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 Configuration
Available Bit Rate Connections
The ABR (available bit rate) category utilizes a congestion flow control mechanism to control
congestion during busy periods and to take advantage of available bandwidth during less busy periods.
The congestion flow control mechanism provides feedback to control the connections flow rate through
the network in response to network bandwidth availability.
The ABR service is not restricted by bounding delay or delay variation and is not intended to support
real-time connections. ABR is characterized by PCR and MCR.
The term ABR is used to specify one of the following:
•
ABR standard without VS/VD (This is ABR standard without congestion flow control.)
– Supported by BXM cards.
•
ABR standard with VS/VD. (This is ABR standard with congestion flow control as specified by the
ATM Traffic Management, Version 4.0)
– Also, referred to as ABR.1
–
Supported only by BXM cards
–
Feature must be ordered
•
ABR with ForeSight congestion control
– Also, referred to as ABR.FST.
–
Supported by BXM cards
– Feature must be ordered
Policing for ABR connections is the same as for VBR connections which are summarized in Table 21-12.
The ABR connections are configured as either ABR Standard (ABRSTD) connections or as ABR
ForeSight (ABRFST) connections.
The parameters for an ABRSTD connection are shown in Figure 21-8 in the sequence in which they
occur during the execution of the
addcon command.
The ABRSTD connection supports all the features of ATM Standards Traffic Management 4.0 including
VS/VD congestion flow control.
VS/VD and flow control with external segments are shown in Figure 21-9.