ATM Connections 7-5
ATM Connection Requirements
Figure 7-2 ABR VSVD Flow Control Diagram
ForeSight Congestion Control
ForeSight may be used for congestion control across BPX/IGX/IPX switches for connections that
have one or both end points terminating on ASI-T3/E3 or BXM cards. The ForeSight feature is a
proprietary dynamic closed-loop, rate-based, congestion management feature that yields bandwidth
savings compared to non-ForeSight equipped trunks when transmitting bursty data across cell-based
networks. The BXM cards also support the VSVD congestion control mechanism as specified in the
ATM Traffic Management 4.0 standards.
ATM Connection Requirements
There are two connection addressing modes supported. The user may enter a unique VPI/VCI
address in which case the BPX switch functions as a virtual circuit switch. Or the user may enter
only a VPI address in which case all circuits are switched to the same destination port and the BPX
switch functions as a virtual path switch in this case. The full ATM address range for VPI and VCI
is supported.Virtual Path Connections are identified by an * in the VCI field. Virtual Circuit
Connections specify both the VPI and VCI fields.
The VPI and VCI fields have significance only to the local BPX switch, and are translated by tables
in the BPX switch to route the connection. Connections are automatically routed by the AutoRoute
feature once the connection endpoints are specified.
ATM connections can be added using either the Cisco StrataView Plus Connection Manager or a
node’s command line interface (CLI). Typically, the Cisco StrataView Plus Connection Manager is
the preferred method as it has an easy to use GUI interface. The CLI may be the method of choice
in some special cases or during initial node setup for local nodes.
Forward flow data cells
Forward RM cells
Backward RM cells
Source Destination
Node
NE
Node
NE
Node
NE
RM cell control loop for forward flow data
Only the flows for forward data cells and their associated RM cell
control loop are shown in this diagram. The flows for backward
flow data cells (destination to source) and their associated RM
cell control loop are just the opposite of that shown for the forward
flow data cells.
NE = Network element
S6156
