Signaling - External Links - 3Com CoreBuilder 9000 User Manual

354 C 13: E
HAPTER STABLISHING
Signaling —
External Links
Transmitting Station
ATM Edge Device
To initiate a virtual
channel a SETUP
command
containing the
requirements for
the call, except for
VPI/VCI,
by the edge
device.
The ATM switch
accepts or rejects
the proposed call
requirements
The VPI/VCI
values are fixed by
the ATM switch
and returned to the
edge device.
ATM C
HANNELS
This section describes establishing a switched virtual channel by signaling.
As discussed previously, a virtual channel is made up of two types of links:


External links (connections) between ports of adjacent ATM devices


Internal links between input and output ports of an ATM device stored
in the ATM Enterprise Switch matrix.
These two types of links are established in two different ways. The
external links are established by signaling; the internal links are
established by routing. Figure 17 illustrates the establishing of a virtual
channel. External links 2 and 4 are established by signaling; internal link 3
is established by routing.
Figure 17 Establishing a Virtual Channel
ATM Switch
VPI=0
VCI=32
The ATM Switch
is sent
selects the best output
port according to the
routing algorithm.
The port and VPI/VCI
information is stored in
the switch matrix.
A SETUP command
containing all
requirements for the
call is sent by the
output port of the
switch.
ATM Edge Device
VPI=1
VCI=44
The edge device
accepts or rejects
the proposed call
requirements.
If accepted, the
VPI/VCI values
are fixed for this
connection.
Destination Station