The Other 40% of the Network: ATIS Addresses TDM Network Call Authentication

Unwanted robocalls and Caller ID spoofing remain the number one consumer complaint to the FCC.  Although there are legitimate uses for robocalls, such as telemarketing, alerts and reminders, the largest portion of robocalls (according to YouMail’s monthly robocall Index) remain spam-related at 37 percent.

Since 2017, the FCC has taken numerous steps towards reducing the number of illegal robocalls and Caller ID spoofing though both regulations and industry-driven technology.  From a technology perspective, this includes enabling voice service providers to block certain obviously-spoofed calls; requiring the creation of a reassigned numbers database so consumers do not get calls intended for others; as well as development and implementation of Caller ID authentication technology known as STIR/SHAKEN that allows voice service providers to verify the Caller ID information transmitted with a particular call.

The widespread implementation of Caller ID authentication plays a key role in helping consumers identify scams and verify who is calling.  Additionally, Caller ID authentication has the potential to alleviate harmful forms of spoofing, such as “neighbor spoofing,” where a caller spoofs a number that matches the first three or six digits of the called 10-digit number, suggesting that the call is legitimate and enticing the consumer to answer the phone.

Congress enacted the Telephone Robocall Abuse Criminal Enforcement and Deterrence Act (TRACED Act) December 30, 2019, to deter unlawful robocalls and enhance enforcement capabilities. The TRACED Act calls for the FCC to require providers of voice services within 18 months (June 30, 2021) to:

  • Implement the STIR/SHAKEN authentication framework in the internet protocol networks of the provider of voice service; and
  • Take reasonable measures to implement an effective call authentication framework in the provider’s non-internet protocol (i.e., TDM) networks.

The recently formed Non-IP Call Authentication Task Force (NIPCA TF), part of ATIS’ Packet Technologies and Systems Committee (PTSC), will focus on the second requirement, addressing the implementation of call authentication in non-internet protocol networks.

Why is this necessary?

There remains a significant portion of the voice network that is not capable of initiating, maintaining and terminating SIP calls, and as a result is not able to authenticate or verify calls under the SHAKEN framework.  Based on the most recently issued Voice Telephone Services Report from the FCC (issued March 2020 for data through 12/31/2018 DOC-362882A1) – approximately 40 percent of voice circuits remain non-IP based. In addition, SHAKEN requires that calls be IP end-to-end, and cannot be used if any portion of the call path is non-IP.

The TRACED Act implicitly recognizes this challenge, allowing for a potential extension to the deadlines if they create undue hardship for voice service providers that use TDM network technology. However, the TRACED Act still requires voice service providers to take “reasonable measures” to implement an effective Caller ID authentication framework in non-IP portions of their networks.  This is an important statement in that the “reasonable measures” clause may be satisfied only if the voice service provider is actively working to implement a Caller ID authentication framework on the non-IP portions of its network by either upgrading to IP so that STIR/SHAKEN may be implemented or by working to develop a non-IP authentication mechanism.  Participation in ATIS’ NIPCA TF can satisfy this requirement. Through it, service providers can demonstrate that they are actively working to address call authentication challenges.

The NIPCA TF leverages ATIS’ deep technical expertise and proven ability to develop communications standards. ATIS has been at the forefront of call authentication initiatives through the joint ATIS/SIP Forum IP-NNI Task Force. In this role, it brings critical expertise to this initiative, including call authentication standards for IP networks, a deep understanding of TDM network standards, and an ability to bring these two areas together to assess call authentication options in non-IP networks.

In a very short period, the ATIS NIPCA Task Force has formed and undertaken the development of a technical report regarding alternatives for caller authentication for non-IP traffic and has already received a number of proposals for Call Authentication Frameworks for TDM networks providing the basis for a robust technical program.

The ATIS NIPCA TF welcomes and encourages all interested parties (including non-ATIS members) to participate.  The goals of the Task Force are to:  1) Understand the problems and challenges; 2) Educate TDM experts on call authentication; 3) Investigate the feasibility of TDM call authentication frameworks, including how these would interwork with SHAKEN; and 4) Evaluate the viability of implementing proposed call authentication mechanisms for TDM networks.  Learn more about the NIPCA TF.

Philip Linse
Philip Linse - Chair, ATIS Non-IP Call Authentication Task Force
As Director of Public Policy, Philip Linse represents CenturyLink in various industry standards forums, and was recently named as the Chair of ATIS’s Non-IP Call Authentication Task Force.  He also Co-chairs the FCC’s North American Numbering Council’s Number Administration Oversight Working Group, Nationwide Number Portability Working Group, and serves on the Call Authentication Trust Anchor Working Group.  Mr. Linse also led the development of the FCC’s Reassigned Numbers Database technical requirements. In addition, he is CenturyLink’s policy subject matter expert on robocall mitigation and the technology transformation as the result of the ongoing transition to IP technology.  Mr. Linse’s background spans over 20 years in telecommunications consisting of, intercarrier and vendor contract negotiations, economic analysis and modeling, outside plant engineering & planning, and subject matter expert on network issues associated with interconnection, switching, signaling, and signaling databases.  Philip holds a Bachelors degree from the University of Northern Iowa.
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