Re: MPLS VPN design - RR in forwarding path?

[Jeff Tantsura <jeff.tantsura () ericsson com>]

Hi,

Right, one is when besides forwarding packets a router also functioning as a RR, another - when RR sets NH to itself 
and hence forces all the traffic to pass thru the router in fast path.
Keep in mind - some architectures, such as seamless MPLS would require a RR to be in the fast path.
There are some other cases where it could be a requirement.
I'd advice to look into vRR space - price/performance looks quite good.

Wrt open source implementations - if you are looking into relatively basic feature set (v4/v6 unicast/vpn) reliability 
is not of main concern and of course- there are hands and brains to support it - could be a viable approach.
Might you be looking into more complex feature set  - EVPN, BGP-LS, FS,
enhanced route refresh, etc,  highly optimized code wrt update rate/ number of peers supported - most probably you'd 
end up with a commercial implementation.

Hope this helps

Regards,
Jeff

> On Dec 31, 2014, at 9:08 AM, Chuck Anderson <cra () WPI EDU> wrote:
>
> > On Wed, Dec 31, 2014 at 01:08:15PM +0100, Marcin Kurek wrote:
> > Hi everyone,
> >
> > I'm reading Randy's Zhang BGP Design and Implementation and I found
> > following guidelines about designing RR-based MPLS VPN architecture:
> > - Partition RRs
> > - Move RRs out of the forwarding path
> > - Use a high-end processor with maximum memory
> > - Use peer groups
> > - Tune RR routers for improved performance.
> >
> > Since the book is a bit outdated (2004) I'm curious if these rules
> > still apply to modern SP networks.
> > What would be the reasoning behind keeping RRs out of the forwarding
> > path? Is it only a matter of performance and stability?
>
> When they say "move RRs out of the forwarding path", they could mean
> "don't force all traffic through the RRs".  These are two different
> things.  Naive configurations could end up causing all VPN traffic to
> go through the RRs (e.g. setting next-hop-self on all reflected
> routes) whereas more correct configurations don't do that--but there
> may be some traffic that natrually flows through the same routers that
> are the RRs, via an MPLS LSP for example.  That latter is fine in many
> cases, the former is not.  E.g. I would argue that a P-router can be
> an RR if desired.