Page 208 - Optical Switching And Networking Handbook

09_200023_CH08/Batesx 1/17/01 8:20 AM Page 193

High-Speed Applications 193

Point-to-Multipoint

The next step is to consider the point-to-multipoint arrangement.
This will use a form of add-drop multiplexing to drop circuits off
along the way. In a large corporate network spanning the country (or
any subset), a single high-speed link may be employed. The SONET
add-drop multiplexer (ADM) is used for the task at hand, dropping
circuits out without demultiplexing the entire high-speed signal.
Figure 8-6 shows an ADM installed between two far-end locations so
that signals can be added or dropped off as necessary. This is a bet-
ter solution than renting three different circuits between points AB,
AC, and BC, which adds to the complexity and cost. By using a cir-
cuit from A to B to C with ADMs, the service usually can be accom-
modated more efficiently.

Hub-and-Spoke

The hub-and-spoke method (sometimes referred to as a star net-
work) enables some added flexibility in case of unpredicted growth or
constant changes in the architecture of the network. A SONET/SDH

Figure 8-6
Chicago
ADMs installed
along the way of a insert 2 DS1 east
insert 2 DS1 west
multipoint circuit OC-1
drop off
4 DS1s Boston

Phoenix
drop off
OC-1
6 DS1,
LA add 6 DS1 east
terminate 22 DS1
originate 22 DS1