Non-Penultimate Hop Popping Behavior and Out-of-Band Mapping for RSVP-TE Label Switched Paths
draft-ietf-mpls-rsvp-te-no-php-oob-mapping-09

MPLS Working Group                                            Z. Ali 
                                                             G. Swallow 
   Internet Draft                                   Cisco Systems, Inc. 
                                                             R. Aggarwal  
                                                        Juniper Networks 
   Intended status: Standard Track                       August 17, 2011 
   Expires: February 16, 2012 
  
                                        
       Non Penultimate Hop Popping Behavior and out-of-band mapping for 
                         RSVP-TE Label Switched Paths 
               draft-ietf-mpls-rsvp-te-no-php-oob-mapping-09.txt 

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   Abstract 

   There are many deployment scenarios which require Egress Label 
   Switching Router (LSR) to receive binding of the Resource 
   ReserVation Protocol Traffic Engineered (RSVP-TE) Label Switched 
   Path (LSP) to an application, and payload identification, using 
   some "out-of-band" (OOB) mechanism. This document defines 
   protocol mechanisms to address this requirement. The procedures 
   described in this document are equally applicable for point-to-
   point (P2P) and point-to-multipoint (P2MP) LSPs. 
       
   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]. 

   Table of Contents 

       
      Copyright Notice ..............................................1 
      1. Introduction ...............................................3 
      2. RSVP-TE signaling extensions ...............................4 
         2.1. Signaling non-PHP behavior ............................4 
         2.2. Signaling OOB Mapping Indication ......................5 
         2.3. Relationship between OOB and non-PHP flags ............7 
         2.4. Egress Procedure for label binding ....................7 
      3. Security Considerations ....................................8 
      4. IANA Considerations ........................................8 
         4.1. Attribute Flags for LSP_ATTRIBUTES object .............8 
         4.2. New RSVP error sub-code ...............................9                         
                        
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      5. Acknowledgments ............................................9 
      6. References .................................................9 
         6.1. Normative References ..................................9 
         6.2. Informative References ...............................10 
       
   1. Introduction 

   When Resource ReserVation Protocol Traffic Engineered (RSVP-TE) 
   is used for applications like Multicast Virtual Private Network 
   (MVPN) [MVPN] and Virtual Private LAN Service (VPLS) [RFC4761], 
   an Egress Label Switching Router (LSR) receives the binding of 
   the RSVP-TE Label Switched Path (LSP) to an application, and 
   payload identification, using an "out-of-band" (OOB) mechanism 
   (e.g., using Border Gateway Protocol (BGP)). In such cases, the 
   Egress LSR cannot make correct forwarding decision until such OOB 
   mapping information is received. Furthermore, in order to apply 
   the binding information, the Egress LSR needs to identify the 
   incoming LSP on which traffic is coming. Therefore, non 
   Penultimate Hop Popping (non-PHP) behavior is required to apply 
   OOB mapping. Non-PHP behavior requires the egress LSRs to assign
   a non-NULL label for the LSP being signaled. 
    
   There are other applications that require non-PHP behavior. When 
   RSVP-TE point-to-multipoint (P2MP) LSPs are used to carry IP 
   multicast traffic non-PHP behavior enables a leaf LSR to identify 
   the P2MP TE LSP, on which traffic is received. Hence the egress 
   LSR can determine whether traffic is received on the expected P2MP 
   LSP and discard traffic that is not received on the expected P2MP 
   LSP. Non-PHP behavior is also required to determine the context of 
   upstream assigned labels when the context is a MPLS LSP. Non-PHP 
   behavior may also be required for MPLS-TP LSPs [RFC5921]. 
       
   This document defines two new flags in the Attributes Flags TLV 
   of the LSP_ATTRIBUTES object defined in [RFC5420]: one flag for 
   communication of non-PHP behavior, and one flag to indicate that 
   the binding of the LSP to an application and payload identifier 
   (payload-Id) needs to be learned via an out-of-band mapping 
   mechanism. As there is one-to-one correspondence between bits in 
   the Attribute Flags TLV and the RRO Attributes subobject, 
   corresponding flags to be carried in RRO Attributes subobject are 
   also defined.  
       
   The procedures described in this document are equally applicable 
   for P2P and P2MP LSPs. Specification of the OOB communication 
   mechanism(s) is beyond the scope of this document.  

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   2. RSVP-TE signaling extensions 

   This section describes the signaling extensions required to 
   address the above-mentioned requirements.  

