WarmTransfer
cisco onprem uc · published

Unified CM call admission control

Verified 2026-09-25 · 56 sources · tier 2

Also known as ELCAC, Enhanced Locations CAC, Enhanced Locations Call Admission Control.

Enhanced Locations Call Admission Control in Unified CM Release 15 regulates audio quality and video availability over complex WAN topologies by modelling the network as locations (LANs) and the WAN links between them, each with bandwidth limits 15. When Enhanced Locations CAC finds no bandwidth available for a call, Unified CM rejects the call and the caller hears a busy signal 8.

In Enhanced Locations CAC a location represents a LAN; it can contain endpoints or serve only as a transit location between links for WAN modelling 33. The Collaboration 14 preferred architecture lists the devices that must be configured in a location: endpoints, conference bridges, gateways, SIP trunks, music on hold servers, and annunciators (via device pool) 11. The intra-location bandwidth for devices within a location defaults to Unlimited for all media types 22. Cisco's Collaboration 14 preferred architecture recommends leaving intra-location bandwidth at its Unlimited default because there is little or no reason to limit bandwidth within a LAN 23.

A link is the connection between two locations, and each link is given bandwidth allocations and a weight 32. Link bandwidth allocations are set separately for 3 traffic types: audio, desktop video and immersive video 7. Cisco describes Enhanced Locations CAC as a model-based, static mechanism that does not take network failures or routing-protocol reroutes into account 51. The Release 15 guide warns that during network failures the bandwidth reservation path Unified CM calculates may not reflect actual network conditions 16. WarmTransfer's reading of the sources is that because ELCAC is static, after a WAN failure or reroute onto a smaller backup path it can keep admitting calls up to the configured link bandwidth, oversubscribing the path actually in use 56.

Regions set the bandwidth that the endpoints in a call between two regions may use, locations set the total bandwidth all calls between those locations may use, and each call's region bandwidth is deducted from the location's available bandwidth 43. Unified CM supports up to 2000 regions 37. A region's maximum audio bit rate works as a filter: Unified CM takes the codecs both sides of a call leg share, drops those above the maximum, and picks the preferred codec from the rest 42. The Collaboration 14 preferred architecture recommends standardizing on 1 audio codec across the organization, LAN and WAN, to keep the region matrix simple 49.

Bandwidth deduction and media handling

Link bandwidth allocations are set separately for audio, desktop video, and immersive video traffic 7.

Traffic type Bandwidth deducted Calculation basis
G.711 or G.722 audio 80 kbps 64 kbps codec bit rate plus 16 kbps IP/UDP headers 17
G.729 audio 24 kbps 8 kbps payload plus 16 kbps IP/UDP overhead 18
Video calls Video payload + audio with headers Video payload counted without IP/UDP overhead; audio counted with IP/UDP overhead (e.g., 384 kbps video with G.711 deducts 320 kbps video and 80 kbps audio) 55

By default, the audio part of a video call is deducted from the video bandwidth pool, not from the audio pool 54. The Collaboration 14 preferred architecture does not use the immersive video bandwidth allocation 41. TelePresence endpoints have a fixed video call classification of Immersive that cannot be changed 53. For SIP trunks, the video classification (Desktop, Immersive or Mixed) is set with the Video Call Traffic Class field in the SIP Profile associated with the trunk 50. The Release 15 guide states that bandwidth for media resources is not allocated through call admission control 38.

Service architecture and intercluster replication

The Cisco Location Bandwidth Manager feature service is off by default and must be activated in Cisco Unified Serviceability for Enhanced Locations CAC to work 27. The Location Bandwidth Manager must run on at least 1 node in the cluster, and Cisco recommends running it on each subscriber node that also runs the Cisco CallManager service 29. By default the Cisco CallManager service talks to its local LBM service; an LBM group can instead point it at an active and a standby LBM for redundancy 24.

LBMs given the hub role actively replicate location and link information between clusters; hubs discover each other through common connections and form a full-mesh replication network 25. LBMs left in the spoke role take part in intercluster replication only indirectly, through the LBM hubs in their own cluster 31. The LBM Intercluster Replication Group is where the administrator chooses which local LBM servers act as hubs and which stay spokes, and lists bootstrap servers that replicate connectivity information to other hubs 21.

