Re: [re-ECN] Two questions about CONEX

"Woundy, Richard" <> Mon, 10 May 2010 12:27 UTC

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Date: Mon, 10 May 2010 08:23:21 -0400
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Thread-Topic: [re-ECN] Two questions about CONEX
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From: "Woundy, Richard" <>
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Subject: Re: [re-ECN] Two questions about CONEX
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If folks in general (not just the IESG) think there are a lot of alternatives to Conex, maybe the ADs should form a design team that uses a real-time form of communication to talk this through? I'm thinking any combination of f2f meeting, conference call, or Webex to start...
-- Rich


From: Stewart Bryant []
Sent: Sat 5/8/2010 1:32 PM
To: Woundy, Richard
Subject: Re: [re-ECN] Two questions about CONEX

On 08/05/2010 14:40, Woundy, Richard wrote:
> So a couple of questions back to you.
> 1. I gave the 'CMTS congestion management' as a representative example. But what if I need similar measurements/mechanisms at my backbone interconnects? (That's probably the second place I would need to worry about congestion.) Can these OAM messages make it there?
That would depend on how they are carried. For example (and only for
example) if they were embedded in the transport protocol itself they
would go where ever the transport went.

2. A typical subscriber host is behind one (or more) Ethernet/WiFi home gateways, then behind a broadband modem that may or may not use Ethernet as a layer two transport over the broadband access network. So are we talking about a layer 2 or 3 OAM message? If layer 3, how would a host behind a NAT know who to address it to? (I don't personally like NAT66 but that may be the subscriber's choice rather than mine.) If layer 2, how do I get the subscriber to upgrade all of their home CPE? Plus how many layer 2 technologies need to define this OAM message? Or do we need to define a new home network layer 2 (please no)?

See above.
> 3. What if the OAM message needs to be originated by the application/content server side, rather than the subscriber side? How would that server know which CMTS / interconnect router to send it to?
See above.
> -- Rich
> P.S. The long time constant in the CMTS congestion management feedback loop is dependent on the state of the art today (DOCSIS specs require 15 minute IPDR polling cycle support for the CMTS). In some ways this is a bug, in some ways this is a feature. :)
I agree, but I was not thinking of 15mins, on the other hand I was not
thinking of packet rate which is where I believe current thinking is.

- Stewart

> ________________________________
> From: on behalf of Stewart Bryant
> Sent: Sat 5/8/2010 2:24 AM
> To:
> Subject: [re-ECN] Two questions about CONEX
> As I was reading the recent email on CONEX I got the impression that a
> lot of the interest in CONEX is to instrument the network so that
> operators can identify the root causes of congestion and understand the
> impact on the network in more detail.
>    I also get the impression that at least some of the operators are
> looking for a relatively long time constant in the feedback loop.
> That causes me to wonder where CONEX fits in relative to IPFIX which is
> a mechanism that is designed to monitor the flows in a network and
> report this information to the network operator.
> As I noted in a earlier thread, I am also interested in understanding
> why the host needs to use the data packets themselves to indicate the
> expected congestion state to the network rather than using a fate
> sharing OAM mechanism?
> - Stewart
> _______________________________________________
> re-ECN mailing list

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