The MPLS WG Archive

[Eric Osborne <eosborne@cisco.com>]

On Mon, Dec 09, 2002 at 08:41:09PM +0800, Jing Shen wrote:
> It's main conclusion of our experiments that policy based routing must 
> be used with MPLS if e2e QoS is considered carefully.

Why?



eric

>  I agree with 
> Naidu that experiments with large scale network consisting of commercial
> router/switch is needed to find out more details, as theoretical 
> analysis of e2e delay relates to same factor set in either MPLS or 
> IP network, Jitter relates closely to queueing mechanism, but also 
> accumulated processing overhead. 
> 
> there has been discussion on difference between MPLS-TE and IP-TE
> on some other list, but I don't think IP-TE based only on traffic
> metrix,
> linear programing and policy database could be easily set up in
> ISP networks, the obstacle exists with both traffic metix derivation, 
> optimization period and the policy dealing with broken links. 
> 
> OMP gives a good start on traffic engineering but its traffic division
> policy is too simple for self-similar internet traffic. 
> 
> I have another question, is OMP implemented in some commerical products?
> if not, why? 
> 
> The overprovisioning of network resource makes current network works
> smooth
> util I come to know that DVE works at Gbps bandwidth requiement.
> 
> 
> 
> > 
> >   I think your discussion is little deviated. What I understood
> >   from Jing's description is that, he didn't apply any form of TE
> >   (neither IP-TE nor MPLS-TE) in his network. Jing's measurements
> >   are based on straight line topology of 3 nodes, comparing IP and
> >   MPLS (forwarding) performance only.
> > 
> >   IMHO, in such a small topologies, the amortized performance
> >   improvements (overall gain of all operations in the worst case)
> >   may not be significant.
> > 
> >   In such straight line topologies (with out applying any form
> >   of queuing differentiation or some form of TE in the topology),
> >   I don't think MPLS out performs IP just because of MPLS
> >   fast forwarding nature (may be small amount of improvement).
> >   Remember that, there is no much difference between IP QoS techniques
> >   and MPLS QoS techniques (same classes, same queuing methodologies).
> >   The major difference between IP and MPLS is in TE techniques.
> > 
> >   This discussion reminds me of old draft:
> >   ftp://ftp.netlab.ohio-state.edu/pub/jain/ietf/draft-bhani-mpls-te-anal-00.
> > txt
> >   Where, it is clearly shown that, there is a significant improvement
> >   in the throughput of the UDP & TCP flows when MPLS-TE is applied.
> > 
> >   However, can the same performance improvements are achieved using
> >   IP-TE methods (at least near to the performance of MPLS-TE) is
> >   still an open ended question?
> > 
> >   Some very interesting research has been done to prove the above
> >   question. But, "at what cost?", "with how much ease of configuration
> >   & maintenance?", "with what added benefits?" are still unanswered.
> > 
> >   Finally, I strongly feel that, the performance matrices change a lot
> >   from small topologies to real-complex topologies. We can't directly
> >   map the simulation results to real-world topologies. In any case,
> >   the average/amortized performance measurements & analysis of
> >   real-world complex topologies is not an easy task. If there is
> >   any such work, I will be very glad to know.
> > 
> >   Thank You.
> > 
> > --
> > Venkata.
> 
> -- 
> Jing Shen
> 
> State Key Lab of CAD&CG
> ZheJiang University(YuQuan)
> HangZhou, Z.J. 310027
> P.R.China
> 
> Tel: +86-571-87932423
> Mobile: (0)13516813753
> Email: jshen@cad.zju.edu.cn
> 
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