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09_200023_CH08/Batesx 1/17/01 8:20 AM Page 199

High-Speed Applications 199

across our networks. A lot of discussion entered the market regard-
ing the use of IP over various data networking protocols and differ-
ent layers of the OSI model.
IP will run anywhere that we want it. The issue is not whether it
can be done, but whether we want to do it? Sales and marketing peo-
ple with a personal stake in selling specific products entered the
foray with a statement that Asynchronous Transfer Mode (ATM) was
too expensive to use for IP datagrams (packets).Therefore, data com-
munications manufacturers developed a marketing strategy to han-
dle IP over SONET (POS) instead of ATM. At the time, the entire
industry was leaning toward IP over ATM. Soon everyone was
expounding the benefits of running IP over SONET.Therefore, enter
a new group of people who began to espouse the benefits of running
IP over dense-wave-division multiplexing (DWDM) without the use
of ATM or SONET.
A number of alternative approaches were developed to address
the limitations of traditional SONET in multiservice access net-
works. These alternatives include IP over ATM over SONET, IP over
SONET (packet on SONET), and IP over DWDM. The protocol
stacks for these three approaches are shown in Figure 8-12.

Services Services Services
Figure 8-12
Various
approaches to
carrying IP
IP

ATM IP
SONET SONET IP

Optical Optical Optical

ATM Packet over IP over Fiber
Transport SONET