[e2e] Packet reordering in Internet

rick jones perfgeek at mac.com
Wed Aug 12 18:06:42 PDT 2009

On Aug 12, 2009, at 8:32 AM, Manish Jain wrote:

> Thanks everyone for the useful pointers.
> Based on the some pointers and past discussions, I understand that
> routers in the current Internet have load-balancing implemented in a
> way to preserve packet order within a TCP flow. Is that a safe
> assumption? Are there any other mechanisms in the routers/switches
> that could lead to packet reordering?

Define "safe." Correct more than 1/2 the time?  More than 3/4? 7/8? 99  
times out of 10?-)

If the "router" is made from "Linux" the Linux bonding (aka load  
balancing, aggregation, teaming, trunking, call-it-what-you-will)  
software does offer a "round-robin" option that will spread packets of  
the same flow across multiple links and will indeed lead to reordering.

rick jones

> --
> Manish
> On Wed, Aug 12, 2009 at 9:50 AM, Bartek Belter<bart at man.poznan.pl>  
> wrote:
>> Hi Manish,
>> Some time ago we did some experiments in the pan-European education  
>> network. The results of experiments were summarized in a paper.
>> It is available here: http://tnc2005.terena.org/core/getfile.php?file_id=626 
>>  (Shall we worry about Packet Reordering?).
>> Hope it helps.
>> Best regards,
>> Bartek
>> -----Original Message-----
>> From: end2end-interest-bounces at postel.org [mailto:end2end-interest-bounces at postel.org 
>> ] On Behalf Of Manish Jain
>> Sent: Tuesday, August 11, 2009 11:57 PM
>> To: end2end-interest at postel.org
>> Subject: [e2e] Packet reordering in Internet
>> Hello,
>> 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?
>> What could be/are other sources of reordering withing a TCP flow?
>> Thanks,
>> Manish

there is no rest for the wicked, yet the virtuous have no pillows

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