Hi, in the IETF transport area there are discussions on DSCP interconnection between networks. It's quite common that operators clear (bleach) the DSCP codepoints when receiving packets from other operators, turning everything into BE (best effort) traffic. Historically CS1 has been proposed as less-than-best-effort (for instance bittorrent traffic), but my opinion is that this is ill suited as I think it's not incrementally deployable. Some networks might use CS1 as something that has higher priority and it would be hard for them to change this incrementally. I have proposed a DSCP codepoint that I believe is incrementally deployable and that is 000010, which I think is deployable because it maps to CS0, PRECEDENCE 0, so any kind of equipment that today takes these bits and imposes it into 802.1p, MPLS TC (former EXP) etc, will just map this to regular BE. If explicitly configured, one can match on 000010 and put this in a different queue, for instance that doesn't have much bandwidth guarantees at all. Since this proposal just comes from my personal experience with equipment in the MPLS/L2/IP world, I'd like to hear wider view/opinion on this and I'll bring it to the TSVWG at the upcoming IETF in Prague July 20-25. It would be great if there could be an operational document as well, giving recommendations on how to configure the above, and it would be great if it could be done with lots of operator input into the matter. ---------- Forwarded message ---------- Date: Thu, 2 Jul 2015 00:32:40 +0000 From: "Black, David" <david.black@emc.com> To: "Ruediger.Geib@telekom.de" <Ruediger.Geib@telekom.de>, "swmike@swm.pp.se" <swmike@swm.pp.se> Cc: "tsvwg@ietf.org" <tsvwg@ietf.org> Subject: RE: [tsvwg] draft diffserv-intercon: Handling of a scavenger class / CS1 <WG chair hat OFF>

- work on a scavenger class standard needs to be done in a separate draft.

And here's what that draft might encompass ... Beyond that, I'd support a (hopefully short) draft that - updates RFC 3662 to change the recommended DSCP for the LE PHB from CS1 to 000010, - recognizes and allows for continued use of CS1 where deployed, and - updates other RFCs (e.g., 4592, 5127) accordingly as needed. As Brian pointed out, this would need to be a standards track draft with a downref to RFC 3662 in order to allocate that DSCP. Writing the draft is straightforward by comparison to figuring out whether this is what we should do, as indicated by the other messages in this thread on operator/operational considerations. This item is on the draft tsvwg agenda for Prague as a discussion topic - I plan to bring slides and only write the -00 draft after I've survived that discussion ;-). </WG chair hat OFF> Thanks, --David

-----Original Message----- From: tsvwg [mailto:tsvwg-bounces@ietf.org] On Behalf Of Ruediger.Geib@telekom.de Sent: Monday, June 29, 2015 4:51 AM To: swmike@swm.pp.se Cc: tsvwg@ietf.org Subject: Re: [tsvwg] draft diffserv-intercon: Handling of a scavenger class / CS1

Hi Mikael,

ok, understood, I'm relaxed.

The relation of Diffserv intercon to scavenger is

- if there is a scavenger class, how should Diffserv intercon handle it (will add text about a 000 xx0 DSCP)? Otherwise Diffserv Intercon says, bleaching may occur for any unexpected DSCP.

- work on a scavenger class standard needs to be done in a separate draft. That's WG consensus and Gorry Fairhurst said during the last meeting: "Scavenger support document been discussed before, if there is renewed interest, then we should take it up again. As an individual contributor, I would be interested. If you are also interested in this topic, please talk to the WG chairs."

- operational issues may be relevant for a bleaching discussion. A bleaching standard is out of scope of Diffserv Intercon (thats WG consensus). I think to recall interest in work on bleaching by others too.

Then I'm happy to meet you in Prague.

Regards,

Ruediger

-----Ursprüngliche Nachricht----- Von: Mikael Abrahamsson [mailto:swmike@swm.pp.se] Gesendet: Montag, 29. Juni 2015 09:38 An: Geib, Rüdiger Cc: tsvwg@ietf.org Betreff: Re: AW: AW: AW: [tsvwg] draft diffserv-intercon: Handling of a scavenger class / CS1

On Mon, 29 Jun 2015, Ruediger.Geib@telekom.de wrote:

...

I repeat that I've talked with my RIPE/NANOG colleagues to get feedback - they came back only with one or two names with whom to discuss QoS interconnection. And I never got any useful response (positive or negative) from those.

This is the problem, that's not how to do this, the way to do this is to announce an idea on the nanog mailing list and see who might be interested.

As far as I read your document, it has nothing in it about how to incrementally get an Internet-wide scavenger class operationally deployed over time. To me it reads more like a document for business VPN Carriers-Carrier services style interconnect/interworking. It has no operational advice at all in it on how to deal with DDoS, how to configure access equipment, how to set up queuing strategies on different kinds of equipment, listing what equipment might do what, etc.

I suggested how to actually make this incrementally and widely deployable across the world, and that is to aim for a 000xxx style scavenger class. This seems to not work for some reason that is unclear to me, your document doesn't seem to be operational at all, it doesn't propose something that is operationally deployable on the wider Internet, so that's why I think we would need another document for this purpose. If that is not a goal we can agree on, then there is no need to write one.

So just to sum up: I'm sure your document is fine for what it intends to do, it just doesn't answer any of the concerns an IP network engineer/architect might have about implementing this on an Internet peering link where there is little or no control over what traffic will pass or what this traffic might do to the rest of their network. It suggests a way to do something with no operational analysis or risk mitigation at all.

The first thing that will pop into any good IP architects head nowadays will be "oh, what happens to my network when I get 200 gigabits/s of 64 byte packets marked EF from that 5 million strong DDoS-drone network all across the world, aimed for my customer base?"

The answer to that is "I'll bleach DSCP it because that's the only way to handle it". So in order to get a scavenger class actually deployable, you have to come up with something that means they can relax the bleaching a little bit by some operators, but their infrastructure would still treat the traffic the same. You also have to take into account that a lot of core IP network equipment can't do DSCP mapping very well. This kind of functionality makes equipment more expensive and thus less likely to exist widely.

-- Mikael Abrahamsson email: swmike@swm.pp.se