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Layer 1 VPN Enhanced Mode - Overlay Extension Service Model
draft-fedyk-ccamp-l1vpn-extnd-overlay-00

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Authors Don Fedyk , Dieter Beller , Lieven Levrau
Last updated 2012-07-09
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draft-fedyk-ccamp-l1vpn-extnd-overlay-00
Network Working Group                                          D. Fedyk 
Internet Draft                                                D. Beller 
Intended status: Standards Track                          Lieven Levrau
                                                         Alcatel-Lucent 
 
 
 
                                                          
Expires: January 2013                                      July 9, 2012 
                                    
 
                                       
        Layer 1 VPN Enhanced Mode - Overlay Extension Service Model 
                draft-fedyk-ccamp-l1vpn-extnd-overlay-00.txt 

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   publication of this document. Please review these documents 
 
 
 

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   carefully, as they describe your rights and restrictions with respect 
   to this document. Code Components extracted from this document must 
   include Simplified BSD License text as described in Section 4.e of 
   the Trust Legal Provisions and are provided without warranty as 
   described in the Simplified BSD License. 

Abstract 

    

   This document builds on the L1VPN framework [RFC4847] to extend the 
   L1VPN from the basic mode to the enhanced mode by including 
   additional constraints, focusing upon the overlay extension service 
   model. Route Diversity for customer LSPs are common requirement 
   applicable to L1VPNs. This document describes L1VPN compatible 
   mechanisms to achieve diversity for sets of customer LSPs. The 
   extended overlay service model can support other extensions for L1VPN 
   signaling, for example, those related to latency requirements. 

Table of Contents 

    
   1. Introduction...................................................3 
   2. Conventions used in this document..............................3 
   3. Contributors...................................................3 
   4. LSP Diversity in the Overlay Extension Service Model...........4 
      4.1. LSP diversity for dual-homed customer edge (CE) devices...5 
         4.1.1. Exchanging SRLG information between the PEs via the CE 
         device......................................................7 
            4.1.1.1. Operational Procedures..........................8 
            4.1.1.2. Error handling procedures.......................8 
         4.1.2. Using Path Affinity Set extension....................9 
            4.1.2.1. Operational Procedures.........................12 
            4.1.2.2. Error handling procedures......................13 
            4.1.2.3. Distribution of the Path Affinity Set information
            ........................................................13 
   5. Latency signaling.............................................14 
   6. Security Considerations.......................................14 
   7. IANA Considerations...........................................15 
   8. References....................................................15 
      8.1. Normative References.....................................15 
      8.2. Informative References...................................15 
   9. Acknowledgments...............................................16 
    

 
 
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1. Introduction 

   This document builds on the L1VPN framework [RFC4847] to extend the 
   L1VPN from the basic mode to the enhanced mode by including 
   additional constraints, focusing upon the overlay extension service 
   model.  

   The overlay model assumes a UNI interface between the edge nodes of 
   the respective transport domains. Route diversity for LSPs from 
   single homed CE and dual-home CEs is a common requirement in optical 
   transport networks. This document describes two signaling variations 
   that may be used for supporting LSP diversity within the overlay 
   extension service model considering dual-homing. Dual-homing is 
   typically used to avoid a single point of failure (UNI link, PE) or 
   if two disjoint connections are forming a protection group.  While 
   both methods are similar in that they utilize common mechanisms in 
   the PE network to achieve diversity, they are distinguished according 
   to whether the CE is permitted to retrieve provider SRLG diversity 
   information for an LSP from a PE1 and pass it on to a PE2 (SRLG 
   information is shared with the CE), or whether a new attribute is 
   used that allows the PE2 that receives this attribute to derive the 
   SRLG information for an LSP based on this attribute value.   

   The extended overlay service model can support other extensions for 
   L1VPN signaling, for example, those related to latency. When 
   requesting diverse LSPs latency may also be an additional 
   requirement.   

    

2. 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 RFC-2119 [RFC2119].  

   In this document, these words will appear with that interpretation   
   only when in ALL CAPS. Lower case uses of these words are not to be    
   interpreted as carrying RFC-2119 significance. 

3. Contributors 

   The Authors would like to thank Eve Varma and Sergio Belotti for 
   their review and contributions to this document.    

