Re: [Dclc] Agenda topics

[Weixinpeng <[e-mail]>]

Hi all,
Thanks for your comments.
Let me give some more detailed clarification on this issue.
You are right that the initial purpose of draft-wei-tsvwg-tunnel-congestion-feedback is to solve network congestion,
ECN is used in the tunnel, ECN marks are used as an indication of congestion status of routers' buffers, and the document
tries to provide a solution to feed back this indication to tunnel ingress for the ingress to implement congestion control.

We assume latency mainly caused by queue length in the network.
For congestion control, the packets are marked when the buffer is filled to a specific threshold; but for latency control, we can
mark packets in another way: the packets are marked according to queue's length, which means as queue grows the number of marked
packets grows, as queue decreases the number of marked packets decreases. So we can collect the number of marked packets to learn about
information of queue length status and to do latency control at tunnel ingress based on this information.

About IPFIX, I am not sure whether it is suitable in DC, we can see it just as a possible method for information feedback, and there could be
other candidates. So I suggest currently we don't focus on this aspect.

Regards,
-Xinpeng

>-----Original Message-----
>From: Bob Briscoe [mailto:[e-mail]]
>Sent: Tuesday, October 28, 2014 6:33 AM
>To: Fred Baker (fred)
>Cc: Eggert, Lars; Weixinpeng; dclc
>Subject: Re: [Dclc] Agenda topics
>
>Fred, Lars,
>
>This is the same technique, but applied to a data centre by implementing the
>tunnel endpoints in the hypervisors:
><https://tools.ietf.org/html/draft-briscoe-conex-data-centre-02>
>
>It's the one I had prepared a presentation for in the last dclc mtg, but I gave
>up the slot so we had longer to discuss the direction of the group.
><http://www.bobbriscoe.net/presents/1407ietf/1407dc-congestion-policing.
>pdf>
>(I'd be happy to present it this time - perhaps in conjunction with Xinpeng if
>you establish that it will be relevant to data centres)
>
>
>And, to respond to Toby's IPR point, back in 2005 BT declared its IPR related to
>this, and updated the declaration in 2012, including royalty-free terms under
>the conditions specified here:
><https://datatracker.ietf.org/ipr/1922/>
>
>
>
>Bob
>
>At 15:39 27/10/2014, Fred Baker (fred) wrote:
>>Content-Language: en-US
>>Content-Type: multipart/signed;
>>
>boundary="Apple-Mail=_44D5A9BE-946A-4C98-96DA-75F726FDCBE8";
>>         protocol="application/pgp-signature"; micalg=pgp-sha1
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>>
>>On Oct 27, 2014, at 2:09 AM, Eggert, Lars <[e-mail]> wrote:
>>
>> > Hi Xinpeng,
>> >
>> > On 2014-10-27, at 09:21, Weixinpeng <[e-mail]> wrote:
>> >> It will be appreciated if there is a timeslot for me to show our
>> work on tunnel-based congestion control.
>> >> The following is a link to the document.
>> >>
>> http://datatracker.ietf.org/doc/draft-wei-tsvwg-tunnel-congestion-feed
>> back/
>> >
>> > could you outline how this draft is related to latency control in
>> datacenters? I read an earlier version and it seemed to be all about
>> wide area networks?
>> >
>> > Thanks,
>> > Lars
>>
>>I'm scratching my head as well. Lingli is a co-author, so maybe she can
>>comment here.
>>
>>The draft does mention NFV, which can be implemented across multiple
>>data centers connected by a WAN, but if primarily implemented within a
>>data center, and specifically mentions data centers. It also mentioned
>>latency in passing, in the third paragraph of the section on 3GPP.
>>
>>Where I'm scratching my head is figuring out what it's actually trying
>>to say. It explains NFV and that tunnels might be implemented in a
>>vSwitch, which is true, and often the case in architectures such as
>>OpenStack. It doesn't seem to make obvious points about that such as
>>are made in RFC 2983: when the tunnel is marked as having experienced
>>congestion, that information needs to be reflected in the interior
>>header at the tunnel endpoint. It talks quite a bit about IPFIX. I'm
>>not sure I walked away with "so do this".
>>
>>
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>
>____________________________________________________________
>____
>Bob Briscoe,                                                  BT