Mapping the topology between clusters requires each cluster to have at least 1 location in common with another cluster 10. A location with the same name in 2 or more clusters is treated as the same, shared location across those clusters 48. Hub_None is a default location that typically serves as a hub linking 2 or more locations, and it comes with unlimited intra-location bandwidth allocations 19. In an intercluster ELCAC design, the Hub_None location must be renamed in each cluster, otherwise it becomes a common location shared across clusters 20.

With Enhanced Locations CAC, SIP intercluster trunks must be assigned to the Shadow location 46. The Shadow location lets a SIP trunk pass ELCAC information, such as the location name, so that Enhanced Locations CAC can work between clusters 47. The Shadow location cannot have links to other locations, so no bandwidth can be reserved between it and any other location 45.

The Release 15 Enhanced Locations CAC task flow runs in this order: activate Location Bandwidth Manager, configure LBM group, configure locations and links, configure the LBM intercluster replication group, configure SIP intercluster trunks, then optionally configure CAC service parameters 52.

Call failure handling and rerouting

When call admission control denies an inter-location call, Unified CM can automatically reroute it to the destination over the PSTN using Automated Alternate Routing (AAR) 4. In Release 15, AAR reroutes calls through the PSTN or other networks when the system blocks a call for insufficient location bandwidth, so the caller does not have to hang up and redial 6. AAR is invoked only when Enhanced Locations CAC denies a call for lack of bandwidth along the effective path 5. WarmTransfer's reading of the sources is that unless AAR is enabled and configured, an inter-location call that Enhanced Locations CAC denies simply ends in a busy signal; there is no automatic PSTN reroute 9.

AAR is enabled cluster-wide by setting the Automated Alternate Routing Enable service parameter to True, under Clusterwide Parameters (System - CCM Automated Alternate Routing) for the Cisco CallManager service 1. An AAR group name can be up to 20 alphanumeric characters and may also contain spaces, periods, hyphens and underscores 2. For AAR to work with hunt pilots, additional configuration is needed in the hunt pilot task flow 3.

If a video call fails CAC, video endpoints or SIP trunks with Retry Video Call as Audio enabled retry the call as audio-only; the option is set on the endpoint or SIP trunk configuration page 44.

For a roaming device, Device Mobility replaces the device's Location and Region, along with other device pool settings such as SRST Reference and Media Resource Group List, with values from the dynamically assigned device pool 13. When a device roams into a different device mobility group, Unified CM uses the Calling Search Space, AAR Group and AAR CSS from the phone record rather than from the roaming location 12.

Monitoring and alarms

The LocationOutOfResources counter counts the calls through Locations that failed for lack of bandwidth 34. The LBMLinkOOS alarm means the local LBM has lost communication with a remote LBM, and LBMLinkISV is the informational alarm raised when communication is regained 26.

Applicability

Applies to: Cisco Unified Communications Manager. Deployments: on-premises. Sources checked 2026-09-25. The specific release requirements stated in the claims include Cisco Unified Communications Manager Release 15 and its Service Updates (SUs) 15, alongside design recommendations from Cisco's Collaboration 14 preferred architecture 23. The LocationOutOfResources counter counts calls through Locations that failed for lack of bandwidth 34. The LBMLinkOOS and LBMLinkISV alarms indicate loss and restoration of communication with a remote LBM 26.

What remains uncertain

Whether the LocationOutOfResources counter and LBM link alarms (LBMLinkOOS, LBMLinkISV) behave identically across Unified CM Release 15 is not covered by the sources below.

Specific configuration parameters for integrating AAR within hunt pilot task flows are not covered by the sources below.

See also

Related to

  • Unified CM Session Management Edition — Intercluster ELCAC relies on SIP intercluster trunks in the Shadow location and on LBM intercluster replication; multi-cluster SME designs are the usual case. Topic id taken from the sibling directory name only; that packet was not read.
  • Unified CM media resources — The Release 15 ELCAC chapter says bandwidth for media resources is not allocated via CAC while the PA 14 guide still lists conference bridges and MoH servers as devices that must sit in a location. Topic id taken from the sibling directory name only; that packet was not read.

