Long Distance Telephone Carriers Industry Terminology

ACD (Average Call Duration)

The average length of successfully connected calls, typically measured in seconds. It’s a key quality and revenue indicator: longer ACDs generally imply conversational traffic and better customer experience, while short ACDs can indicate dialing campaigns, poor quality, or fraud.

- Our India route’s ACD fell to 70 seconds, so we shifted traffic to a higher quality vendor. - Retail traffic usually shows higher ACD than call center traffic. - Low ACD alongside low ASR often signals poor route quality or false answer supervision.

Access Charge

A per-minute or per-connection fee a carrier pays to a local exchange carrier (LEC) or other network for originating, transporting, or terminating long-distance calls. Historically central to the intercarrier compensation regime, though many elements have shifted toward bill-and-keep.

- Access charges on rural routes are eroding our margins. - With access reform moving to bill-and-keep, terminating access revenue declined. - We validated the LEC’s access bills with CABS data before paying.

ANI (Automatic Number Identification)

A network-supplied calling party number used primarily for billing, routing, and analytics in the PSTN. In the U.S., ANI underpins jurisdictional rating and intercarrier billing; internationally it’s often called CLI (Calling Line Identification).

- The ANI is missing on these calls, which breaks our jurisdictional rating. - We use ANI for fraud scoring and caller analytics. - ANI and CLI don’t always match on international traffic.

ASR (Answer-Seizure Ratio)

A key call-completion metric calculated as answered calls divided by total call attempts (seizures). Higher ASR indicates better network performance and route quality; low ASR can indicate congestion, blocking, or routing/fraud issues. Not to be confused with Access Service Request in provisioning.

- The ASR dropped after we changed vendors on Brazil mobile; switch back to the premium route. - We target ASR above 45% for this outbound call center campaign. - Combine ASR with ACD to assess true route quality.

A-Z Termination

A wholesale offering to terminate calls to all (A–Z) global destinations, typically priced in cents per minute by country and network. Quality, CLI delivery, and price tiers vary by destination and vendor.

- We received the weekly A-Z rate deck update from the wholesaler. - Our A-Z blend needs more premium quality on Africa mobile. - The vendor offers A-Z with CLI-guaranteed and non-CLI options.

Backbone

The carrier’s core transport network interconnecting major nodes (POPs, data centers, cable landing stations). It carries high-volume traffic with redundancy and QoS policies for reliability.

- We backhaul voice over our IP/MPLS backbone between POPs. - Congestion on the backbone is driving up packet loss on transatlantic routes. - We’re adding diverse backbone paths across two subsea cables.

Bill-and-Keep

An intercarrier compensation model where each carrier bills its own customers and generally does not charge other carriers for termination. Adopted in many jurisdictions to simplify settlements and reduce arbitrage.

- Under bill-and-keep, terminating carriers recover costs from their own customers, not from other carriers. - Access stimulation rules limit arbitrage under bill-and-keep. - This interconnect agreement is bill-and-keep for local and tandem functions.

CABS (Carrier Access Billing System)

Standardized processes and data formats used primarily in North America for billing intercarrier access charges (e.g., switched access). Supports invoice generation, disputes, and settlements between carriers.

- We reconciled the LEC’s CABS invoice against our CDRs. - Disputes on tandem transit charges were resolved via CABS records. - Automating CABS validation cut our access cost leakage.

Call Detail Record (CDR)

A transaction record for a call, typically including call start/stop times, calling and called numbers, route identifiers, codec, and quality metrics. Used for billing, routing optimization, fraud detection, and performance reporting.

- We flagged CDRs with abnormal PDD and zero-duration as potential FAS. - The billing team exports monthly CDRs to rate and invoice. - LCR decisions are informed by real-time CDR analytics.

Carrier Identification Code (CIC)

A unique code assigned to an interexchange carrier used for routing and billing, especially with Feature Group D and PIC selection in North America. Enables end users or systems to choose a long-distance carrier.

- The customer dialed 1010XXXX to select our CIC on that call. - Feature Group D usage is tracked by CIC. - We verified the PIC change to the correct CIC in the LEC’s records.

Class 4 Switch

A carrier-grade interexchange (tandem/long-distance) switch for high-volume trunking, interconnection, and routing decisions. In modern networks, this is often a softswitch function handling SIP and SS7 interworking.

- We upgraded our Class 4 to support SIP-I and advanced LCR. - The Class 4 aggregates interexchange trunks and handles least cost routing. - Disconnect the legacy TDM Class 4 after migrating to the softswitch.

