[e2e] traffic dispersion and blocking probality

Jing Shen jshen at cad.zju.edu.cn
Tue Apr 2 06:14:53 PST 2002


thanks for your comment.

But, why do you think  OMP do nothing  on maintaining  efficiency in
overload and can arguably lead to the spread of congestion?   As I think
OMP direct traffic based on local routing computation,  the exact
problem is
with its dispersion method (hash or random ).

And , you means those elastic traffic as  traffic without strict qos
requirement ? ( I'm sorry if I'm too new to this )


> While it is true that the current connectionless IP architecture
> offers limited possibilities for flow blocking, it may be argued that
> the introduction of admission control would be a desirable
> development, notably to allow intelligent traffic aware routing.
> Congestion can be defined as a situation where traffic demand (flow
> arrival rate x average flow size) exceeds capacity. In this case, the
> number of flows in progress continues to increase while their realized
> throughput tends to zero. This phenomenon is analysed in "Statistical
> bandwidth sharing: a study of congestion at flow level" by S. Ben
> Fredj et al. (http://www.acm.org/sigs/sigcomm/sigcomm2001/p9.html).
> If a link is congested it would be preferable to reroute flows over an
> alternative path. A lot of work has been performed on routing
> strategies under the assumption that flows can be assimilated to
> constant rate streams (or circuits) and admission control is performed
> in the control plane. Dynamic traffic aware routing is generally
> regarded as preferable to fixed path routing. In the Internet, routing
> is essentially fixed path (flows cannot choose their path depending on
> current load) and this can lead to bad quality and inefficiency if
> that path happens to be overloaded.
> Some work on adaptive flow level routing for elastic traffic is
> reported in papers on the site
> http://www.enst.fr/~oueslati/publienglish.html. An essential component
> is implicit admission control (realized in the data plane) as
> discussed in papers on the same site.
> OMP (and similar approaches proposed in MPLS Traffic engineering)
> attempt to adapt load sharing between a number of possible paths and
> would avoid the problem of the overloaded fixed  path. They do
> nothing, however, to maintain efficiency in overload (demand greater
> than the sum of available capacities) and can arguably lead to the
> spread of congestion.
> Jim Roberts

Jing Shen

* The SunShine of life is made up of very little beams which is      *
*  bright all the time                                               *

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.postel.org/pipermail/end2end-interest/attachments/20020402/e4bbb81f/attachment.html

More information about the end2end-interest mailing list