Referenced by

Sources

  1. 1
    AAR is enabled cluster-wide by setting the Automated Alternate Routing Enable service parameter to True, under Clusterwide Parameters (System - CCM Automated Alternate Routing) for the Cisco CallManager service.
    System Configuration Guide for Cisco Unified Communications Manager Release 15 and SUs - Configure Call Routing · Configure Call Routing; Enable Automated Alternate Routing procedure · Checked 2026-09-25
  2. 2
    An AAR group name can be up to 20 alphanumeric characters and may also contain spaces, periods, hyphens and underscores.
    System Configuration Guide for Cisco Unified Communications Manager Release 15 and SUs - Configure Call Routing · Configure Call Routing; Configure AAR Groups procedure · Checked 2026-09-25
  3. 3
    For AAR to work with hunt pilots, additional configuration is needed in the hunt pilot task flow.
    System Configuration Guide for Cisco Unified Communications Manager Release 15 and SUs - Configure Call Routing · Configure Call Routing; AAR task flow (optional hunt pilot step) · Checked 2026-09-25
  4. 4
    When call admission control denies an inter-location call, Unified CM can automatically reroute it to the destination over the PSTN using Automated Alternate Routing (AAR).
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Automated Alternate Routing) · Checked 2026-09-25
  5. 5
    AAR is invoked only when Enhanced Locations CAC denies a call for lack of bandwidth along the effective path.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Automated Alternate Routing) · Checked 2026-09-25
  6. 6
    In Release 15, AAR reroutes calls through the PSTN or other networks when the system blocks a call for insufficient location bandwidth, so the caller does not have to hang up and redial.
    System Configuration Guide for Cisco Unified Communications Manager Release 15 and SUs - Configure Call Routing · Configure Call Routing; Automated Alternate Routing overview · Checked 2026-09-25
  7. 7
    Link bandwidth allocations are set separately for three traffic types: audio, desktop video and immersive video.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations CAC Components (Bandwidth Allocations) · Checked 2026-09-25
  8. 8
    When Enhanced Locations CAC finds no bandwidth available for a call, Unified CM rejects the call and the caller hears a busy signal.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations Call Admission Control Overview · Checked 2026-09-25
  9. 9
    Unless AAR is enabled and configured, an inter-location call that Enhanced Locations CAC denies simply ends in a busy signal; there is no automatic PSTN reroute.inferred
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations Call Admission Control Overview; combined with Configure Call Routing AAR enable procedure (cisco-cucm-sysconfig-15-call-routing) · Checked 2026-09-25
  10. 10
    Mapping the topology between clusters requires each cluster to have at least one location in common with another cluster.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Enhanced Locations CAC, intercluster) · Checked 2026-09-25
  11. 11
    The Collaboration 14 preferred architecture lists the devices that must be configured in a location: endpoints, conference bridges, gateways, SIP trunks, music on hold servers, and annunciators (via device pool).
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Enhanced Locations CAC, device location assignment) · Checked 2026-09-25
  12. 12
    When a device roams into a different device mobility group, Unified CM uses the Calling Search Space, AAR Group and AAR CSS from the phone record rather than from the roaming location.
    Feature Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Device Mobility · Device Mobility Overview (device mobility groups) · Checked 2026-09-25
  13. 13
    For a roaming device, Device Mobility replaces the device's Location and Region, along with other device pool settings such as SRST Reference and Media Resource Group List, with values from the dynamically assigned device pool.
    Feature Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Device Mobility · Device Mobility Overview (roaming device pool parameters) · Checked 2026-09-25
  14. 14
    Link weights set the relative priority of links, and Unified CM uses them to calculate the effective path between two locations as the path with the least cumulative weight.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations CAC Components (Weight); Configure Locations and Links · Checked 2026-09-25
  15. 15
    Enhanced Locations Call Admission Control in Unified CM Release 15 regulates audio quality and video availability over complex WAN topologies by modelling the network as locations (LANs) and the WAN links between them, each with bandwidth limits.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations Call Admission Control Overview · Checked 2026-09-25
  16. 16
    The Release 15 guide warns that during network failures the bandwidth reservation path Unified CM calculates may not reflect actual network conditions.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations CAC Interactions Restrictions · Checked 2026-09-25
  17. 17
    For audio, Enhanced Locations CAC deducts 80 kbps per G.711 or G.722 call: the 64 kbps codec bit rate plus 16 kbps of IP/UDP headers.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Enhanced Locations CAC, bandwidth deduction) · Checked 2026-09-25
  18. 18
    For a G.729 call, Enhanced Locations CAC deducts 24 kbps: the 8 kbps payload plus 16 kbps of IP/UDP overhead.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Enhanced Locations CAC, bandwidth deduction) · Checked 2026-09-25
  19. 19
    Hub_None is a default location that typically serves as a hub linking two or more locations, and it comes with unlimited intra-location bandwidth allocations.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Enhanced Locations CAC, Hub_None) · Checked 2026-09-25
  20. 20
    In an intercluster ELCAC design, the Hub_None location must be renamed in each cluster, otherwise it becomes a common location shared across clusters.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Intercluster Topology Management · Checked 2026-09-25
  21. 21
    The LBM Intercluster Replication Group is where the administrator chooses which local LBM servers act as hubs and which stay spokes, and lists bootstrap servers that replicate connectivity information to other hubs.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Configure LBM Intercluster Replication Group (Role Assignments and Bootstrap Servers areas) · Checked 2026-09-25
  22. 22
    The intra-location bandwidth for devices within a location defaults to Unlimited for all media types.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Configure Locations and Links · Checked 2026-09-25
  23. 23
    Cisco's Collaboration 14 preferred architecture recommends leaving intra-location bandwidth at its Unlimited default because there is little or no reason to limit bandwidth within a LAN.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Enhanced Locations CAC; intra-location bandwidth) · Checked 2026-09-25
  24. 24
    By default the Cisco CallManager service talks to its local LBM service; an LBM group can instead point it at an active and a standby LBM for redundancy.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Configure LBM Group · Checked 2026-09-25
  25. 25
    LBMs given the hub role actively replicate location and link information between clusters; hubs discover each other through common connections and form a full-mesh replication network.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Intercluster LBM Replication · Checked 2026-09-25
  26. 27
