ProSBC:Robocall Mitigation

 

Introduction

This document provides instructions on how to configure ProSBC to operate with the TransNexus ClearIP server for Robocall Mitigation. ClearIP is a SIP redirect server that provides advanced Least Cost Routing (LCR), fraud control and STIR (Secure Telephony Identity Revisited) / SHAKEN (Secure Handling of Asserted information using toKENs) features.

ProSBC 3.0.90 or a later version is needed to support Robocall Mitigation with TransNexus.

Typical Call Scenarios

This section provides the simplified network diagram with typical call flows.

1. Source of ServiceProvider sends a call to ProSBC.
2. ProSBC forwards the call to ClearIP for Robocall Mitigation process
3. ClearIP analyzes the call for robocall mitigation and toll fraud, then sends one of the following responses to ProSBC
   1. a.SIP 404 Not Found: No fraud is detected, not a robocall.
   2. b.SIP 503 Service unavailable: No fraud is detected, not a robocall.
   3. c. SIP 603 Decline: Fraud is detected, block the call.
4. Upon receiving 404 or 503

    4a: - ProSBC returns SIP 503 (or mapping to the TDM cause code) to the Source switch to perform route advance  
    Call Source (TDM or SIP) --------Invite or SETUP or IAM ---------> ProSBC ----Invite--> ClearIP
    Call Source (TDM or SIP) <---SIP 503 or REL with 41 or 34 -------- ProSBC < ----503---- ClearIP

    4b: - ProSBC route advances on SIP 503 and sends call to next destination, does not return response to the Source switch  
    Call Source (TDM or SIP) ---Invite or SETUP or IAM ---> ProSBC ----Invite--> ClearIP
                                                            ProSBC < ----503---- ClearIP
                                                            ProSBC  ----Invite---Next Routes
 Upon receiving 603
  4c: ProSBC returns SIP 603 (or mapping to the TDM cause code) to the Source switch, then release the call 
   Call Source (TDM or SIP) -----Invite or SETUP or IAM ------> ProSBC ----Invite--> ClearIP
   Call Source (TDM or SIP) <---SIP 603 or REL with 21 -------- ProSBC < ----603---- ClearIP

ProSBC Configuration

This section provides ProSBC configuration for the solution.

Configure Routing Script

ProSBC is configured to use routing script to send some SIP headers to ClearIP to identify the source of the call.

1. Enable routing script

Gateway->Use script

2. Load routing scripts

Gateway->Routes->Routing Script->Import Script File
   File->Main_Robo.rb
   ScriptType->Filter
   Load on startup->unchecked
Gateway->Routes->Routing Script->Edit the main script:

1. 1- Add the "require 'CearIP_Robo' unless defined?(ClearIPQuery)" statement at the top of the main script.
2. 2- Add the "include ClearIPQuery" statement in the main routing class.
3. 3- Add the filter " before_filter :method => :clearip_query" in the main routing class.

Configure Transport Server for ClearIP NAP

 SIP -> Create New Transport Server
    Name->TS_TCP_5060
    Port Type->TCP
    Port->5060
    IP Interface-> Select the IP interface which can reach to ClearIP on the public network

Configure ClearIP NAP

NAPs->Create New NAP
    Name->NAP_ClEAEIP
    Proxy address->sip.clearip.com (FQDN of ClearIP-A)

Configure Routes

A static route to NAP_ANY should be configured on both ProSBC’s to allow ProSBC to try the destination in the SIP 3xx response.

Gateway->Routes->Create New Static Route
    Name->ToEndpoints
    NAP->any
    Remapped_NAP->NAP_ANY

Enable SIP Custom Header

Enable SIP Custom Headers must be checked to pass SHAKEN Identity header and several other headers used by the solution.

Profiles->SIP->Enable SIP Custom Headers

Disable Legacy Redirection Mode

Use legacy redirection mode must be unchecked to allow ProSBC to use routing script to handle SIP 3xx response.

SIP->Editing SIP Configuration->Header Parameters->Use legacy redirection mode [uncheck]

Configure Route Retry Action

Route retry action of 3xx, 404 and 603 must be configured to allow ProSBC to perform failover, fraud control and SHAKEN AS/VS request.

Profiles->Edit Reason Cause Mapping
    404 Not found->Route retry action->Continue call
    503 Service unavailable->Route retry action->Continue call
    603 Decline->Route retry action->Stop call

Notes:

• The default route retry action of 404 is Stop call.
• The default route retry action of 603 is Continue call.