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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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RTP<br />

R<strong>TCP</strong><br />

audio<br />

G.711, G.723.1, etc.<br />

RSVP<br />

Figure 20-4 H.323 protocol stack<br />

20.6 Summary of Vo<strong>IP</strong> protocols<br />

An <strong>IP</strong> telephony environment consists of a number of individual protocols. These<br />

protocols interoperate in a hierarchical fashion to provide the required services.<br />

The protocol interaction can be represented as a stack, similar to the method<br />

used to represent many other communications systems.<br />

One way to depict the stack is to divide the protocols into two functional sections,<br />

which are illustrated in Figure 20-5 on page 743. The two sections of the protocol<br />

stack provide the following functions:<br />

► Transport <strong>and</strong> quality protocols<br />

These protocols are used to transport the voice traffic.<br />

► Signaling <strong>and</strong> support protocols<br />

The majority of <strong>IP</strong> telephony activities have been devoted to developing<br />

signaling protocols.<br />

742 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong><br />

H.225<br />

Call Control<br />

system control <strong>and</strong><br />

user interface<br />

H.225<br />

RAS Control<br />

Transport Layer (SCTP, UDP or <strong>TCP</strong>)<br />

Network Layer (<strong>IP</strong>)<br />

Data Link Layer<br />

Physical Layer<br />

H.245<br />

Conference Control

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