Network Working Group                                      Evelyne Roch
Internet Draft                                               Lyndon Ong
Intended status: Informational                                    Ciena
                                                          March 5, 2012

         Requirements for Combined Protection and Restoration
            draft-roch-ccamp-combined-recovery-reqts-00.txt


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Abstract





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   This Internet-Draft proposes requirements for combinations of
   rerouting and protection schemes that are of interest to carrier
   networks.

Table of Contents


   1. Introduction and Problem Statement.............................2
   2. Maintenance operations of protected services...................2
   3. Combined restoration and protection schemes....................4
      3.1. Second Level Restoration..................................4
      3.2. Always on protection......................................5
   4. Security Considerations........................................6
   5. IANA Considerations............................................6
   6. Acknowledgments................................................7

1. Introduction and Problem Statement

   Combination of protection and rerouting mechanisms allow carriers
   to:

   - Perform maintenance activities on the protected/protection LSPs
   while maintaining the protection.

   - Offer services with higher availability by automatically combining
   restoration and protection schemes.

   This document defines use cases for the combination of protection
   and rerouting mechanisms that are of interest to carriers that could
   be candidates for support in GMPLS.

2. Maintenance operations of protected services

   The first area to consider is the combination of maintenance
   activities with the protection and restoration schemes. For example,
   it is possible to perform maintenance operation on one of the legs
   of a 1+1 connection but the operator may want to maintain the 1+1
   protection during the maintenance activity. Temporarily or
   permanently rerouting the traffic of one of the legs for maintenance
   purposes requires proper support in the signaling procedures.

   The requirement is to support up to 3 related LSPs that have
   resources reserved but of which at most 2 are instantiated end-to-
   end in the data plane.

   Consider the following network topology:



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                     B --- C --- D
                   /               \
                  A --- E --- F --- Z
                   \               /
                     G --- H --- I


   The detailed signaling scenario for rerouting is as follows:

   -  Preconditions: The working (A-B-C-D-Z) and protecting (A-E-F-Z)
     LSPs are both established and neither of them has a failure
     condition.

   -  A third LSP (A-G-H-I) is established with resources reserved and
     established on nodes G, H and I but reserved only at nodes A and
     Z.

   -  The LSP that is put under maintenance is de-activated by keeping
     the resources reserved but no established at nodes A and Z while
     maintaining resources reserved and established at nodes B, C and
     D if maintenance is applied to working LSP or nodes E and F if
     maintenance is applied to protecting LSP.

   -  The maintenance LSP is activated by establishing the resources
     for the maintenance LSP at nodes A and Z.

   -  At this stage, if this is a permanent reroute operation, the
     original working or protecting LSP is torn down. Otherwise, the
     LSP is maintained for reversion at a later stage.

   The reversion stage:

   -  The maintenance LSP is deactivated by de-establishing the
     resources for the maintenance LSP at nodes A and Z.

   -  The original LSP (working or protecting) is activated at nodes A
     and Z by establishing resources (working or protecting) at nodes
     A and Z.

   -  The maintenance LSP is torn down.






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3. Combined restoration and protection schemes

   In order to provide higher reliability, some service levels may
   combine restoration and protection. Two combinations that are useful
   to operators are included here. These combinations may require more
   than two LSPs to be associated together in case of make-before-break
   or when reversion is desired. Signaling extensions that support
   combined protection and restoration are required by identifying the
   type of recovery as a combination of protection (e.g. 1+1 bi-
   directional) and restoration types (e.g. full rerouting). The
   signaling extensions should also provide an indication of the
   relationship between the two mechanisms to distinguish the following
   scenarios:

   -  Second level restoration: offers protection against dual failures
     in the case of protected services. It offers the option to
     restore the LSP if both working and protection LSPs fail.

   -  Always on protection: offers the assurance of fast protection
     even after a failure by restoring the failed leg of a protected
     service.

3.1. Second Level Restoration

   The requirement is to support up to 3 related LSPs that have
   resources reserved but of which at most 2 are instantiated end-to-
   end in the data plane. When both the working and protecting LSPs are
   under failure condition, this triggers restoration.

   Consider the following network topology:



                     B --- C --- D
                   /               \
                  A --- E --- F --- Z
                   \               /
                     G --- H --- I


   The detailed signaling scenario for rerouting is as follows:

   -  Preconditions: The working (A-B-C-D-Z) and protecting (A-E-F-Z)
     LSPs are both established and both are under failure condition.




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   -  One of the original LSPs (working or protecting), as determined
     by the head-end local policy is deactivated at the A and Z nodes
     while maintaining the resources reserved.

   -  A restoration LSP (A-G-H-I) is established with resources
     reserved and established.

   -  At this stage, if this is non-revertive restoration, the original
     working or protecting LSP is torn down. Otherwise, the LSP is
     maintained for reversion at a later stage.

   The reversion stage:

   -  The restoration LSP is deactivated by de-establishing the
     resources for the restoration LSP at nodes A and Z.

   -  The original LSP (working or protecting) is activated at nodes A
     and Z by establishing resources (working or protecting) at nodes
     A and Z.

   -  The restoration LSP is torn down.



3.2. Always on protection

   The requirement is to support up to 4 related LSPs that have
   resources reserved but of which at most 2 are instantiated end-to-
   end in the data plane. When one of the working or protecting LSPs is
   under failure condition, this triggers restoration of that LSP.

   Consider the following network topology:



                     B --- C --- D
                   /               \
                  A --- E --- F --- Z
                  \ \             / /
                   \ G --- H --- I /
                    \             /
                      J ------- L


   The detailed signaling scenario for rerouting is as follows:



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   -  Preconditions: The working (A-B-C-D-Z) and protecting (A-E-F-Z)
     LSPs are both established and at least one is under failure
     condition. For the purpose of this example, let's assume working
     has failed.

   -  The failed LSP (working in this example), is deactivated at the A
     and Z nodes while maintaining the resources reserved.

   -  A restoration working LSP (A-G-H-I) is established with resources
     reserved and established.

   -  At this stage, we have 3 LSPs that are associated but only 2 are
     established end-to-end in the data plane. If this is a non-
     revertive restoration, the working LSP (A-B-C-D-Z) is torn down.
     Otherwise, it is maintained until reversion.

   -  If the second original LSP also fails (protecting LSP in this
     example), it is also deactivated at the A and Z nodes while
     maintaining the resources reserved and a restoration protecting
     LSP (A-J-L-Z) is established with resources reserved and
     established. Similarly to the previous bullet, if this is a non-
     revertive restoration, the protecting LSP is torn down.
     Otherwise, it is maintained until reversion.

   The reversion stage:

   -  The working or protecting restoration LSP is deactivated by de-
     establishing the resources for the restoration LSP at nodes A and
     Z.

   -  The original LSP (working or protecting) is activated at nodes A
     and Z by establishing resources (working or protecting) at nodes
     A and Z.

   -  The working or protecting restoration LSP is torn down.



4. Security Considerations

   None identified at this time

5. IANA Considerations

   None identified at this time




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6. Acknowledgments

The authors would like to thank members of the OIF Network & Operations
WG and the CCAMP co-chairs for their comments and suggestions to this
document.












































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Authors' Addresses

   Evelyne Roch
   Ciena
   Email: eroch@ciena.com

   Lyndon Ong
   Ciena
   Email: lyong@ciena.com








































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