| Acronym | Definition |
| 2G | Second Generation |
| 3DES | Triple DES encryption (Security) |
| 3G | Third Generation |
| AAA | Authentication, Authorization, Accounting (generic RADIUS or TACACS+) |
| AAL | ATM Adaptation Layer -- several forms of chopping frames into ATM cells exist (ATM) |
| ABR | Available Bit Rate (ATM) |
| ABR | Area Border Router (OSPF--Routing) |
| ADSL | Asymmetric DSL |
| AIN | Advanced Intelligent Network (SS7, Voice) |
| AMA | Automatic Message Accounting (Voice) |
| AMPS | Advanced Mobile Phone Service |
| ANI | Automatic Number Identification (Wholesale Dial) |
| API | Application Programming Interface |
| APS | Automatic Protection Switching (Optical) -- failover for SONET |
| AS | Autonomous System |
| ASBR | Autonomous System Border Router (OSPF--Routing) |
| ATM | Asynchronous Transfer Mode |
| BAF | Bellcore Automatic Message Format |
| BBFW | Broadband Fixed Wireless |
| BERT | Bit Error Rate Tester |
| BGP | Border Gateway Protocol |
| BICSI | Building Industry Consulting Service International |
| B-ISDN | Broadband ISDN (includes ATM) |
| BITS | Building Integrated Time Supply (Voice) |
| BRI | Basic Rate Interface (ISDN) |
| CA | Certificate Authority (Security) |
| CAP | Competitive Access Provider |
| CAR | Committed Access Rate (QoS) |
| CAS | Channel Associated Signaling or Call-path Associated Signaling (Voice) |
| CASA | Cisco Application Services Architecture |
| CBQ | Class-Based Queuing |
| CBR | Constant Bit Rate (ATM) |
| CCS | Common Channel Signaling (Voice) |
| CCSN | Common Channel Signaling Network |
| CDMA | Code Division Multiple Access |
| CDR | Call Detail Record (SS7, Voice) |
| CE | Customer Edge |
| CE1 | Channelized E1 |
| CEMF | Cisco Element Manager Framework |
| CES | Circuit Emulation Service (ATM) |
| CIC | Cisco InfoCenter |
| CIDR | Classless Inter-Domain Routing (using routing entries like /8 masking to summarize a block of Class B's) |
| CIM | Common Information Management (Net Mgmt) |
| C-ISUP | Cisco ISUP (Voice) |
| CLASS | Custom Local Area Signaling Services (signaling used in a LATA; Voice) |
| CLEC | Competitive Local Exchange Carrier |
| CLI | Command-line interface |
| CLID | Calling Line Identification |
| CLNP | Connectionless Network Protocol (OSI Layer 3 protocol implemented via CLNS) |
| CLNS | Connectionless Network Services (DECnet Phase V and OSI standard network protocol) |
| CLNS | Connectionless Network Protocol (see CLNS) |
| CNR | Cisco Network Registrar (Net Mgmt) |
| CNS/AD | Cisco Network Services for Active Directory |
| CO | Central Office (Voice) |
| CODEC | COder-DECoder originally, now COmpression/DECompression (Voice) |
| COGS | Cost Of Goods Sold (accounting term) |
| COI | Community Of Interest |
| COIN | Community Of Interest |
| CORBA | Common Object Request Broker Architecture (Databases) |
| COT | Central Office Termination (Voice) |
| CPC | Cisco Provisioning Center (Net Mgmt) |
| CPE | Customer Premises Equipment |
| CQ | Custom Queuing (IOS) |
| CRTP | Compressed Real-Time Protocol |
| CSM | Cisco Service Management (Net Mgmt) |
| CSRC | Cisco Subscriber Registration Center (Cable) |
| CT1 | Channelized T1 |
| CTI | Computer Telephony Interface (Microsoft) |
| CY | Calendar Year |
| DACS | Digital Access and Crossconnect System |
| DBS | Direct Broadcast Satellite |
| DCOM | Distributed Component Object Model (Microsoft equivalent to CORBA) |
| DES | Data Encryption Standard (Security) |
| DFE | ??? (wireless) |
| DFP | Dynamic Feedback Protocol |
| DHCP | Dynamic Host Configuration Protocol |
| DIAMETER | Next-generation RADIUS IETF standards effort |
