Information Technology Reference
In-Depth Information
Foundation Topics
Multiservice Networks
This section discusses several concepts related to the support of multiservice networks, which
are networks that run integrated voice, video, and data traffic. This section covers the following
written exam blueprint topics:
•
H.323
•
Codecs
•
SS7
•
RTP
•
RTP Control Protocol (RTCP)
•
Session initiation protocol (SIP)
Packet Voice
With the converging data and voice networks, the introduction of packet-voice technology
provides the ability for companies to save toll charges on voice telephone calls. Voice is
digitized (coded) into packets, cells, or frames; sent as data throughout the networks, and
converted back to analog voice. Coding for this is covered in the Codecs section.
An example of packetized voice is when calls are placed on phones that are attached to routers,
as shown in Figure 12-1. The routers digitize the voice and then forward calls on the wide-area
network (WAN) links. If the router determines that bandwidth is not available on the data net-
work, the call can be forwarded over the public switched telephone network (PSTN). Calls
placed outside the company's intranet are forwarded to the PSTN.
With Voice over IP (VoIP) technology, voice is digitized (coded) into IP packets. A dial plan
is created to list the IP destinations of VoIP phones and outbound phones. When a number is
dialed on phones attached to a router, it looks at the digits and routes the calls to the appropriate
destination. Phones are attached to Foreign Exchange Station (FXS) ports.
For example, in Figure 12-1, if a call to 8-1234 is placed from phone 6-1234, Router A forwards
the packets with voice data to Router B. Router B converts the digitized voice into analog
signals out its voice interface to phone 8-1234.
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