CLI (Calling Line Identification)

The presentation of the calling party number to the called party or downstream network. CLI is used for billing, analytics, and regulatory compliance; loss of CLI is common on grey routes or with certain signaling interworks.

- This vendor guarantees CLI delivery on European routes. - The regulator fines for CLI spoofing on domestic calls. - CLI dips feed our CNAM service in the U.S.

Codec (e.g., G.711, G.729)

A method for encoding and compressing voice for transmission. Common codecs include G.711 (PCM), G.729 (compressed), AMR-WB (HD). Codec choice affects bandwidth, latency sensitivity, and call quality.

- We prefer G.711 on premium routes for better MOS. - Transcoding from G.729 to G.711 degraded quality on that path. - The SBC negotiates the codec set during SIP call setup.

E.164 Numbering Plan

The international public telecommunication numbering plan standard defining a maximum of 15-digit numbers with country codes. E.164 normalization underpins routing, portability, and database dips.

- Ensure all dialed numbers are normalized to E.164 format. - The ENUM database maps E.164 numbers to SIP URIs. - Fraud filters validate E.164 structure before routing.

False Answer Supervision (FAS)

A fraud or mis-billing condition where a call is marked as answered before a human answers, inflating billable duration. Often manifests as long PDD, short ACD, and poor user experience.

- ACD is short and PDD is long—classic FAS symptoms. - We blacklisted a vendor for persistent FAS on African mobiles. - The customer disputed charges citing FAS evidence in the CDRs.

Fraud: International Revenue Share Fraud (IRSF)

A scheme where fraudsters drive traffic to numbers that pay revenue share to the terminating party. Carriers can incur large losses from artificially stimulated international calls.

- We blocked high-risk country codes to mitigate IRSF. - A spike in short-duration calls to premium-rate ranges signaled IRSF. - Our fraud engine uses hotlists to prevent IRSF exposure.

Fraud: Wangiri

A one-ring callback scam where victims return missed calls to expensive international or premium numbers, generating revenue for the fraudster’s terminating partner.

- We detected Wangiri callbacks to high-cost Caribbean numbers. - Customer care warned users about one-ring scam calls. - Blacklist ranges associated with Wangiri campaigns.

Gateway (Media Gateway)

A network element that converts between different signaling and media formats (e.g., SS7/TDM and SIP/RTP). It handles bearer interworking, transcoding, and echo/noise mitigation as needed.

- The media gateway interworks TDM trunks with SIP/RTP. - Codec transcoding happens in the gateway when endpoints differ. - We added echo cancellation resources on the gateway.

Grey Route

An unofficial or semi-illegal routing path that bypasses official interconnects (e.g., via SIM boxes or refile). Grey routes are cheaper but often degrade quality and violate regulations or contracts.

- The cheap grey route into Country X drops CLI. - Regulators blocked SIM boxes used for grey traffic. - Quality KPIs on grey routes are volatile; use for price-sensitive traffic only.

ICC (Intercarrier Compensation)

The regime governing payments between carriers for call origination, transport, and termination (e.g., switched access, reciprocal compensation). Policies vary by jurisdiction and have been reformed to reduce arbitrage.

- Access stimulation rules changed the ICC economics for rural LECs. - Our ICC disputes focus on jurisdictional rating errors. - We moved certain traffic to bill-and-keep under the new ICC framework.

IXC (Interexchange Carrier)

A long distance carrier that provides interLATA or international services across exchanges. IXCs interconnect with LECs, mobile operators, and other carriers to originate and terminate calls.

- The customer presubscribed us as their PIC with the IXC code. - As an IXC, we operate POPs in all LATAs. - The IXC’s backbone peers at multiple IXPs for international reach.

LATA (Local Access and Transport Area)

A U.S. geographic concept from divestiture defining areas within which local carriers operate. InterLATA calls are handled by IXCs; boundaries still matter for routing and billing in some contexts.

- InterLATA calls require an IXC; intraLATA may be handled by the LEC. - PIC changes are tracked by LATA in provisioning systems. - Routing plans reference LATA boundaries for jurisdictional rating.

LCR (Least Cost Routing)

An algorithmic approach to select the most cost-effective termination route per destination and quality constraints. Considers rates, quality metrics, CLI delivery, and vendor performance.

- The LCR engine balances price and quality KPIs like ASR and ACD. - We maintain separate LCR tables for retail vs wholesale traffic. - Number portability dips are part of LCR preprocessing.

LERG (Local Exchange Routing Guide)

A North American database mapping NPA-NXX codes to operating companies, switches, LATAs, and routing points. Used for routing, rating, and interconnection planning.

