The FCC Requires Blocking Notification Using SIP Code 603+ and Use of a Reasonable Do Not Originate List.

The FCC has finally resolved the issue of how terminating providers must notify originating providers and callers that their calls have been blocked using reasonable analytics. Providers must return SIP Code 603+ and no other code. The Cloud Communications Alliance, along with its partner INCOMPAS, urged the FCC to resolve this issue. In the same order, the FCC requires all voice service providers in the call chain to block calls from numbers that are on a reasonable do not originate list. Finally, the FCC urges, but does not require, use of branded calling solutions. The order can be found here: FCC-25-15A1.pdf

Notification

FCC rules require terminating providers that block calls to have redress mechanisms available for quickly reversing the erroneous blocking of legitimate traffic. To trigger redress, however, the caller must know that its calls are being blocked and by whom. The notification mechanism – which SIP Code to use – has been a subject of controversy for several years.

The FCC has resolved this issue. All terminating providers that block calls using reasonable analytics must immediately return a SIP Code 603+ to the origination point of the call. The 603+ standard is at ATIS-1000099. No other codes can be used for blocking notifications. All intermediate providers must transmit the code to the originating point. If a TDM network is involved, the 603+ must map to ISUP 21. Originating providers should consider ensuring that their caller customers receive this notification. The notification requirement becomes effective one year after this order is published in the Federal Register.

This notification is only required when reasonable analytics are used to block a call. It does not apply if the call is blocked for other reasons, such as being on a do not originate list. Also, the notification only applies to calls, not texts and does not apply to mislabeling.

Do Not Originate (DNO) Lists

One of the first steps the FCC took to curb illegal robocalls was to authorize (but not require) voice service providers to block calls using numbers on a reasonable do not originate list. Subsequently, the FCC required gateway providers to block calls using numbers on a DNO list. Wireless providers also must block texts based on a reasonable DNO list. Now, the FCC is requiring all voice service providers – originating, terminating and intermediate providers – to scrub calls against a reasonable DNO list. Thus a call may be subject to multiple scrubs as it transmits from provider to provider, each of whom may have a different DNO list.

The order does not mandate the use of any particular list, as long as it is reasonable. Providers may develop their own lists or use lists such as those developed by the Industry Traceback Group or Somos. The list, however, may only include invalid, unallocated and unused numbers or numbers for which the subscriber has requested blocking because the number is only used for inbound calling. A reasonable DNO list must include, at a minimum: 1) any inbound-only government numbers where the government entity has requested the number be included; and 2) private inbound only numbers that have been used in imposter scams, when a request is made by the private entity assigned such a number. A reasonable DNO list must also be kept up to date, especially if it includes unused numbers.

The DNO list requirement becomes effective 90 days after it has been approved by the Office of Management and Budget.

Branded Calling

The order recognizes that CNAM databases are insufficient to provide a consumer with reliable information. Although not prepared to mandate branded calling at this time, the FCC strongly encourages industry to develop and standardize tools to ensure that caller information is provided to consumers without additional charge to the call recipient.

Please contact the CCA regulatory committee if you have any questions.