North American Network Operators Group
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Re: packet reordering at exchange points

  • From: Iljitsch van Beijnum
  • Date: Mon Apr 08 18:35:51 2002 
On Mon, 8 Apr 2002, Paul Vixie wrote:

> > packet reordering at MAE East was extremely common a few years ago. Does
> > anyone have information whether this is still happening?

> more to the point, does anybody still care about packet reordering at
> exchange points?  we (paix) go through significant effort to prevent it,
> and interswitch trunking with round robin would be a lot easier.  are
> we chasing an urban legend here, or would reordering still cause pain?

Obviously some applications care. In addition to the examples mentioned
earlier: out of order packets aren't really good for TCP header
compression, so they will slow down data transfers over slow links.

But how is packet reordering on two parallell gigabit interfaces ever
going to translate into reordered packets for individual streams? Packets
for streams that are subject to header compression or for voice over IP or
even Mbone are nearly always transmitted at relatively large intervals, so
they can't travel down parallell paths simultaneously.