- We pulled OCN ownership changes from the latest LERG. - NPA-NXX to OCN mapping comes from LERG for routing. - The LERG update triggered a routing table refresh.

LNP (Local Number Portability)

The ability for end users to keep their phone number when switching providers. Requires LRN dips for accurate routing and may alter billing jurisdiction.

- Always do an LRN dip to avoid misrouting ported numbers. - LNP affects jurisdictional rating and CNAM delivery. - Our LNP cache updates from NPAC every few minutes.

LRN (Location Routing Number)

A 10-digit number assigned to a switch that serves a ported telephone number. Carriers query for LRN to correctly route calls to ported destinations.

- We route to the LRN rather than the dialed NPA-NXX. - Carriers charge per-query fees for LRN dips. - LRN-based routing reduced ported call failures.

NANP (North American Numbering Plan)

The numbering plan for the U.S., Canada, and certain territories, defining area codes (NPAs) and central office codes (NXX). Key for routing, rating, and toll-free services.

- NANP numbers follow the format NPA-NXX-XXXX. - Toll-free 8YY codes are part of NANP. - Our dial plans normalize to NANP and E.164.

NPA-NXX

The first six digits of a NANP number (area code and exchange). Used for routing, rating, and identifying the serving carrier or switch.

- Rate decks are often priced at the NPA-NXX level. - The LERG shows which OCN owns a given NPA-NXX. - Jurisdictional rating may depend on the calling/called NPA-NXXs.

Origination and Termination

Core wholesale voice services: origination is receiving inbound calls from the PSTN to a carrier’s network; termination is delivering outbound calls from a carrier to the called party’s network. Priced and contracted separately.

- We sell U.S. origination and global termination as separate products. - CLI delivery depends on both origination and termination paths. - Our A-Z termination excludes domestic origination services.

PIC (Primary Interexchange Carrier)

The presubscribed long-distance carrier selected by an end user for interLATA calling. Managed by LECs and identified by a carrier’s CIC.

- The customer changed PIC from Carrier A to us. - PIC disputes arise when the CIC is misassigned. - PIC freezes prevent unauthorized carrier changes (slamming).

POP (Point of Presence)

A carrier facility or data center where networks interconnect and exchange traffic. POPs host switching, SBCs, gateways, and interconnect equipment.

- We turn up SIP trunks at the New York POP. - Diverse POPs reduce latency for transcontinental traffic. - The interconnect agreement specifies each party’s POPs.

PSTN (Public Switched Telephone Network)

The global circuit-switched telephony network comprising local exchanges, tandems, and international gateways. Interworks with IP networks via media gateways and SBCs.

- Our VoIP interconnects bridge into the PSTN via gateways. - SS7 signaling still carries most PSTN call setup. - The PSTN handoff is at the tandem switch.

QoS (Quality of Service)

Mechanisms and policies to prioritize and manage traffic performance. For voice, QoS focuses on latency, jitter, packet loss, and outcomes like MOS and call completion.

- Enforce QoS policies to keep packet loss below 0.1%. - SLA targets on MOS and jitter are part of our QoS commitments. - Backbone QoS classes separate voice from bulk data.

Rate Deck

A structured list of per-minute prices by destination (country, network, or NPA-NXX). Used in wholesale buying and selling, LCR, and margin management.

- The vendor sent a new rate deck with 7-day notice. - We applied margin rules across the rate deck before publishing retail rates. - The LCR engine ingests multiple supplier rate decks daily.

RespOrg

A Responsible Organization authorized to manage and administer toll-free (8YY) numbers in the SMS/800 database in North America. Handles provisioning, routing, and number transfers.

- As the RespOrg, we manage the customer’s 8YY numbers in SMS/800. - RespOrg change requests require LOA documentation. - We ported the toll-free numbers by submitting a RespOrg transfer.

Robocall Mitigation

Operational and compliance measures to detect, block, and deter illegal automated calling. Includes analytics, call labeling/blocking, attestation policies, and regulatory filings.

- Our FCC-filed Robocall Mitigation Plan details how we block illegal traffic. - We tightened analytics to curb high-volume short-duration robocalls. - STIR/SHAKEN and traceback cooperation are core to our mitigation program.

RTP/RTCP

Real-time Transport Protocol carries voice media packets in IP networks; RTCP is its companion control protocol reporting statistics like jitter, packet loss, and round-trip time.

- RTP carries the media; RTCP provides quality feedback. - Packet capture showed RTP jitter spikes during peak hours. - The SBC relays RTCP stats for MOS estimation.

