7.3 Enhanced Location CAC Characteristics

This topic describes the characteristics of the Cisco Unified Communications Manager Enhanced Location CACfeature.

Limitations of Locations in Cisco Unified CM before Release 9:

  • Limited topology support
  • Limited support for multiple clusters serving devices at same physical location
  • No support for end-to-end bandwidth management of intercluster calls
  • No separation of desktop video calls versus immersive video calls
  • No bandwidth control within a location

Enhanced Location CAC in Cisco Unified CM Release 9 and higher:

  • Enhancements have been added to address limitations.
    1. Support for bandwidth control within a location
    2. Support for three types of bandwidth pools
      • Audio calls
      • (Desktop) video calls
      • Immersive video calls
    3. Support for complex network topologies
  • Traditional configuration is still possible.

The traditional Location CAC feature that is available in Cisco Unified Communications Manager before version 9 has several limitations:

  • Limited topology support: Only hub-and-spoke topologies or MPLS network deployments can be supported correctly by Location CAC. Multitier or multihop topologies are not supported.
  • Limited support for overlapping Cisco Unified Communications Manager clusters: When some devices in a physical site are registered with one Cisco Unified Communications Manager cluster and other devices are registered with another Cisco Unified Communications Manager cluster, there is no way to manage the network bandwidth at an enterprise level. Instead, the available bandwidth must be logically split among the clusters so that each cluster has its dedicated bandwidth. This situation results in inefficient use of bandwidth because one cluster cannot use bandwidth that is assigned to the other cluster, even if one cluster reaches its limit and the other cluster has only low-bandwidth utilization.
  • No support for end-to-end bandwidth management of intercluster calls: When a call is placed over anICT, bandwidth management is performed separately in each cluster. There is no end-to-end bandwidth management.
  • Issues in some Cisco Unified Communications Manager Session Management Edition deployments:When using Cisco Unified Communications Manager Session Management Edition for centralized call control but allowing endpoints to exchange RTP traffic directly between each other, the media stream does not flow through the Cisco Unified Communications Manager Session Management Edition cluster. This situation makes it difficult to configure location CAC in a way that represents the actual network traffic.
  • Location CAC only supports audio and (desktop) video bandwidth pools: There is no support for a separate immersive video bandwidth pool.
  • No bandwidth limits: Bandwidth limits cannot be configured for calls that are placed within a single location.

Enhanced Location CAC, introduced with Cisco Unified Communications Manager Release 9, is based on the existing Location CAC feature of Cisco Unified Communications Manager. As the name suggests, enhancements have been added to the Location CAC feature. Using these enhancements is not mandatory, and a traditional Location CAC configuration is still possible.

The enhancements that have been added are the following:

  • Support for bandwidth control within a location: Bandwidth limits can be configured for calls that are placed within the same location.
  • Support for three separate bandwidth pools: Enhanced Location CAC allows the configuration of separate bandwidth limits for audio calls, (desktop) video calls, and immersive video calls.
  • Support for complex network topologies: Multitier and multihop WANs are supported. Furthermore, Enhanced Location CAC supports end-to-end bandwidth management for intercluster calls. The actual network topology is represented by a network model that is configured by locations and links.

Enhanced Location CAC Network Model

This section describes the Enhanced Location CAC network model.

  • Static CAC mechanism based on configured network model:
    1. Does not adapt to network changes (different from RSVP).
    2. No support for asymmetric or unidirectional bandwidth management.
  • Network model consists of locations and links:
    1. Multiple paths between two locations may exist.
    2. Effective path (best path based on configured link weights) is chosen per pair of locations.

Enhanced Location CAC is a static CAC mechanism. It does not adapt to network changes as RSVP does. In addition, Enhanced Location CAC does not support asymmetric or unidirectional bandwidth management.

Enhanced Location CAC, however, allows the administrator to create a network model that represents sites and links between sites, and it is not limited to a hub-and-spoke topology. In fact, any network topology can be modeled by Enhanced Location CAC. The configuration elements that are used to create an Enhanced Location CAC network model are locations, and the newly created links are connections between two locations.

Multiple paths may exist between any pair of locations. If multiple paths exist, Cisco Unified Communications Manager will choose the best path, called the effective path, based on link weights. The weight is configured per link, and the path with the lowest cumulative weight is chosen as the effective path.

Note

Location and link configurations are static. This situation means that changes in the network topologies, such as link failures, will not cause a new effective path to be chosen. The effective path is only reconsidered if the location or link configuration changes.

The figure shows an example of an Enhanced Location CAC network model. The network model does not follow a hub-and-spoke topology and is not a fully meshed network. The network model includes redundant path and multihop network segments. For example, there are three possible paths between location 4 and location 1 (4-3-1, 4-3-2-1, and 4-1). Locations 1, 3, and 4 are fully meshed while location 2 is directly attached to locations 1 and 3, but there is no direct link between location 4 and location 2.

The chosen effective path between location 2 and location 6 is indicated.

Enhanced Location CAC Concept

This section describes the bandwidth management concept of Enhanced Location CAC.

Successful admission of a call depends on the following:

  • Required bandwidth (based on region and endpoint codec configuration)
  • Type of call (audio, video, or immersive video)
  • Available end-to-end bandwidth for the requested call type
    1. If source and destination location are different:
      • Each link is configured with bandwidth limits (per type of call).
      • If sufficient bandwidth is available on all links along the effective path, the call is admitted.
    2. If source and destination location are identical:
      • Bandwidth limits for calls within a location can be configured.
      • If sufficient bandwidth is available within the location, the call is admitted.

When using Enhanced Location CAC, admission of a call depends on the following parameters:

  • Required bandwidth: This parameter indicates how much bandwidth will be consumed by the call. The bandwidth calculation is identical to the traditional Location CAC configuration. It includes VoIP packetization overhead (that is, it includes the actual media information, the RTP header, the UDP header, and the IP header). For G.711, this overhead is 80 kbps when using the default packetization period of 20 ms. A G.729 call is calculated with 24 kbps.
  • Type of call: Audio calls, (desktop) video calls, and immersive video calls have dedicated bandwidth pools. Each bandwidth pool is configured with its own bandwidth limit. For example, a new audio call is denied when the audio bandwidth limit is used up, even when there is available video or immersive video bandwidth.
  • Available end-to-end bandwidth: In contrast to the standard Location CAC feature, Enhanced Location CAC requires the bandwidth to be available end-to-end. Each link along the effective path has bandwidth limits that are assigned, and the call is only successful when all of these links have sufficient bandwidth that is available.
  • Intralocation bandwidth: If the source and the destination locations of a call are the same, then Enhanced Location CAC may have intralocation bandwidth limits that are configured. By default, the intralocation bandwidth limits are unset. Therefore, all calls that are placed within a location are admitted. If, however, intralocation bandwidth limits are applied, the call is only successful if enough bandwidth is available in the applicable bandwidth pool (audio, video, or immersive video).
Advertisements