.691| 
   |   |         |         |or fiber    |         |                  | 
   |   +---------+         +------------+---------+                  | 
   |   |Ethernet |lambda   |Ethernet    |Ethernet |Specified in IEEE | 
   |   |         |or fiber |or lambda   |         |                  | 
   |   |         |         |or fiber    |         |                  | 
   |   +---------+         +------------+---------+                  | 
   |   |OTN      |         |OTN         |OTN      |Specified in G.709| 
   |   |         |         |or lambda   |         |                  | 
   |   |         |         |or fiber    |         |                  | 
   +---+---------+---------+------------+---------+                  | 
   |BW |X        |<=bw     |=bw         |=bw      |                  | 
   |   |         |         |or *<=bw    |         |                  | 
   +---+---------+---------+------------+---------+------------------+ 
    
   The case of ingress link with the specific encoding and egress link 
   with lambda encoding also follows as the same manner. 
    


     
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   If an interface supports only a specific bit-rate and format such as 
   SONET/SDH or Ethernet encoding, BW X must be equal to bw so as to 
   match bit-rate and its framing. 
    
   *In the case of an interface with a lambda encoding and a transparent 
   to bit-rate and framing, BW X must be equal to or less than bw.  
    
   Although the interface with FSC can switch the entire contents to 
   another interface, this interface should only be used for optical 
   wavelength or waveband switching. 
    
    
    
    
 
   (4) Layer 2 Switch Capable (L2SC) 
    
   The guideline for the calculation must be created after the 
   definition and discussion about L2SW are settled down. 
    
   (5) Packet Switch Capable (PSC) 
    
           Table 4: Desired GMPLS Attributes in the case of PSC 
   +-------------+---------+------------+---------+------------------+ 
   |LSP attribute|Ingress  |Transit     |Egress   |Remarks           | 
   +---+---------+---------+------------+---------+------------------+ 
   |SC |PSC      |PSC      |PSC         |PSC      |                  | 
   +---+---------+---------+------------+---------+                  | 
   |Enc|Packet   |Packet   |Packet      |Packet   |                  | 
   +---+---------+---------+------------+---------+                  | 
   |BW |X        |<=bw     |<=bw        |<=bw     |                  | 
   +---+---------+---------+------------+---------+------------------+ 
    
    
   Since the interface with PSC supports only packet-by-packet switching, 
   BW X must be equal to or less than bw, and must be larger than the 
   minimum LSP bandwidth. 
    
   These GMPLS constraints must be considered for computing paths and 
   creating GMPLS LSPs. 
    
   This document does not discuss domain based multilayer path 
   computation considerations where specific routing policies, which are 
   sometimes independent from the underlying domains and sometimes take 
   the underlying domains' policies into consideration, are required. 
 
   
5. Security consideration 
    

     
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        Anything that can be done to change the output of a path 
   computation algorithm can significantly affect the operational 
   stability of a network, could force traffic to traverse undesirable 
   or costly links, and could place data into less secure parts of the 
   network. Therefore, the integrity of the path computation mechanism 
   is very significant in a GMPLS network. 
    
        The path computation algorithm, itself, and the mechanisms for 
   conveying computed paths to and between the LSRs in the network are 
   out of scope for this document. But misuse or confusion with respect 
   of the handling of the attributes described in this document could 
   leave a network open to various security attacks. In particular, if 
   there is a known mismatch between the interpretation or handling of 
   TE attributes within a network this might be exploited by an attacker 
   to cause disruption or to waste network resources in an integrated 
   multi-technology network. Therefore, network operators are 
   Recommended to use a consistent approach across the whole network.  
    
6. Acknowledgements 
    
   Thanks to Adrian Farrel for his review of this document. 
    
7. Intellectual Property Considerations 
    
        The IETF takes no position regarding the validity or scope of 
   any Intellectual Property Rights or other rights that might be 
   claimed to pertain to the implementation or use of the technology 
   described in this document or the extent to which any license under 
   such rights might or might not be available; nor does it represent 
   that it has made any independent effort to identify any such rights. 
   Information on the procedures with respect to rights in RFC documents 
   can be found in BCP 78 and BCP 79. 
    
        Copies of IPR disclosures made to the IETF Secretariat and any 
   assurances of licenses to be made available, or the result of an 
   attempt made to obtain a general license or permission for the use of 
   such proprietary rights by implementers or users of this 
   specification can be obtained from the IETF on-line IPR repository at 
   http://www.ietf.org/ipr. 
    
        The IETF invites any interested party to bring to its attention 
   any copyrights, patents or patent applications, or other proprietary 
   rights that may cover technology that may be required to implement 
   this standard.  Please address the information to the IETF at 
   ietf-ipr@ietf.org. 
    




     
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8. IANA Considerations  
 
   This document does not require any IANA consideration. 
 
9. References 
 
9.1 Normative References 
   
  [RFC2119]      Bradner, S., "Key words for use in RFCs to Indicate 
                  Requirement Levels", BCP 14, RFC 2119, March 1997. 
  [RFC4202]      K. Kompella and Y. Rekhter, "Routing Extensions in 
                  Support of Generalized Multi-Protocol Label Switching", 
                 RFC4202, October 2005. 
  [RFC4203]      K. Kompella and Y. Rekhter, "OSPF Extensions in 
                  Support of Generalized Multi-Protocol Label Switching", 
                 RFC4203, October 2005. 
 
9.2 Informative References 
 
  [RFC3477]      K. Kompella and Y. Rekhter, "Signalling Unnumbered 
                  Links in Resource ReSerVation Protocol - Traffic 
                  Engineering (RSVP-TE)", RFC3477, January 2003. 
  [RFC3630]      Katz, D., et al, "Traffic Engineering (TE) Extensions 
                  to OSPF Version 2", RFC3630, September 2003. 
  [RFC3945]      E. Mannie, "Generalized Multi-Protocol Label Switching 
                  Architecture", RFC3945, October, 2004. 
   
    
Author's Addresses 
    
   Tomohiro Otani 
   KDDI R&D Laboratories, Inc. 
   2-1-15 Ohara Fujimino-shi 
   Saitama, 356-8502 Japan 
   Phone: +81-49-278-7357 
   Email: otani@kddilabs.jp 
    
   Kenichi Ogaki 
   KDDI R&D Laboratories, Inc. 
   2-1-15 Ohara Fujimino-shi 
   Saitama, 356-8502 Japan 
   Phone: +81-49-278-7897 
   Email: ogaki@kddilabs.jp 
    
   Arthi Ayyangar 
   Nuova Systems 
   2600 San Tomas Expressway 
   Santa Clara, CA  95051 
   Email: arthi@nuovasystems.com 
    
     
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   Rajiv Papneja 
   Isocore 
   12359 Sunrise Valley Drive 
   Suite 100, Reston, VA 20191 US 
   Email: rpapneja@isocore.com 
    
   Kireeti Kompella 
   Juniper Networks 
   1194 N. Mathilda Ave. 
   Sunnyvale, CA 94089 US 
   Email: kireeti@juniper.net 
    
   Daniel King 
   Aria Networks Ltd. 
   44-45 Market Place 
   Chippenham, SN153HU UK 
   EMail: daniel.king@aria-networks.com 
 
Document expiration 
    
   This document will be expired in May 2008, unless it is updated. 
    
    
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