    The Cisco Location Bandwidth Manager feature service is off by default and must be activated in Cisco Unified Serviceability for Enhanced Locations CAC to work.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Activate Location Bandwidth Manager; Enhanced Locations CAC Components (Location Bandwidth Manager bullet) · Checked 2026-09-25
  27. 28
    The Cisco Locations LBM performance object exposes BandwidthMaximum, BandwidthAvailable and CallsInProgress, which can be read from the CLI with show perf query class "Cisco Locations LBM".
    Configure Location Bandwidth Manager and Related Alerts · Verify section; show perf query commands · Checked 2026-09-25
  28. 29
    The Location Bandwidth Manager must run on at least one node in the cluster, and Cisco recommends running it on each subscriber node that also runs the Cisco CallManager service.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Activate Location Bandwidth Manager · Checked 2026-09-25
  29. 30
    The LBM supplies configured and dynamic data to serviceability and updates the Location Real-Time Monitoring Tool (RTMT) counters.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Core Components / Architecture (Location Bandwidth Manager functions) · Checked 2026-09-25
  30. 31
    LBMs left in the spoke role take part in intercluster replication only indirectly, through the LBM hubs in their own cluster.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Intercluster LBM Replication · Checked 2026-09-25
  31. 33
    In Enhanced Locations CAC a location represents a LAN; it can contain endpoints or serve only as a transit location between links for WAN modelling.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations CAC Components (Locations) · Checked 2026-09-25
  32. 34
    The LocationOutOfResources counter counts the calls through Locations that failed for lack of bandwidth.
    Configure Location Bandwidth Manager and Related Alerts · Configure section; RTMT alerts (LocationOutOfResources) · Checked 2026-09-25
  33. 35
    One supported way to manage an intercluster topology is to configure every location and link, with bandwidth allocations and weights, for the whole network in a single management cluster and let replication distribute it.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Intercluster Topology Management · Checked 2026-09-25
  34. 36
    Unified CM supports up to 2000 locations per cluster.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Configure Enhanced Locations Call Admission Control chapter; sentence stating support for up to 2000 locations (sub-heading not confirmed) · Checked 2026-09-25
  35. 37
  36. 38
    The Release 15 guide states that bandwidth for media resources is not allocated through call admission control.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations CAC Interactions Restrictions · Checked 2026-09-25
  37. 39
    Where bandwidth values assigned to a call conflict, the Release 15 guide says Unified CM uses the minimum of the assigned values.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations CAC Interactions Restrictions · Checked 2026-09-25
  38. 40
    Cisco advises against changing LBM bandwidth settings during production hours because doing so can cause unnecessary CPU spikes.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations CAC chapter; restriction/caution about modifying LBM bandwidth (heading not confirmed) · Checked 2026-09-25
  39. 41
    The Collaboration 14 preferred architecture does not use the immersive video bandwidth allocation.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Immersive Video Bandwidth) · Checked 2026-09-25
  40. 42
    A region's maximum audio bit rate works as a filter: Unified CM takes the codecs both sides of a call leg share, drops those above the maximum, and picks the preferred codec from the rest.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Core Settings for Device Pools · Regions Overview · Checked 2026-09-25
  41. 43
    Regions set the bandwidth that the endpoints in a call between two regions may use, locations set the total bandwidth all calls between those locations may use, and each call's region bandwidth is deducted from the location's available bandwidth.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Locations Relationship to Regions · Checked 2026-09-25
  42. 44
    If a video call fails CAC, video endpoints or SIP trunks with Retry Video Call as Audio enabled retry the call as audio-only; the option is set on the endpoint or SIP trunk configuration page.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Enhanced Locations CAC, video call failure) · Checked 2026-09-25
  43. 46
    With Enhanced Locations CAC, SIP intercluster trunks must be assigned to the Shadow location.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Configure SIP Intercluster Trunks · Checked 2026-09-25
  44. 47
    The Shadow location lets a SIP trunk pass ELCAC information, such as the location name, so that Enhanced Locations CAC can work between clusters.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Enhanced Locations CAC, shadow location) · Checked 2026-09-25
  45. 48
    A location with the same name in two or more clusters is treated as the same, shared location across those clusters.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Enhanced Locations CAC, intercluster) · Checked 2026-09-25
  46. 49
    The Collaboration 14 preferred architecture recommends standardizing on one audio codec across the organization, LAN and WAN, to keep the region matrix simple.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (regions) · Checked 2026-09-25
  47. 50
    For SIP trunks, the video classification (Desktop, Immersive or Mixed) is set with the Video Call Traffic Class field in the SIP Profile associated with the trunk.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations CAC Interactions Restrictions · Checked 2026-09-25
  48. 51
    Cisco describes Enhanced Locations CAC as a model-based, static mechanism that does not take network failures or routing-protocol reroutes into account.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Architecture / Bandwidth Management Deployment (Enhanced Locations CAC) · Checked 2026-09-25
  49. 52
    The Release 15 Enhanced Locations CAC task flow runs in this order: activate Location Bandwidth Manager, configure LBM group, configure locations and links, configure the LBM intercluster replication group, configure SIP intercluster trunks, then optionally configure CAC service parameters.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations CAC Task Flow · Checked 2026-09-25
  50. 53
    TelePresence endpoints have a fixed video call classification of Immersive that cannot be changed.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations CAC Interactions Restrictions · Checked 2026-09-25
  51. 54
    By default, the audio part of a video call is deducted from the video bandwidth pool, not from the audio pool.
    System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control · Enhanced Locations CAC Interactions Restrictions · Checked 2026-09-25
  52. 55
    For video calls Unified CM counts only the video payload, without IP/UDP overhead, while the audio stream is counted with IP/UDP overhead; a 384 kbps video call with G.711 audio therefore deducts 320 kbps of video plus 80 kbps of audio.
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Bandwidth Management Deployment (Enhanced Locations CAC, video bandwidth) · Checked 2026-09-25
  53. 56
    Because ELCAC is static, after a WAN failure or reroute onto a smaller backup path it can keep admitting calls up to the configured link bandwidth, oversubscribing the path actually in use.inferred
    Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management · Architecture / Bandwidth Management Deployment (static CAC statement) · Checked 2026-09-25

