Subject: RE: [NSIS] Re: qos-nslp-00

From: "Hancock, Robert" <[email-masked]>
Date: Wed, 24 Sep 2003 12:59:16 +0100

hi all,

a specific comment:

> - section 3. messages
> *couldn't the four messages used be simplified to two? It 
> seems to me that
> a Notify or a Response purpose could be served by a Reserve.
> * also, this section overlaps a bit with 2., in the sense that the
> reservation setup, queries, notifications and so on are exemplified
> here...perhaps these two sections should be re-written...
> 
> Regards,
> Rute

you wouldn't believe the amount of discussion there was about
this sort of thing. in the end, some of the message distinctions
can get slightly blurred, but I'm very keen to keep a clear 
border around 'RESERVE' because that message has a number of
unique properties:
*) processing it is supposed to change signalling application state
*) therefore in particular authorisation for a RESERVE matters more
than for most other messages
*) also, RESERVEs need to have lifetimes associated (whereas no
other message does) to represent the lifetime of the state
*) you only care about the latest in sequence you have received
*) probably some other differences too.

in formally analysing protocol behaviour - especially a protocol
which is at least partly a container protocol (for qspecs and
policy objects and so on, whose details are deliberately not
constrained) - I think it's very important to have conceptual
distinctions between different message types laid down like this.

(you could also ask if these distinctions should be encoded in 
message types or object types. for near term activities i prefer
the former, but it's a good question.)

cheers,

r.

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