   2.1. Signaling non-PHP behavior 

   In order to request non-PHP behavior for an RSVP-TE LSP, this 
   document defines a new flag in the Attributes Flags TLV of the 
   LSP_ATTRIBUTES object defined in [RFC5420]: 
       

   Bit Number (to be assigned by IANA): non-PHP behavior requested flag.  

   In order to indicate to the Ingress LSR that the Egress LSR 
   recognizes the "non-PHP behavior requested flag", the following 
   new bit is defined in the Flags field of the Record Route object 
   (RRO) Attributes subobject:  
       
   Bit Number (same as bit number assigned for non-PHP behavior 
   requested flag): Non-PHP behavior acknowledgement flag. 

   An Ingress LSR sets the "non-PHP behavior requested flag" to 
   signal the egress LSRs SHOULD assign non-NULL label for the LSP 
   being signaled.  This flag MUST NOT be modified by any other LSRs 
   in the network. LSRs other than the Egress LSRs SHOULD ignore 
   this flag.  
       
   If an egress LSR receiving the Path message, supports the 
   LSP_ATTRIBUTES object and the Attributes Flags TLV, and also 
   recognizes the "non-PHP behavior requested flag", it MUST 
   allocate a non-NULL local label. The egress LSR MUST also set the 
   "Non-PHP behavior acknowledgement flag" in the Flags field of the 
   RRO Attribute subobject.  
       
   If the egress LSR  

   - supports the LSP_ATTRIBUTES object but does not recognize the 
     Attributes Flags TLV; or  

   - supports the LSP_ATTRIBUTES object and recognize the Attributes 
     Flags TLV, but does not recognize the "non-PHP behavior requested 
     flag";  

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   then it silently ignores this request according to the processing 
   rules of [RFC5420].  
          

   An ingress LSR requesting non-PHP behavior SHOULD examine "Non-
   PHP behavior acknowledgement flag" in the Flags field of the RRO 
   Attribute subobject and MAY send a Path Tear to the Egress which 
   has not set the "Non-PHP behavior acknowledgement flag". An 
   ingress LSR requesting non-PHP behavior MAY also examine the 
   label value corresponding to the Egress LSR(s) in the RRO, and 
   MAY send a Path Tear to the Egress which assigns a Null label 
   value.  

   When signaling a P2MP LSP, a source node may wish to solicit 
   individual response to the "non-PHP behavior requested flag" from 
   the leaf nodes. Given the constraints on how the LSP_ATTRIBUTES may 
   be carried in Path and Resv Messages according to RFC5420, in 
   this situation the source node MUST use a separate Path message for 
   each leaf in networks where [ATTRIBUTE-BNF] is not supported.  In 
   networks with [ATTRIBUTE-BNF] deployed either separate Path 
   message for each leaf or multiple leafs per Path message MAY be 
   used by the source node.     

   2.2. Signaling OOB Mapping Indication 

   This document defines a single flag to indicate that the normal 
   binding mechanism of an RSVP session is overridden.  The actual 
   out-of-band mappings are beyond the scope of this document.  The      
   flag is carried in the Attributes Flags TLV of the LSP_ATTRIBUTES 
   object defined in [RFC5420] and is defined as follows:  

   Bit Number (to be assigned by IANA): OOB mapping indication flag.  

   In order to indicate to the Ingress LSR that the Egress LSR 
   recognizes the "OOB mapping indication flag", the following new 
   bit is defined in the Flags field of the Record Route object 
   (RRO) Attributes subobject:  
       
   Bit Number (same as bit number assigned for OOB mapping 
   indication flag): OOB mapping acknowledgement flag.  

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   An Ingress LSR sets the OOB mapping indication flag to signal the 
   Egress LSR that binding of RSVP-TE LSP to an application and 
   payload identification is being signaled out-of-band. This flag 
   MUST NOT be modified by any other LSRs in the network. LSRs
   other than the Egress LSRs SHOULD ignore this flag.  
 
   When an Egress LSR which supports the "OOB mapping indication 
   flag", receives a Path message with that flag set, the Egress LSR 
   MUST set the "OOB mapping acknowledgement flag" in the Flags 
   field of the RRO Attribute subobject. The rest of the RSVP 
   signaling proceeds as normal.  However, the LSR MUST have 
   received the OOB mapping before accepting traffic on the LSP.  
   This implies that the Egress LSR MUST NOT setup forwarding state 
   for the LSP before it receives the OOB mapping.  
       
   Note that the payload information SHOULD be supplied by the OOB 
   mapping. If the egress LSR receives the payload information from 
   OOB mapping then the LSR MUST ignore L3PID in the Label Request 
   Object [RFC3209]. 
    
