[j-nsp] Application of L2 VPN in Real World Scenario

[Mark Tinka]

On Wednesday 16 July 2008 21:19:47 Abhi wrote:

>     And how well do L2 VPN and L2 Ciruit scale up in the
> SP environment and which are more preferred ones for
> deploying these services.

This is likely to start a heated debate, but I guess scaling 
of L2VPN's comes down to the signaling + discovery 
mechanisms in play (and perhaps, which "Kompella" you 
prefer as in the case for VPLS).

Someone chime in in case I over-simplify the issue:

Cisco primarily went for Martini L2VPN's based on targeted 
LDP sessions to signal l2circuits between PE routers. 
Juniper support this also.

Juniper, on the other hand, felt that BGP should be used to, 
both, signal and autodiscover L2VPN's, including VPLS.

Later, Cisco merged both schools of thought and, through the 
Rosen draft, support BGP Autodiscovery but maintain LDP 
signaling.

Personally, I'm for the Juniper proposal. It makes sense to 
me, but like I said, this could get religious :-).

There is another scaling technique (also supported by Cisco) 
called H-VPLS (Hierarchical VPLS), in which the concept of 
u-PE's (user-facing PE routers) and n-PE's (network-facing 
PE routers) are used to partition the VPLS domain into 
smaller, more manageable chunks that need to hold only a 
subset of LDP forwarding information, rather than that of 
the whole network.

Choose your poison :-).

Mark.
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