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

[Hummel Heinrich]

Jing
see my inserted comments.
Heinrich 


Hummel,

> 
> Gold:  A smallest size tree of toll roads, highways, state roads, country roads.
> Silver:A smallest size tree of highways, state roads, country roads.
> Bronze:A smallest size tree of state roads, country roads, and highways only if no path otherwise.
> 
> QoS parameters (speed, packet loss rate, MTU size,..) may define the type of road.

Do you means to restrict DSCP to be 3bits? 
HH=> No. In general we may  correlate several, e.g. m,  "gold-like" DSCPs 
          a) to their currently defined "gold-like" DiffServ functionality
          and b) to one Gold-1st road system,
    
     Furthermore, we may identify m additional and  suitable  DSCPs which shall trigger the same
     "gold-like" DiffServ functionality like above, but which are correlated to Gold-2nd road system.

   

> 
> 1st and 2nd road system may be different at least  w.r.t. their kernel parts. (The kernel part be that
> center of the smallest size tree, which is used by at least m ingress/egress combinations).
> Either traffic starts out with a) proper DSCP-Y-1st, resp. DSCP-Y-2nd, or b) is  changed from DSCP-Y-1st to
> DSCP-Y-2nd at the rim of the kernel if some current traffic load information advises so. I prefer a) and if possible such
> that any microflow will entirely take one single route.

So, that means to use alternative path for overflowed traffic?  In fact,
someone has proposed similar

method. Perhaps you are interested in the following paper:

http://www.cs.virginia.edu/~rv3s/pubs/compnet_paper.pdf 

HH=> I will go and read this paper.
     I am not surprised and I really welcome that there are others who write such papers.
     I only believe, that sqeezing/locking some traffic into e.g. some smallest size tree-road system
     enables much more effectiveness, both for the better and the worse:
     for the worse: Best-Effort-Traffic may even be handled worse, if locked into an overcrowded road system of
                    bad condition.
     for the better: Gold-traffic will be handled better, if best roads are available and if Best-Effort-Traffic is
                     kept out of the way.  

> 
>
> Stability:
> We may toss a dice at the ingress,i.e. determine a random number Y between 0.0 and 1.0. 

I think this determines when a second path is adopted for traffic
routing, in fact we do not
need to use a random number if MPLS is used. At this situation, I think
what we need is to 
monitor load on a LSP, if the load is more than 70% of the effective
bandwidth another LSP is
adpoted. If distributed routing is used ( as that of current IP
network), traffic dispersion 
have to be triggerred by heuristic method mentioned by you.

HH=> Fine.

> 
> Extensibility:
> So far I have no solution, on how to determine a smallest size tree made out of OSPF-links and EBGP/IBGP-hops.

As I think, a routing system built on time-varying network status will
do harm to both
stability and extensibility, because it could not be expected to all
routers converge to the same 
point within a short time period.

HH=> We should really ask students to program simulations and to investigate whether it will harm or improve stability. 

Some others have been working on resource management in DiffServ
networks, the page located 
at:

http://standards.ericsson.net/rmd/

In deed, I'm very interested in this idea but I think it need more
clarification.

HH=> I will read this paper, too. But again: If you have (at least)  N shortest path trees rooted at  N ingress edge router,
they will disperse traffic all over the network and it is fairly vague what bandwidth on which link shall be reserved.
Whereas if you lock all this traffic into one single  smallest size tree, you may allocate bigger BWs to fewer links.

Hope to hear from others.
HH=> Hope so, too.





-- 
Jing Shen

State Key Lab of CAD&CG
ZheJiang University(YuQuan)
HangZhou, Z.J. 310027
P.R.China

Tel: +86-571-87932423

Email: jshen@cad.zju.edu.cn

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