Subject: Re: [Sip] Communications Resource Priority Header

From: [email-masked]
Date: Fri, 9 Nov 2001 14:57:01 EST

In a message dated 11/9/01 1:27:55 PM Eastern Standard Time, 
[email-masked] writes:

> [email-masked] wrote:
>  >  
>  > 2. To allow greater flexibility, we should define the values in the CRP
>  > header without referencing the actual English words used for the 
specific 5
>  > levels (for MLPP). Other applications may use more levels and would 
certainly
>  > call them something else. Note that other IETF work efforts on "Priority"
>  > have suggested 16 or 65k numeric values. Within a network or domain, the
>  > association between numeric values and the meaning in that network could 
be
>  > defined by local practices. It is assumed that there is no need to 
compare
>  > values between different networks or domains (just like MLPP does not 
include
>  > preemption of calls in other "domains".)
>  
>  Having different name spaces in the same header doesn't seem wise to me.
>  Either the name space needs to be labeled (CRP: 16 ;domain="foo.com") or
>  it should be the same. Messages always "leak" between domains, which
>  would make things confusing.
>  
>  Just like message encoding, I find textual labels less error-prone, so
>  the basic 791 set should, in my opinion, have names, not numbers.
> 
 
I agree, having mulitiple name spaces is not wise. I think what I was 
suggesting would not actually cause that.

I understand the need to either label the name space or have them be equal. I 
was not suggesting that a "Domain" identity be carried to label the name 
space. But given the wide variety of requirements, I don't see how one single 
set could be defined to cover all, especially considering that an order (for 
each application) must be defined. It would be sufficient to define values 
as: LEVEL00, LEVEL01, LEVEL02, ... LEVEL 255 if you must utilize textual 
labels, with an explicit ordering. Within each application, some of these 
would be associated with specific uses, like:
    LEVEL00 CRITIC/ECP
    LEVEL01 Flash Override
    LEVEL02 Flash
    LEVEL03 Immediate
    LEVEL04 Priority
    LEVEL05 Routine
    LEVEL06 - LEVEL 255 Not used

As far as calls "leaking" from other domains, it should not be important how 
their values are compared with the set above. Other steps should be taken to 
prevent or detect "leaks" even without these priorrities being the issue. If 
"leaks" are a real problem, then there is a much bigger issue than how one 
interpets the priority header.

Yes, it would be a problem if messages "leaked" between domains. The "Domain" 
concept was added to MLPP in the circuit switched world because of some 
concern that phone calls could "leak" between domains, and some wanted 
assurance that calls in one Domain could not preempt calls in another domain. 
Guess they didn't care if normal calls from one domain were erroneoulsy 
carried in another domain and prevented calls in it from ever being setup, 
just whether they were disrupted after being setup.

Mike Pierce

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