WAN Terminology Related to Packet Switching

You have already read about how both Frame Relay and ATM are considered to be packet-switching services but how, more often, Frame Relay is called a frame-switching service and ATM is called a cell-switching service. Table 4-9 lists the key terms about WANs, plus a few related terms and a brief explanation.

Table 4-9 Terms Describing Types of WAN Connections

Dedicated Circuit

Another Term for a Leased Point-to-Point Line

Packet switching

Service in which each DTE device connects to a telco using a single physical line, with the possibility of being able to forward traffic to all other sites. The telco switch makes the forwarding decision based on an address in the packet header.

Frame switching

In concept, it is identical to packet switching. However, when the protocols match OSI Layer 2 more than any other layer, it is called frame switching. Frame Relay is a frame-switching technology.

Cell switching

In concept, it is identical to packet switching. However, because ATM DTEs break frames into small, fixed-length cells, these services are also called cell switching. ATM is a cell-switching technology.

Circuit switching

A circuit is a point-to-point link between only two sites, much like a leased line. However, circuit switching refers to the process of dialing, setting up a circuit, and then hanging up—in other words, the circuit is switched on and off. Dialed lines using modems and ISDN, as covered in Chapter 15, are examples of circuit switching.

*Speeds rounded to commonly used values

*Speeds rounded to commonly used values

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