The MPLS WG Archive

[Jing Shen <jshen@cad.zju.edu.cn>]

It's main conclusion of our experiments that policy based routing must 
be used with MPLS if e2e QoS is considered carefully. 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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