Cisco Cisco IP Contact Center Release 4.6.2 Leaflet

over a given time period, thereby smoothing network usage. The 802.1p capability, a LAN QoS handling 
mechanism, allows high-priority packets to enter the network ahead of low-priority packets in a 
congested Layer-2 network segment.

Cisco recommends not implementing Microsoft Packet Scheduler for Unified ICM 7.x unless bandwidth 
requirements are clearly understood and correctly configured and unless the convergent network link is 
occasionally congested and shaping Unified ICM traffic at the source can be helpful.

While using the Microsoft Packet Scheduler does provide shaping and 802.1p features, the following 
significant risks exist when using this option with Unified ICM 7.x:

Multiple defects have been submitted to Microsoft. Currently, some fixes are have been released by 
Microsoft, but some have not.

If the shaping bandwidth is configured too low, the Packet Scheduler might introduce excessive 
delay and as a result it might cause timed-out calls, queue overflows, and buffer exhaustion.

Shaping at the Unified ICM server might be neither necessary nor helpful given that the LAN is 
rarely the bottleneck of communications over the WAN and that a QoS-enabled network is more 
capable of shaping, queuing, and policing traffic based on the resource usage.

There are several disadvantages to marking traffic in Unified ICM. First, it is hard to make changes. For 
instance, if you want to change the marking values for the public network traffic, you have to make 
changes on all the PGs. For a system with more than 30 PGs, for example, all those changes would 
require quite a lot of work. Second, QoS trust has to be enabled on access-layer routers and switches, 
which could open the network to malicious packets with inflated marking levels.

In contrast, marking traffic at the network edge allows for centralized and secured marking policy 
management, and there is no need to enable trust on access-layer devices. A little overhead is needed to 
define access lists to recognize Unified ICM packets. For access-list definition criteria on edge routers 
or switches, see 

, 

, and 

. Do not use port numbers in the access lists for 

recognizing Unified ICM traffic (although they are provided in the tables for reference purposes) 
because port numbers make the access lists extremely complex and you would have to modify the access 
lists every time a new customer instance is added to the system.

A typical Unified ICM deployment has three IP addresses configured on each NIC, and the Unified ICM 
application uses two of them. For remote monitoring using PCAnywhere or VNC, because the port 
numbers are not used in the access lists, the third IP address should be used to prevent the remote 
monitoring traffic from being marked as the real Unified ICM traffic.

The default Unified ICM QoS markings are set in compliance with Cisco Unified Communications 
recommendations but can be overwritten if necessary. 

, 

default markings, latency requirement, IP address, and port associated with each priority flow for the 
public and private network traffic respectively, where i# stands for the customer instance number. Notice 
that in the public network the medium priority traffic is sent with the high-priority public IP address and 
marked the same as the high-priority traffic, while in the private network it is sent with the 
non-high-priority private IP address and marked the same as the low priority traffic.