Re: [re-ECN] RE-ECN without ECN.

[Fred Baker <[e-mail]>]

On Oct 1, 2009, at 9:36 AM, Matt Mathis wrote:

> If you add the assumption that the network itself does not reorder
> packets, then the number of out-of-order packets is a direct measure
> of the upstream congestion.  (e.g. the first transmission was lost,
> and I see the retransmission).

The assumption concerns me. There are probably places in the Internet  
where loss is unusual and reordering is unusual, but making it a  
baseline assumption... The Internet is still a best effort service,  
which is to say that datagrams may be lost, duplicated, or reordered.

I personally am very much in favor of congestion signaling that  
doesn't involve loss, and supported the development of RFC 3168 as a  
result. I scratch my head on re-ecn - not opposed per se, but noting  
that there are issues with any traffic in which the flags may not be  
visible - tunnels especially come to mind - and in asking the first  
hop router to do something. What is a "first hop router"? Is it the  
CPE router, such as Linksys-etc, or the first ISP hop, or something  
else?