| DID | Direct Inward Dialing (switch passes last 2 to 4 digits of number dialed to PBX for direct dial of extensions) |
| DLC | Digital Loop Carrier |
| DMTF | Desktop Management Task Force (Net Mgmt) |
| DMZ | De-militarized Zone (Security) |
| DNIS | Dialed Number Identification Service |
| DNS | Domain Name Service |
| DOCSIS | Data Over Cable Service Interface Specifications (Cable) |
| DOSBS | Data Over Speech Bearer Service (Wholesale Dial) |
| DOVBS | Data Over Voice Bearer Service |
| DPNSS | Digital Private Network Signaling Scheme (Voice, European) |
| DPT | Dynamic Packet Transport (Optical) |
| DR | Designated Router (Routing) |
| DS0 | Digital Signal, level 0 (see SDH) |
| DSB | Digital Serial Bus |
| DSL | Digital Subscriber Line |
| DSLAM | DSL Access Multiplexer |
| DSMP | RPMS Distributed Session Management Protocol (Wholesale Dial) |
| DTMF | Dual-tone Multi-Frequency |
| DUAL | Diffusing Update Algorithm (Routing) |
| DV | Distance Vector (Routing) |
| DWDM | Dense Wave Division Multiplexing (Optical) |
| E&M | Ear and mouth (PBX to PBX signaling method) (Voice) |
| EBGP | External BGP |
| ECAN | Echo Cancellation |
| EGP | External Gateway Protocol (external AS routing protocol, also the name of obsolete EGP protocol) |
| EIGRP | Enhanced IGRP (routing protocol -- Routing) |
| EM | Element Manager (e.g. in CEMF) |
| EMS | Element Management System |
| EPD | Early Packet Discard (ATM) |
| ES | End System (IS-IS--Routing) |
| ESMTP | Extended Simple Mail Transport Protocol (Voice) |
| ETSI | European Telecommunications Standards Institute |
| FCAPS | Fault, Configuration, Accounting, Performance, Security (Net Mgmt) |
| FCC | Federal Communications Commission |
| FCS | Field Customer Shipment |
| FDM | Frequency Division Multiplexing (wireless) |
| FDMA | Frequency Division Multiple Access |
| FE | Fast Ethernet (100 Mbps) |
| FGD | Feature Group D: equal access CoS, e.g. IXC's to ILEC's for access to any IXC via 1+number. (Voice) |
| FIB | Forwarding Information Base (MPLS, VPN, Routing) |
| FOIP | FAX Over IP |
| FR | Frame Relay |
| FRF | Frame Relay Forum |
| FTP | File Transfer Protocol |
| FTTC | Fiber To The Curb |
| FTTH | Fiber To The Home |
| FTTN | Fiber To The Neighborhood |
| FW | Firewall (Security) |
| FXO | Device emulating a phone to attach to station side of another PBX (Voice) |
| FXS | Device emulating a PBX so you can attach a phone or FAX machine to it (Voice) |
| GK | Gatekeeper (H.323) (Voice) |
| GRE | Generic Route Encapsulation (Cisco IOS) |
| GSM | Global System for Mobile Communications (European cell phone standard; some use in U.S.) |
| GSM | Groupe Special Mobile (standard used in European cell phones, Sprint digital cell phones) |
| GSR | Giga-Switch Router (a Cisco model name) |
| GSR | Generic SONET Repeater (Optical) |
| GUI | Graphical user interface |
| H.225 | H.323 call signaling protocol |
| H.245 | H.323 call control protocol |
| H.323 | VoIP signaling protocol |
| HDSL | High-speed DSL |
| HFC | Hybrid Fiber Coax (Cable) |
| HPOV | HP OpenView (Net Mgmt) |
| HSRP | Hot Standby Routing Protocol (a Cisco IOS feature used with redundant routers) |
| HTTP | HyperText Transfer Protocol |
| IBGP | Internal BGP |
| ICMP | Internet Control Message Protocol |
| ICW | Internet Call Waiting (Services) |
| IDS | Intrusion Detection System (Security) |
| IDSL | ISDN DSL |
| IDU | Indoor unit (wireless) |
| IETF | Internet Engineering Task Force |
| I-FAX | Internet FAX |
| IGP | Internal Gateway Protocol (any routing protocol used within an AS) |
| IGRP | Interior Gateway Routing Protocol (Routing) |
