Glossary

Voice Termination Glossary

Plain-English definitions of the terms you'll hit when buying or selling US call termination.

Regulatory & Compliance

RMD (Robocall Mitigation Database): The FCC's database where every provider in a call's path must be listed with a certification and mitigation plan. If a provider isn't listed, everyone downstream is required to block its traffic — effectively an on/off switch for network access.
STIR/SHAKEN: The call-authentication framework that cryptographically signs caller ID on SIP/IP calls, so the receiving carrier can verify the call really originated from where it claims.
PASSporT: The signed token STIR/SHAKEN uses to carry authentication data (attestation level, originating number, timestamp) with a call.
Attestation Levels (A / B / C): How confidently a carrier vouches for a call. A (Full) — knows the customer and verifies their right to use the calling number. B (Partial) — knows the customer, but hasn't verified the number. C (Gateway) — no relationship with the originator (typically inbound international traffic).
SPC Token (Service Provider Code Token): The credential a provider obtains from the STI Policy Administrator to get its own STIR/SHAKEN signing certificate — required as of September 2025, since providers can no longer rely on an upstream's certificate.
Gateway Provider: A US-based carrier that receives calls directly from a foreign provider and passes them into the US network. This role triggers extra obligations: authentication of foreign traffic, 24-hour traceback response, and "know your upstream" duties.
Traceback / Industry Traceback Group (ITG): The industry-run process (via USTelecom) for tracing suspicious or illegal call traffic back to its source. Providers must respond to traceback requests — 24 hours for gateway providers.
CPNI (Customer Proprietary Network Information): Data about a customer's calls and network usage, protected under FCC rules. Applies even to wholesale-only carriers with no retail end users.
CPCN (Certificate of Public Convenience and Necessity): State-level authorization required to carry intrastate traffic or operate as a facilities-based CLEC in a given state.
USF (Universal Service Fund): A federal fund that telecom providers contribute to based on certain revenues; wholesale "carrier's carrier" traffic can often be exempted if the buyer certifies it contributes directly.
Form 499-A / 499-Q: The FCC/USAC registration and revenue-reporting forms every telecom provider (including wholesale-only carriers) must file — annually (499-A) and quarterly if non-de-minimis (499-Q).
OCN (Operating Company Number): A unique identifier assigned to a carrier, required to obtain numbering resources directly and to get an SPC token.
LERG (Local Exchange Routing Guide): The industry-standard database (maintained via BIRRDS) that carriers use to route and rate calls based on numbering assignments.
IRSF (International Revenue Share Fraud): A fraud scheme where compromised accounts are used to pump traffic to premium-rate international numbers, generating payouts for colluding parties. The single costliest fraud vector in the industry.
DNO (Do-Not-Originate) List: A list of numbers (e.g., known government or bank numbers) that legitimate calls should never originate from — used to block spoofed robocall traffic.
FAS (False Answer Supervision): When a call is marked "answered" for billing purposes even though it wasn't actually answered by a person — a red flag for fraud or shady routing.

Technical & Network

Class 4 Softswitch: The core switching platform that routes carrier-to-carrier (wholesale) SIP traffic — as opposed to a "Class 5" switch, which serves retail end users directly.
SBC (Session Border Controller): The network-edge device that handles SIP normalization, security, topology hiding, and per-call attestation at the boundary between networks.
BYOC (Bring Your Own Carrier): A model where a platform (e.g., an AI voice agent or CPaaS product) uses its own chosen termination provider rather than a carrier bundled by the platform vendor.
SIP (Session Initiation Protocol): The signaling protocol used to set up, manage, and tear down voice calls over IP networks.
CLI (Calling Line Identification): The caller ID number presented on an outbound call. "Clean CLI" means the number is accurate and not spoofed or mismatched.
DID (Direct Inward Dialing): A phone number assigned to route calls directly to a specific line or user without going through a shared switchboard number.
LCR (Least-Cost Routing): The practice of automatically selecting the cheapest available route for a call that still meets quality thresholds.

Quality & Performance Metrics

ASR (Answer-Seizure Ratio): The percentage of call attempts that get answered. A core route-quality metric — generally 40-50%+ is acceptable, 60%+ is considered excellent (varies heavily by destination and traffic type).
ACD (Average Call Duration): The average length of answered calls. Typically 4-5 minutes is average, 6+ minutes is considered excellent for most traffic types.
PDD (Post-Dial Delay): The time between dialing and hearing ringback or connection. Under ~4-5 seconds is the target; longer delays hurt user experience and can signal routing problems.
NER (Network Effectiveness Ratio): A refinement of ASR that excludes network-caused failures (vs. genuine no-answers/busy), isolating true network performance.
MOS (Mean Opinion Score): A standardized score (typically 1-5) for perceived call audio quality.

Commercial & Billing

CDR (Call Detail Record): The record of a completed call's metadata — origin, destination, duration, timestamps — used for billing, reconciliation, and dispute resolution.
Billing Increment: The unit calls are billed in — commonly "1/1" (billed per second from the first second) or "6/6" (billed in 6-second increments).
Rate Deck: The table of per-destination termination rates a carrier charges or is charged.
Float: The working-capital gap in wholesale voice: you must pay your upstream carrier for completed calls regardless of whether your downstream customer has paid you yet.

CPaaS / Platform Terms

CPaaS (Communications Platform as a Service): A cloud platform that lets developers add voice, messaging, and video into applications via APIs, often reselling or brokering underlying carrier capacity.
UCaaS (Unified Communications as a Service): Cloud-delivered business communications (voice, video, messaging) typically sold to enterprises as a complete phone-system replacement.
CCaaS (Contact Center as a Service): Cloud-delivered contact center software (routing, IVR, analytics) — often the platform layer sitting on top of underlying voice termination.

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