[This is pre-release documentation and subject to change in future releases. This topic's current status is: Milestone-Ready]

Topic Last Modified: 2010-05-08

Let’s walk through an example of how to plan for and implement call admission control. At a high level, this consists of the following activities:

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

After you have gathered the required information, CAC deployment and management is performed in the Communications Server Management Shell.