    

 
 
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4. LSP Diversity in the Overlay Extension Service Model 

   The L1VPN Framework [RFC4847] (Enhanced Mode) describes the overlay 
   extension service model, which builds upon the UNI Overlay [RFC4208] 
   serving as the interface between the CE edge node and the PE edge 
   node. In this service model, a CE receives a list of CE-PE TE link 
   addresses to which it can request a L1VPN connection (i.e., 
   membership information) and may include additional information 
   concerning these TE links.  This document further builds on the 
   overlay extension service model by adding shared constraint 
   information for path diversity in the optical transport network.  

   This document describes two signaling variations that may be used for 
   supporting LSP diversity within the overlay extension service model 
   considering dual-homing.  While both methods are similar in that they 
   utilize common mechanisms in the PE network to achieve diversity, 
   they are distinguished according to whether the CE is permitted to 
   retrieve provider SRLG diversity information for an LSP from a PE1 
   and pass it on to a PE2 (SRLG information is shared with the CE or 
   whether a new attribute is used that allows the PE2 that receives 
   this attribute to derive the SRLG information for an LSP based on 
   this attribute value. The selection between these methods is governed 
   by both PE-network specific policies and approaches taken (i.e., in 
   terms of how the provider chooses to perform routing internal to 
   their network). 

   The first method (see 3.1.1) assumes that provider Shared Resource 
   Link Group (SRLG) Identifier information is both available and 
   shareable (policy decision) with the CE.  Since SRLG IDs can then be 
   used (passed transparently between PEs via the dual-homed CE) as 
   signaled information on a UNI message, a mechanism supporting LSP 
   diversity for the overlay extension service model can be provided via 
   straightforward signaling extensions.  

   The second method (see 3.1.2) assumes that provider SRLG IDs are 
   either not available or not shareable (based on provider network 
   operator policy) with the CE.  For this case, a mechanism is provided 
   where information signaled to the PE on UNI messages does not require 
   shared knowledge of provider SRLG IDs to support LSP diversity for 
   the overlay extension model.   

   Both approaches follow the L1VPN framework.    

   While both methods could be implemented in the same PE network, it is 
   likely that an L1VPN CE network would use only one mechanism at a 
   time. 

 
 
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4.1. LSP diversity for dual-homed customer edge (CE) devices    

   Single-homed CE devices are connected to a single PE device via a 
   single UNI link (could be a bundle of parallel links which are 
   typically using the same fiber cable). This single UNI link may 
   constitute a single point of failure. Such a single point of failure 
   can be avoided when the CE device is connected to two PE devices via 
   two UNI interfaces as depicted for CE1 in Figure 1 below.  

   For the dual-homing case, it is possible to establish two connections 
   from the source CE device to the same destination CE device where one 
   connection is using one UNI link to, for example, PE1 and the other 
   connection is using the UNI link to PE2. In order to avoid single 
   points of failure within the provider network, it is necessary to 
   also ensure path (LSP) diversity within the provider network in order 
   to achieve end-to-end diversity for the two LSPs between the two CE 
   devices. This document describes how it is possible to enable such 
   path diversity to be achieved within the provider network (which is 
   subject to additional routing constraints). [RFC4202] defines SRLG 
   information that can be used to allow GMPLS to provide path diversity 
   in a GMPLS controlled transport network. As the two connections are 
   entering the provider network at different PE devices, the PE device 
   that receives the connection request for the second connection needs 
   to be capable of determining the additional path computation 
   constraints such that the path of the second LSP is disjoint with 
   respect to the already established first connection entering the 
   network at a different PE device. The methods described in this 
   document allow a PE device to determine the SRLG information for a 
   connection in the provider network that is entering the network on a 
   different PE device. 

   PE SRLG information can be used directly by a CE if the CE 
   understands the context, and the CE view is limited to its L1VPN 
   context. In this case, there is a dependency on the provider 
   information and there is a need to be able to query the SRLG in the 
   provider network.  

   It may, on the other hand, be preferable to avoid this dependency and 
   to decouple the SRLG identifier space used in the provider network 
   from the SRLG space used in the client network. This is possible with 
   both methods detailed below. Even for the method where provider SRLG 
   information is passing through the CE device (note the CE device does 
   not need to process and decode this information) the two SRLG 
   identifier spaces can remain fully decoupled and the operator of the 
   client network is free to assign SRLG identifiers from the client 
 
 
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   SRLG identifier space to the CE to CE connection that is passing 
   through the provider network. 

