|
Guest Column
Voice over Packet Protocols
VoIP and VoATM (VoAAL1, VoAAL2)
By
Michel Laurence, CEO,
Doug Morrissey, VP and Chief Technology Officer,
and Nigel Harney, Senior Product Manager
Octasic
25-August-2003
Fueled by the growth of the Internet, data traffic is increasing across telecom networks at a much faster rate than voice traffic. Indeed, it is estimated that by 2010 voice bits will represent only about 1% of the overall network traffic. Based on this estimate, economic and operational forces alone will mandate that all voice networks and traffic eventually be overlaid or transported over data (packet) networks.
Today, for good reasons, several
VoP protocols such as VoIP and VoATM co-exist. These protocols
will continue to co-exist for many years to come, due to the
fact that each protocol has unique strengths and weaknesses in
resolving challenges presented by the conversion of legacy
telephony systems. The fact that the underpinning protocol of
the Internet is IP will, however, give it an irresistible
momentum over time. Therefore, VoIP should eventually
dominate the Voice over Packet scene.
Given the existing legacy TDM
telephony network, it’s important to understand some key
technical issues and challenges associated with the conversion
of legacy digital public telephony systems to packet telephony
and how the most popular current Voice over Packet (VoP)
protocols resolve those challenges or are affected by them. A particularly important issue is voice handling and
transport itself – what are often called the bearer
services. These
include voice encoding and delays, which are
interrelated and create at the same time both opportunities
and challenges.
Voice Encoding and Delay
There are numerous technical
issues and challenges arising from the transition of telephony
voice services from legacy TDM networks to packet networks. Voice encoding and transmission
delays are the two issues and challenges addressed here,
and are related to the most basic voice bearer services. Other
issues and challenges, such as Timing
Recovery and Synchronization, Signaling, and Quality of
Service, are not directly related to the bearer services
and are not covered in this article.
Next
page >> Page 1 of
4
|
