SIP 603+ blocking notification
The Federal Communications Commission adopted a new rule that requires immediate notification of analytics-based call blocking.
TransNexus has added features to its ClearIP and NexOSS platforms that enable service providers to comply. These features provide the following benefits:
- Service providers can continue to protect their subscribers by blocking bad calls.
- The call blocking notification keeps service providers in full compliance.
Frequently asked questions
What does the new rule require?
Here is the new rule:
Any terminating provider that blocks calls based on any analytics program, either itself or through a third-party blocking service, must immediately return, and all voice service providers in the call path must transmit, an appropriate response code to the origination point of the call. For purposes of this rule, an appropriate response code is:
- In the case of a call terminating on an IP network, the use of Session Initiation Protocol (SIP) code 603+, as defined in ATIS-1000099, adopted August 16, 2022;
- In the case of a call terminating on a non-IP network, the use of ISDN User Part (ISUP) code 21 with the cause location “user”;
- In the case of a code transmitting from an IP network to a non-IP network, SIP code 603+ must map to ISUP code 21; and
- In the case of a code transmitting from a non-IP network to an IP network, ISUP code 21 must map to SIP code 603 or 603+ where the cause location is “user.”
When does this rule take effect?
The immediate blocking notification rule takes effect on March 25, 2026.
What are the options for a service provider to remain in compliance?
A service provider can either:
- Stop blocking calls based on analytics, which makes the notification requirement inapplicable, or
- Continue with analytics-based blocking, which requires the provider to implement immediate blocking notification.
If a service provider stops call blocking, then they would further expose their subscribers to possibly illegal calls. This would degrade their quality of service. Unhappy subscribers might go elsewhere for their telephone service.
Why did the FCC adopt this rule?
The rule ensures that callers will know when their calls are blocked based on reasonable analytics. This will enable them to access redress when blocking errors occur.
Without this rule, legitimate callers struggle to request redress when their calls are blocked by mistake.
Are there any unforeseen consequences of implementing blocking notification?
Service providers might find themselves ill-prepared to handle redress requests. Here are a few of the potential redress issues that a service provider should consider:
- How many calls do we block using analytics?
- How many redress requests might we receive?
- How can we verify that we blocked the calls associated with a redress request?
- How much time and effort will redress research require?
- How can we protect ourselves from a flood of invalid redress requests?
TransNexus SIP 603+ blocking notification
Our ClearIP and NexOSS software platforms support SIP 603+ immediate blocking notification. Providers can enable this feature in locations, e.g., within the United States, where they are required to provide such notification and leave it disabled by default in their facilities located in other countries.
Redress management
Because ClearIP is a hosted platform, we can include a turnkey redress management feature to enable ClearIP service provider customers to easily manage redress requests. These features verify that redress requests are related to calls blocked by ClearIP. This protects the service provider staff from spending time researching calls that they did not block.
Because NexOSS is a fully customizable platform that service providers install in their data centers, they can implement redress management features according to their specific requirements.
TransNexus solutions
TransNexus is a leader in developing innovative software to manage and protect telecommunications networks worldwide. The company has over 25 years of experience in providing telecom software solutions including toll fraud prevention, robocall mitigation and prevention, CDR and call analytics, advanced call routing, billing support, STIR/SHAKEN, and branded calling.
Contact us today to learn more.