   Referring to Figure 1, the UNI signaling mechanism must support at 
   least one of the two mechanisms described in this document for CE 
   dual homing to achieve LSP diversity in the provider network. 

   The described mechanisms can also be applied to a scenario where two 
   CE devices are connected to two different PE devices. In this case, 
   the additional information that is exchanged across the UNI 
   interfaces also needs to be exchanged between the two CE devices in 
   order to achieve the desired diversity in the provider network. 

   This information may be configured or exchanged by some automated 
   mechanism not described in this document.  

   In the dual-homing example, CE1 can locally correlate the LSP 
   requests. For the slightly more complicated example involving CE2 and 
   CE3, both requiring a path that shall be diverse to a connection 
   initiated by the other CE device, CE2 and CE3 need to have a common 
   view of the SRLG information to be signaled.  In this document, we 
   detail the required diversity information and the signaling of this 
   diversity information; however, the means for distributing this 
   information within the PE domain or the CE domain is out of scope.  

    

    

    
                         +---+    +---+ 
                         | P |....| P | 
                         +---+    +---+ 
                        /              \ 
                   +-----+               +-----+    +---+ 
          +---+    | PE1 |               |     |----|   | 
          |CE1|----|     |               |     |    |CE2| 
          +---+\   +-----+               |     |----|   | 
                \     |                  | PE3 |    +---+ 
                 \ +-----+               |     | 
                  \| PE2 |               |     |    +---+ 
                   |     |               |     |----|CE3| 
                   +-----+               +-----+    +---+ 
                         \              / 
                         +---+    +---+ 
                         | P |....| P | 

 
 
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                         +---+    +---+ 
 
               Figure 1: Generalized Layer 1 VPN Reference Model 
    
                     Figure 1 Overlay Reference Diagram 

   In an overlay model, the information exchanged between the CE and the 
   PE is kept to a minimum.   

   How diversity is achieved, in terms of configuration, distribution 
   and usage in each part of the transport networks should be kept 
   independent and separate from how diversity is signaled at the UNI 
   between the two transport networks. 

   Signaling parameters discussed in this document are: 

   o  SRLG information (see [RFC4202]) 

   o  Path Affinity Set 

4.1.1. Exchanging SRLG information between the PEs via the CE device 

   SRLG information is defined in [RFC4202] and if the SRLG information 
   of an LSP is known, it can be used to calculate a path for another 
   LSP that is SRLG diverse with respect to an existing LSP. SRLG 
   information is an unordered list of SRLGs. SRLG information is 
   normally not shared between the transport network and the client 
   network; i.e., not shared with the CEs of a L1VPN in the L1VPN 
   context. However, this becomes more challenging when a CE is dual-
   homed.   For example, CE1 in Figure 1 may have requested an LSP1 from 
   CE1 to CE2 via PE1 and PE3.  CE1 could subsequently request an LSP2 
   to CE2 via PE2 and PE3 with the requirement that it should be 
   maximally SRLG disjoint with respect to LSP1. Since PE2 does not have 
   any information about LSP1, PE2 would need to know the SRLG 
   information associated with LSP1. If CE1 could request the SRLG 
   information of LSP1 from PE1, it could then transparently pass this 
   information to PE2 as part of the LSP2 setup request, and PE2 would 
   now be capable of calculating a path for LSP2 that is SRLG disjoint 
   with respect to LSP1.  

   The exchange of SRLG information is achieved on a per L1VPN LSP basis 
   using the existing RSVP-TE signaling procedures. It can be exchanged 
   in the PATH (exclusion information) or RESV message in the original 
   request or it can be requested by the CE at any time the path is 
   active.  

 
 
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   It shall be noted that SRLG information is an unordered list of SRLG 
   identifiers and the encoding of SRLG information for RSVP signaling 
   is already defined in [SRLG_info]. Even if SRLG information is known 
   for several LSPs it is not possible for the CEs to derive the 
   provider network topology from this information.  

