Enterprise QoS Solution Reference Network Design Guide

WAN Edge Link-Specific QoS Design
3-38
description T1 ATM-IMA to Branch#60
pvc 0/100
vbr-nrt 1536 1536 ! ATM PVC defined under ATM IMA sub-int
max-reserved-bandwidth 100 ! Overrides the default 75% BW limit
service-policy output WAN-EDGE ! Attaches MQC policy to PVC
!
!
Verification commands:
show policy map
show policy-map interface
show atm pvc
show ima interface atm
High-Speed (Multiple T1/E1) ATM Links
Enterprise QoS Solution Reference Network Design Guide
Chapter 3 WAN Aggregator QoS Design
Recommendation: Use ATM IMA and add members to the IMA group, as needed.
Previous options for accommodating multiple T1/E1 links were software-based load-sharing solutions
(MLP bundling and IP CEF per-packet load sharing). As such, these methods require additional CPU
cycles to accommodate load-sharing multiple physical links. However, with ATM IMA, inverse
multiplexing over multiple T1/E1 links, illustrated in Figure 3-17, is done in hardware on the port
adaptor/network module. Therefore, ATM IMA scales much more efficiently.
Figure 3-17 High-Speed ATM Links
WAN Aggregator
ATM T1/E1 IMA Link
(Multiple Active Group Members)
ATM
Cloud
Branch Router
As mentioned, ATM IMA makes bandwidth expansion easy to manage. For example, all that is required
to add another T1 line to the previous example is to add an ima-group statement to the next ATM
interface and increase the PVC speed, as shown in Example 3-31.
Example 3-31 High-Speed (Multiple T1/E1 and Greater) ATM IMA QoS Design Example
!
interface ATM3/0
no ip address
no atm ilmi-keepalive
ima-group 0 ! ATM3/0 added to ATM IMA group 0
no scrambling-payload
!
interface ATM3/1
no ip address
no atm ilmi-keepalive
ima-group 0 ! ATM3/1 added to ATM IMA group 0
no scrambling-payload
!
…
!
interface ATM3/IMA0
no ip address
Version 3.3