Gathering the Required Information

To prepare for call admission control, gather the information described in the following steps:

1. Identify your network regions. In example shown in the following figure, there are three network regions: North America, APAC (Asia and the Pacific), and EMEA (Europe, Middle East, and Africa).
   
   
   
   

   An example enterprise network divided into three network regions

2. Identify each network region’s associated central site. A central site is a data center that contains at least one Communications Server 2010 Front End Server and is the Communications Server 2010 deployment at which all users in the network region are homed.
   
   In the example in the preceding figure, a Communications Server 2010 deployment named CHICAGO-NA-MCS-DEPLOYMENT01 at the Chicago network site is the central site for the North America region.
   
   All Communications Server 2010 users in North America are homed on servers in CHICAGO-NA-MCS-DEPLOYMENT01, so the North America network region is assigned to central site CHICAGO-NA-MCS-DEPLOYMENT01, as shown in the following table.
   
   

   Network Regions and their Associated Central Sites

   Network Region	Central Site
   North America	CHICAGO-NA-MCS-DEPLOYMENT01
   EMEA	LONDON-EMEA-MCS-DEPLOYMENT01
   APAC	BEIJING-APAC-MCS-DEPLOYMENT01

3. For each network region, identify all of the network sites (offices or locations) that are not constrained by WAN bandwidth (that is, the offices or locations that are inside the network hub or backbone of the network region).
   
   Because these sites are not bandwidth constrained, their WANs do not need to be monitored and they do not need CAC policies that limit media (voice or video) traffic flow to and from the network region.
   
   In the example shown in the following figure, there are three network sites that are not constrained by WAN bandwidth: New York, Chicago, and Detroit.
   
   

   Network Sites not Constrained by WAN Bandwidth

   Network Site	Network Region
   New York	North America
   Chicago	North America
   Detroit	North America

4. For each network region, identify all of the network sites (offices or locations) that connect to the network region through bandwidth-constrained WAN links.
   
   To ensure audio and video quality, we recommend that these bandwidth-constrained network sites have their WANs monitored and CAC policies that limit media (voice or video) traffic flow to and from the network region.
   
   In the example shown in the following figure, there are three network sites that are constrained by WAN bandwidth: Portland, Reno and Albuquerque.
   
   

   Network Sites Constrained by WAN Bandwidth

   Network Site	Network Region
   Albuquerque	North America
   Reno	North America
   Portland	North America

   
   

   CAC network region North America with three network sites that are unconstrained by bandwidth (Chicago, New York, and Detroit) and three network sites that are constrained by WAN bandwidth (Portland, Reno, and Albuquerque)

5. For each of the bandwidth-constrained WAN connections in step 3, determine the following:
   
   
   • Total bandwidth capacity of the WAN link
     
     
   • Bandwidth limit that you want to set for audio. If a new audio session will cause this limit to be exceeded, Communications Server does not allow the session to start.
     
     
   • Bandwidth limit that you want to set for each audio session. (The default CAC bandwidth limit is 200 kbps, but it can be modified by the administrator.)
     
     
   • Bandwidth limit that you want to set for video. If a new video session will cause this limit to be exceeded, Communications Server does not allow the session to start.
     
     
   • Bandwidth limit that you want to set for each video session. (The default CAC bandwidth limit is 700 kbps, but it can be modified by the administrator.)
     
     
   
   

   Network Sites with WAN Bandwidth Constraint Information (Bandwidth in kbps)

   CAC network region North America showing the bandwidth capacities and bandwidth limits for each of its bandwidth-constrained WANs

   Network Site	Network Region	BW Limit	Audio Limit	Audio Session Limit	Video Limit	Video Session Limit
   Albuquerque	North America	5,000	2,000	200	1,400	700
   Reno	North America	10,000	4,000	200	2,800	700
   Portland	North America	5,000	4,000	200	2,800	700
   New York	North America	(no limit)	(no limit)	(no limit)	(no limit)	(no limit)
   Chicago	North America	(no limit)	(no limit)	(no limit)	(no limit)	(no limit)
   Detroit	North America	(no limit)	(no limit)	(no limit)	(no limit)	(no limit)

6. For every subnet in your network, specify its associated network site.
   
   

   Important:
   Every subnet in your network must be associated with a network site. This is because call admission control uses subnet information to determine at which network site an endpoint is located. When the locations of both parties in the session are determined, call admission control can determine if there is sufficient bandwidth to establish a call.

