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.

• For CNAM Verification and Robocall Analytics, please check the instruction here: https://docs.telcobridges.com/tbwiki/ProSBC:CNAM_Verification_Robocall_Analytics

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

• 3a.SIP 404 Not Found: No fraud is detected, not a robocall.

• 3b.SIP 503 Service unavailable: No fraud is detected, not a robocall.

• 4c. 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->ClearIP_Query.rb
   ScriptType->filter
   Load on startup->checked
Gateway->Routes->Routing Script->Edit the main script:

• - Add the "require 'ClearIP_Query' unless defined?(ClearIPQuery)" statement at the top of the main script.
• - Add the "include ClearIPQuery" statement in the main routing class.
• - Add the filter " before_filter :method => :ClearIP_query" in the main routing class.

Click here to download CleaarIP_Query.rb (the fitler script) and Main_ClearIP.rb (just to show how the main script should look like) Routing Scripts

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_CLEARIP
    Proxy address->sip.clearip.com (FQDN of ClearIP-A)

Configure Routes

 You need to configure other routes after the ClearIP routes if you want ProSBC to perform route advances.
 Check the below link for the detail instruction to create static routes:
 https://docs.telcobridges.com/tbwiki/Toolpack:Creating_a_First_Call_Route_E

 It could also combine with other Routeset routing:
 https://docs.telcobridges.com/tbwiki/Toolpack:Tsbc_Call_Routes_Settings_3.1#Label_Routing

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.