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High Probability of Completion (HPC) features comprise a set of functionalities that provide an enhanced probability of call completion to authorized Government Emergency Telecommunications Service (GETS) and Wireless Priority Service (WPS) users during network stress and/or congestion. There are two methods in HPC call classification:
The SBC supports the use of different Differentiated Services Code Point (DSCP) marking for signaling traffic that is associated with HPC and non-HPC calls. To support different DSCP marking for HPC and non-HPC calls in a SIP trunk group, the The outbound SIP signaling messages associated with HPC and non-HPC calls are marked with the DSCP value configured in the SIP signaling port when the
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dscpValue
parameter is modified, the new value applies only to new HPC calls while the existing HPC calls use the previously configured value.The following call flow illustrates the DSCP marking for HPC calls.
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The SIP 100 Trying provisional response is handled as an exception. The SBC sends this provisional response with a DSCP value that is configured in the SIP signaling port because the provisional response is sent before an incoming call is determined as an HPC or non-HPC call (see the preceding call flow). |
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The following call flow illustrates the DSCP marking for non-HPC calls.
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HPC capable switches such as GSX9000 enable HPC calls to receive additional network support to increase the chances of successful call completion.
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Related articles: |
In previous releases, the SBC supported Differentiated Services Code Point (DSCP) marking for non-audio streams (video and T.140 text) for both High Priority Calls (HPC) and non-HPC calls. The SBC Core is enhanced to support alternative DSCP marking for T.140 text media stream types from what is used for video and audio media stream types irrespective if the request has an RPH header.
For Government Emergency Telecommunications Service (GETS) / Wireless Priority Service (WPS) calls ( high priority calls), DSCP markings are associated with the provisioned ETS value and in the outgoing message includes an RPH containing the provisioned ETS.x. When the message is destined for the internal network, there is a single DSCP associated with that ETS value and assigned to all associated signaling and media packets. When it is destined for an external network, there is a single DSCP associated for every peer. In other words, there is a set of DSCP values rather than a single DSCP value in each case, one each for signaling, audio, video and text.
A new parameter "T140 DSCP" is added to QosValues for DSCP marking of T.140 text. The DSCP value for T.140 packets is configured on Packet Service Profile (PSP) basis.
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When the parameter "DSCP Passthrough" is enabled, DSCP Pass-through takes precedence over the "T.140 DSCP" setting. |
The following figure depicts a T.140 media call.
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