Re: Re-charter?

Closely related to the question "what is a session" is the question"what is
pre-emption?"  In the circuit switched world, a connection is "nailed up"
and there is little confusion on what constitutes a "session" or
"pre-emption".

But in the IP world, even if we restrict our discussion to SIP related
sessions, it is not so clear. Once a session has been established, how many
packets need to be dropped, how bad does the "quality" need to get, before
we declare that the  session has "failed" or been "pre-empted"?

Looking at it from another perspective, If traffic engineering indicates
that a given (IP) interface or route can accept 100 simultaneous calls with
a given QoS, but there is a mechanism to allow "special" calls to be
accepted (without actually tearing down existing calls) above that
threshold, at what point do I declare that the "special" calls are
pre-empting "regular calls"? As soon as I exceed the engineered
capacity(typically a utilization less than 100%)?  Once I exceed the raw
capacity (even though all calls may continue to meet the specified QoS)?
When a single call drops below its QoS specification? For how long?

And so on.

While the CONCEPT of "pre-emption based" vs. "non-pre-emption based"
carries over from the circuit switched world, and is useful in the IP world
(especially when IP networks are operating under rules and regulations
developed for the circuit switched world), the specific definition do not
carry over with any intrinsic clarity.

If we are going to go down this path, I think the first step is to agree on
a consistent set of definitions.

Janet


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                      Henning                                                                                               
                      Schulzrinne <hgs         To:      "King, Kimberly S." <[email protected]>                      
                      @cs.columbia.edu         cc:      "Jon Peterson \([email protected]\)"                         
                      >                        <[email protected]>, [email protected], "Ieprep \([email protected]\)"    
                      Sent by:                 <[email protected]>                                                            
                      ieprep-bounces           Subject: Re: [Ieprep] Re-charter?                                            
                                                                                                                            
                                                                                                                            
                      06/30/2005 10:48                                                                                      
                      AM                                                                                                    
                                                                                                                            




Brief remark: I'm not sure what "sessions" refers to in the snippet
below. Is this addressed to the application layer session (say, SIP), a
network layer session (RSVP, NSIS) or something else entirely?

In general, given the tortuous history of IEPREP discussions, more
specificity as to the types of mechanisms and protocols affected would
be helpful, in my opinion. Are there existing drafts that will be used
as baseline (or input) or this is a from-scratch effort?

King, Kimberly S. wrote:

> 3. Some countries require civil networks to preempt sessions
> under state circumstances, and preemption is considered an
> absolute requirement in governmental networks in most
> countries. Unless implementation of these requirements can
> be objectively shown to threaten network health (via
> simulation or in operations), then the requirement needs to
> be considered by IEPREP and specific solutions must be
> developed.
>

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