   Network Sites with WAN Bandwidth Constraint Information and Associated Subnets (Bandwidth in kbps)

   Network Site	Network Region	BW Limit	Audio Limit	Audio Session Limit	Video Limit	Video Session Limit	Subnets
   Albuquerque	North America	5,000	2,000	200	1,400	700	172.29.79.0/23, 157.57.215.0/25, 172.29.90.0/23, 172.29.80.0/24
   Reno	North America	10,000	4,000	200	2,800	700	157.57.210.0/23, 172.28.151.128/25
   Portland	North America	5,000	4,000	200	2,800	700	172.29.77.0/24 10.71.108.0/24, 157.57.208.0/23
   New York	North America	(no limit)	(no limit)	(no limit)	(no limit)	(no limit)	172.29.80.0/23, 157.57.216.0/25, 172.29.91.0/23, 172.29.81.0/24
   Chicago	North America	(no limit)	(no limit)	(no limit)	(no limit)	(no limit)	157.57.211.0/23, 172.28.152.128/25
   Detroit	North America	(no limit)	(no limit)	(no limit)	(no limit)	(no limit)	172.29.78.0/24 10.71.109.0/24, 157.57.209.0/23

7. In Communications Server 2010 call admission control, the connections between network regions are called region links. For each region link, determine the following, just as you did for the WAN links:
   
   
   • Total bandwidth capacity of the region link
     
     
   • Bandwidth limit that you want to set for audio. If a new audio session will cause this limit to be exceeded, Communications Server does not allow the session to start.
     
     
   • Bandwidth limit that you want to set for each audio session. (The default CAC bandwidth limit is 200 kbps, but it can be modified by the administrator.)
     
     
   • Bandwidth limit that you want to set for video. If a new video session will cause this limit to be exceeded, Communications Server does not allow the session to start.
     
     
   • Bandwidth limit that you want to set for each video session. (The default CAC bandwidth limit is 700 kbps, but it can be modified by the administrator.)
     
     
   
   

   Region Link Bandwidth Information (Bandwidth in kbps)

   Bandwidth capacities and bandwidth limits for the links between three network regions

   Region Link Name	First Region	Second Region	BW Limit	Audio Limit	Audio Session Limit	Video Limit	Video Session Limit
   NA-EMEA-LINK	North America	EMEA	50,000	20,000	200	14,000	700
   EMEA-APAC-LINK	EMEA	APAC	25,000	10,000	200	7,000	700

8. Define a route between every pair of network regions.
   
   

   Note:
   Two links are required for the route between the North America and APAC regions because there is no direct region link that connects them.

   Region Routes

   Region Route Name	First Region	Second Region	Region Links
   NA-EMEA-ROUTE	North America	EMEA	NA-EMEA-LINK
   EMEA-APAC-ROUTE	EMEA	APAC	EMEA-APAC-LINK
   NA-APAC-ROUTE	North America	APAC	NA-EMEA-LINK, EMEA-APAC-LINK

9. For every pair of network sites that share a direct link (for example, the link between Reno and Albuquerque in the following figure), determine the following:
   
   
   • Total bandwidth capacity of the site link
     
     
   • Bandwidth limit that you want to set for audio. If a new audio session will cause this limit to be exceeded, Communications Server does not allow the session to start.
     
     
   • Bandwidth limit that you want to set for each audio session. (The default CAC bandwidth limit is 200 kbps, but it can be modified by the administrator.)
     
     
   • Bandwidth limit that you want to set for video. If a new video session will cause this limit to be exceeded, Communications Server does not allow the session to start.
     
     
   • Bandwidth limit that you want to set for each video session. (The default CAC bandwidth limit is 700 kbps, but it can be modified by the administrator.)
     
     
   
   

   Bandwidth Information for a Direct Link between Two Network Sites (Bandwidth in kbps)

   CAC network region North America showing the bandwidth capacities and bandwidth limits for the direct link between the network sites Reno and Albuquerque

   Crosslink Name	First Site	Second Site	BW Limit	Audio Limit	Audio Session Limit	Video Limit	Video Session Limit
   RENO-ALBU-CROSSLINK	Reno	Albuquerque	20,000	12,000	200	5,000	700

Next Steps