Document ID: 10484
Contents
Introduction
Prerequisites
Requirements
Components Used
Conventions
Supported Versions
Configure
Sample Configuration
show and debug Commands
Related Information
Introduction
This document provides a sample configuration for IP to ATM Class of Service (CoS) features on the PA-A3-8T1/E1IMA port adapter. These features include class-based weighted fair queueing (CBWFQ), low latency queueing (LLQ), weighted random early detection (WRED), and virtual circuit (VC) bundling.
Prerequisites
Requirements
Ensure that you understand IP to ATM CoS. Refer to these resources for information on these features:
Components Used
The information in this document is based on a PA-A3 in a 7200 Series Router that runs Cisco IOS® Software Release 12.1(5)T1.
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
Conventions
Refer to Cisco Technical Tips Conventions for more information on document conventions.
Supported Versions
These Cisco IOS Software Releases introduce support for IP to ATM CoS on the IMA port adapter:
|
Platform |
12.0S |
12.1T |
12.1E |
|---|---|---|---|
|
7200 Series |
Not supported |
12.0(7)XE, 12.1(5)T |
Not supported |
|
7500 Series |
Not supported |
12.1(12c)E (CSCdu89722) |
As of Cisco IOS Software Releases 12.1(5)T, 12.1(5)E and 12.0(14)S, only VIP-based or distributed per-VC queueing is supported on the 7500 Series. RSP-based QoS is no longer supported. The configuration of a service policy with distributed LLQ (dLLQ) in a Cisco IOS image without dLLQ support leads to VIP crashes (CSCdt78618).
Configure
In this section, you are presented with the information to configure the features described in this document.
Note: Use the Command Lookup Tool (registered customers only) to find more information on the commands used in this document.
Sample Configuration
This document uses a sample configuration created with a PA-A3 in a 7200 Series Router that runs Cisco IOS Software Release 12.1(5)T1. The IMA group consists of three physical T1 links, and the vbr-nrt PVC is configured with a peak cell rate and sustained cell rate of 4 Mbps.
Our traffic generator sent two types of traffic, one that emulates voice and the other "disturbing" data to congest the VC hardware or driver-level first-in-first-out (FIFO) queue. By virtue of LLQ, the voice traffic received the expected priority.
When you configure LLQ for voice traffic, ensure that you decrease the size of the hardware FIFO queue, known as the transmit ring, with the tx-ring-limit command. Otherwise, the voice traffic can experience excessive latency. Normally, a TX-ring-limit value of three or four is fine. In this sample configuration, voice latency averaged 7ms, compared to 3ms in the absence of competing traffic.
|
LLQ on a PA-A3-8T1IMA |
|---|
class-map match-all rtp
match ip rtp 5000 10000
!
policy-map llq
class rtp
priority 1000
!
interface ATM3/0
no ip address
ima-group 0
!
interface ATM3/ima0
no ip address
no atm ilmi-keepalive
!
interface ATM3/ima0.34 point-to-point
ip address 5.0.34.3 255.255.255.0
pvc 0/34
tx-ring-limit 3
vbr-nrt 4000 4000
service-policy output llq
!
interface ATM3/1
no ip address
ima-group 0
!
interface ATM3/2
no ip address
ima-group 0 |
Note: All commands entered in VC configuration mode take effect only when you exit for this mode. This exit causes the VC to be removed and recreated with the new configuration parameters, which can include QoS policies, shaping rates, etc. If you wish to remove a QoS service policy, you must enter exit or CTRL-Z to ensure that the no form of the command actually takes effect.
show and debug Commands
The Output Interpreter Tool (registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.
-
show queueing int atm and show queue int atm—Display the flows inside the queue. These commands only apply to the 7200 Series. Enable NetFlow in order to display flow information on the 7500 Series.
-
show policy-map—Displays any configured queueing strategies.
-
show policy-map interface—Displays the queueing statistics of an interface or a VC. Refer to Understanding Packet Counters in show policy-map interface Output for guidance on how to interpret the output from this command.
r3#show policy-map interface atm3/ima0.34
ATM3/ima0.34: VC 0/34 -
Service-policy output: llq (1089)
Class-map: rtp (match-all) (1091/2)
2242843 packets, 435111542 bytes
! -- Number of packets matching the criteria of the class.
30 second offered rate 775000 bps, drop rate 0 bps
Match: ip rtp 5000 10000 (1095)
Weighted Fair Queueing
Strict Priority
Output Queue: Conversation 136
Bandwidth 1000 (kbps) Burst 25000 (Bytes)
(pkts matched/bytes matched) 2016845/391267930
! -- Number of packets matching the class during periods
! -- of congestion, when the interface's transmit ring was full.
(total drops/bytes drops) 0/0
Class-map: class-default (match-any) (1099/0)
3987455 packets, 6028018316 bytes
30 second offered rate 8051000 bps, drop rate 0 bps
Match: any (1103)
Related Information
| Updated: Nov 13, 2006 | Document ID: 10484 |