Subject: Re: Flow Label

From: Scott Bradner <[email-masked]>
Date: Wed, 2 Jan 2002 08:42:09 -0500 (EST)

Brian sez:
> In the intserv case, it is no different. In the diffserv case, the presumption
> is that we would use IANA-assigned, globally meaningful values, that are
> specific to a desired QOS treatment rather than to any individual traffic flow.
> The implementation details (including the DSCP value and router configurations)
> may differ from ISP to ISP, but the flow label bits convey end to end
> semantics. This is more powerful than port numbers whose semantics are poor at
> best for QOS purposes, and it works when the port numbers are invisible.

this still begs the question 
why do folk think that ISPs half way around the world would find it useful
to know what the sending computer wanted for QoS?  

at least in the case of difserv if an ISP gets a DSCP there is some
implied authorization by the previous network (ISP or enterprise) - how
does authorization happen in the case of imutable globally meaningful
values?

I see no reason to believe that such a field will be any use whatsoever
in providing QoS in the Internet - and it is redundant in an enterprise
because the enterprise can decide to not change the DSCP field

unless there is some hint of a way for this change to serve any useful
purpose we should just leave things as they are

Scott

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From: Brian E Carpenter <[email-masked]>
Date: Wed, 02 Jan 2002 15:39:18 +0100

> to know what the sending computer wanted for QoS?

s/computer/customer/

If A is a customer of ISP X in some distant country, there might be (and
I am only saying might be) an SLA in place that says "whenever you get
a packet from or to A, with 1234 in its flow label, give it such a level
of service."

I'm not saying that this is especially likely or plausible, but it
certainly isn't impossible.

> does authorization happen in the case of imutable globally meaningful

In both cases you need an SLA in place - with the upstream ISP, or with
the ultimate traffic source or destination. I agree that it certainly
doesn't happen because the ISP is a nice guy.

> because the enterprise can decide to not change the DSCP field

I bet I could construct an enterprise scenario where you could use it,
but you're basically correct, the only real use is when you jump over
intermediate ISPs and need a field that hasn't been changed en route.

> purpose we should just leave things as they are

No, I don't agree that we can leave the vagueness in 2460. IMNSHO we
should either accept the rewording we've hammered out (which carefully
doesn't say anything about QOS) or change it to MBZ. 

   Brian

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From: Keith Moore <[email-masked]>
Date: Wed, 02 Jan 2002 10:02:48 -0500

> to know what the sending computer wanted for QoS?

because the sending computer (application) knows the nature of the traffic?

Keith

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From: Randy Bush <[email-masked]>
Date: Wed, 02 Jan 2002 07:11:26 -0800

>> why do folk think that ISPs half way around the world would find it
>> useful to know what the sending computer wanted for QoS?

no need to signal.  we already know that they think their traffic is more
important than everybody else's.

randy

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From: Michael Thomas <[email-masked]>
Date: Wed, 2 Jan 2002 11:01:11 -0800 (PST)

> purpose we should just leave things as they are

   Since you can make the identical argument about
   5-tuple based classification, all you're saying
   here is that you don't believe in Intserv/RSVP. 
   Fine. There's a lot of people who disagree. With
   the current wording, a new flow spec for RSVP
   can be created ala RFC 2207 and we can all
   agree to disagree.

	    Mike