    
   If the egress LSR  

   - supports the LSP_ATTRIBUTES object but does not recognize the 
     Attributes Flags TLV; or  

   - supports the LSP_ATTRIBUTES object and recognizes the 
     Attributes Flags TLV, but does not recognize the "OOB mapping 
     indication flag"; 

   then it silently ignores this request according to the processing 
   rules of [RFC5420].  
       

   An ingress LSR requesting OOB mapping SHOULD examine "OOB mapping 
   acknowledgement flag" in the Flags field of the RRO Attribute 
   subobject and MAY send a Path Tear to the Egress which has not 
   set the "OOB mapping acknowledgement flag".  

   When signaling a P2MP LSP, a source node may wish to solicit 
   individual response to the "OOB mapping indication flag" from the
   the leaf nodes. Given the constraints on how the LSP_ATTRIBUTES 
   may be carried in Path and Resv Messages according to RFC5420, in 
   this situation the source node MUST use a separate Path message for 
   each leaf in networks where [ATTRIBUTE-BNF] is not supported.  In 

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   networks with [ATTRIBUTE-BNF] deployed either separate Path 
   message for each leaf or multiple leafs per Path message MAY be 
   used by the source node. 
       
   In deploying applications where Egress LSR receives the binding 
   of the RSVP-TE LSP to an application, and payload identification, 
   using OOB mechanism, it is important to recognize that the OOB 
   mapping is sent asynchronously with respect to the signaling of 
   RSVP-TE LSP. Egress LSR only installs forwarding state for the LSP  
   after it receives the OOB mapping. In deploying applications using 
   OOB mechanism, an Ingress LSR may need to know when the Egress is 
   properly setup for forwarding (i.e., has received the OOB mapping). 
   How the Ingress LSR determines that the LSR is properly setup for 
   forwarding at the Egress LSR is beyond the scope of this document. 
   Nonetheless, if the OOB mapping is not received by the Egress LSR 
   within a reasonable time, the procedure defined in section 2.4 to 
   tear down the LSP is followed.   
       

   2.3. Relationship between OOB and non-PHP flags 

   "Non-PHP behavior desired" and "OOB mapping indication" flags can 
   appear and be processed independently of each other. However, as 
   mentioned earlier, in the context of the applications discussed in 
   this document, OOB mapping requires non-PHP behavior. An Ingress 
   LSR requesting the OOB mapping MAY also set the "non-PHP behavior 
   requested flag" in the LSP_ATTRIBUTES object in the Path message.  

   2.4. Egress Procedure for label binding 

   RSVP-TE signaling completion and the OOB mapping information 
   reception happen asynchronously at the Egress. As mentioned in 
   Section 2.2, Egress waits for the OOB mapping before accepting 
   traffic on the LSP. Nonetheless, MPLS OAM mechanisms, e.g., LSP 
   Ping and Trace route as defined in [RFC4379], [P2MP-OAM], are 
   expected to work independent of OOB mapping learning process.  
        
   In order to avoid unnecessary use of the resources and possible 
   black-holing of traffic, an Egress LSR MAY send a Path Error 
   message if the OOB mapping information is not received within a 
   reasonable time. This Path Error message SHOULD include the error 
   code/sub-code "Notify Error/ no OOB mapping received" for all 
   affected LSPs. If notify request was included when the LSP was 
   initially setup, Notify message (as defined in [RFC3473]) MAY 
   also be used for delivery of this information to the Ingress LSR. 
   An Egress LSR MAY implement a cleanup timer for this purpose. The 

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   time-out value is a local decision at the Egress, with a 
   RECOMMENDED default value of 60 seconds.  

   3. Security Considerations 

   Addition of "non-PHP behavior" adds a variable of attacks on the 
   label assigned by the Egress node. As change in the value of the 
   egress label reported in the RRO can cause the LSP to be torn 
   down, additional security considerations for protecting label 
   assigned by the Egress node are required. Security mechanisms as 
   identified in [RFC5920], [RFC2205], [RFC3209], [RFC3473], 
   [RFC5420] and [RFC4875] can be used for this purpose. This 
   document does not introduce any additional security issues above 
   those identified in [RFC5920], [RFC2205], [RFC3209], [RFC3473], 
   [RFC5420] and [RFC4875].     
    
   4. IANA Considerations 

   The following changes to the Resource Reservation Protocol-Traffic 
   Engineering (RSVP-TE) Parameters registry are required. 

