📄 CallerID.com and AT&T Office@Hand — Compatibility, SIP Architecture, and Setup Guide
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Will CallerID.com Vertex work with AT&T Office@Hand?

Short answer: Not with a standard passive SIP capture installation, because AT&T Office@Hand does not deliver SIP signaling to the local network in readable form. Compatibility requires one of three paths: (1) AT&T enabling the SIP trunk add-on on the Office@Hand account, (2) an SBC (Session Border Controller) to bridge the encrypted TCP SIP to local UDP, or (3) switching to AT&T IP Flexible Reach (their traditional SIP trunking product).

Why standard installation does not work with Office@Hand

The CallerID.com Vertex reads SIP INVITE messages from the local network to extract inbound caller name and number. This works when the phone carrier delivers a traditional SIP trunk to the premises with plaintext UDP SIP on port 5060.

AT&T Office@Hand is a cloud-hosted UCaaS (Unified Communications as a Service) platform powered by RingCentral. All call signaling flows between AT&T's cloud servers and registered endpoint devices. Two facts make passive SIP capture impossible:

  • No SIP trunk to premises. Office@Hand does not deliver a SIP trunk to on-site equipment. Signaling stays in AT&T/RingCentral's cloud.
  • UDP SIP retired April 15, 2016. AT&T Office@Hand completed a full migration from UDP to TCP for all SIP signaling on April 15, 2016. All SIP is now encrypted with TLS over TCP. Even if SIP traffic were present on the local LAN, it would appear only as opaque TLS Application Data — undecodable by a passive capture or the Vertex. Source: AT&T Support Article #8119 — asecare.att.com/tutorials/sip-migration-8119/

The RingCentral Security Whitepaper confirms: "TLS secures the SIP signaling communication between supported endpoint devices and the RingCentral cloud servers. SRTP provides encryption to the RTP packet stream." AT&T also offers a completely separate product — AT&T IP Flexible Reach — for traditional SIP trunking, confirming Office@Hand does not include it by default.

What a packet capture looks like at an Office@Hand site

A Wireshark capture at an AT&T Office@Hand site will show zero SIP packets — no REGISTER, no INVITE, no OPTIONS, no BYE on any port. This is the expected result given the carrier architecture. It does not indicate a Vertex malfunction or network problem. Any SIP gateways physically on the LAN will be silent — they have no carrier SIP endpoint to register against.

Can an SBC convert TCP to UDP and fix this?

Yes, but only in conjunction with AT&T's SIP trunk add-on for the Office@Hand account.

An SBC (Session Border Controller) acts as a Back-to-Back User Agent (B2BUA): it terminates TLS/TCP SIP on the cloud side, then re-originates the call as plaintext UDP SIP on the local LAN. The Vertex reads the local UDP SIP and delivers caller ID to the POS normally.

Critical limitation: AT&T Office@Hand SIP device registrations are per-extension. An SBC registered as a SIP device only receives calls to its own extension — not all inbound calls to the business. Whole-business caller ID requires trunk-level access, meaning AT&T must enable the SIP trunk add-on. Without it, the SBC captures only one extension's calls. With it, the SBC connects at trunk level, decrypts all inbound SIP, and re-presents as local UDP SIP for the Vertex.

Certified SBCs for this role: Ribbon/Sonus SBC Edge, AudioCodes Mediant, Oracle Acme Packet, Edgewater Networks. See also: CallerID.com Tech Bulletin — Cisco Meraki vs. Edgewater SBC — VoIP Decryption for Vertex Caller ID.

Three resolution paths in order of preference

Path 1 — AT&T Office@Hand SIP Trunk add-on (recommended). Call AT&T Business Support (1-800-321-2000), ask for the SIP trunk gateway feature on the Office@Hand account. If enabled, on-site SIP gateways can register against the trunk endpoint. If the trunk delivers TLS/TCP, add a certified SBC to bridge to UDP locally.

Path 2 — SBC bridge (requires trunk add-on first). After the trunk add-on is provisioned, deploy a certified SBC on-site. The SBC converts encrypted TCP SIP to plaintext UDP. The Vertex reads the local UDP traffic normally.

Path 3 — Switch to AT&T IP Flexible Reach. AT&T's traditional SIP trunking product delivers standard UDP SIP trunk to premises equipment with no SBC required. The existing on-site SIP gateways connect directly, the Vertex reads SIP from the LAN, caller ID populates the POS.

Key questions to ask AT&T (1-800-321-2000)

  • "Does our Office@Hand plan support a SIP trunk add-on or SIP trunk gateway feature?"
  • "We understand Office@Hand completed a migration from UDP to TCP for SIP signaling on April 15, 2016. We need SIP signaling accessible to our on-site caller ID system. What options do you have?"
  • "If a SIP trunk is available, does AT&T have a certified SBC compatibility list for that trunk endpoint?"
  • "If SIP trunking is not available on Office@Hand, can we migrate to AT&T IP Flexible Reach while keeping our existing phone numbers?"

Sources

  • AT&T Office@Hand SIP Migration — Article #8119: asecare.att.com/tutorials/sip-migration-8119/ (UDP to TCP migration completed April 15, 2016)
  • RingCentral Security Whitepaper: netstorage.ringcentral.com/documents/cloud_communications_security.pdf (TLS/SRTP confirmed)
  • AT&T IP Flexible Reach (separate SIP trunking product): attgtadirect.com/ip-flexible-reach/
  • AT&T Office@Hand Network Requirements — Article #91404: asecare.att.com/tutorials/network-requirements-att-officehand/
  • CallerID.com Field Confirmation — Pivot site, 12 August 2026: AT&T support confirmed on-site that Office@Hand does not provide SIP signaling to premises equipment