Subject: Re: [Sip] Comments on Resource Priority Header

From: [email-masked]
Date: Mon, 4 Mar 2002 13:10:43 EST

In a message dated 3/1/02 8:32:10 PM Eastern Standard Time, 
[email-masked] writes:

>  
>  Somebody (you?) argued that ignoring the value should not be the same as
>  having the lowest priority value. 
>  
We don't have a lot of choice. It has to state what will happen to a call 
attempt if the priority value is not understood. A statement that it is 
treated as the lowest known value is about all that could be done. I don't 
see the value in defining a "default" other than the lowest.
>  > 
>  
>  Frankly, I don't see this as a problem in practice. Almost all of these
>  namespaces will be inherited from some existing scheme, so the
>  likelihood that somebody suddenly adds a value is pretty low.
>  
I guess if the current version of "resource priority" prevents adding 
priority values, it would only mean that, if a network wanted to add a new 
value, there would need to be a revision to the RFC to tell IANA that it was 
allowed. You're right - not too significant of a problem.
Mike

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---

From: Henning Schulzrinne <[email-masked]>
Date: Mon, 04 Mar 2002 20:22:48 -0500

> see the value in defining a "default" other than the lowest.

There are two choices:

(1) If there's an unknown value, simply ignore the Resource-Priority
header. (Any unknown namespace will have to cause the RP header to be
ignored.)

(2) Treat unknown values as the lowest priority.

The two are the same if and only if "no RP header = well-defined RP
value". I tend to think that that's a good general choice. I
intentionally say "well-defined", since it may not be the lowest value.
One could imagine a system where you can define a priority lower than a
normal, unadorned call. As a contrived example, imagine a gas meter
reader call, like the one my house gets around 10 pm each night, that
would label itself as "left-over". (As I mentioned, there is something
like that for IP QoS called scavenger service, or
worse-than-best-effort, which scrounges up the bandwidth crumbs left
over by BE traffic. Used for huge file transfers in Internet2.)

From what I can tell, no such systems exist today, so this may be
academic.

---

From: "James M. Polk" <[email-masked]>
Date: Mon, 04 Mar 2002 21:35:49 -0600

>intentionally say "well-defined", since it may not be the lowest value.

I believe #2 above is more appropriate as it gives to local policy within a
domain, and prevents the case where the RP header might be required or the
packet(s) *do* get dropped for not complying with some local rule stating
something like "every session packet must have RP included, if it doesn't, it
wasn't authorized in the first place -- action: delete it"

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