Subject: [NEXTEL-1] Making Push-to-Talk Look Easy

From: [email-masked]
Date: Mon, 03 Nov 2003 15:04:54 -0500

Making Push-to-Talk Look Easy
November 3, 2003 11:26am
Wireless Review

Messaging — not the instant kind most teenagers are familiar with, but
the kind that ping-pongs across a network carrying all the necessary
information about a call that can tell a brainless network who you are,
who you want to talk to and whether or not they want to talk to you —
can be an insufferably tedious but indispensable tool for
troubleshooting a network. For non-Nextel networks — those not built
from the ground up to do push-to-talk and that carry their signaling and
session control across separate paths from their traffic — messaging can
be 100 times as insufferable and just as indispensable.

That's how many more control messages are required to maintain a typical
push-to-talk (P2T) call in emerging networks. And when conferencing or
broadcast calling are involved — well, you can either break out the
Tylenol or break out the Agilent.

Brian Moody, software engineer for VoIP analysis applications at Agilent
Technologies, took on the task of building an analysis system capable of
corralling, correlating and analyzing the enormous number of messages in
this seemingly pregnant P2T technology. Last month, the company
introduced the fruits of his labor: a system the company says is the
first to monitor and manage wireless SIP-based push-to-talk services. It
is an extension of Agilent's NgN Analysis System, which is a
distributed, remote-controllable network monitoring system for
next-generation networks.

Moody came over from the insurance biz, having developed systems for
that data intensive industry as well as for imaging systems. “The
real-time aspect [of voice] is a fun challenge,” he said.
It also is critical — not just for Agilent itself to get out in front of
this market, but for the wireless industry overall, which will be
squabbling ad infinitum about what constitutes a quality P2T service.
Will it be the speed of the initial connection, or only subsequent
connections? Will it be ubiquity or consistency? Will SIP trump IDEN?
Ultimately the consumer will decide, but without a proper analysis
system to help operators build the best service possible, operators may
find themselves supporting a push-to-walk service.
Moody said operators recognize that to ensure the service level they are
communicating to their customers, they have to have a system in place.

“We believe we are the only ones who can give a networkwide view of the
signaling traffic from all the softswitches in a network,” he said.
“Your only other option is a standard protocol analyzer, but that is not
a coordinated effort and doesn't correlate messages from across the
network.”
Agilent already has its VoIP analysis tools in many Tier 1 networks. The
P2T extension is currently under trial with three operators, two of
which are in the U.S.

The NgN Analysis System is both a testing and analysis tool as well as
an OSS component. It correlates the SIP signaling messages from every
leg of a call into a single call record and applies performance metrics
to determine the service level of each call. It also stores historical
records on which it can do trend analysis to identify service
degradation and assist in troubleshooting, using Agilent's NetExpert
network management system.

So far, Agilent has been able to identify erroneous connectivity
statuses between servers and handsets when determining presence and
availability of the handset. And more often than not, it has been able
to point to the mundane issues of improper provisioning. But Agilent
also has been able to help equipment makers fix bugs in their software
logic.

“They sometimes make certain assumptions that just aren't accurate and
have not been factored into certain scenarios,” Moody said. One area
Agilent may have trouble with is the SIP protocol itself. While SIP has
been accepted by the 3GPP as the call control standard, implementations
tend to be anything but standard. Moody cited the core voice-call
feature, “intent-to-transfer,” as one example.
“That they haven't gotten around to standardizing that means vendors all
over the place have been implementing that however they see fit,” Moody
said. “That opens the door for all kinds of coroner case problems and
connectivity issues.”

Analysts agree. “People forget that while they may be using SIP, with
all the proprietary extensions, it is by no means standard.

And I would put push-to-talk in that same category,” said David Fraley,
principal analyst at Gartner Dataquest.

Fraley added that because of Agilent's size, it could add any P2T SIP
stack it needed in short order.
At the heart of SIP is the ability to communicate presence and
availability not only to the network but also to other users.
Dynamicsoft, the company whose chief scientist, Jonathan Rosenberg, is
largely responsible for developing the SIP protocol, said that the
“buddy list” concept (inherent to P2T) increases the call completion
rate by 40%.

However, at the heart of presence and availability is the abundance of
messaging required to communicate them. And initial call completion is
just the beginning.

“To work properly in push-to-talk, you need to know if the other person
is available. There is no reason for you to push the button if they are
not,” Moody said.

The challenge for Agilent and its customers is keeping track of presence
status and communicating that status in real time to the network and
those within the users' circles of friends. If presence information is
wrong or a handset doesn't respond when the network thinks it should,
both the user and the network complicate the problem by adding
unnecessary retransmissions.

“It creates a very complex call flow and if just one person isn't able
to talk when they think they should, that goes into the call center as a
complaint,” said Paul Capozzoli, [director] of marketing for Agilent.
November being the month that wireless number portability goes into
effect, mobile customers are likely to call into their carriers' call
centers less often than they used to. They'll simply jump ship — and
maybe take all their buddies with them.
http://www.hoovers.com/free/news/detail.xhtml?ArticleID=NR200311032500.2.11_eea6004b68317256

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