    

4.1.1.1. Operational Procedures 

   Retrieving SRLG information from a PE for an existing LSP: 

   When a dual-homed UNI-C intends to establish an LSP to the same 
   destination UNI-C via another PE node, it can request the SRLG 
   information for an already established LSP by setting the SRLG 
   information flag in the LSP attributes sub-object of the RSVP PATH 
   message (IANA to assign the new SRLG flag). As long as the SRLG 
   information flag is set in the PATH message, the PE node inserts the 
   SRLG sub-object as defined in [SRLG_info] into the RSVP RESV message 
   that contains the current SRLG information for the LSP. If the 
   provider network's policy has been configured so as not to share SRLG 
   information with the client network, the SRLG sub-object is not 
   inserted in the PATH message even if the SRLG information flag is 
   set. The PE passes on the SRLG information for the LSP.  Note the 
   SRLG information is expected to be up-to-date.   

   Establishment of a new LSP with SRLG diversity constraints: 

   When a dual-homed CE device sends an LSP setup requests to a PE 
   device for a new LSP that is required to be SRLG diverse with respect 
   to an existing LSP that is entering the network via another PE 
   device, the UNI-C sets the SRLG diversity flag (note: IANA to assign 
   the new SRLG diversity flag) in the LSP attributes sub-object of the 
   PATH message that initiates the setup of this new LSP. When the PE 
   device receives this request it calculates a path to the given 
   destination and uses the received SRLG information as path 
   computation constraints. 

    

4.1.1.2. Error handling procedures  

   To be added in the next version of the document. 

 
 
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4.1.2. Using Path Affinity Set extension 

   The Path Affinity Set (PAS) is used to signal diversity in a pure CE 
   context by abstracting SRLG information. There are two types of 
   diversity information in the PAS. The first type of information is a 
   single PAS identifier. Optionally, more detailed PATH information of 
   an exclude path or set of paths can be specified. The motive behind 
   the PAS information is to have as little exchange of diversity 
   information as possible between the L1VPN CE and PE elements.  

   Rather than a detailed CE or PE SRLG list, the Path Affinity Set 
   contains an abstract SRLG identifier that associates the given path 
   as diverse. Logically the identifier is in an L1VPN context and 
   therefore only unique with respect to a particular L1VPN.  

   How the CE determines the PAS identifier is a local matter for the CE 
   administrator. A CE may signal PAS as a diversity object in the PATH 
   message. This identifier is a suggested identifier and may be 
   overridden by a PE under some conditions.  

   For example, PAS can be used with no prior exchange of PAS 
   information between the CE and the PE. Upon reception of the PAS 
   information the PE can infer the CEs requirements.  The actual PAS 
   identifier used will be returned in the RESV message. Optionally an 
   empty PAS identifier allows the PE to pick the PAS identifier. 
   Similar to the section 4.1.1 on SRLG information, a PE can return PAS 
   identifier as the response to a Query allowing flexibility.   

   A PE interprets the specific PAS identifier, for example, "123" as 
   meaning to exclude that identifier and by association any PE related 
   SRLG information, for any LSPs associated with the resources assigned 
   to the L1VPN. For example, if a Path exists for the LSP with the 
   identifier "123", the PE would use local knowledge of the PE SRLGs 
   associated with the "123" LSPs and exclude those SRLGs in the path 
   request.  In other words, two LSPs that need to be diverse both 
   signal "123" and the PEs interpret this as meaning not to use shared 
   resources.  Alternatively, a PE could use the PAS identifier to 
   select from already established LSPs. Once the path is established it 
   becomes associated with the "123" identifier or optionally another 
   PAS identifier for that L1VPN.   

   The PAS Source and Destination Address tuple represents one or more 
   source addresses and destination addresses associated with the CE 
   Path Affinity Set identifier. These associated address tuples 
   represent paths that use resources that should be excluded for the 
   establishment of the current LSP.  The address tuple information 
   gives both finer grain details on the path diversity request and 
 
 
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   serves as an alternative identifier in the case when the PAS 
   identifier is not known by the PE.  The address tuples used in 
   signaling is within a CE context and its interpretation is local to a 
   PE that receives a Path request from a CE. The PE can use the address 
   information to relate to PE Addresses and PE SRLG information.  When 
   a PE satisfies a connection setup for a (SRLG) diverse signaled path, 
   the PE may optionally record the PE SRLG information for that 
   connection in terms of PE based parameters and associate that with 
   the CE addresses in the Path message.    

   The L1VPN Port Information table (PIT) [RFC5251] can be leveraged to 
   translate between CE based addresses and PE based addresses. The Path 
   Affinity Set and associated PE addresses with PE SRLG information can 
   be distributed via the IGP in the provider transport network (or by 
   other means such as configuration); they can be utilized by other PEs 
   when other CE Paths are setup that would require path/connection 
   diversity. This information is distributed on a L1VPN basis and 
   contains a PAS identifier, PE addresses and SRLG information.   

