Overview

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.

Note

The use of the GETS SOFTWARE is restricted in the U.S. and U.S. TERRITORIES to NS/EP users authorized by the Office of the Manager, National Communications System (OMNCS).

 The SBC supports the following HPC capabilities:

  • Identification of an HPC call based on the presence of either a GETS-Access Number (AN), or GETS-Number Translation (NT) string.
  • Rejection of a call based on the presence of GET-Feature Code (FC) string.
  • Identification of an HPC call based on the code point in the Calling Party Category (CPC) parameter of the ISUP MIME.
  • Prioritization or rejection of a call based on Resource-Priority Header (RPH) r-values in an initial INVITE. The SBC also processes mid-call RPH.
  • Generation of an RPH for inclusion in egress SIP messages.
  • Support for early or late HPC call classification.
  • Detection and logging of error conditions.
  • HPC Call Admission Controls - ingress CAC for early HPC classified calls, and egress CAC treatment for early and late HPC classified calls.
  • Call Queuing, if an HPC call request fails to get a resource it is queued; when the required resource is available, the processing resumes.
  • Exemption of HPC messages from congestion control.
  • DSCP marking and priority treatment for HPC packets - SIP, Diameter and Media packets.
  • High Priority Media Port Range (HPMPR) - packets received on ports in (HPMPR) are prioritized.
  • Statistics and alarms for monitoring HPC traffic.

There are two methods in HPC call classification:

  • Early HPC classification—An HPC call is recognized based on the received SIP RPH content in the incoming INVITE or the code point in Calling Party's Category (CPC) parameter of the ISUP-MIME. For ANSI, the CPC parameter is National Security/Emergency Preparedness (NS/EP) and for ITU, the CPC parameter isInternationalEmergency Preference Scheme (IEPS).
  • Late HPC classification—An HPC call can also be recognized by the PSX during analysis of the Called Party Number.
Note

The SBC must be configured to use the external PSX for this feature. For more information on using the PSX for GETS / WPS, refer to the PSX document Government Emergency Telecommunications Service.

Caution

Preferential servicing of HPC calls is conditional on the installation of NW-HPC license on the EMS. For more information on EMS licenses, refer to the EMS documentation Licensed Applications and Features.

 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 dscpValue parameter in the HPC profile configuration marks HPC calls and the DSCP configuration in the SIP signaling port marks non-HPC calls. The DSCP value configured in the HPC profile takes precedence over the DSCP value configured in the SIP signaling port and applies to all outbound traffic (IPv4 and IPv6) associated with HPC calls.

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 hpcCallProfile is not configured in a SIP trunk group.

Caution

Setting the DSCP on the UDP or TCP network socket is a system call, which impacts the system performance if the DSCP frequently switches between HPC and non-HPC calls. 

Note

This feature only applies to HPC calls over UDP transport. This feature does not apply to TCP transport since TCP is byte stream oriented and does not preserve message boundaries.

This section describes the CLI syntax and parameter descriptions of the HPC Call Profile.

The SBC must be configured to use the external PSX for this feature. The SBC supports configuring up to 256 HPC Call Profiles.

 

Command Syntax

% set profiles services hpcCallProfile <hpcCallProfile name>
	dscp <egress | ingress>
		useRecvdValue <diabled | enabled>
	dscpValue <0-63>
	getsStrings    
		accessNumber an <3-10 digits>
		featureCode fc <3-10 characters>
		numberTranslation nt <3-10 digits>
	queue
		length <1-256>
		state <disabled | enabled>
		timeout <1-90>
	rph 
		egress
			nonEtsWps <dontInclude | include>
			validEtsWps <dontInclude | include>
		etsCpcPrecedence <cpc | ets | hpc>
		etsDefaultValue <0-4>
		includeAcceptIn417 <disabled | enabled>
		includeRequire <disabled | enabled> 
		ingress
			invalidEtsWps <ignore | reject>
			nonEtsWps <accept | ignore>
			validEtsWps <accept | ignore | reject>
		rejectNotEtsDn <disabled | enabled>
		useIncomingEts <disabled | enabled>
		usePrecedence <disabled | enabled>
		useWpsPrecedence <disabled | enabled>
		wpsMlppPrecedence <mlpp | wps>
	state <disabled | enabled>

The HPC Call Profile parameters are defined below:

HPC Call Profile Parameters

Parameter

Description

hpcCallProfile<profile name, up to 23 characters> – HPC Call Profile name.
dscp

The SBC uses the DSCP value received in the initial INVITE for the DSCP marking of the SIP message.

