User guide

Release Notes for Cisco 2500 Series for Cisco IOS Release 12.0 T 17

New Software Features in Release 12.0(3)T

The DLSw+ RSVP feature permits new DLSw+ peer connections to automatically request

bandwidth reservations upon connection, thereby removing the need for user intervention after the

peer is connected. This feature assures the reservation will survive a network or device failure and

that the DLSw+ trafﬁc carried over a TCP connection is not affected by congestion.

Fancy Queuing on Frame Relay for Cisco HDLC

In previous releases, when the voice-encap option was conﬁgured on Frame Relay or Cisco HDLC,

all fancy queuing (such as weighted fair queuing, custom queuing, and priority queuing) on the

interface was disabled, and queuing was handled on a ﬁrst-come ﬁrst-served (FCFS) basis. In this

release, new enhancements have been made to support fancy queuing on Frame Relay and Cisco

HDLC.

For Frame Relay, a new interface command, frag-pre-queuing, has been added that allows you to

set the queuing to be performed after the data segmentation. The command is available for Frame

Relay interfaces only. The syntax for this new command is the following:

frag-pre-queuing

no frag-pre-queuing

By default, this command is enabled, which allows only FCFS queuing at the interface level. If you

enter no frag-pre-queuing, you can conﬁgure weighted fair queuing, custom queuing, or priority

queuing at the interface level. Note that if you enter no frag-pre-queuing, you still must explicitly

conﬁgure the fancy queuing type on the interface.

For HDLC encapsulation, the queuing now takes place after segmentation when the voice-encap

option is entered. Weighted fair queuing, custom queuing, and priority queuing are now supported

on an interface conﬁgured for Cisco HDLC.

Flow-based WRED

This feature provides a mechanism to penalize the ﬂows that do not respond to Weighted Random

Early Detection (WRED) drops. This feature is provided as an extension to the existing WRED

functionality and can be turned on after WRED is turned on.

Flow-WRED ensures that no single ﬂow can hog all the buffer resources at the output interface

queue. With WRED alone, this can occur in the presence of trafﬁc sources that do not back off during

congestion. Flow-WRED maintains minimal information about the buffer occupancy per ﬂow.

Whenever a ﬂow exceeds it's share of the output interface buffer resource the packets of the ﬂow are

penalized by increasing the probability of their drop (by WRED).

IP to ATM CoS with VC Bundle Management

This feature comprises the second phase of the IP to ATM Class of Service (CoS) feature made

available with Release 11.1(22)CC. IP to ATM CoS with VC Bundle Management carries forward

support for all commands and functionality provided by the ﬁrst released phase of the feature,

extending that support to operation on the Cisco 7200 series routers and enhancing it to include

support for ATM VC bundle management.

ATM VC Bundle Management allows you to conﬁgure multiple permanent virtual circuits (PVCs)

that have different quality of service (QoS) characteristics between any pair of ATM-connected

routers. These VCs are grouped together in a bundle and are referred to as bundle members.

You deﬁne an ATM VC bundle and add VCs to it. Each VC of a bundle has its own ATM trafﬁc class

and ATM trafﬁc parameters.You can apply attributes and characteristics to discrete VC bundle

members or you can apply them collectively at the bundle level.