Subject: BGP CE Identifier allocation

From: [email-masked]
Date: Sun, 10 Aug 2003 11:17:14 +0100

As discussed on the mailing list, BGP can only broadcast the same
information to every peer in the network it has a session with, i.e. it
cannot signal information on a point to point basis. As a result of this,
the VPLS draft that uses BGP for signalling has to use a label block to
signal different labels to each PE participating in a VPN. A different label
must be sent to each PE participating in a VPN so that MAC address learning
can take place, i.e. the VPN label identifies which VPN the packet belongs
to and which PE it was received from in order to populate the MAC forwarding
tables. This is not necessary on RFC2547 as it doesn't matter where packets
come from, i.e. the VPN label just tells the PE which VPN the packet belongs
to.

The BGP signalling label block function requires each CE to have a CE ID,
which must be unique in the context of a VPN. It is suggested that the CE ID
can be used as an index in an algorithm to determine which label is
allocated to which CE. This is fine in the intra-provider case as the CE ID
can be locally administered, but what about the inter-provider VPN case?

One solution would be to make a single provider the CE ID authority for each
VPN, i.e. a single provider controls the CE IDs for any given VPN and all
other providers must request CE IDs from the relevant provider. Another
solution would be to make CE IDs globally unique, IPv6?

Thoughts on the above would be appreciated.

Thanks,

Richard