Re: [re-ECN] Two questions about CONEX

>For example (and only for example) if they were embedded in the transport protocol itself they would go where ever the transport went.

True. But let's follow this example all the way through. The congestion signal would need to be defined for every transport protocol, right? And how do you account for UDP, since UDP doesn't have any unused/option bits? At a minimum, the congestion signal would need to be defined for RTP/RTCP, SNMP, and proprietary protocols such as uTP.

Are you implying that congestion control and monitoring in the network will require deep packet inspection by network elements? Sorry, I do NOT want to be the one carrying *that* message to the network neutrality crowd...

-- Rich

________________________________

From: Stewart Bryant [mailto:stbryant@cisco.com]
Sent: Sat 5/8/2010 1:32 PM
To: Woundy, Richard
Cc: re-ecn@ietf.org
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: re-ecn-bounces@ietf.org on behalf of Stewart Bryant
> Sent: Sat 5/8/2010 2:24 AM
> To: re-ecn@ietf.org
> 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
>
>
>
>
>
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>   

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