   The CE Path Affinity Set may be used to signal paths without CE 
   Source and Destination addresses; however, the PE will always 
   associate the CE SRLG Group with a list of PE SRLG plus the PE 
   addresses associated with this LSP.  

   If diversity is not signaled, the assumption is that no diversity is 
   required and the Provider network is free to route the LSP to 
   optimize traffic. No Path affinity set information needs to be 
   recorded for these LSPs.  If a diversity object is included in the 
   connection request, the PE in the Provider Network should be able to 
   look-up the existing Provider SRLG information from the provider 
   network and choose an LSP that is maximally diverse from other LSPs. 
   The mechanisms to achieve this are outside the scope of this 
   document.  

   A new L1VPN Diverse LSP LABEL object is specified: 

     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 
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    |       Length                  |    Type (TBA) |0| C-type (TBA)| 
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      
                         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 
     
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    | ADDR Length   |Number of PAS  |D|           reserved          | 
 
 
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    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    |                 Path Affinity Set identifier                  |                 
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    |                 Source Address (variable)                     |  
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    |                 Destination Address (variable)                |                 
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
      
                      Figure 2 Diverse LSP information 

     
    
   1. The Address Length field (8 bits) is the number of bytes for both 
      the source address and destination address. The address may be in 
      any format from 1 to 32 bytes but the key point is the customers 
      can maintain their existing addresses.  A value of zero indicates 
      there are no addresses included.  

   2. The Number of Path Affinity (8 bits)sets is included in the 
      object. This is typically 1. Addition of other sets is for further 
      study.  

   3. The Path affinity Set identifier (4 bytes) is a single number that 
      represents a summarized SRLG for this path. Paths with that same 
      Path Affinity set should be set up with diverse paths and 
      associated with the path affinity set.  A value of all zeros 
      allows the PE to pick a PAS identifier to return.  A PAS 
      identifier of an established path may be different than the 
      requested path identifier.   

   4. The diversity Bit (D) (one Bit) indicates if the diversity must be 
      satisfied when set as a one. If a PE finds an established path 
      with a Path Affinity set matching the signaled Path Affinity Set 
      or the signaled Address tuple it should attempt find a diverse 
      path. 

 
 
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   5. The Diverse Path Source address/destination address tuple is that 
      of an established LSP in the PE network that belongs to the same 
      Path Affinity Set identifier. If the path for these addresses is 
      not setup or cannot be determined by the PE edge processing the 
      UNI then the path is only with the Path Affinity set constraint. 
      If the path(s) for these address tuples are known by the PE the PE 
      uses the SRLG information associated with these addresses. If in 
      any case a diverse path cannot be setup then the Diverse bit 
      controls whether a path is established anyway. The PE must use a 
      mechanism to translate CE Addresses into provider addresses when 
      correlating with provider SRLG information. How SRLG information 
      and network address tuples are distributed is for future study.   

    
4.1.2.1. Operational Procedures 

    
   When a UNI-C constructs a PATH message it may optionally specify and 
   insert a Path Affinity Set in the PATH message. This Path Affinity 
   Set may optionally include the address of an LSP that that could 
   belong to the same Path Affinity Set. The Path Affinity Set 
   identifier is a value (0 through 2**32-255) that is independent of 
   the mechanism the CE or the PE use for diversity. The Path Affinity 
   Set is a single identifier that can be used to request diversity and 
   associate diversity.   

   When processing a CE PATH message in a L1VPN Overlay, the PE first 
   looks up the PE based addresses in the Provider Index Table (PIT). If 
   the Path Affinity Set is included in the PATH message, the PE must 
   look up the SRLG information (or equivalent) in the PE network that 
   has been allocated by LSPs associated with a Path Affinity Set and 
   exclude those resources from the path computation for this LSP if it 
   is a new path.  The PE may alternatively choose from an existing path 
   with a disjoint set of resources. If a path that is disjoint cannot 
   be found, the value of the PAS diversity bit determines whether a 
   path should be setup anyway. If the PAS diversity bit is clear, one 
   can still attempt to setup the LSP.  A PE should still attempt to 
   minimize shared resources but that is an implementation issue, and is 
   outside the scope of this document.  

