the result by 2—and thus the data portion of the ATM cell contains 48 bytes.
Figure 8.1: The ATM cell.
The fixed size of the ATM cells provides some the following benefits:
Efficient bandwidth use of the physical medium
•
Ability of applications to share the network more fairly
•
Accommodation for bursty applications
•
Effective recovery of data loss on the physical wire
•
Note ATM is based on the switching and multiplexing techniques proposed by the ITU for Broadband
Integrated Services Digital Network (BISDN) access.
Time Division Multiplexing
ATM uses a switching and multiplexing method called Time Division Multiplexing (TDM). This method
places voice, multimedia, and data into fixed−length cells. These cells are then routed to their destination
without regard to content.
TDM combines the information from different resources onto a single serial trunk link that dedicates a
predefined timeslot on the multiplexed line for a piece of each resource’s data, as shown in Figure 8.2. If a
source has nothing to send, then the timeslot goes unused, and the bandwidth is considered wasted.
Figure 8.2: Data from multiple switch ports (resources) is sent down a single multiplexed serial link.
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