RE: A possible solution for source-based site-exit routing

["marcelo bagnulo" <marcelo@it.uc3m.es>]

Hi Aldrin,

Have you checked draft-huitema-multi6-hosts-01.txt section 4.2 Source
address dependent routing?
I think it presents something related to this.

Regards, marcelo

> -----Mensaje original-----
> De: owner-multi6@ops.ietf.org [mailto:owner-multi6@ops.ietf.org]En
> nombre de Aldrin Isaac
> Enviado el: jueves, 21 de noviembre de 2002 23:56
> Para: IETF-Multi6
> Asunto: A possible solution for source-based site-exit routing
>
>
> I would like to present a method for operationally simple source-based
> site-exit routing that may or may not have been presented before.
> Those who are familiar with MPLS VPNs will find analagies.
>
> There are four new "things" defined by this method.
>
> Source-constrained Route Table (SRT): is a routing table instance used
> to distinguish destinations route entries that are reachable for a
> specific Source Prefix (SP) from the same destination route entries
> that are reachable for other SPs.  Route metrics for routes within an
> SRT are processed independently of route metrics for routes in other
> SRTs and the Base Routing Table (BRT).  ** There is one SRT per every
> unique SP. **
>
> Base Route Table (BRT): This one isn't new.  This route table carries
> all routes that are not constrained by the source address.  Generally
> this would be all internal routes.
>
> Source-constrained Route Distinguisher (SRD): is an attribute given to
> an external route (external-destination-prefix +
> border-address/border-nexthop) that can be used for routing packets
> whose source address matches a particular SP.  The value of the SRD is
> simply the SP.  A destination route prefix with a particular SRD value
> must not be considered by a routing protocol to be equivalent to the
> same destination route prefix with another SRD value.  Border routers
> import routes from an external peer directly into SRTs for each SP
> routable via that peer.  The border routers export routes from the
> BRT/SRTs into IGP/IBGP as normal, but routes from the SRTs are
> additionally exported with the associated SRD.  Other routers within
> the site import routes with an SRD into the SRT associated to the SP.
>
> SRT Lookup Table (SRTLT): is the SP table whose input is a source
> address and output is a reference to the SRT associated to the source
> address.
>
> Tying it all together is the...
>
> Three Point Lookup (TPL): When a packet arrives at a router, the
> router will first perform a lookup of the destination in the BRT.  If
> the route does not exist in the BRT, it does a lookup in the SRTLT to
> find the SRT whose SP best matches the packets source address.  If
> SRTLT lookup fails for the source address or a destination route does
> not exist in the SRT, then an ICMP Destination Unreachable is sent to
> the source address.
>
> If used, this feature would need to be enabled on all routers
> participating in the sites IGP.  An SRD attribute would need to be
> defined for all IGPs including IBGP.
>
> In a simplified configuration, each border router would import a
> static ::/0 route pointed towards each of it's external peers into the
> SRTs whose SPs can be routed via those peers.  In which case ::/0
> route should not exist in the BRT.  More precisely, a route should not
> exist in the BRT if it exists in an SRT.
>
> Comments?
>
> -- aldrin
>
>