 
  • egress - Use to relate dscp to the egress trunk group. Use the following flag for further configuration:
    • useRecvdValue - When the HPC call profile attaches to a trunk group acting as an egress trunk group, use this flag to control DSCP marking for SIP messages the SBC sends forward (for example, INVITE or ACK).
      • disabled (default)
      • enabled
  • ingress - Use to relate dscp to the ingress trunk group. Use the following flag for further configuration:
    • useRecvdValue - When the HPC call profile attaches to a trunk group acting as an ingress trunk group, use this flag to control DSCP marking for SIP messages the SBC sends backward (for example, 18x or 200 OK).
      • disabled (default)
      • enabled
dscpValue<0-63>The DSCP code for the HPC Call.
getsStrings

A set of Government Emergency Telecommunications Service (GETS) Access Number (AN), Number Translation (NT), and Feature Code (FC) strings that the SBC uses to determine whether a call is an HPC call or is rejected.

  • accessNumber an < 3-10 digits> - The SBC classifies HPC calls using digits in the Request-URI of an initial INVITE request that match GETS-AN. You can configure a maximum of 10 GETS-AN strings.
  • featureCode fc < 3-10 characters without visual separators> - The SBC rejects HPC calls using strings in the Request-URI of an initial INVITE request that match GETS-FC. You can configure a maximum of 4 GET-FC strings.
  • numberTranslation nt < 3-10 digits> - The SBC classifies HPC calls using digits in the Request-URI of an initial INVITE request that match GETS-NT. You can configure a maximum of 10 GETS-NT strings.
queue

Use this parameter to configure HPC call queuing for trunk groups.

  • length <1-256> - Specifies the maximum number of calls that can simultaneously queue at each trunk group. Default: 5.
  • state - Use this flag to enable or disable the queuing of HPC calls.
    • disabled (default)
    • enabled
      Note: Do not enable HPC call queuing for ingress and egress trunk groups simultaneously.
     
  • timeout<1-90> - Specifies the maximum time (in seconds) that an HPC call remains queued before the SBC stops the attempt to connect the call in the associated trunk group. Default: 30.
    Note: When call is queued on the egress trunk group and the queue timer expires, the SBC sends a 408 response towards the ingress side to release the queued call. For the same scenario in a GW-GW call, the ingress SBC sends a 503 response instead of 408. 


Note: By default, the SBC sends a response code 600 when the call queue is full. To configure the SBC to send the response code 503 when the call queue is full, execute  similar commands as described below:

    % set profiles signaling sipCauseCodeMapping cpcToSipCauseMapProfile TEST baseProfile defaultCpcSip causeMap 161 sipCause 503

    % set addressContext default zone ZONE1 sipTrunkGroup INGRESS_TG signaling causeCodeMapping cpcSipCauseMappingProfile TEST

    % commit

rph

Resource Priority Header (RPH) configuration options to specify how the RPH or ISUP-MIME affects call handling and building of the RPH for HPC calls.

  • egress - Determines how the SBC handles the ets and wps namespaces in the RPH (built by the SBC).
    • nonEtsWps - Determines if the SBC includes or does not include namespaces other than ets and wps in the RPH (built by the SBC).
      • dontInclude (default)
      • include
    • validEtsWps - Determines if the SBC includes or does not include valid ets and wps namespaces in the RPH (built by the SBC).
      • dontInclude
      • include (default)

  • etsCpcPrecedence – This parameter is used for deriving a call's CPC during ingress processing when a conflict exists between the CPC based on RPH and the ISUP-MIME (SIP-I) calling party category parameter.
    • cpc – The call's CPC parameter is derived from the ISUP-MIME CPC parameter.

    • ets – The call’s CPC parameter is derived based on the SIP RPH ETS value.

    • hpc (default) – The call’s CPC parameter is derived based on SIP RPH ETS, or else it is derived from ISUP-MIME CPC parameter.


  • etsDefaultValue <value> – Default priority value used for the ETS namespace. (range: 0-4 / default = 0)

  • includeAcceptIn417 – Enable this flag to include the Accept-Resource-Priority header when sending a 417 response.
    • disabled (default)
    • enabled

  • includeRequire – Enable this flag for the SBC to include the Require header with the resource-priority option tag in an egress INVITE.
    • disabled (default)
    • enabled

  • ingress - Determines how the SBC handles namespaces in the received RPH.
    • invalidEtsWps - Determines if the SBC ignores or rejects invalid ets and wps namespaces in the RPH of an ingress SIP INVITE request.
      • ignore (default)
      • reject
    • nonEtsWps - Determines if the SBC accepts or ignores namespaces other than ets and wps in the RPH of an ingress SIP INVITE request.
      • accept (default)
      • ignore
    • validEtsWps - Determines if the SBC accepts, ignores, or rejects valid ets and wps namespaces in the received RPH.
      • accept (default)
      • ignore
      • reject

  • rejectNotEtsDn – Enable this flag for the SBC to reject a call when SBC classifies the call as HPC based on the received RPH and the PSX determines Directory Number (DN) to be a non-ETS DN.
    • disabled (default)
    • enabled

