3Com CoreBuilder 9000, Руководство пользователя

Страница: 338 / 468

338 C
HAPTER
12: E-IISP P
ROTOCOL
Each of the fields RD and AREA is two bytes long and a byte is
represented by two hexadecimal digits 0-F so that fields RD and AREA
together are represented by eight hexadecimal digits. These eight digits
represent the location of a device in the network tree hierarchy. The
device is assigned an ATM address with these digits set according to its
position in the hierarchy.
The system works as follows: The left digit
—
the first digit in the RD field
—
represents the top level of the network hierarchy. This digit is assigned
to those switches that are connected as roots in the network, for
example, A, B, and C in Figure 11. The ATM address of these switches has
A, B, or C as the first digit in the RD field and the remaining seven digits
are zero. (Putting “*” as the second digit has the same effect
—
it marks
the end of the significant digits.)
The second digit identifies all switches that are attached to the root
switches where the first digit is retained in the address to point to the
root switch, for example, A1 and A2 in Figure 11. The digit A points to
the root A, and the digits 1 and 2 denote the second-level switches that
are attached to the root A. Note that because a hexadecimal digit can
range from 0 to F, each switch can have up to 15 second level switches
emanating from it. These digits are used in the ATM address that is
assigned to these switches.
The third digit identifies switches that are attached to the second-level
switches in a similar fashion and similarly up to the eighth digit.
Using eight digits with values from 0 through F allows a tree structure of
up to eight levels, where each node can have 15 branches.
Configuring Network
ATM Addresses
After the addressing scheme is established, you use either the Integrated
Fast Setup procedure or specific LMA commands (see “Update Network
Prefix” on page 150) to register the network prefixes at each CoreBuilder
9000 ATM Enterprise Switch. See the
CoreBuilder 9000 ATM Switch
Fabric Module Getting Started Guide for a detailed description of the
Integrated Fast Setup procedure.