BGP-based Auto-Discovery for L2VPNs draft-hlmu-l2vpn-bgp-discovery-00.txt

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BGP-based Auto-Discovery for L2VPNs
draft-hlmu-l2vpn-bgp-discovery-00.txt

• Sue Hares - shares_at_nexthop.com
• Vasile Radoaca - vasile_at_nortelnetworks.com
• Wei Luo - luo_at_cisco.com
• Praveen Muley - pmuley_at_nortelnetworks.com
• Paul Unbehagen - paulu_at_nortelnetworks.com

March 2, 2004, 59th IETF
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Intent

• Use BGP to provide an Auto-discovery method for
  LDP and L2TP signaled L2VPNs.
• Intent is to work for VPWS VPLS (distributed
  and Non-distributed)
• Information needed by the Signaling protocol
  include
• Remote PE IP address
• VPN ID
• VPN endpoints
• This provides
• Automatic PW establishment
• Can also provide automatic establishment of
  targeted signaling sessions

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Overview

• Use RT to color routes and control topology.
• Capability Negotiation
• MP Extensions (capability 1)
• And the list of AFI/SAFI pairs for L2VPNs.
• i.e. AFI x / SAFI 1, AFI x / SAFI 2, AFI x / SAFI
  3
• AGI AII Encoded in the portion of the
  MP_Reach_NLRI for creation announcement

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AFI/SAFI Encoding

• AFI to be assigned by IANA
• The SAFI value will be set to the following bit
  pattern
• 0000 00LW
• where L is the presence of VPLS
• W is the presence of VPWS
• SAFI value is set 3 to signify that the NRLI
  encoding can be used for both

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NLRI Encodings

• The encoding of the NRLI in the MP-BGP attribute
  is based on the AFI/SAFI identifiers.
• For L2VPNs, the SAFI values of 1-3 will have the
  following NLRI encoding
• Length of NLRI in bits, NLRI field (variable
  length)
• Where the NLRI field is further defined as
• Length of AGI (in bits), AGI (variable)
• Length of AII (in bits), AII (variable)

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Discovery Process
PE1
PE2
CE
CE
Next Hop RT MP_Reach_NLRI AFI xxxx
SAFI 0000 000W Length of NH Next Hop
AGI Length (bits) AGI value (variable)
AII Length (bits) AII Value (variable)
3. BGP filters on RT and LDP receives the
discovery message. 4. AII from the update
message becomes the TAII in the signaling
protocol.
1. New Forwarder created
2. BGP sends AD Update message

• BGP transmit Next Hop, AGI, AII
• LDP/L2TP receive Target, AGI, SAII, TAII

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Inter-AS Options
Transparent mode
AS 2
AS 1
ASBR1
ASBR1
PE1
PE2
CE
CE
PW 1

• 2 modes available to provide inter-AS
• Transparent
• Proxy
• Transparent mode allows the ASBRs to pass
  reachabilties of L2VPN information through to the
  next AS directly to the remote PEs
• This also requires the network reachabilities for
  the originating PE to be announced as well

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Inter-AS Options
Proxy mode
AS 2
AS 1
ASBR1
ASBR2
PE1
PE2
CE
CE
PW 1
PW 2
PW 3

• 2 modes available to provide inter-AS
• Proxy
• Transparent
• Proxy mode requires ASBRs to create PW for
  inter-AS communications and be L2VPN aware
• ASBR1 sends an Update to ASBR2 with next-hop
  address of ASBR-1, and SNPA1 filled with PE-1 BGP
  Identifier
• When ASBR-2 receives the update from ASBR-1, it
  performs the same procedures as ASBR-1 and
  announces the update to all PEs in AS2 with
• next-hop address of ASBR-2, and
• SNPA1 with PE1 BGP Identifier, and
• SNPA2 with ASBR-1 BGP Identifier.

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Conclusion

• Provide a method of Auto-discovery for LDP based
  L2VPNs
• Works for VPWS VPLS (distributed and
  Non-distributed)
• New AFI needed for L2VPNs
• Do we need to support PW-id?