Definition of Common Abbreviations 10B2 10 MHz baseband LAN using thin coaxial cable (of IEEE 802) 10B5 10 MHz baseband LAN using thick coaxial cable (of IEEE 802) 10BFL 10 MHz baseband LAN using fibre (extended) (of IEEE 802) 10BT 10 MHz baseband LAN using twisted pair cable (of IEEE 802) 100BFx 100 MHz baseband LAN using fibre (of IEEE 802) 100BT 100 MHz baseband LAN using twisted pair cable (of IEEE 802) 1000BT 1 Gbps baseband LAN using twisted pair cable (of IEEE 802) 10GBE 10 Gbps baseband LAN 4b5b Line encoding method (physical layer) 5-4-3 Rule governing connection of IEEE 802.3 Ethernet segments 64b/66b Line encoding method (physical layer) 8b10b Line encoding method (physical layer) 802 Family of network standards specified by the IEEE 802.1d Specification for a bridge 802.1pQ Tag format used for VLANs and priority marking 802.3 A LAN standard based on Ethernet (see 802, 10Bx) ACK Sequence number indicating correct reception in a CO protocol ALOHA Random Access (lit. translated means Hello) AMI Alternate Mark Inversion ARP Address Resolution Protocol (translating IP -> HA) ARQ Automatic Repeat reQuest (i.e. frame retransmission procedure) AUI Attachment Unit Interface (interface to a 10 Mbps MAU) (c.f., MII) b bit bps Bits per second (unit of clock, utilisation, throughput) B Byte (group of 8 bits) (sometimes known as an octet) baud Smallest signalling unit at physical layer (i.e. symbol) BER Bit Error Ratio in digital circuit (cf SNR in an analogue circuit) bit Binary digit (unit of data transmission or storage) (c.f .baud) CAM Contents Addressable Memory (lookup table) (c.f. RAM) CAT5 Category 5 cabling (UTP cable certified for 10/100 Mbps LANs) CAT6 Category 6 cabling (UTP cable certified for 10/100 Mbps and higher speed LANs) CD Collision Detection circuit (of CSMA/CD) CPU Central Processing Unit (or microprocessor) CRC Cyclic Redundancy Check (i.e., a frame check sequence) CRC-32 32-bit CRC (as used in Ethernet) CS Carrier Sense CSMA/CD Carrier Sense Multiple Access with Collision Detection (LAN) CSMA/CA Carrier Sense Multiple Access with Collision Avoidance (WiFi) DF IPv4 Don't Fragment (bit in IP header used for MTU Discovery) Demux Demultiplexer (separates previously multiplexed circuits) (cf mux) DHC Dynamic Host Configuration DHCP Dynamic Host Configuration Protocol (network layer of TCP/IP) DL Data Link layer (Layer 2) (e.g., Ethernet) DMX Digital Multiplex DNS Domain Name Service (converts IP name to/from IP address) DPLL Digital Phase Locked Loop clock recovery for synchronous circuits DSCP Differentiated Services Code Point - of IP layer Echo Request for remote ES to reply (e.g., Echo-Request in ICMP) EIA-232 Successor to RS-232. Email Electronic Mail messaging (e.g. SMTP) ES End System (i.e., user?s computer) supporting all protocol layers FDX Full duplex FIB Forwrading Information Base of a router FIFO First-In First-Out (i.e. a queue or buffer) FIN TCP flag bit indicating the end of a TCP connection FTP File Transfer Protocol (of IP stack) (also generic term) GBE Gigabit Ethernet - 1000 Mbps Ethernet HA Hardware Address in IP and Ethernet (PL address of an interface) HDX Half duplex HTTP HyperText Transfer Protocol (using TCP) (WWW applications) I/O Input or Output of a computer interface ICMP Internetworking Control and Monitoring Protocol (of IP Suite) IEEE Institute Of Electrical and Electronic Engineers (US) IETF Internet Engineering Task Force (of ISOC) IGMP Internet Group Management Protocol (in IP multicast) IHL Internet Header Length (length of the PCI in an IP datagram) INET Internet (or IP network layer) IP Internetworking Protocol (CL network protocol of IP suite)\ IPv6 IP version 6 IS Intermediate System (e.g. router, switch) ISOC Internet Society (standards organisation for IP protocol suite) ISO International Standards Organisation (standards committee of UN) ISP Internet Service Provider KB KiloByte (1024 bytes) (2 to the power 