Cisco BPX 8650, Installation And Configuration Manual

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Cisco BPX 8600 Series Installation and Configuration
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
Chapter 21 Configuring ATM Connections
ATM Connection Requirements
A source generates forward RM cells which are turned around by the destination and returned to the
source as backward RM-cells. These backward RM-cells may carry feedback information from the
network elements and/or the destination back to the source.
The parameter Nrm is defined as the maximum number of cells a source may send for each forward RM
cell, that is, one RM cell must be sent for every Nrm-1 data cells. Also, in the absence of Nrm-1 data
cells, as an upper bound on the time between forward RM cells for an active source, an RM cell must be
sent at least once every Trm msecs.
BXM Connections
The BXM-T3/E3, BXM-155, and BXM-622 cards support ATM Traffic Management 4.0.
The BXM cards are designed to support all the following service classes:
•
Constant Bit Rate (CBR)
• Real time Variable Bit Rate (rt-VBR)
•
Nonreal time Variable Bit Rate (nrt-VBR)
•
Available Bit Rate (ABR with VS/VD
•
ABR without VS/VD, and ABR using ForeSight)
• Unspecified Bit Rate (UBR)
ABR with VS/VD supports explicit rate marking and Congestion Indication (CI) control.
ForeSight Congestion Control
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.
ForeSight may be used for congestion control across BPX and IGX switches for connections that have
one or both end points terminating on BXM cards. The BXM cards also support the VS/VD congestion
control mechanism as specified in the ATM Traffic Management 4.0 standards.
ATM Connection Requirements
Two connection addressing modes are supported:
•
You may enter a unique VPI/VCI address in which case the BPX switch functions as a virtual circuit
switch.
•
You 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 Automatic Routing
Management feature once the connection endpoints are specified.