Subject: Re: [Fwd: Re: IPSP proposed text (1st approach)]]

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Fri, 2 Nov 2001 15:46:46 -0600

Dennis,

Dennis Niermann wrote:  (Fri, 02 Nov 2001 14:56:23)
> Hi Tolga,
> Here are my reasons for disagreeing with your conclusion that it
> is better to define the RC as representing a pair of AS's.
> 
> 1. It makes the definition of AS semantically different for the
> IPSP-IPSP case (a pair of AS's) versus the ASP-SGP case (where the
> RC must still represent a single AS because the AS is not paired
> up with another).

The definition of AS does not change.  An RC is used to identify a
forward routing key describing traffic towards an AS.  This does not
change.  At the originator, the RC is still obtained by applying the
forward RK to the message and obtaining the RC of the AS to which
is is being routed.  The ASP performs this function in the same way
as the SGP routes ougoing message.  There is no change.

> 2. It changes the semantics of the ASPAC request from its current
> meaning of "to tell a remote M3UA that this ASP is ready to
> process signalling traffic for a particular AS" to something else
> that I am not even sure makes any sense.

This is why the RC must represent the incoming AS as well so that
the receiver of the message can verify that the sending AS is
ACTIVE.  This does not change from the AS/SG case where the SGP
makes the same determination based on a single RC value. There is
no change.

> 3. It breaks the ability to use the registration messages and
> procedures in their current form since they depend on a RC value
> to be assigned to a single routing key (one AS).

Nothing breaks.  In a point to point network only a single routing
key is required.

> 4. I believe that it is much easier to manage and understand RCs
> assigned to AS's than to pairs of AS's. An RC per AS grows
> linearly with the number of AS's, whereas an RC per AS-AS pair
> grows exponentially.  It is true that for the simple case of a
> single AS serviced by a single IPSP that this is all a non-issue
> since in both the single ended and the double ended case you don't
> even need to use an RC, it is only interesting when you consider
> the more complicated cases.  Even though between any two pairs of
> AS's it is point-to-point.

For one point-to-point connection per association, there are no
RC values required.  You only need a lot of RC values if you are
trying to run a whole bunch of point to point connections over
the same association, but this is really not in fitting with the
concept of a point to point network.  In practice, there will
likely be one or more associations per point to point relationship.
Even SS7 has this (F-links).

> It is also true that a given IPSP is certainly going to have
> associations with many other IPSPs and/or SGPs. And, its AS(s) is
> going to be paired up with many other ASs.

If it has associations with many other IPSPs, there will be no
need for RC on the associations because the point-to-point traffic
will be implicit.

> 5. I think that it is a mistake to create specialized behavior and
> semantics for when communicating with another IPSP versus
> communicating with a SG.

This approach permits the ASP to be unaware of whether it is
communicating with an SG or another ASP.  You are write: double-
ended is so specialized that it requires the ASP to know it is in
IPSP mode to change to the double-ended procedure.  Single-ended
relieves this obligation from the ASP and is the simpler approach.

--brian

> 
>    Dennis
> 
> 
> 
> 
> 
> 
> [email-masked] wrote:
> > 
> > Hi,
> > 
> > Because of the point-to-point nature of IPSP communciation, it seems to me
> > now more logical to identify every AS pair with a unique RC. ASs are
> > corresponding to endnodes of the communication. As the name implies, in
> > point-to-point communication messages are sent and received between two
> > points. This can be achieved only by identifying both of the endpoints for
> > a message, if over a single association traffic of more than one AS pairs
> > is transferred (if the whole traffic belongs only to one AS pair, then it
> > is implied by the association itself)
> > 
> > As pointed out by Dennis, similar result can be achieved by putting two RCs
> > in DATA (one for source AS one for destination AS) but personally I find
> > single ended approach more elegant from this point of view.
> > 
> >     Tolga
> 
> [snip]
> 
> 
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-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/

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