This allowed the operators to make investments in their packet networks
without having to expand the capabilities of the voice switches in the network.
Wireline operators have followed this path as well, deploying IP in their backbone
transport networks, and moving bearer traffic over these transport networks. This is
the first step toward an all-IP network.
This is where the VoIP elements come into play. In order to support the IP backbone,
there needs to be conversion of traditional voice to packetized voice. This is the job performed
by media gateways, under the control of media gateway controllers.
VoIP networks were developed to convert voice transmission from its traditional
analog format into a digital packet format that could be transported over the new IP
backbone. However, there is more to this than simply converting the voice to packet
formats. Voice transmission is not tolerant of delays. If there is a delay in the delivery
of the voice packets, conversation becomes intolerable.
This is the challenge faced by many VoIP providers. While many have solved the
latency and QoS problems for peer-to-peer calls, there is still work to be done for calls
that begin in one network and are transported to IP networks.
VoIP introduced many other challenges as well, but this is outside the scope of this
book, so I won??™t go into those details.
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