[e2e] packet reordering in OC 48 links

Nischal Piratla nischal at lamar.colostate.edu
Sun May 15 13:42:41 PDT 2005

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
>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
>Are these numbers (reordering) indicative of current OC 48 links,
>Any comments and/or suggestions on the above  is most welcome
>Thanking You,

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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