3Com SuperStack II PathBuilder S330 Reference Manual page 265

CBR Module
Each PVC represents the logical circuit being used to connect one PathBuilder
S330/S310 port to a remote PathBuilder S330/S310 port. Once you have entered
all PVCs, the bridge will learn the network addresses for the local and remote sites
and start bridging packets to the correct destination by segmenting the packets
into cells which are destined to a remote PathBuilder S330/S310 port. See
Figure 184. The ATM network will transport the cells according to the VPI/VCI
headers.
Figure 185 shows three PathBuilder S330 switches configured to provide LAN
connectivity between three different LAN segments. Each Ethernet port will run
Bridging (Learning) programs to determine if received LAN packets should be
passed to the WAN on a specific PVC. In the above example, multi-port bridging
software will determine if packets will be passed or dropped. When a packet
comes in from LAN 1 port and the bridge code does not have the destination
MAC address associated with one of its logical ports (Ethernet, PVC #1, PVC #2), it
will broadcast the packet on all PVCs associated with this port.
Once packets are received from the WAN on specific PVC logical ports, their
source addresses will be learned and associated with the logical port. Once you
and your carrier have set up PVCs to all remote PathBuilder S330/S310 Ethernet
ports, the bridging code will do the rest.
Figure 185 LAN Connectivity
Bridge
Forward Known
Table
DS3 UNI 1
LAN
1
Broadcast
Unknown
PathBuilder
S330/S310 #1
The optional T1-DSX/E1 CBR module provides three T1-DSX or E1 ports (one on
the PathBuilder S310 switch) and one serial port. This module services traffic
generated by your existing PBXs, channels, T1/E1 multiplexers, CSU/DSUs, and
video conferencing devices. This service maps the T1-DSX/E1 service through the
AAL1 adaptation layer over a CBR virtual channel connection (VCC). The VCC is
established as a permanent virtual circuit (PVC) and mapped from the ATM port on
the PathBuilder S330/S310 switch to another PathBuilder S330/S310 switch or to
an ATM Forum circuit emulation compliant device.
ATM
Switched
Network
Port P1
Circuits Set Up by the Carrier
PVC END1 VPI/VCI1 End2
#1 P1 0/200 P2
#2 P1 0/250 P3
#3 P2 0/250 P3
CBR Module
PathBuilder
S330/S310 #2
DS3 UNI 2
Port P2
Port P3
DS3 UNI 3
VPI/VCI2
0/100
0/100
0/200
PathBuilder
S330/S310 #3
257
LAN
2
LAN
3