Configuring Regions and Locations based CAC

When working with slow WAN link in the past, it was crucial to manage your bandwidth effectively. It was pretty common to have leased lines or frame relay services with 64, 128, or 256 Kbps, and we were using these lines to carry all business-related critical information, such as email, accounting software, voice traffic, and so on. However, these setups often faced bandwidth limitations, impacting the number of simultaneous calls and data transmissions. To prevent bandwidth oversubscription and ensure quality of service, call admission control becomes essential in managing the number of active calls at any given time. Thankfully, Internet access and speeds are better solutions today. Yet, despite these improvements, many organizations still rely such lines in their WAN infrastructure.

Call Admission Control

As you can imagine, when you have a leased line with 64 kbps capacity, using it for voice traffic with the G.711 codec is technically impossible. By definition, G.711 requires a throughput of precisely 64 kbps, thereby preventing excess voice traffic or any available bandwidth for other applications during an active call on this line. As a result, Cisco introduced a feature known as Call Admission Control (CAC), enabling system administrators to specify the codecs to utilize across various branches and allocate a specific portion of the available bandwidth for voice traffic calls. Nowadays, there are automated QoS processes that can dynamically reserve bandwidth, but here we are going to do it the old-fashioned way—manually. CAC mechanisms, therefore, play a crucial role in managing resources effectively to ensure call quality and prevent network congestion.

As we mentioned earlier, in order to implement Call Admission Control in a centralized call processing system, you need to configure two things: the codecs to be used between two sites and the amount of bandwidth available for that kind of traffic. The audio codec determines the compression algorithm and maximum amount of bandwidth per single call. During the call set up phase, CAC ensures that sufficient bandwidth is available to maintain call quality. Additionally, managing data traffic is crucial to prevent it from oversubscribing network bandwidth, which could negatively impact voice traffic.

For only calculation on exactly how much bandwidth it is, assume that each call stream consumes the following amount of bandwidth:

• G.711 call uses 80 kb/s.
• G.722 call uses 80 kb/s.
• G.723 call uses 24 kb/s.
• G.728 call uses 16 kb/s.
• G.729 call uses 24 kb/s.
• GSM call uses 29 kb/s.
• Wideband call uses 272 kb/s.

In the case of the Cisco Unified Communications Manager centralized call-processing system, the entire CUCM cluster, along with a variety of devices such as phones and gateways, are typically housed in a central location (HQ). Implementing CAC is, therefore, essential to manage network bandwidth for voice and video traffic effectively. To achieve this, the Resource Reservation Protocol (RSVP) is often used to facilitate bandwidth reservations, ensuring quality of service during calls. In the remote branches, it is possible to have the same type of devices but without CUCM nodes. Here, we are defining locations in order to determine the maximum available bandwidth for audio and video calls. This is crucial for maintaining voice quality, as any packet loss can lead to issues like clipping, which negatively impacts user experience.

In addition to locations, Regions are the other parameter, which is used to define the maximum allowed codec between two endpoints. It is important to mention that you might have branches with the same network regions configured (for example, restricting them to G.729) but in different locations. As a result, one of the branches may establish more simultaneous calls than the other.

 

Task 1: Configure Call Admission Network Regions

Configure Regions in Cisco Communications Manager.

Activity Procedure

Complete these steps:

1. To begin, From the menu, select System > Region Information > Region.
2. Next, Click Add New.
3. Then, On the Region Configuration page, use SJC-Region for the region name.
4. Click Save.
5. Then On the Region Configuration page, on Modify Relationships to other region, click SJC-Region and change the Maximum Audio Bit Rate to 64 kbps (G.722, G.711), and click Save.
6. Next, Click Add New.
7. This time, On the Region Configuration page, use CHI-Region for the region name.
8. As before, Click Save.
9. On the Region Configuration page, on Modify Relationships to other region, click CHI-Region and change the Maximum Audio Bit Rate to 64 kbps (G.722, G.711), and click Save.
10. Following that, still on the Region Configuration page, on Modify Relationships to other region, click SJC-Region and change the Maximum Audio Bit Rate to 8 kbps (G.729), and click Save.
11. On the Cisco Unified Communications Manager Administration page, from the menu, select System > Device Pool.
12. Click Find.
13. Click on device pool SanJose.
14. Change the region to SJC-Region.
15. Click Save.
16. Click Reset, Reset and Close.
17. On Cisco Unified Communications Manager Administration page, from the menu, select System > Device pool.
18. Click Find.
19. Click on device pool Chicago.
20. Change the region to CHI-Region
21. Click Save.
22. Click Reset, Reset and Close the window.

Activity Verification

You have completed this task when you attain these results:

• Establish call between Phone1-1 and Phone1-2, verify that G711 codec is used.
• Establish call between Phone2-1 and Phone2-2, verify that G711 codec is used.
• Establish call between Phone1-1 and Phone2-1, verify that G729 codec is used.

You can see the codec being used by hitting the “I” button on the VTGO softphone or by double-click the “?” button on the CIPC.

Task 2: Configure Locations for Call Admission Control

Configure Cisco Unified Communications Manager to use location based Call Admission Control between 2 sites. This configuration can utilize any type of IP network, providing flexibility and the ability to operate over diverse network infrastructures. The management of IP packets is crucial in Call Admission Control (CAC) mechanisms to ensure efficient traffic flow and prevent congestion.

Activity Procedure

Complete these steps:

1. From the Navigation menu, select Cisco Unified Serviceability and click Go.
2. Then from the menu, select Tools > Service Activation.
3. Activate the service Cisco Location Bandwidth Manager and click Save and OK.
4. On Cisco Unified Communications Manager Administration page, from the menu select System > Location Info > Location.
5. Click Add New.
6. Use SJC-Location for Location name.
7. Allow two (2) G729 voice traffic calls from this location. Set the Audio Bandwidth to 48 kbps.
8. Click Save.
9. Click Add New.
10. Use CHI-Location for Location name.
11. Allow one (1) G729 voice traffic call from this location. Set the Audio Bandwidth to 24 kbps.
12. Click Save.
13. For Phone1-1 and Phone1-2, assign the correct location. On the Cisco Unified Communications Manager administration page, from the menu, select Device > Phone. Click Find to display all phones.
14. Click on Phone1-1, change location to SJC-Location, click Save, and Reset.
15. Repeat steps 10 and 11 for Phone 1-2.
16. For Phone 2-1 and Phone 2-2, assign the correct location. On the Cisco Unified Communications Manager administration page, from the menu, select Device > Phone. Click Find to display all phones.
17. Click on Phone 2-1, change location to CHI-Location, click Save, and Reset.
18. Repeat steps 13 and 14 for Phone2-2.

 

Activity Verification for Voice Traffic

Once you achieve these results, you have successfully completed this task.

• Establish a call between Phone 1-1 and Phone 2. While this call is still active, establish another call between Phone 1-2 and Phone 2-2. To protect voice traffic, “Not enough bandwidth” will appear on the IP phone screen, preventing the call from connecting.