Subject: Re: [Sip] Why not ISUP?

From: "Paul Long" <[email-masked]>
Date: Thu, 6 Sep 2001 20:46:40 -0500

I think the main cause is that we have moved complexity from the core of the
network out to its edge--from centralized complexity, e.g., in switches, to
distributed complexity, e.g., in UAs--thus increasing the size/complexity of
the channels between all entities and probably the overall complexity of the
system, even without the added complexity due to new capabilities. Here's
another way to think about it, protocol-wise. If the PSTN is ordering a
combo meal at McDonalds, XoIP is cooking at home. Freedom has a price.

Paul Long
ipDialog, Inc.

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From: Nathan Nelson <[email-masked]>
Date: Thu, 6 Sep 2001 23:34:04 -0400

Why not ISUP.  Like all good things ISUPs time is limited, ISUP was designed
to move voice calls efficiently in a closed network. If SIP is half as
successful as ISUP it will be very impressive.  The reality is this.  SIP
supports an economically disruptive network model that allows a service
provider to provide not only the features supported by ISUP but does it with
less network, more cost effective hard ware platforms and through cheaper
and fast access methods.  SIP is an enabling protocol that will allow
consumers to take advantages of product offerings from ASPs while having
service from whom ever.

SIP is not a prefect protocol but it is very flexible.  The thing that
allows SIP to be as successful has it has been in such a short time is its
ability to adapt quickly to needs of either ASP or Service Providers to meet
new customer demands.  

ISUP is a traditionally ridge protocol that has limit capacity to adapt to
changes.  Each time a new feature is added it takes 18 months of debate, 18
months of development, and then you get Calling Name Delivered.  If it does
not work in SIP send an email and next month you have an RFC.  If people
like it they develop to it, if not next month you have a new RFC.  This
ability to move quickly allows products to be designed, coded, tested and
deployed in the time it use to take us to determine which spare bit in a
ASN1 model that could be used to perform the required operation.     

Thx,
Nate Nelson

-----Original Message-----
From: P Villa [mailto:[email-masked]]
Sent: Thursday, September 06, 2001 10:51 AM
To: [email-masked]
Subject: [Sip] Why not ISUP?

Hello,

I have a question for the people on this list:

Why does SIP continue to get so complex in order to provide the same basic 
telephony services that other telephony protocols developed long ago?

I'm studying the SIP protocol in school and ran across this list, so I 
figured I'd ask. It doesn't seem obvious to me what the real answer is.

P

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