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Overview
In voice communications, traffic volume is regulated using the Call Admission Control (CAC) feature. CAC prevents over subscription of a managed network by monitoring packets entering the network in the call setup phase. CAC averts voice traffic congestion by ensuring that there is enough bandwidth for authorized flows.
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supports bandwidth Call Admission Control (CAC) per supported media type
1 by limiting video streams to specified bandwidth limits in order to provide a level of protection from video calls consuming call bandwidth otherwise needed for audio calls. This protection is implemented on
by setting video thresholds (
bandwidthVideoThreshold) to specific limits at the zone, trunk group, endpoint and shared CAC levels. The thresholds are a percentage of the total bandwidth limit such that any traffic above this level is reserved for audio-only calls. This video threshold limit behaves the same for emergency as well as non-emergency calls. Any video calls above the video threshold limit are dropped to allow audio calls to use this bandwidth.
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The Registration control policer addresses the fact that the SBC, as
, as a whole, can support a limited number of SIP endpoint registrations. With no limit restrictions, subscribers belonging to a customer network might over-register resulting in no registration space for other customers/subscribers.
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If the emergency oversubscription percentage is non-zero, then emergency calls are given preference over normal calls when restricting call rates. For example, if the allowed rate is 10 cps, and the SBC the
is presented with a call rate of 10 cps of normal calls and 5 cps of emergency calls, then, on average,
the SBC will allow the allows 5 cps of emergency calls and just 5 cps of normal calls.
Shared CAC Limits Pool
SBC uses the Shared CAC-Limits Pool global object to support connectivity to multiple peering partners concurrently through one or more IP Trunk Groups to each partner network. Call Admission Control for a given IP Trunk Group limits the total number of calls exchanged and/or bandwidth consumed between
the SBC the and a peering partner, or limits only ingress or egress calls based on IP Trunk Group.
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A shared CAC limits pool is not tied to a specific zone or address context. There may be up to 2,000 shared CAC limits pools on SBC
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Figure 1 CAC-Limits Pool and Trunk Group Hierarchy
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The ability to limit call establishment for an individual endpoint is an important factor in helping to prevent voice-spam or abusive use of network resources. The SBC The
supports CAC controls for both registered and statically configured peers on a per SIP endpoint basis. With this feature, each SIP registered or static endpoint can have individualized limits on the number of active calls and the call rate. The control for the active call limit applies to calls in either direction. The call rate policing controls apply to ingress and egress calls separately. All three controls are provisioned on the SIP CAC Profile. For statically configured peers, the SIP CAC Profile is applied to the IP Peer object. For peers that register, the SIP CAC Profile is provisioned on the SIP trunk object associated with the SIP trunk group.
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SIP CAC Profile also supports extendedEmergencyIpLimit feature which allows an additional configurable number of emergency calls in case the call limit quota and emergency oversubscription factor quota are exhausted. See SIP CAC Profile (EMA) or SIP CAC Profile - CLI for SIP CAC Profile CLI command details.
SBC can be configured from EMA or CLI using SIP CAC Profile to limit the message rate of the following messages on a per IP trunk group basis:
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Call gapping is only supported in the centralized PSX. Please see PSX documentation for details.
References
EMA:
CLI:
Active and Stable Sessions for a Configurable Time Interval
supports a percentage of sessions beyond the purchased session license capacity to measure the maximum amount of simultaneously active and stable sessions over a configurable time interval. For example, you can configure the time interval for 5 minutes or more. This enhanced statistics is used to validate if the 's maximum licensed session capacity is breached along with the level of breach during the configured intervals. These measurement samples collected from many s determine the actual peak session usage. This statistics is also used by Sonus to perform periodic audits.Two new objects, callCountCurrentStatistics and callCountIntervalStatistics are added to Global object.
A new performance table, callCountStatistics with Current and Interval options are introduced.
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Currently, only the Max Session Count is supported under the performance table. |
A new configuration flag, callCountTimeInterval, is added to Interval Statistics object in the same lines of existing interval configuration. The default value of this configuration is 15 minutes and the value ranges from 5 minutes to 60 minutes.
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Currently, applies a single interval period across all performance table with default value of 15 minutes. However, for Maximum Session Count, a more granular interval of 5 minutes is required. Hence, the need arises for a separate interval period configuration. |
After an
switchover, all the callCountTimeInterval configuration values are retained. The currentIntervalStatistics value is re-calculated and updated based on the number of stable calls post the switchover process which are in-line with the other statistics.EMS supports this new metric such that the values are polled by the Insight Performance Reporting Engine and exported in .CSV format. The EMS support is inline with how other performance statistics are reported.