[e2e] packet reordering in OC 48 links

Alia Atlas aatlas at avici.com
Sun May 15 16:30:10 PDT 2005

In general, a router shouldn't reorder packets.  This doesn't lead to 
acceptable behavior for many applications. While parallelism is reasonable 
and necessary, there are a number of mechanisms possible to ensure that 
packet re-ordering doesn't occur as a result.


At 04:42 PM 5/15/2005, Nischal Piratla wrote:
>We feel that it is quite reasonable to see such high amounts of 
>reordering. In
>fact, we are working on this very problem.
>Most of the reordering that occurs within the routers is countered by either
>input reordering (packets of same flow are added to same queue) or output
>reordering (packets from same flow are tagged at the input, and are collected
>to be sent in order at the output). However, due to increasing table sizes,
>difference in the rates of increase in network speeds vs. the computing
>speeds, etc., higher parallelism is inevitable and the methods stated above
>may not be useful. We discussed a little more about it in our recent paper:
>Also, to understand the amount and extent of reordering, we suggest 'Reorder
>Density' metric that comprehensively illustrates reordering. There are perl
>scripts and Java applets readily available for the same on this site:
>- Nischal Piratla
> >===== Original Message From "S.Govind" <sgovind at hpc.serc.iisc.ernet.in> 
> =====
> >hi all
> >
> >
> >I have currently programmed the intel IXP 2400 Network Processor for IPv4
> >forwarding.
> >Iam able to support line rates up to 3 Gbps (without any QoS provisioning)
> >but an area of concern is the reordering, i obtain reordering up to 33%
> >(ie: 33 % packets are reordered )for a link with 4000 flows a second
> >each TCP flow of size 6.4 KB and 14% reordering for flow size of 640 B.
> >
> >The packets are assumed to be arriving at a constant interval of time and
> >of constant size (64 B ), this assumption is used for DoS attacks.
> >
> >I am novice in networking, i have a few queries regarding the above
> >results.
> >
> >Are these numbers (reordering) indicative of current OC 48 links,
> >
> >
> >Any comments and/or suggestions on the above  is most welcome
> >
> >Thanking You,
> >Govind
> >
> >
> >--
>Research Assistant
>Computer Networking Research Laboratory
>Department of Electrical and Computer Eng.
>1373, Colorado State University,
>Fort Collins, CO 80523 USA

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