| IKE | Internet Key Exchange (Security) |
| ILEC | Incumbent Local Exchange Carrier |
| IMA | Inverse Multiplexing over ATM (ATM) |
| IMT | Inter-Machine Trunk (connects two SS7 switching centers, owned by same company) (Voice) |
| IN | Intelligent Network (SS7, Voice) |
| INA | Intelligent Network Architecture |
| INAP | Intelligent Network Application Protocol (SS7 way of rolling out new services)(Voice) |
| IOC | Independent Operating Companies |
| IOS | Internetwork Operating System (Cisco term for router Operating System and Command Line Interface) |
| IP | Internet Protocol |
| IPDC | IP Device Control, see SGCP (Voice) |
| IPS | Intelligent Protection Switching (Optical) -- failover for DPT |
| IPSEC | IP Security standards (Security) |
| IS | Intermediate System (IS-IS--Routing) |
| ISDN | Integrated Service Digital Network |
| IS-IS | Intermediate System to Intermediate System (routing protocol -- Routing) |
| ISP | Internet Service Provider |
| ISUP | ISDN User Part (Voice) |
| ITSP | Internet Telephony Service Provider |
| ITU | International Telecommunications Union |
| ITU-T | International Telephony Union Telecommunications Standardization Sector |
| IVR | Interactive Voice Response |
| IXC | Inter-eXchange Carrier |
| KTS | Key Telephone System (Voice) |
| L2 | Layer 2 (OSI model: Data Layer) |
| L2F | Layer 2 Forwarding (VPN) |
| L2TP | Layer 2 Tunneling Protocol (VPN) |
| L3 | Layer 3 (OSI model: Network Layer) |
| LAN | Local Area Network |
| LATA | Local Access Transport Area |
| LC | Line Card |
| LCR | Least Cost Routing (Voice) |
| LD | Long Distance |
| LDAP | Lightweight Directory Access Protocol |
| LDP | Label Distribution Protocol (MPLS) |
| LEC | Local eXchange Carrier |
| LEO | Low Earth Orbit |
| LFI | Link Fragmentation and Interleaving (Voice) |
| LHE | Local Head End (Cable) |
| LMDS | Local Multipoint Distribution System: 27.5-28.35, 29.10-29.25, 31.00-31.30 GHz (wireless) |
| LMI | Local Management Interface (FR) |
| LOS | Line of Sight (Wireless) |
| LS | Link-State (Routing) |
| LSA | Link-State Advertisement |
| LSP | Link-State Packet |
| LSR | Label Switch Router (MPLS) |
| LVC | Label Virtual Circuit (established via a LDP) (MPLS) |
| MAC | Media Access Control |
| MAN | Metropolitan Area Network |
| MCML | Multiclass Extensions to Multilink PPP |
| MCU | H.323 Multipoint Control Unit |
| MED | Multi-Exit Discriminator |
| MF | Multi Frequency (old signaling method, e.g. touch-tone phones) |
| MFJ | Modification of Final Judgment (FCC ruling on AT&T) |
| MGCP | Media Gateway Control Protocol (Voice) |
| MGCP | Media Gateway Control Protocol (Voice) |
| MGCP | Media Gateway Controller |
| MIME | Multipurpose Internet Mail Extensions |
| MLPPP | Multi-link PPP |
| MMDS | Microwave Multipoint Distribution System: 2.50 to 2.690 GHz (wireless) |
| MMP | Multi-link Multi-chassis PPP |
| MoU | Minutes of Use; Memorandum of Understanding |
| MP | Multi-link PPP |
| MPLS | Multi-Protocol Label Switching |
| MSDP | Multicast Source Discovery Protocol |
| MSO | Multiple System Operator (Cable) |
| MTBF | Mean Time Between Failure |
| MTP | Message Transfer Part (SS7; Voice) |
| MTTR | Mean Time To Repair |
| NANP | North-American Numbering Plan |
| NAS | Network Access Server |
| NAT | Network Address Translation |
| NBAR | Network-based Application Recognition |
| NEBS | Network Equipment Building Standards (Voice -- standards for telco equipment) |
| NI-2 | National ISDN Phase 2 (Voice) |
| NIUF | North American ISDN Users Forum |
| NLOS | Non-Line of Sight (Wireless) |
| NNI | Network-to-Network Interface (FR, ATM) |
