[LARTC] Layer 3 switching...

[Grant Taylor]

On 10/06/07 07:27, Mohan Sundaram wrote:
> CISCO CEF works somewhat in this fashion for routing only. I've been 
> building network gear for a while now.

*nod*

> I had this idea but no buyers. Route cache is for destination IPs 
> normally. If the router does stateful filtering, then it has 
> connections / flows. Once a look up is done for a flow based on 
> destination or policy routing, the exit interface with new packet header 
> values and frame header value is also made part of the route cache. Thus 
> the resultant of all L3/L2 actions are attached to a flow and used. This 
> would include NAT translations.

Sounds like the route cache has been well thought out in the Cisco gear.

> The above idea gives good speed but fails for encapsulations, packet 
> based load balancing and effecting inline change in configurations for 
> existing flows. Being a commercial product, unless it is fully baked, it 
> does not fly. User is responsible is also an arguement that is not 
> accepted in such scenarios. Further this is IP specific and cannot do 
> well in multi-protocol routers unless IP encapsulations like GRE are 
> used as a standard.

I don't think that L3 switching that I'm referring to is meant to be 
used in all locations, especially some of the ones that you reference. 
However L3 switching would be good in a core network between edge and 
core networks (presuming that there is no firewalling / filtering going 
on between the two).  I would never use a L3 switch as the interface to 
WANs and / or the ISPs, at least not today in this day and age.

> An extension was to tie flows to MPLS labels but this was getting into 
> core routing / switching space while focus was on CPE side.

I think MPLS in and of its own right is a very promising technology, all 
be it somewhat isolated to larger networks with their own complex core. 
  Rather it is my understanding that MPLS is primarily intra company, 
not inter company which is where I think it could have more benefit. 
However I could be wrong about this.  (If a discussion is going to 
ensue, let's start a new thread.)



Grant. . . .