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

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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, ... – PowerPoint PPT presentation

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

1
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
2
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

3
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

4
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

5
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)

6
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

7
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

8
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.