[c-nsp] Downsides of combining P and PE functions into a single box

[Keegan Holley]

2011/10/19 Dobbins, Roland <rdobbins at arbor.net>

> On Oct 19, 2011, at 10:46 AM, Keegan Holley wrote:
>
> > If you can connect all your PE's without adding aggregation and core
> layers you'd obviously time, money and avoid complexity.
>
> On the contrary, while collapsed-core designs have some of the advantages
> you mention and have certainly been implemented successfully, the need for
> edge features/functionality *adds* complexity, IMHO.
>
>
It depends on the features.  Whatever features you need on the PE are always
going to be there.  Whether you connect your PE to a core of P routers or
connect the PE routers to each other doesn't affect this in most cases.
Mark had a good example with the need for ingress re-marking, but even that
is not required in all networks.  Beyond that I don't see alot of reasons to
go with P routers unless you have a need for route/traffic aggregation which
many networks do need.