Documents

tier 2 current vendor documentation

Configure Location Bandwidth Manager and Related Alerts

Cisco Systems (TAC) · 2018-10-09 · accessed 2026-09-25

tier 2 current vendor documentation

Feature Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Device Mobility

Cisco Systems · 2026-09-16 · accessed 2026-09-24

tier 2 current vendor documentation

Preferred Architecture for Cisco Collaboration 14 Enterprise On-Premises Deployments, CVD - Bandwidth Management

Cisco · 2021-05-21 · accessed 2026-09-24

tier 2 current vendor documentation

System Configuration Guide for Cisco Unified Communications Manager Release 15 and SUs - Configure Call Routing

Cisco · accessed 2026-09-21

tier 2 current vendor documentation

System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Core Settings for Device Pools

Cisco Systems · 2026-09-22 · accessed 2026-09-24

tier 2 current vendor documentation

System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure Enhanced Locations Call Admission Control

Cisco Systems · 2026-09-22 · accessed 2026-09-25

Cite this page

APA

WarmTransfer. (2026, September 25). Unified CM call admission control. WarmTransfer. https://warmtransfer.net/knowledge/cucm-call-admission-control

BibTeX

@misc{warmtransfer-cucm-call-admission-control,
  title  = {Unified CM call admission control},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/cucm-call-admission-control},
  note   = {Verified 2026-09-25}
}