| NOC | Network Operations Center |
| NSSA | Not-So-Stubby Area (OSPF--Routing) |
| OADM | Optical Add/Drop Multiplexer |
| OAM | Operation and Maintenance (Optical and ATM) |
| OC | Optical Carrier (optical counterpart to STS rate)(SONET) |
| OC | Optical Carrier |
| OCCS | Optical Cross Connect System |
| OCN | Optical Carrier Networks |
| OCX | Optical Switch |
| ODU | Outdoor unit (wireless) |
| OFDM | Orthogonal Frequency Division Multiplexing (wireless) |
| OOB | Out-of-band |
| OODB | Object Oriented Database |
| OPT | Open Packet Telephony (Voice) |
| OSP | Open Settlement Protocol (Voice) |
| OSPF | Open Shortest Path First (routing protocol -- Routing) |
| OSS | Operating Support System (Net Mgmt) |
| PANS | Pretty Amazing New Stuff (joke: POTS and PANS) |
| PBX | Private Branch Exchange (Voice) |
| PCM | Pulse Code Modulation |
| PCS | Personal Communications Service |
| PDH | Plesiochronous Digital Hierarchy (see SDH) |
| PDU | Protocol Data Unit |
| PE | Provider Edge |
| PHY | Physical (layer) |
| PIN | Personal Identification Number |
| PMP | Point-to-Multipoint |
| POP | Point of Presence |
| POS | Packet Over SONET |
| POSIP | Packet Over SONET Interface Processor |
| POTS | Plain Old Telephone Service |
| PPTP | Point-to-point Tunneling Protocol (VPN) |
| PQ | Priority Queuing (IOS) |
| PRI | Primary Rate Interface (ISDN) |
| PSTN | Public Switched Telephone Network |
| PTP | Point-to-Point |
| PTT | Post, Telephone, and Telegraph (company) |
| PVC | Permanent Virtual Circuit (ATM and Frame Relay) |
| Q.931 | ISDN signaling |
| Q.SIG | Q.931 variant for PBX-PBX standardized signaling |
| QAM | Quadrature Amplitude Modulation (Wireless) |
| QoS | Quality of Service |
| QPPB | QoS Policy Propagation by BGP (QoS) |
| QPSK | Quadrature Phase Shift Keying (Wireless) |
| RADIUS | Remote Authentication Dial-In User Service |
| RAS | Remote Access Server |
| RAS | H.323/Voice: Registration, Admission, Status (e.g. on a gatekeeper) |
| RBOC | Regional Bell Operating Company |
| RDC | Regional Data Center (Cable) |
| RED | Random Early Detection (QoS) |
| RF | Radio Frequency (wireless) |
| RHE | Regional Head End (Cable) |
| RIP | Routing Information Protocol (Routing) |
| RIPv2 | Routing Information Protocol version 2 (Routing) |
| RMP | Resource Management Protocol (Wholesale Dial) |
| ROI | Return On Investment (accounting term) |
| RPM | Resource Pool Manager (Wholesale Dial) |
| RPMS | Resource Pool Management Server (Wholesale Dial) |
| RRR | Routing for Resource Reservation |
| RSVP | Resource Reservation Protocol |
| RTCP | Real-Time Control Protocol (QoS, Voice) |
| RTP | Real-Time Protocol (QoS, Voice) |
| RTR | Response Time Reporter |
| RTSP | Real-Time Streaming Protocol |
| SA | Service Assurance |
| SAA | Service Assurance Agent |
| SAP | Session Announcement Protocol (Voice, IP) |
| SAP | Service Access Point (LAN and Novell) |
| SAR | Segmentation and Reassembly (ATM) |
| SCN | Switched Circuit Network |
| SCP | Service Control Point (SS7, Voice) |
| SDH | Synchronous Digital Hierarchy |
| SDP | Session Description Protocol (Voice) |
| SDR | Session Detail Record (Cisco's version of CDR) (Voice) |
| SDSL | Symmetric DSL |
| SDT | Structured Data Transfer |
| SE | Support or Sales Engineer |
| SF | Single Frequency (old signaling method between Class 4 switches) |
| SGCP | Simple Gateway Control Protocol (Voice) |
| SID | Service ID (Cable) |
| SIP | Session Initiation Protocol (Voice) |
| SLA | Service Level Agreement (Net Mgmt) |
| SMB | Small-Medium Business (market) |
| SNA | Systems Network Architecture (SNA) |
| SNMP | Simple Network Management Protocol |
