Re: Info aggregation

Cheng-Yin> Are the  proponents of  these models considering  loop prevention
Cheng-Yin> measures?  

Once the  PWs are  properly set up  according to the  provisioned hierarchy,
split  horizon   prevents  loops.   Perhaps  you  are   asking  whether  the
auto-discovery process  can be guaranteed to provide  the information needed
to  set up  a cycle-free  hierarchy, even  in the  presence  of provisioning
errors.  

With BGP-based auto-discovery,  this could be an issue if  the pws needed to
go through  an arbitrary set of  ASes, each of  which summarizes information
from its  neighbors before passing it on.   If we wanted to  support a model
like that, we could  use AS-path to prevent loops.  But I'm  not at all sure
that that would be  useful, as I don't think we want  the VPLS pws to travel
through arbitrary sets of ASes. 

Eric> Both  models bound the  number of  signaling inter-AS  connections, so
Eric> that the  number of these connections  does not grow as  the number of
Eric> PEs  grows.  The  hierarchical  model  limits some  of  the  signaling
Eric> information to the hierarchy boundaries. 

Cheng-Yin> I think this is limiting  distribution of L2VPN info to a smaller
Cheng-Yin> number of devices

I don't think so, when you impose hierarchy or add inter-AS gateways you are
explicitly  distributing the info  to more  devices, in  order to  bound the
amount of something or other that each device must deal with. 

Cheng-Yin> How  to aggregate  VPLS membership  ID, VPLS_ID/VPN_ID  ?  (cf IP
Cheng-Yin> addresses/routes can be aggregated). 

VPN ids obviously cannot be aggregated.  Probably the best we can do is make
the inter-AS  discovery process scale  linearly with the number  of inter-AS
VPLSes. But  I don't really think the  discovery process is going  to be the
bottleneck here.