10) kbps Kilobits per second (1000 bps) unitof utilisation & throughput kHz KiloHertz, unit of frequency (1000 cycles / second) (c.f.. kbps) L1 Physical Layer L2 Link Layer L3 Network Layer L4 Transport Layer LAN Local Area Network (e.g. Ethernet) (c.f. WAN, MAN) LDPC Low Density Parity Code LIFO Last-In First-Out (as ina computer stack) LLC Logical Link Control (DL of IEEE stack) (used by STP) lsb Least significant bit (right most bit of a byte or word) MAC Medium Access Control (lower part of DL in IEEE 802 stack) MAN Metropolitan Area Network (or regional network) (cf LAN, WAN) MAU Medium Attachment Unit (LAN transceiver electronics) (PL) Mbps Megabits per second (1000 kbps) unit of utilisation & throughput MHz MegaHertz, unit of frequency (1000 kHz) (c.f.. Mbps) MII Media Independent Interface for 100Mbps LAN (c.f., AUI) MLT3 Multi-level transmission (of Fast Ethernet) MODEM Modulator/Demodulator converts digital to/from analogue (PL) More Flag in IP header indicating additional fragments follow MPLS Multi-Protocol Label Switching msb Most significant bit (left most bit of a byte or word) MSS Maximum Segment Size (largest allowed payload at TCP layer) MTU Maximum Transfer Unit (max size of DL frame in IP) (cf MSS) Mux Multiplexer (combines circuits into a single bit stream) (cf demux) ND Neigbour Discovery for IPv6 (see also arp for IPv4) NSP Network Service Provider (providing infrastrcuture to ISP) NFS Network File System (UDP/IP file sharing application) NL Network Layer (layer 3) (e.g. IP) NRZ Non Return to Zero coding (1=high, 0=low) (Physical Layer) OSI Open Systems Interconnection (reference model) PAM Pulse Amplitude Modulation PCI Protocol Control Information (header) PDU Protocol Data Unit (of OSI) (e.g. a packet at NL, or frame at DL) Phy Physical Layer (also known as L1) ping Network testing application protocol (uses ICMP Echo-request) PL Physical Layer (Layer 1 of OSI stack) (e.g. RS-232, RS-449) PLL Phase Locked Loop clock recovery at PL (see also DPLL) PMTU Path MTU (smallest MTU over an entire path between ES) pps Packets per second (packet transmission rate) PROM Programmable Read Only Memory (permanent storage) (cf RAM) RAM Random Access Memory (working memory) (cf CAM, PROM) RARP Reverse Resolution Protocol (translates HA -> IP address) (cf ARP) RIB Routing Information Base of a routing protocol RFC Request For Comments (document issued by IETF/ISOC) RG58/U Type of flexible coaxial cable used for IEEE 802.3 10B2 LANs RJ-11 Connector used for telephones / modems RJ-45 Connector used for URP (used by IEEE 802.3 10BT/100BT/100BT LANs RS-232 V.24 serial interface using 25 pin D-connector (c.f., RS-449) RTT Round Trip Time (time to receive a response from remote system) RZ Return to Zero coding (as NRZ with a 0 between bits) (in Physical Layer) SALOHA Slotted ALOHA SAP Service Access Point (of OSI) (e.g. port in UDP or TCP) STA Spanning Tree Algorithm STP Spanning Tree Protocol; Shielded Twisted Pair TCAM Tertiary Cpntents Addressable Memory TCP Transmission Control Protocol (Transport protocol specified by TCP/IP). tftp Trivial File Transfer Program (UDP/IP application program) ToS Type of Service in IP (indicates type of data being transported, replaced by DSCP) TTL (i) Time To Live in IP (number of hops before packet is discarded) TTL (ii) Transistor-Transistor Logic family of Integrated Circuits working at 5V UART Universal Asynchronous Receiver Transmitter (device) UDP Universal Datagram Protocol (Transport protocol specified by TCP/IP) UNIX A common open operating system used by many computers USART Universal Synchronous / Asynchronous Receiver Transmitter UTP Unshielded Twisted Pair cabling (used in 10BT LANs) (CAT-5) V.24 Recommendation for serial communication (of CCITT) (EIA/RS-232) VC Virtual Circuit VLAN Virtual LAN WAN Wide Area Network (e.g., the Internet) (cf LAN) WWW World Wide Web (Internet document sharing application) (TCP/IP)