[e2e] packet reordering in OC 48 links

Nischal Piratla nischal at lamar.colostate.edu
Sun May 15 15:37:20 PDT 2005

Thank you for the pointer. 
However, I am still concerned about a couple of things:
1. Will we be able to continue the handling of the order of packets in 
routers, with the known trends of network speeds?
2. As you mentioned in your posting earlier:
Will we still see reordering with multiple interfaces on NPUs?

- Nischal

>===== Original Message From cannara at attglobal.net =====
>The problem has been solved by some network-processor vendors for a few years
>now.  For example, see the specs for the IQ2200 by Vitesse, that's been used
>to handle 4 parallel, FDX 1Gb/s ports in equipment by various manufacturers,
>including Cisco.
>Nischal Piratla wrote:
>> Govind,
>> We feel that it is quite reasonable to see such high amounts of reordering. 
>> fact, we are working on this very problem.
>> Most of the reordering that occurs within the routers is countered by 
>> 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 
>> 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:
>> http://lamar.colostate.edu/~nischal/Papers/Networking2005_RD.pdf
>> Also, to understand the amount and extent of reordering, we suggest 
>> Density' metric that comprehensively illustrates reordering. There are perl
>> scripts and Java applets readily available for the same on this site:
>> http://www.cnrl.colostate.edu/packet_reorder.html
>> - 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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