Message-Id: <200103011553.KAA12005@guns.lerc.nasa.gov> From: Mark Allman <mallman@grc.nasa.gov> Subject: Re: out of order packets Date: Thu, 01 Mar 2001 10:53:11 -0500
> My second question is again about out-of-order packets. I have a
> dedicated network where two computers are connected using a hub
> where one connection is wireless. Is it possible to get out of
> order packets in this scenario?
Probably unlikely.
> I am getting lots of out-of-order packets from my experiments
> using Tcptrace. In INTERNET it is common to have out of order
> packets since packets are routed through different routers.
Actually, the following paper argues that reordering in the Internet
is mostly caused by load balancing.
J. Bennett, C. Partridge, N. Shectman. Packet Reordering is Not
Patalogical Network Behavior, IEEE/ACM Transactions on
Networking, December 1999.
But, anyway...
> But how can this happen on a dedicated network? Is it because of
> bit errors in the wireless medium that forces corrupted packets to
> spend more time in data link layer employing FEC whereas
> uncorrupte packets are processed quicker and passed on the
> transport layer?
Where are you observing the traffic? If your vantage point is the
receiver retransmits will look out-of-order.
Being completely accurate about measuring out-of-order packets
really requires traces from both the sender and receiver side and a
tool that will compare the order the packets were sent and the order
in which they were received. My hit is that when you have a
receiver trace, tcptrace accuratly measures reordering in a global
sense. But, probably overestimates the amount of reordering caused
by the network itself (due to being fooled by retransmits).
allman
--- Mark Allman -- BBN/NASA GRC -- http://roland.grc.nasa.gov/~mallman/ ---------------------------------------------------------------------------- To unsubscribe, send a message with body containing "unsubscribe tcptrace" to majordomo@tcptrace.org.
This archive was generated by hypermail 2b30 : 03/01/01 EST