   4.1. Attribute Flags for LSP_ATTRIBUTES object 

   The following new flags are defined for the Attributes Flags TLV 
   in the LSP_ATTRIBUTES object.  The numeric values are to be 
   assigned by IANA. 
   o  Non-PHP behavior flag:
   This flags is used in the Attributes Flags TLV in a Path message. 
   The flags have corresponding new flag to be used in the RRO 
   Attributes subobject. As per [RFC5420], the bit numbering in the 
   Attribute Flags TLV and the RRO Attributes subobject is 
   identical. That is, the same attribute is indicated by the same
   bit in both places. This flag is not allowed in the Attributes 
   Flags TLV in a Resv message. Specifically, Attributes of this 
   flag are as follows:  

         - Bit Number: To be assigned by IANA. 

         - Attribute flag carried in Path message: Yes 

         - Attribute flag carried in Resv message: No 

         - Attribute flag carried in RRO message: Yes 

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   o  OOB mapping flag:   

   This flags is used in the Attributes Flags TLV in a Path message. 
   The flags have corresponding new flag to be used in the RRO 
   Attributes subobject. As per [RFC5420], the bit numbering in the 
   Attribute Flags TLV and the RRO Attributes subobject is 
   identical. That is, the same attribute is indicated by the same 
   bit in both places. This flag is not allowed in the Attributes 
   Flags TLV in a Resv message. Specifically, Attributes of this 
   flag are as follows:  

         - Bit Number: To be assigned by IANA. 

         - Attribute flag carried in Path message: Yes 

         - Attribute flag carried in Resv message: No 

         - Attribute flag carried in RRO message: Yes  

   4.2. New RSVP error sub-code  

   For Error Code = 25 "Notify Error" (see [RFC3209]) the following 
   sub-code is defined. 
       
            Sub-code                    Value 
            --------                    ----- 
       
            No OOB mapping received     to be assigned by IANA.  
       

   5. Acknowledgments 

   The authors would like to thank Yakov Rekhter for his suggestions 
   on the draft.   

    
   6. References 

   6.1. Normative References 

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate                 
             Requirement Levels", BCP 14, RFC 2119, March 1997.
                
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   [RFC5420] A. Farrel, D. Papadimitriou, J. P. Vasseur and A. 
             Ayyangar, "Encoding of Attributes for Multiprotocol 
             Label Switching (MPLS) Label Switched Path (LSP) 
             Establishment Using RSVP-TE", RFC 5420, February 2006. 

   [RFC3209] D. Awduche, L. Berger, D. Gan, T. Li, V. Srinivasan, 
             and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP 
             Tunnels", RFC 3209, December 2001. 

   [RFC4875] R. Aggarwal, D. Papadimitriou, S. Yasukawa, et al, 
             "Extensions to RSVP-TE for Point-to-Multipoint TE 
             LSPs", RFC 4875. 

   [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label 
             Switching (GMPLS) Signaling Resource ReserVation 
             Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 
             3473, January 2003.. 

   [RFC2205] R. Braden, Ed., "Resource ReSerVation Protocol (RSVP) -
             - Version 1 Functional Specification", RFC 2205, 
             September 1997.   

   [ATTRIBUTE-BNF] Berger, L. and Swallow, G., "LSP Attributes Related
             Routing Backus-Naur Form", draft-ietf-ccamp-attribute-
             bnf, work in progress.
    
   6.2. Informative References 

   [MVPN] E. Rosen, R. Aggarwal et al, "Multicast in MPLS/BGP IP 
          VPNs", draft-ietf-l3vpn-2547bis-mcast-10.txt, work in 
          progress.  

   [RFC4761] Kompella, K., Ed., and Y. Rekhter, Ed., "Virtual 
             Private LAN Service (VPLS) Using BGP for Auto-Discovery 
             and Signaling", RFC 4761, January 2007.   

   [RFC5921] M. Bocci, S. Bryant, et al, "A Framework for               
             MPLS in Transport Networks", RFC 5921, January 2007. 

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

                        
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   [RFC4379] K. Kompella, and G. Swallow, "Detecting Multi-Protocol 
             Label Switched (MPLS) Data Plane Failures", RFC 4379, 
             February 2006.
   [P2MP-OAM] S. Saxena, Ed., G. Swallow, Z. Ali, A. Farrel, S. 
             Yasukawa, T. Nadeau, "Detecting Data Plane Failures in 
             Point-to-Multipoint Multiprotocol Label Switching 
             (MPLS) - Extensions to LSP Ping", draft-ietf-mpls-p2mp-
             lsp-ping-17.txt, work in progress. 

   Author's Addresses 

       
      Zafar Ali 
      Cisco Systems, Inc. 
      Email: zali@cisco.com 
       
      George Swallow 
      Cisco Systems, Inc. 
      Email: swallow@cisco.com 
       
      Rahul Aggarwal 
      Juniper Networks 
      rahul@juniper.net 
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