Specifications

31
Release Notes for Cisco IOS Release 12.0 S
78-7130-11 Rev. B0
New and Changed Information
Virtual Path Traffic Shaping
Platforms: Cisco 12000 series
Virtual path (VP) traffic shaping allows multiple virtual circuits (VCs) to be bundled into one VP. This
“bundling” is also called traffic shaping because all VCs bundled within the VP are shaped as one traffic
rate. In addition, bundling the VCs improves the error detection for the bundled VCs.
New Features in Cisco IOS Release 12.0(7)S
Many of the new features in Cisco IOS Release 12.0 S were originally introduced in other Cisco IOS
releases. For more complete information, refer to the original release.
ATM CLP Setting
Platforms: Cisco 7500/RSP series
The use of the Cell Loss Priority (CLP) bit in the ATM header of a cell provided a method of controlling
the discarding of cells in a congested ATM environment. A CLP bit contains two settings: 0 or 1. Cells
with a CLP bit setting of 1 are discarded before cells with a CLP bit setting of 0. Before the introduction
of the ATM CLP Setting feature, the CLP bit was automatically set to 0 when Cisco routers converted
packets into ATM cells for ATM networks.
The ATM CLP Setting feature allows users to control the CLP bit setting on routers running the PA-A3
port adapter. CLP bits are set on each packet individually, and the default CLP bit setting is 0. The
application of the ATM CLP feature changes the CLP bit setting to 1. Therefore, users have the option
of leaving each packet with the default CLP bit setting of 0 or establishing a new CLP bit setting of 1.
See the following document for further information:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120limit/120s/120s7/atm
clp.htm
Distributed Traffic Shaping
Platforms: Cisco 7500/RSP series
Many enterprise and service provider customers need to shape traffic in their networks and sometimes
need to shape IP traffic independently of the underlying interface. In other cases, the goal is to perform
traffic shaping to ensure adherence to committed information rates on Frame Relay links.
The dTS feature is one element used to manage the bandwidth of an interface to avoid congestion, meet
remote site requirements, and conform to a service rate that is provided on that interface.
The distributed Traffic Shaping (dTS) feature uses queues to buffer traffic surges that can congest a
network. Data is buffered and then sent into the network at a regulated rate, which ensures that traffic
will behave in accordance with the configured descriptor, as defined by committed information rate
(CIR) (mean rate), Bc (burst size), and Be (excess burst size). With the defined average bit rate and burst
size that are acceptable on that shaped entity, you can derive a time interval value.
The excess burst size (Be) allows more than the burst size to be sent during a time interval under certain
conditions. Therefore, dTS provides two types of shape commands: average and peak. When
shape average is configured, the interface sends no more than the burst size for each interval, achieving
an average rate no higher than the mean rate (CIR). When shape peak is configured, the interface sends
Bc plus Be bits in each interval.