SBC (Session Border Controller)

A network element at VoIP interconnect borders providing security, signaling interworking, media anchoring, policy enforcement, and topology hiding. Critical for SIP trunking and carrier interconnects.

- The SBC enforces SIP security and topology hiding. - We do SIP normalization and transcoding at the SBC. - Rate limiting on the SBC mitigated a SIP flood attack.

SIP (Session Initiation Protocol)

An application-layer signaling protocol for initiating, modifying, and terminating voice and video sessions over IP. Supports features like registration, codec negotiation, and call transfer.

- Our international interconnects use SIP with TLS and SRTP. - We map SIP response codes to routing failover logic. - SIP-I is used for SS7 interworking on some routes.

SMS/800

The North American database and management system for toll-free (8YY) numbers, used by RespOrgs to provision, route, and manage these numbers.

- We updated the routing for 8YY numbers in SMS/800. - New toll-free activations flow through SMS/800 provisioning. - RespOrgs access SMS/800 to manage inventory and templates.

SS7 (Signaling System No. 7)

A suite of telephony signaling protocols used in the PSTN for call setup, routing, and control. Components include ISUP for call control and STP nodes for signaling transfer and routing.

- The STP reroutes SS7 traffic on link failure. - We translate between SS7/ISUP and SIP at the gateway. - Caller ID presentation relies on SS7 signaling in the PSTN.

STIR/SHAKEN

A framework using signed caller identity tokens to authenticate and verify caller ID in IP networks, aimed at reducing spoofing and illegal robocalls. Widely mandated in North America for SIP interconnects.

- We provide full A-level attestation for on-net originated calls. - SHAKEN tokens let downstream carriers verify caller ID. - Non-compliant traffic faces blocking under STIR/SHAKEN rules.

Switched Access

Usage-based charges for using a LEC’s switching and transport facilities to originate or terminate long-distance calls. Historically central to U.S. intercarrier billing.

- We pay switched access charges for terminating interstate calls. - Access reform is phasing certain switched access elements to bill-and-keep. - CABS invoices detail switched access usage by trunk group.

Tandem Switch

A switch that aggregates and routes calls between end offices and interexchange networks. In long distance, tandems provide interconnection points and transit services.

- The access tandem aggregates traffic from multiple end offices. - Tandem routing reduces trunking complexity but can add latency. - We peer at the tandem to reach rural OCNs.

TDM (Time Division Multiplexing)

Legacy circuit-switched transport that dedicates time slots on digital circuits (e.g., T1/E1). Still used in parts of the PSTN and at interconnect boundaries.

- We still have TDM interconnects in markets without SIP. - Echo cancellers are required on certain TDM trunks. - We’re decommissioning TDM in favor of SIP trunks.

Termination Rate

The price per minute charged by the terminating carrier or network to accept incoming calls. Often regulated, especially for mobile networks, and a key component of wholesale pricing.

- The mobile termination rate increased, raising our A-Z price for that destination. - We negotiate blended termination rates with CLI guarantee. - Regulatory caps on termination rates improve retail competition.

Toll-Free (8YY)

A service where the called party pays for inbound calls to numbers with 8YY prefixes (800, 888, 877, etc.). Managed via RespOrgs and SMS/800 in North America, with specialized routing options.

- The enterprise wants nationwide 8YY with geographic routing. - We ported the customer’s 8YY numbers via a RespOrg change in SMS/800. - Inbound 8YY charges are billed to the called party, not the caller.

Traffic Pumping (Access Stimulation)

A practice where entities artificially inflate call volumes to high-access-charge destinations to generate intercarrier revenue. Regulators have implemented measures to curb such arbitrage.

- Abnormally high volumes to a rural OCN suggest traffic pumping. - We applied routing blocks due to access stimulation schemes. - New rules reduce incentives for pumped traffic under bill-and-keep.

USF (Universal Service Fund)

A funding mechanism supporting telecommunications service in high-cost, rural, and low-income areas (e.g., in the U.S.). Carriers contribute a percentage of revenue to the fund.

- We calculate USF contributions on assessable revenues. - USF audits require accurate classification of services. - Shifts in the USF contribution factor affect pricing.

VoIP (Voice over IP)

Transmission of voice communications over IP networks using protocols like SIP and RTP. Enables flexible, scalable interconnects and converged services, but requires QoS controls for call quality.

- Our wholesale VoIP interconnect uses SIP over private peering. - VoIP quality depends on jitter and packet loss control. - We migrated TDM trunks to VoIP with SBC-mediated security.