Subject: [Sigtran] Comments on draft-ietf-sigtran-signalling-over-sctp-applic-04.txt

From: Tom George <[email-masked]>
Date: Thu, 07 Mar 2002 14:43:39 -0600

These comments were sent to me by one of my colleagues down the hall. 

tomG.

-------- Original Message --------

My first concern is 3.1 - Congestion Control. I would point
out that the internals of the STP and the management / engineering
of the IP network are 2 different things. The internals of the
system are our concern, we have to be able to receive and send
IP messages with the same accuracy as we do with MTP 2 and ATM/T1.
Receive congestion is handled at the receiving proc, transmit
congestion is handled MTP 3. Much of how this is engineered is
independent of the IP network. In fact our customers want us
to remove the system engineering so that they can engineer the
SS7 traffic in their network without having to worry about
component engineering in the STP.

On the other hand, our design and implementation should not be
engineered around a narrow view of the customer network. We need
to have our product operate correctly under a variety of network
conditions while still providing reliable service. Therefore, I
don't understand how an SCTP congestion control implementation
should be expected to know what applications are using the IP
transport. Nor do I understand how to anticipate variations
in congestion based on how well the IP network is managed.

A second thing I have concerns over is section 3.2.1 Retransmission
TimeOut (RTO) calculation. How can the SS7 network, which expects
GTT look-ups are supposed to deliver a response to the requester
500 millisecond, wait for more than 1000 milliseconds to get an ack
on one leg of the communication path?

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