May 25, 2022

Call Blocking Notifications: What are SIP Codes 603, 607, and 608?

Since January 1, 2022, the federal government has required phone carriers to provide call blocking notifications. However, there has been some debate about the best way to relay these notifications.

Call Blocking Notifications: What are Sip 603, 607 and 608 Codes?

Due to this confusion, USTelecom recently submitted a petition to delay enacting these requirements and allow more flexible notification methods. Although the FCC ultimately decided to reject the delay, it did ease the requirements to allow SIP Codes 603, 607, and 608 to serve as blocking notifications. 

Importance of Call Blocking Notifications

While the FCC recognizes the need to block unwanted calls, it knows there may be errors in these notification systems. To address these errors, calling parties must have a way to stop legitimate calls from being unfairly blocked. Improved SIP headers are a way to correct this problem.

SIP 603, 607, and 608 response codes indicate that a call did not reach its intended recipient. While 603 codes are already in use by most providers, they only relay the most generic information about why the call did not connect with its intended recipient. Because the code is generic, a caller cannot determine the source of the call's rejection. Thus, making it almost impossible to remediate.

To temporarily address this issue, the FCC is now allowing the use of 603+, 607, and 608 SIP codes. These codes give the caller more information on the reason of a call's rejection.

Benefits of SIP 603 Headers

SIP 603 is already in use by most service providers and can be easily implemented by those who do not already use it. This code has some serious limitations, however.

SIP Code 603 only indicates that a call was not completed without providing a specific reason why. The call recipient could have blocked the call or declined to answer. Call blocking is a deliberate choice to never hear from the caller again, but rejecting the call might mean the recipient is in a meeting or driving their car.

Because of this lack of specificity, the FCC initially wanted to force service providers to use SIP 607 or SIP 608 for blocking notifications in order to provide better information. But AT&T developed a Sip 603+ code to alleviate these issues and make the 603 code more useful. This code provides enhanced information to explain why the call was not connected. The SIP 603+ aims to address the following:

  • Relay header information on why the call was blocked and by whom.
  • Provide contact information about the call blocker (for redress purposes).
  • Create a consistent framework for greater flexibility in relaying blocking notifications.

These improvements to SIP 603 make it more helpful to your company. You can use the additional information to address issues with your calling campaigns and ensure a higher connection rate. 

Benefits of 607/608 SIP Headers

Those in the telecom industry prefer 607 SIP codes and SIP 608 codes because they relay more detailed information on blocked calls. Sadly, many service providers do not have these codes built into their existing frameworks, so their current use is limited.

Full implementation of these codes would require more time and cause difficulties for some service providers. Ultimately, the industry's aim is to use these codes, but for now, SIP 603s will have to fill the gap. 

What does SIP 607 Relay?

A SIP 607 offers more actionable information than a SIP 603. It indicates that the called party rejected your call. Feedback provided by the called party or logic from the user agent generates a SIP 607 response.

Essentially, this code means that the call is unwanted by the called party. This code provides specific information on why the call is rejected, making it superior to the 603 code. 

What does SIP 608 Mean?

While the 607 code comes from the user agent or the called party, a SIP 608 response indicates that an "upstream intermediary" rejected the call. With a SIP 607 code, an analytics engine determines if a call should connect with the end user.

Blocking codes enable the calling party to redress issues with the call. The SIP 608 header must provide contact information to aid in redress concerns. A SIP 608 code does this by providing a Call-Info Header with a means to contact the intermediary.

Generally, the intermediary should relay their name and email address in this information. With a SIP 608 code, your company will be able to directly challenge the decision to block your call from reaching its intended recipient. 

Ensuring Fairness with SIP 607 and 608

STIR/SHAKEN protects consumers from robocalls and other illegitimate calls by mitigating call spoofing efforts. However, some of these new regulations have made it more difficult for legitimate companies to conduct their calling campaigns. SIP codes 607 and 608 can help restore fairness to the process. 

Your company deserves to know why your calls are not reaching their intended recipients. With these two enhanced codes, you will be able to determine the reason for a call's rejection. These codes can determine the source of rejection between the consumer, the carrier, or an analytics program. A SIP 608 code provides vital contact information to seek redress for erroneously blocked calls. 

More informative call blocking notifications protect call centers and consumers and allow better communication for all involved parties. 

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