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					A Framework for Softwire Mesh Signaling,
      Routing and Encapsulation
      across Backbone Networks

  draft-wu-softwire-mesh-framework-00
                    Jianping Wu
                      Yong Cui
                       Xing Li
            Tsinghua University / CERNET
                     Chris Metz
                  Gargi Nalawade
                    Simon Barber
                 Pradosh Mohapatra
                 Cisco Systems, Inc.
          Problem to Solve
• draft-ietf-softwire-problem-statement-02.txt
  – describes softwire mesh scenario and
    requirements
• Basically we need a generalized, network-
  based solution for supporting client IP
  AF(i)-over-backbone IP AF(j) routing and
  forwarding
  – e.g. IPv4-over-IPv6, IPv6-over-IPv4, VPNv6-
    over-IPv4, etc.
               CERNET2 Requirements
                                                                                  Same as
                                                                                a dual-stack
                              SW
                                                                                  backbone
IPv4 static or eBGP peering               Encapsulation and Setup


        IPv4 Access                                                                      IPv4 Access

                                   edge                                  edge

       IPv4 Access        edge                                                            IPv4 Access
                                      CERNET2 Backbone                       edge


            IPv6 Access                                                              IPv6 Access


                                                               Native IPv6
                                                                backbone
Reference Model of Mesh Solution
    |              |                            |               |
    |              |                            |               |
    |              |<------<SW Signaling>------>|               |
    |              |                            |               |
    |<---AF(i)---->|<----<BGP: AF(i)prefixes,-->|<-----AF(i)--->|
    |   Routing    |           SW_NHOP>         |     Routing   |
    |              |                            |               |
+-------+      +-------+                    +-------+      +-------+
|AF(i) |       |       |   (Single AF(j))   |       |      |AF(i) |
|Access |------| AFBR |===(Transit Core)===| AFBR |------|Access |
|Island |      |AF(i,j)|                    |AF(i,j)|      |Island |
+-------+      +-------+                    +-------+      +-------+
                  /|\                          /|\
                   |                            |
                   |         [STH]              |
 ---[SPH]---->SW Encap=======[SPH]==========>SW Decap---[SPH]--->
   [payload]               [payload]                  [payload]




                                          AFBR=Address Family Border Router
                                          SPH=Softwire Payload Header
                                          STH=Softwire Transport Header
                 Softwire Signaling
                                                            BGP Update

                                      RR                   SW Encap Set
                                                           SW Tunn ID
                                                           SW End-Point Addr

    IP AF (i)
     Access     AFBR
     Island       2                IP AF (j)            AFBR          IP AF (i)
                  .                                                    Access
                                 Transit Core             1            Island
                  .
    IP AF (i)
                AFBR
     Access
     Island      N                                                = Softwire

• AFBR 1 advertises the following to AFBR 2, …, AFBR N:
   – softwire encap set, softwire tunnel ID and softwire end-point

• Now AFBR 2, … AFBR N have learned the SW encap set and SW
  tunnel with end-point address to use when forwarding packets to
  prefixes advertised by AFBR 1
           Softwire Signaling Drafts
•   draft-nalawade-kapoor-            MP_REACH_NLRI
    tunnel-safi-05.txt                +---------------------------------------------------------+
                                      | AFI (IPv4=1, IPv6=2)                                    |
     – defines a new tunnel           +---------------------------------------------------------+
                                      | SAFI (TUNNEL=64)                                        |
       SAFI=64 contained in           +---------------------------------------------------------+
       MP_REACH_NLRI                  | Length of Next Hop Network Address (1 octet)            |
                                      +---------------------------------------------------------+
     – NLRI value contains tunnel     | Network Address of Next Hop (variable)                  |
       ID: tunnel IPv4/IPv6 address   +---------------------------------------------------------+
                                      | Reserved (1 octet)                                      |
                                      +---------------------------------------------------------+
                                      | SW Tunnel ID=2 Octets: SW End-Point Address (IPv4/IPv6) |
                                      +---------------------------------------------------------+
•   draft-nalawade-softwire-
    mesh-encap-attribute-00.txt
     – defines a payload type
       carried inside softwire
     – TLVs for encap types (e.g.
       IPnIP, GRE, etc.), encap
       parameters, and
       preferences
         Softwire Routing and Tunnel
                   Selection                              BGP Update
                                                        IP AF(i) Prefix
                                   RR
                                                        specific SW to
                                                        use to reach that
                                                        prefix


   IP AF (i)                                                          IP AF (i)
               AFBR              IP AF (j)           AFBR
    Access                                                             Access
    Island       2             Transit Core            1               Island



                                                                 = Softwire


• AFBR 1 advertises:
    – IP AF(i) prefixes using BGP protocols
    – specific softwire-to-use to reach those prefixes (via SW_NHOP)
• SW_NHOP attribute contains:
    – pointer to softwire tunnel-to-use leading to AFBR1
    – IP AF(j) address that overrides next-hop address contained in
      MP_REACH_NLRI
• draft-nalawade-softwire-nhop-00.txt
     Additional Softwire Items
• OAM/MIBs
• Security
  – control plane via TCP MD5
  – data plane via encryption (e.g. IPsec)
  – apply L3VPN practices (RFC4111)
• Multicast
  – possibilities are tunnel over unicast softwire mesh,
    extend mVPN, etc.
• Inter-AS
  – Options A, B and C
                     In summary
• Dynamic and scalable method for IP(x)-over-IP(y)
  routing and forwarding needed
• BGP ideal of softwire signaling
   – conveys softwire end-point addresses and sw encap sets
• BGP ideal for softwire routing and tunnel selection
   – employ existing multi-AF BGP solutions
   – include SW_NHOP attribute to link reachability with softwire
     encap action and next_hop address
• Re-use existing IP (and MPLS) tunnel encapsulation
  schemes
• Generalized for any client IP AF(x)-over-IPv4/IPv6/MPLS
  backbones
                   Next Steps
• Request that the following become
  Softwires WG documents
  –   draft-wu-softwire-mesh-framework-00
  –   draft-nalawade-kapoor-tunnel-safi-05.txt
  –   draft-nalawade-softwire-mesh-encap-attribute-00.txt
  –   draft-nalawade-softwire-nhop-00.txt

				
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posted:10/19/2011
language:English
pages:10