| SNPA | Sub-Network Point of Attachment (IS-IS--Routing |
| SOHO | Small-Office Home-Office (market) |
| SONET | Synchronous Optical Network |
| SP | Service Provider |
| SPE | Synchronous Payload Envelope |
| SQL | Structured Query Language (database language) |
| SRP | Spatial Reuse Protocol (Optical) |
| SRTS | Synchronous Residual Time Stamp |
| SS7 | Signaling System 7 |
| SSL | Secure Socket Layer (Web; Security) |
| SSP | Service Switching Point (SS7, Voice) |
| STM | Synchronous Transport Module (like STS, but for SDH, different framing and numbering) |
| STP | Signal Transfer Point (SS7, Voice) |
| STP | Shielded Twisted Pair |
| STS | Synchronous Transport Signal (electrical signal rate, counterpart of OC rate)(SONET) |
| SVC | Switched Virtual Circuit (ATM and Frame Relay) |
| TACACS+ | Terminal Access Controller Access Control System -- Cisco's AAA service |
| TCAP | Transactional Capabilities Application Part (SS7 signaling to data bases)(Voice) |
| TCP | Transmission Control Protocol |
| TDM | Time-Division Multiplexing |
| TDMA | Time Division Multiple Access |
| TFTP | Trivial File Transfer Protocol (used for transfer of IOS images and Cisco configurations) |
| TIFF | Tag Image File Format |
| TIPHON | Telecommunications IP Harmonization Over Networks (ETSI Voice) |
| TLS | Transparent LAN Service |
| TLV | Type, Length, Value (see IS-IS slides) |
| TMN | Telecommunications Management Network |
| TOS | Type of Service |
| TUP | Telephone User Part (now ISUP) |
| UBR | Unspecified Bit Rate (ATM) |
| UDP | User Datagram Protocol |
| UNI | User-to-Network Interface (FR, ATM) |
| UNII | Unlicensed National Information Infrastructure: 5.725-5.825 GHz (wireless) |
| UTP | Unshielded Twisted Pair |
| V.110 | See V.120. Terminal rate adaptation protocols for ISDN B-channel with V-type interface. |
| V.120 | See V.110. Terminal rate adaptation protocols for ISDN B-channel with V-type interface. |
| VAD | Voice Activity Detection |
| VBR-nrt | Variable Bit Rate -- Non-Real-Time (ATM) |
| VBR-rt | Variable Bit Rate -- Real-Time (ATM) |
| VC | Virtual Circuit |
| VCC | Virtual Channel Connection (ATM) |
| VCI | Virtual Channel Identifier (ATM, MPLS) |
| VDSL | Very high bitrate DSL |
| VLSM | Variable Length Subnet Masks (Routing) |
| VoATM | Voice over ATM |
| VoD | Video On Demand |
| VOFDM | Vector Orthogonal Frequency Division Multiplexing (wireless) |
| VoFR | Voice over Frame Relay |
| VoIP | Voice over IP |
| VoIPoATM | Voice over IP over ATM |
| VoIPoFR | Voice over IP over Frame Relay |
| VPDN | Virtual Private Dial Network |
| VPI | Virtual Path Identifier (ATM, MPLS) |
| VPN | Virtual Private Network |
| VPNID | VPN Identifier |
| VSI | Virtual Switch Interface |
| WAN | Wide Area Network |
| WCCP | Web Cache Communication Protocol |
| WDM | Wave Division Multiplexing (Optical) |
| WFQ | Weighted Fair Queuing (WFQ) |
| WRED | Weighted Random Early Detection (QoS) |
Dr. Peter J. Welcher (CCIE #1773, CCSI #94014) is a Senior Consultant with Chesapeake NetCraftsmen. NetCraftsmen is a high-end consulting firm and Cisco Premier Partner dedicated to quality consulting and knowledge transfer. NetCraftsmen has nine CCIE's, with expertise including large network high-availability routing/switching and design, VoIP, QoS, MPLS, network management, security, IP multicast, and other areas. See http://www.netcraftsmen.net for more information about NetCraftsmen. Pete's links start at http://www.netcraftsmen.net/welcher . New articles will be posted under the Articles link. Questions, suggestions for articles, etc. can be sent to pjw@netcraftsmen.net .