<div>In our past experience packet reordering is seen most commonly at very small time scales; that is, packets that get sent back to back on a high-speed network are likely to be reordered, but with even a millisecond or so spacing between packets (such as if the packets originated on a 10BaseT net) the chance of reordering is far less. So thats why you usually never see them on LANs but is very common on a GigE WAN.<br>
</div><div><br></div><div>That said RFC 4737 is a good read to decide which metric of packet reordering that you want to focus upon.</div><div><br>>Is that a safe assumption? <br></div><div><br></div><div>I dont think so. The following paper clearly details the role of transmit buffer allocation in packet reordering.</div>
<div><br></div><div>S. Govind, R. Govindarajan and Joy Kuri Packet Reordering in Network Processors, Proceedings of the International Parallel and Distributed Processing<br> Symposium (IPDPS-07), CA, USA, 2007</div>
<div><br></div><div>Also this paper details why the assumption is not safe: </div><div><br></div><div>A. Bare, A. Jayasumana, N. Piratla, On Growth of Parallelism within Routers and Its Impact on Packet Reordering, Proceedings of the<br>
2007 15th IEEE Workshop on Local and Metropolitan Area Networks, , Princeton, NJ, 2007.<br></div><div><br></div><div>>Are there any other mechanisms in the routers/switches that could lead to packet reordering?<br>
</div><div><br></div><div>Link-Layer Retransmissions and Router Forwarding Lulls are also causes. Please see the following paper for details</div><div><br></div><div>K. Leung, Victor O.K. Li, Daiqin Yang, An Overview of Packet Reordering in Transmission Control Protocol; Problems, Solutions, and Challenges,<br>
IEEE Transactions on Parallel and Distributed Systems, Vol. 18. No. 4, 2007<br><br></div><div><br></div><div>Finally the following papers might be of interest to you as well<br></div><div><br></div><div>L. Gharai et al., Packet reordering, high speed networks and transport protocol performance, In Proceeding of the 13th ICCCN,<br>
Chicago, IL, October 2004<br><br>Yi Wang, Guohan Lu and Xing Li, "A Study of Internet Packet Reordering," in Proceedings of International Conference on Information<br> Networking (ICOIN), Lecture Notes in Computer Science 3090, Springer-Verlag, 2004<br>
<br>S. Jaiswal, et al., Measurement and Classification of Out-of-sequence Packets in Tier-1 IP Backbone, IEEE/ACM Transactions on<br> Networking, Vol. 15, No. 1, February 2007.<br><br>S. Kandula, D. Katabi, S. Sinha, A. Berger, Dynamic load balancing without packet reordering, ACM SIGCOMM Computer<br>
Communication Review, 37(2), April 2007<br><br></div><div class="gmail_quote">Hope this helps.</div><div class="gmail_quote"><br></div><div class="gmail_quote">-Paddy</div><div class="gmail_quote"><br></div><div class="gmail_quote">
On Wed, Aug 12, 2009 at 8:32 AM, Manish Jain <span dir="ltr"><<a href="mailto:jain.manish@gmail.com">jain.manish@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Thanks everyone for the useful pointers.<br>
<br>
Based on the some pointers and past discussions, I understand that<br>
routers in the current Internet have load-balancing implemented in a<br>
way to preserve packet order within a TCP flow. Is that a safe<br>
assumption? Are there any other mechanisms in the routers/switches<br>
that could lead to packet reordering?<br>
<br>
--<br>
<font color="#888888">Manish<br>
</font><div><div class="h5"><br>
On Wed, Aug 12, 2009 at 9:50 AM, Bartek Belter<<a href="mailto:bart@man.poznan.pl">bart@man.poznan.pl</a>> wrote:<br>
> Hi Manish,<br>
><br>
> Some time ago we did some experiments in the pan-European education network. The results of experiments were summarized in a paper.<br>
> It is available here: <a href="http://tnc2005.terena.org/core/getfile.php?file_id=626" target="_blank">http://tnc2005.terena.org/core/getfile.php?file_id=626</a> (Shall we worry about Packet Reordering?).<br>
><br>
> Hope it helps.<br>
><br>
> Best regards,<br>
> Bartek<br>
><br>
> -----Original Message-----<br>
> From: <a href="mailto:end2end-interest-bounces@postel.org">end2end-interest-bounces@postel.org</a> [mailto:<a href="mailto:end2end-interest-bounces@postel.org">end2end-interest-bounces@postel.org</a>] On Behalf Of Manish Jain<br>
> Sent: Tuesday, August 11, 2009 11:57 PM<br>
> To: <a href="mailto:end2end-interest@postel.org">end2end-interest@postel.org</a><br>
> Subject: [e2e] Packet reordering in Internet<br>
><br>
> Hello,<br>
><br>
> I was wondering if there are measurement studies of Internet traffic quantifying the magnitude of packet reordering within a TCP flow. Is reordering a common problem for TCP in the current Internet? How about the load balancing features in the routers from major vendors : is it per flow basis or per packet basis, and if flow based load balancing is done, then how is the flow classification is done these routers?<br>
> What could be/are other sources of reordering withing a TCP flow?<br>
><br>
> Thanks,<br>
> Manish<br>
><br>
><br>
><br>
<br>
</div></div></blockquote></div><br>