Thank you very much for your answer. Searching the Internet about this topic, I've found a draft that seems to be a near future solution for some major MPLS networks, called "seamless MPLS". As written in the laymann draft ( http://tools.ietf.org/id/draft-ietf-mpls-seamless-mpls-00.txt), the implementation uses 2 levels of IS-IS (or 2 OSPF areas).
Also, pseudowires and LDP downstream on demand are used. I know it's only a draft, but I find it usefull. Anyway, thank you for your advices. 2011/10/20 Mark Tinka <[email protected]> > On Thursday, October 20, 2011 06:39:38 AM Livio Zanol Puppim > wrote: > > > About MPLS features in multiple areas, aren't there > > solutions that can be implemented to overcome the > > limitations like LDP prefix leaking or some solutions > > with mGRE? > > The IGP already knows about the individual infrastructure > addresses between areas, which is what helps LDP to work. > > But MPLS-TE is something else. Paths have to be signaled, > and by default, ingress routers signaling paths tend to > prefer that the tail-end of the LSP be in the same area or > level. If that isn't the case, Inter-Area TE is required. > > > What issue do you see keeping a lot of routers in a > > single area (let's say 400) versus routers in different > > areas? > > In OSPFv2, Areas help the routing protocol to scale, > primarily due to the close ties between Type 1 and Type 2 > LSA's. This isn't an issue in OSPFv3 or IS-IS, as Topology > and Reachability information is separated. > > At the risk of starting a routing protocol war, IS-IS has > been known to scale very well in single level environments > (see Vijay Gill's OSPF-to-IS-IS migration at ATDN). > > We have two networks, one where we run IS-IS in one level > (L2) and one where we use multiple levels. It scales very > well in both, and both are fairly large. > > There are rumours that OSPF can scale to some 10,000 routes > on today's kit, but I'm not sure as I don't run it. > > > Are there any recommendations about that or about the > > maximum number of routers in a single area, or maybe > > something about benefits/problems in both designs? > > The problem with a single area/level is that one router > sneezing a million miles away is heard by all other routers > at the topology level. For such a problem, OSPFv3 or IS-IS > will react better. > > Areas/levels help to scale the network, but introduce issues > like MPLS-TE. In our IPTv network, where we use NG-MVPN for > Multicast (p2mp RSVP-TE), we use a single L2 IS-IS domain, > just to avoid issues or configuration complexities with > signaling p2mp paths across different parts of the country. > The risk is increased noise, but the kit can take it. > > Mark. > -- []'s Lívio Zanol Puppim _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