   Optionally the CE may use a value of all zeros in the PAS identifier 
   allowing the PE to select an appropriate PAS identifier. Also the PE 
   may to override the PAS identifier allowing the PE to re-assign the 
   identifier if required. A CE should not assume that the PAS 
   identifier used for setup is the actual PAS identifier.  

 
 
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4.1.2.2. Error handling procedures  

   The PAS object must be understood by the PE device. Otherwise, the CE 
   should not use the PAS object. Path Message processing of the PAS 
   object SHOULD follow CTYPE 0. An Error code of IANA (TBD) indicates 
   that the PAS object is not understood.  

   When a PAS identifier is not recognized by a PE it must assume this 
   LSP defines that PAS identifier however the PE may override PAS 
   identifier under certain conditions.  

   If the identifier is recognized but the Source Address-Destination 
   address pair(s) are not recognized, this LSP must be set up using the 
   PAS identifier only.   

   If the identifier is recognized and the Source Address-Destination 
   address pair(s) are also recognized, then the PE SHOULD use the PE 
   SRLG information associated with the LSPs identified by the address 
   pairs to select a disjoint path.  

   The Following are the additional error codes: 

   1) Route Blocked by Exclude Route Value IANA (TBA). 

        

4.1.2.3. Distribution of the Path Affinity Set information  

   Information about SRLG is already available in the IGP TE database. A 
   PE network can be designed to have additional opaque records for 
   Provider paths that distribute PE paths and SRLG on a L1VPN basis.  
   When a PE path is setup, the following information allows a PE to 
   lookup the PE diversity information: 

   -  L1 VPN Identifier 8 bytes  
   -  Path Affinity Set Identifier 
   -  Source PE Address 
   -  Destination PE Address 
   -  List of PE SRLG (variable)  
    
   The source PE address and destination PE address are the same 
   addresses in the L1VPN PIT and correspond to the respective CE 
   address identifiers.                                                  
    
    
   Note that all of the information is local to the PE context and is 
   not shared with the CE.  The L1VPN Identifier is associated with a 
 
 
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   CE.  The only value that is signaled from the CE is the Path Affinity 
   Set and optionally the addresses of an existing LSP. The PE stores 
   source and destination PE addresses of the LSP in their native format 
   along with the SRLG information. This information is internal to the 
   PE network and is always known.    

   PE paths may be setup on demand or they may be pre-established. When 
   paths are pre-established, the Path Affinity Set is set to unassigned 
   0x0000 and is ignored. When a CE uses a pre-established path the PE 
   may set the Path SRLG Path Affinity Set value if the CE signals one 
   otherwise the Path Affinity Set remains unassigned 0x0000.  

5. Latency signaling 

   A latency requirement can be added to signaling in the form of a 
   constraint [DRAFT OBJECTIVE FUNCTION]. The constraint can take the 
   form of:   

   -  Minimize latency 

   -  Maximum acceptable   

   While some systems may be able to compute routes based on delay 
   metrics it is usual that minimizing hops subject to bandwidth 
   reservation are satisfied as the object function and delay is not 
   considered. When considering diversity latency falls after diversity 
   constraints have been satisfied.  

   Recording the latency of existing paths [DRAFT_TE_METRIC RECORD] to 
   ensure they meet a maximum acceptable latency can be utilized to 
   ensure latency constraint is met.   

   When a low latency path is required, the minimize latency subject to 
   other constraints criteria should be signaled.  A CE device can use 
   the record latency to ensure that the maximum acceptable latency has 
   been met.  

   More detail to be added in a future revision.     

     

6. Security Considerations 

   Security for L1VPNs is covered in [RFC4847], [RFC5251] and [RFC5253].  
   In this document, the model follows the L1VPN control plane model 
   where CE addresses are completely distinct from the PE addresses. 

 
 
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   The use of a private network assumes that entities outside the 
   network cannot spoof or modify control plane communications between 
   CE and PE.  Furthermore, all entities in the private network are 
   assumed to be trusted.  Thus, no security mechanisms are required by 
   the protocol exchanges described in this document.   

   However, an operator that is concerned about the security of their 
   private control plane network may use the authentication and 
   integrity functions available in RSVP-TE [RFC3473] or utilize IPsec 
   ([RFC4301], [RFC4302], [RFC4835], [RFC5996], and [RFC6071]) for the 
   point-to-point signaling between PE and CE.  See [RFC5920] for a full 
   discussion of the security options available for the GMPLS control 
   plane.   

