Metaswitch partner solutions

Metaswitch

Metaswitch solutions are powering more than 1,000 service providers in today’s global, ultra-competitive and rapidly changing communications marketplace. Their Call Feature Server enables a complete suite of powerful residential and enterprise communications tools that network operators can deploy on-demand as they grow. Their Perimeta is a cloud-native virtualized session border controller (vSBC) that delivers Session Initiation Protocol (SIP) interworking and security performance demanded of large-scale rich communications services.

TransNexus software products are tightly integrated with Metaswitch products. For example, our software products use the OTG paramater in the SIP FROM header, which contains the source trunk group identified by the Metaswitch. This enables more granular control over call handling.

Integration framework

TransNexus software uses standard SIP messaging to integrate with Metaswitch solutions. Either ClearIP or NexOSS is set up as a SIP realm and is placed at the top of the routing table.

When a SIP INVITE, either inbound or outbound, arrives at the Metaswitch Call Feature Server (CFS), it sends the invite to the TransNexus software as if it were an actual SIP destination for call completion.

The TransNexus software performs the services configured for the call and returns a SIP message to the Metaswitch CFS according to the result of the services. Here are a few illustrative examples of typical SIP message communications:

ServicesResultReply (configurable)Metaswitch action
outbound fraud analysisno fraud foundSIP 404 Not Foundroute call using routing tables
outbound fraud analysisfraud detectedSIP 603 Declinedo not route call, return decline to source
outbound routing and fraud analysisno fraud foundSIP 302 Moved Temporarilyroute call using Contact header
inbound robocall preventionnot a robocallSIP 404 Not Foundroute call using routing tables
inbound robocall prevention with blockingrobocall detectedSIP 603 Declinedo not route call, return decline to source
inbound robocall prevention with diversionrobocall detectedSIP 302 Moved Temporarilyroute call to CAPTCHA gateway for call screening
SHAKEN authenticationauthenticated, attested and signedSIP 302 Moved Temporarily with Identity headercopy Identity header, route call using routing tables
SHAKEN verificationidentity header and certificate are validatedSIP 302 Moved Temporarily with verstatcopy verstat, route call using routing tables

Call handling

Select tabs to view call flows for various call handling scenarios:

Block the call

SIP ladder – block the call

If a TransNexus service determines that the call should be blocked, then it returns a SIP 603 Decline message to the CFS.

Diversion call flow

Divert the call to CAPTCHA

If you have scenarios where a call might be bad but you’d prefer a less severe alternative to call blocking, you can set up the software to divert the call instead. The default diversion is to the TransNexus CAPTCHA gateway. Here are the steps:

  1. The call arrives at the Metaswitch CFS.
  2. The CFS routes the call to the TransNexus software for services.
  3. If the TransNexus software determines the call should be diverted, it replies to the CFS with a SIP 302 Moved Temporarily. The CFS routes the call to the CAPTCHA gateway.
  4. The CAPTCHA gateway answers the call and prompts the caller to enter a random two-digit code. If the code is not entered correctly, the CAPTCHA gateway ends the call with a BYE.
  5. If the code is entered correctly, the CAPTCHA gateway sends a SIP REFER back to the CFS.
  6. The CFS receives the SIP REFER from the CAPTCHA gateway and sends an INVITE to the called party to complete the call. It also sends an INVITE to the calling party to enable audio codec renegotiation with the called party.

Alternative diversion destinations can be set up. For example, some customers have set up diversion to voicemail.

Route the call using routing tables

SIP ladder – send the call using routing tables

If there is no fraud detected and TransNexus software is not set up to perform routing services, then the software will return a SIP 404 Not Found to have the CFS route the call using routing tables.

Route the call using Contact header

SIP ladder – send the call with using routes from TransNexus

TransNexus software can provide a list of routes for the CFS to use. The list of routes can either be set up as static routes or generated in the TransNexus software using jurisdictional least cost routing.

If there is no fraud detected and TransNexus software is set up to do routing, then the software will return a SIP 302 Moved Temporarily with a list of routes in preference order for the CFS to use.

Similar call flow for both authentication and verification

SHAKEN call flow

TransNexus software can provide SHAKEN authentication, verification, and certificate management services.

Authentication

If SHAKEN authentication is requested, then the TransNexus Authentication Service (AS) will use policy controls to determine the attestation level to use, create a SIP Identity header and insert it into a SIP 302 response to the CFS. The CFS will copy the Identity header from the response into the outbound INVITE using a header manipulation rule.

If AS policies determine that the call should be blocked, then the AS will return a SIP 603 Decline.

Verification

If a call has a SHAKEN SIP Header and verification is requested, then the TransNexus Verification Service (VS) will use information in the SIP Header to fetch certificate information from Certificate Repositories for the Certificate Authority and the originating service provider that signed the call. The VS will validate the certificates and use the public key to verify that the call information has not be tampered with or replayed.

For call termination, the VS will generate a SIP 302 with verstat information in the P-Asserted-Identity field. The CFS will copy the verstat information into the terminating INVITE using a header manipulation rule. Depending on the handset, this verstat information may be used to display information to the user about the verification results.

If VS policies determine that the call should be blocked or diverted, then the VS will return either a SIP 603 Decline or SIP 302 Moved Temporarily respectively.

Contact us

Please contact us for more information, assistance and guidance in connecting your Metaswitch solution to TransNexus software products.

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