Switching to VoIP

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Chapter 2

CHAPTER 2

Voice over Data: Many

Conversations, One Network

Conversations are the basis of human communication. Conversations can be spo-

ken, written, or gestured. Conversations can even be one directional, such as a coach

bawling out his star quarterback after an uncharacteristic interception. Conversa-

tions may be “one-to-many” (such as a political candidate giving a stump speech) or

“many-to-one” (such as a constituency lobbying that candidate after she’s in office).

Conversations are more than just an analogy for networks—they literally are mod-

ern networking.

The underpinnings of enterprise networks are also conversations. IP data networks

run on protocols that use a conversational approach to data exchange. The most

common protocols for web browsing (HTTP) and email (SMTP) use a two-way

“data conversation” in order to communicate. The process is simple: a client host

sends an inquiry to a server host or a peer host, and then the server or peer sends a

response back to the client.

Conversations between hosts on an Internet Protocol (IP) network are similar to

those between people, except that instead of using words, the messages are commu-

nicated across the networks using units called datagrams. A datagram is like a letter

in an envelope. Once it has the proper markings, ...