7. IANA Considerations 

   TBD 

8. References 

 Normative References 

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

   [RFC4202] Kompella, K., Rekhter, Y., "Routing Extensions in Support 
             of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 
             4202, October 2005. 

   [RFC5251] Fedyk, D., Rekhter, Y., Editors "Layer 1 VPN Basic Mode", 
             RFC 5251, July 2008.  

   [SRLG_info] Zhang, F., Gonzalez de Dios, O., Margaria, C., "RSVP-TE 
             Extensions for Collecting SRLG Information", draft-zhang-
             ccamp-srlg-fa-configuration-05.txt, March 2012. 

8.2. Informative References 

   [RFC6071] S. Frankel, S. Krishnan, " IP Security (IPsec) and Internet 
             Key Exchange (IKE) Document Roadmap", RFC 6071, February 
             2011. 

   [RFC3473] Berger, L. (editor), "Generalized MPLS Signaling - RSVP-TE 
             Extensions", RFC 3473, January 2003. 

 
 
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   [RFC4208] G. Swallow, J. Drake, H. Ishimatsu, Y. Rekhter, 
             "Generalized Multiprotocol Label Switching (GMPLS) User-
             Network Interface (UNI): Resource ReserVation Protocol-
             Traffic Engineering (RSVP-TE) Support for the Overlay 
             Model", RFC 4208, October 2005. 

   [RFC4301] S. Kent, K. Seo, "Security Architecture for the Internet 
             Protocol," December 2005. 

   [RFC4302] S. Kent, "IP Authentication Header," December 2005. 

   [RFC5996] C. Kaufman, P. Hoffman, Y. Nir, P. Eronen " Internet Key 
             Exchange Protocol Version 2 (IKEv2)", September 2010. 

   [RFC4835] V. Manral, "Cryptographic Algorithm Implementation   
             Requirements for Encapsulating Security Payload (ESP) and   
             Authentication Header (AH)", April 2007. 

   [RFC4847] Takeda, T., Editor "Framework and Requirements for Layer 1 
             Virtual Private Networks", RFC 4847, April 2007.  

   [RFC5253] Takeda, T., Editor "Applicability Statement for Layer 1 
             Virtual Private Network (L1VPN) Basic Mode", RFC 5253, July 
             2008. 

   [RFC5920] L. Fang, Ed., "Security Framework for MPLS and GMPLS 
             Networks", RFC 5920, July 2010.  

   [DRAFT OBJECTIVE FUNCTION] Ali, Z., Swallow, G., Filsfils, C., Fang, 
             L., Kunze, R.,"Resource ReserVation Protocol-Traffic 
             Engineering (RSVP-TE) extension for signaling Objective 
             Function and Metric Bound", draft-ali-ccamp-rc-objective-
             function-metric-bound-01.txt, March 2012.   

    

   [DRAFT_TE_METRIC RECORD] Ali, Z., Swallow, G., Filsfils, C., Kunze, 
             R., "Resource ReserVation Protocol-Traffic Engineering 
             (RSVP-TE) extension for recording TE Metric of a Label 
             Switched Path", draft-ali-ccamp-te-metric-recording-01.txt, 
             March 2012.  

    

9. Acknowledgments 

   This document was prepared using 2-Word-v2.0.template.dot. 
 
 
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   Copyright (c) 2012 IETF Trust and the persons identified as authors 
   of the code. All rights reserved. 

   Redistribution and use in source and binary forms, with or without 
   modification, is permitted pursuant to, and subject to the license 
   terms contained in, the Simplified BSD License set forth in Section 
   4.c of the IETF Trust's Legal Provisions Relating to IETF Documents 
   (http://trustee.ietf.org/license-info). 

 
 
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Authors' Addresses 

   Don Fedyk 
   Alcatel-Lucent 
   Groton, MA, 01450 
   Email: donald.fedyk@alcatel-lucent.com 
    

   Dieter Beller 
   Alcatel-Lucent 
   Email: Dieter.Beller@alcatel-lucent.com 
    
   Lieven Levrau 
   Alcatel-Lucent 
   Email: Lieven.Levrau@alcatel-lucent.com 
    
    

 
 
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