According to Verizon, there's one very specific calling scenario in which it's unable to block potential robocalls: toll-free calls from foreign consumers that terminate at call centers belonging to US-based enterprises. As a result, the company is requesting a waiver of some FCC rules designed to block robocalls.

In its FCC filing, Verizon argues that it has long worked to block all kinds of robocalls and that this scenario doesn't pose a robocall threat to its customers. Also, according to Verizon, it would be unnecessarily expensive to implement a technology that could block toll-free robocalls from foreign consumers that terminate at US call centers.

"The replacement of the specialized existing toll-free infrastructure with new infrastructure capable of handling the DNO [do not originate] obligation [to block robocalls] would be a major project that would only care for this narrow call flow yet would cost millions of dollars and require thousands of person-hours of internal resources," according to Verizon.

Do not call

At issue is the DNO registry that's essentially an outbound-calling blacklist of phone numbers. According to the FCC, that registry is designed to protect consumers from foreign-originated, illegal robocalls. It's one mechanism of many that call providers and others use to prevent robocalls from reaching their intended victims.

Figure 1: (Source: Albert Barden | Flickr)

But Verizon told the FCC that it is unable to apply DNO blocking to some calls. "Toll-free voice traffic from foreign carriers to Verizon's US networks arrives at legacy gateway switches that ... cannot be configured with DNO Blocking capabilities," according to the company.

In a declaration attached to its waiver request, Verizon's Lulia Ann Barakat, a senior manager in Verizon's Infrastructure Network Planning organization, explained why. She said such traffic currently runs over a "legacy platform" that has no alternative capable of processing the calls at the SIP (session initiation protocol) layer and with the necessary business support systems.

Barakat explained that developing such a capability would "involve millions of dollars and thousands of person-hours of work" – and would be unnecessary anyway. She said Verizon has conducted several recent studies that found that none of the incoming toll-free calls to international gateways for termination in the US included traffic on the DNO list.

"That makes sense because illegal robocallers attempting to perpetrate impersonation scams by spoofing legitimate organizations' numbers (which is the category of calls stopped by DNO) are targeting US consumers, not US call centers receiving toll-free traffic from consumers," she explained.

An ongoing problem

Regulators, network operators and phone users worldwide have long bemoaned robocalls. In the US, the FCC has mandated a wide range of technologies designed to prevent them.

Verizon argues that it has helped lead the way in the prevention of robocalls. The operator noted to the FCC that it offers a Spam Alerts service, as well as features that block millions of illegal robocalls in its network before they reach a customer. The carrier also said it uses STIR/SHAKEN call authentication technologies, and that it "operates industry-leading 'honeypot' and 'traceback' programs to identify, track down, and shut down illegal robocallers."

As for DNO specifically, Verizon said it "pioneered the DNO approach to protecting consumers from robocall fraud, working initially with the Social Security Administration to stop wide-spread impersonation involving spoofing of its numbers." The company said it has worked with trade association USTelecom to develop a widely used list of DNO numbers.

Interestingly, Verizon is the only company to file a robocall waiver to the FCC in recent months. The only other recent waiver was filed by texting provider Hustle. The company asked the FCC for a waiver of fees associated with the agency's Reassigned Numbers Database (RND) so that Hustle could use that database to protect against text spam.

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— Mike Dano, Editorial Director, 5G & Mobile Strategies, Light Reading | @mikeddano