Re: PQC and QOSPF

[Zhaohui Zhang <[e-mail]>]

Yao-Min,

I have not read the paper yet, so my response is based your email only.

> 
> A criticism on QOSPF made in the PQC paper
> (http://www.isoc.org/inet97/proceedings/F4/F4_2.HTM) 
> was the scaling issue with the Resource Reservation
> Advertisements (RRAs).  RRA, being per-flow 
> information, is flooded thoughput an OSPF area. 
> 
> The approach proposed in PQC is to have the resource 
> reservation information for a flow only propagated 
> to routers that are on the path of the flow.   
> The propagation mechanism uses RSVP.  

Flooding RRAs anywhere does cause the scaling problem, but from day one
we proposed an alleviation - use Explicit Routing.

With ER, reservation information is sent only to the "first hop"
routers - even better than sending to routers on the path of the flow.

We also tried to put it into RSVP so that only routers on the path would
get the info, but RSVP folks did not think that was a good idea, so we
had to give up.

> 
> Is there a compelling reason in the design of 
> QOSPF to have RRAs flooded throughout an area?  

The resource information is needed to deal with "step over your own
shadow" problem. Any router involved in the calculation of the path for
a flow needs to know the reservation info for the flow - I believe you
share the same view.

Flooding them anywhere does not scale and is not necessary, yet it is easy
to understand and simple to implement, so we did not put ER up front but
put it in the appendix instead.

>  
> -- 
> Yao-Min Chen, Fujitsu Labs of America, [e-mail]  
> 595 Lawrence Expressway, Sunnyvale, CA 94086-3922
> Phone: [phone] Fax: [phone]
> 

Thanks.

Jeffrey