[Irtf-rr] AW: Differentiated Routing, not only plain rambo-SPF

[Hummel Heinrich]

Hummel, was your original proposal same like Diffserv-aware-TE. I thought
it was different.

My answer:
DiffRout is definitively different.

My motivation and my key thoughts to open this discussions have been:
- combine the best of Intserv/MPLS and Diffserv and as a result do stateless IP forwarding but get
     what  Intserv/MPLS are providing: Qos/BW/Policy/Traffic balancing/rerouting.

- therefore construct road systems and do IP forwarding/routing also based on DSCP.

- the road systems may have assigned bandwidth. This is reasonable/feasable because some traffic can really
  be locked into some slim road system (smallest size tree, smallest ring) just like MPLS traffic can be locked into
  some LSP. Whereas with rambo-SPF bandwidth assignment makes no sense as the sum of all
  shortest path trees computed by all the nodes would span the entire network, i.e. spread traffic all over it.
  The price for staying within some road system should be acceptable: Eventually, make a few hops more.
  Based on my computations, the smallest size tree may be smaller than the avarage shortest path tree by 15-20 %. 
  So I think the detour for the packets will not be very big either.   

- be guided by what you can observe on daily road traffic: Especially in the U.S. there are so many ramp-based
  road junctions, which are more impressive than any traffic light controlled junction, so that motor-cyclists may
  jump the queue of waiting cars (=DiffServ) if the traffic light is red. 
  There are so many observations that can be made watching how the traffic is managed for cars, 
  trains, airplanes, pedestrians, etc. We all are used to it and don't discern extra smartness in it. However there is.
      
- and I realized what is the big obstacle: Yes it is this rambo-SPF routing paradigma. It does not represent the  
  surveillant view, only the egomanic view, combined with the hope that in total you get best results because 
  "the streets are emptiest when each car takes the shortest route":-). 



Heinrich