| Video over IP
applications have soared in popularity over the
last five years. Companies have increased their
video conferencing usage as a means to reduce
travel expenses, speed up the lead time needed
to hold critical meetings, and offer investors
access to high level board meetings. Traditional
phone service providers are rushing to provide
video services as a way of locking in customers
and increasing revenues. Cable TV operators have
been steadily upgrading their analog systems to
offer consumers enhanced digital services. All
of these applications focus on delivering digital
video content over data services. As these video
services evolve from luxuries and novelties to
commodities and everyday expectations, video IP
equipment vendors and service providers are scrambling
to establish themselves as the dominant players
in this maturing industry.

IP video applications have struggled with two
main challenges for high quality video experience:
the ability to deliver the high bandwidth at an
acceptable price and overcoming the imperfect
world of IP networks. Relatively inexpensive DSL
and cable modem services have helped to solve
some of the high bandwidth issues, but typically
the achieved bandwidth is much lower than the
published access data rate. New techniques lower
the bandwidth requirements needed for quality
transmission and compression methods are two ways
currently being developed to address the bandwidth
issue.
In addition to high bandwidth, high quality video
must overcome the imperfect world of IP networks.
There is another very important factor that must
be designed for: The imperfect world of IP networks.
Network impairments are expected in IP communications.
Network delays, dropped packets, traffic congestion,
reordered packets, fragmented packets, and duplicated
packets are all facts of life in IP communications.
Many higher level protocols such as TCP are designed
with error correction mechanisms to ensure that
data is moved nearly error free from point to
point. TCP dictates that endpoints resend packets
when errors are encountered, and application delays
may incur because of this, but most likely the
correct information will eventually be delivered
and the application can operate as it should.
Video streaming and other real time IP applications
can't afford the overhead time associated with
error correction protocols, and typically rely
on UDP protocols. VoIP also uses UDP protocols,
and is subject to similar network impairment problems.
Although it can be an annoying experience to use
VoIP service with poor quality, humans can negotiate
their own 'error correction'. "Sorry, I didn't
hear that last statement. Could you repeat that?"
IP video does not have the luxury of higher level
or human intervention error correction. It is
subject to the most demanding endpoint of all;
the human eye and human visual experience.
If uncorrected, dropped packets can cause 'skips'
in the experienced video. Variable network delays
(jitter) can cause the video to appear 'jerky'
and 'jumpy'. Data errors can significantly delay
video quality. The onus now lays on the IP video
equipment vendors to design recovery algorithms
that can operate in this environment to reassemble
packets into a satisfactory video experience for
the end user.
PacketStorm Communications manufactures the equipment
needed to test IP video applications and equipment:
Repeatable network impairment control:
The PacketStorm network emulators provide precise
control and repeatability of the various conditions
that will be encountered in WAN and LAN data communications
networks. Development engineers and QA personal
can now have a controlled emulated infrastructure
to develop and test IP video signal recovery mechanisms,
thus ensuring that their equipment will provide
a positive experience for the end users. Service
providers can also emulate their networks to gauge
acceptable limits for error conditions and then
set network alarm thresholds based on these values.
Configuring QoS setting and internal
routing equipment configuration:
The PacketStorm systems provide adjustable QoS
capabilities and emulate router queuing algorithms
that can provide valuable information for dictating
procedures that mandate how internal routing devices
should be configured.
Determining the required bandwidth needed:
PacketStorm network emulators offer the capability
to throttle the available connection bandwidth
so that it is possible to determine the minimum
required rates for acceptable video transmissions
for various compression algorithms. |