  • useIncomingEts – Enable this flag for the SBC to use the received ETS value. If set to disabled, the SBC uses the provisioned etsDefaultValue.
    • disabled (default)
    • enabled

  • usePrecedence – Specifies whether the ETS value in outgoing SIP messages for the call takes the priority/precedence value received in the ingress.
    • disabled (default) – The ETS priority value in outgoing SIP messages is derived from the etsDefaultValue, when either of the usePrecedence at the ingress trunk group’s HPC profile or useWpsPrecedence at the egress trunk group’s HPC profile fields are disabled, or when there is no incoming priority/precedence value.
    • enabled – When usePrecedence is enabled at the ingress trunk group’s HPC profile and useWpsPrecedence is enabled at the egress trunk group’s HPC profile, the ETS value in outgoing SIP messages is derived from the incoming Wireless Priority Service/Multilevel Precedence and Preemption (WPS/MLPP) priority/precedence value.
  • useWpsPrecedence – Enable this flag for the SBC to take the ETS priority value from WPS/ MLPP precedence, if available, when adding ETS. If set to disabled, the SBC uses the configured etsDefaultValue when adding ETS.
    • disabled (default)
    • enabled

  • wpsMlppPrecedence – Use this parameter to determine how to handle the call when the WPS value in the SIP RPH and a MLPP parameter in the associated ISUP-MIME indicate different handling:
    • mlpp (default) – Handle the call as indicated by the ISUP-MIME MLPP parameter.
    • wps – Handle the call as indicated by the SIP RPH WPS value.
state

Administrative state of HPC Call Profile.

  • disabled (default)
  • enabled

 

Command Examples

Assuming all other parameters and flags have their default values, the following command example shows a minimal configuration for hpcCallProfile:

% set profiles services hpcCallProfile testHpcProfile
% commit

 

To enable the hpcCallProfile created in the previous example, with an allowed dscpValue:

% set profiles services hpcCallProfile testHpcProfile dscpValue 50 stated enabled
% commit

 

To enable useRecvdValue for dscp egress:

% set profiles services hpcCallProfile testHpcProfile dscp egress useRecvdValue enabled
% commit

 

To enable useRecvdValue for dscp ingress:

% set profiles services hpcCallProfile testHpcProfile dscp ingress useRecvdValue enabled
% commit

 

To configure a GETS-AN string:

% set profiles services hpcCallProfile testHpcProfile getsStrings accessNumber an 7106274387
% commit

 

To configure a GETS-FC string:

% set profiles services hpcCallProfile testHpcProfile getsStrings featureCode fc *272

 

To configure a GETS-NT string:

% set profiles services hpcCallProfile testHpcProfile getsStrings numberTranslation nt 7102001234
% commit

 

To configure a HPC call queue:

% set profiles services hpcCallProfile testHpcProfile queue length 50 state enabled timeout 60
% commit
Caution

Do not enable HPC call queuing for ingress and egress trunk groups simultaneously.

Note

When call is queued on the egress trunk group and the queue timer expires, the SBC sends a 408 response towards the ingress side to release the queued call. For the same scenario in a GW-GW call, the ingress SBC sends a 503 response instead of 408.

Note

By default, the SBC sends a response code 600 when the call queue is full.

To configure the SBC to send the response code 503 when the call queue is full, execute similar commands as described below:

    % set profiles signaling sipCauseCodeMapping cpcToSipCauseMapProfile TEST baseProfile defaultCpcSip causeMap 161 sipCause 503

    % set addressContext default zone ZONE1 sipTrunkGroup INGRESS_TG signaling causeCodeMapping cpcSipCauseMappingProfile TEST

    % commit

 

To configure RPH for the egress of a HPC Call Profile:

% set profiles services hpcCallProfile testHpcProfile rph egress nonEtsWps include validEtsWps dontInclude

 

To configure RPH for the ingress of a HPC Call Profile:

% set profiles services hpcCallProfile testHpcProfile rph ingress invalidEtsWps reject nonEtsWps ignore validEtsWps accept

 

To display a configured HPC call profile:

% show profiles services hpcCallProfile testHpcProfile

state     enabled;
rph {
    ingress {
        invalidEtsWps reject;
        validEtsWps   accept;
        nonEtsWps     ignore;
    }
    egress {
        validEtsWps dontInclude;
        nonEtsWps   include;
    }
}
getsStrings {
    featureCode {
        fc *272;
    }
    accessNumber {
        an 7106274387;
    }
    numberTranslation {
        nt 7102001234;
    }
}
queue {
    state   enabled;
    length  50;
    timeout 60;
}
dscp {
    egress {
        useRecvdValue enabled;
    }
}
dscpValue 50;

 

To delete a configured HPC call profile:

% delete profiles services hpcCallProfile testHpcProfile
% commit