The MPLS WG Archive

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

Although Eric's idea is taken by many people , our experiements shows
this
is not the truth at least with the situation of our testbed.

In fact we set up a small testbed consisting a Linux based MPLS engine.
In order to focus on difference between forwarding performance
difference
 between MPLS and IP, we use CBR traffic with static routing table.

The testbed is consist of  3 hops of MPLS(IP) forwarder between source
and 
destination. The experiments shows that:

  If the hardware and software system is kept at the same level, then:
  1) TCP throughput of MPLS is a little smaller than IP when path MTU is
the same.
     and difference increases when path MTU decreases.
  2) For UDP traffic,
     a) when best-effort policy is applied, if link along the path is
lightly loaded (below 30%)
        e2e performance difference IP and MPLS is nearly the same while
the IPDV of MPLS is 
        smaller than IP forwarding; if the link along the path is
heavily loaded, QoS of MPLS
        is worse than IP forwarding. the same result is applied to loss
rate.
     b) when resource reservation is applied, both method could
guarantee the e2e delay but
	MPLS shows better IPDV value with a little longer e2e delay.

  We found the reason for this phenomenon is the
encapsulation/decapsulation procedure of MPLS, and
the processing of MPLS forwarding. 

  Although we have not experimented with Cisco's express forwarding and
the like, and we do not 
experiment with large scale system with real internet traffic pattern,
we concern that the result could 
applied to large scale network. The reason is, 1) a small testbed could
be considered as a 
emulation of tunnel through large network , and some of large network
use LER-to-LER LSP; 2)
we focus on forwarding difference between IP  and MPLS, and we think
technique like CEF and per-port
cache could be applied to both technologies. 3) the same queueing
mechanism is applied to both 
technologies in our experiments. 4) comparison should be taken at the
same level of cost.

The paper on this experiment will be published on Communication Journal
( Chinese) this month. 
any comment will be highly appreciated.

regards
        

> 
> No, not really.  MPLS lets you apply QoS using EXP bits, just like you
> can with IP Precedence; any mechanisms you can use with IP Precedence
> to reduce jitter (various queing schemes) are equally applicable with
> MPLS.  Using MPLS-TE can make you more likely to avoid congestion and
> therefore less likely to experience delay and jitter, but from a
> queueing perspective it's the same with MPLS and with IP routing.
> 
> eric
> 
> > Please let me know
> >
> > Thanks
> >
> > J.C.Ramesh Babu
> > Technical Specialist.
> > Communications and Products Division
> > Infosys Technologies Limited
> > Electronic City,
> > Hosur Road,
> > Bangalore.
> >
> > Ph #
> > Off : 91-80-4166472
> > Res: 91-80-6592375
> 
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-- 
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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