[rbridge] Questions - VLANs & MPLS
trill at punk.co.nz
Sat Sep 27 00:10:59 PDT 2008
I was recently introduced to RBridges by Radia Perlman's interesting
techtalk at Google. Is there a digest somewhere that explains the
options considered or the iterations it has been through?
It seems (on the face of it) that RBridges may reconnect partitioned
VLANs or allow access to VLANs used for security (rightly or wrongly).
E.g. when two RBridges are separated by an Ethernet that has partitioned
VLANs (or some VLANs disallowed on a trunk ports) the RBridges will
complete the link for those VLANs. Do I understand right?
Also, I was curious why MPLS wasn't used as the forwarding method..?
I searched the mailing list, but google stops at 93 posts, and most of
the references I could find mentioning MPLS were about using the header
in some form, not LSPs for forwarding. But if it's feasible to use LSPs
to forward frames. The LSRs would only need to understand encap/decap of
Ethernet frames onto these TRILL LSPs and a new protocol to establish
the LSPs at the same time as distributing the MAC addresses. E.g.
perhaps modified IS-IS as with RBridges. The drawbacks would seem to be
loss of MAC learning. But I'd have thought much of the hardware is
already there to support such forwarding.
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