Basic Networking Terms&Definitions

Numeric

10base2: A thin coax network cable running at 10 Mbps speed

10base5: A thick coax network cable running at 10 Mbps speed

10baseT: Ethernet running on UTP (unshielded twisted pair) cable at 10 Mbps speed

100baseTX: Ethernet running on UTP (unshielded twisted pair) cable at 100 Mbps speed

A

ADSL (Asymmetric Digital Subscriber Line)

These are the modems attached to twisted pair copper cable (telephone wire) which

Can transmit 1.5-9 Mbps downstream and 16-800 Kbps upload stream (speed varies depending on the distance)

ANSI (American National Standards Institute)

This consensus body consists of volunteer safety professionals who create or revise documents on test requirements, procedural methods and product specifications.

AppleTalk

Protocol developed by apple computer for networking between Macintosh systems

Application Layer

The top layer of the network protocol stack. The application layer is concerned with the semantics of work, such as formatting electronic mail messages.

ARP (Address solution Protocol)

Protocol used to discover physical network address (MAC address) that corresponds to IP address for a host. ARP is used to map a IP address to physical network address.

ASCII (American Standard Code for Information Interchange)

A seven-level code (128 possible characters) used for data transfer.

ATM (Asynchronous Transfer Mode)

Standard implementations of cell relay packet switching technique using packets of a fixed length, called cells. It is asynchronous because the recurrence of cells containing information from an individual user is not periodic.

Authentication

Process of determining identity of user attempting to access system

Authorization

Process of determining what types of activities are permitted.

B

Binaries

Binary, machine-readable forms of programs that are compiled or assembled, as opposed to source language forms of programs.

Binary Characteristic of having only two states, such as current on and current off. Binary number system uses only ones and zeros

BNC connector used with Thin net and coaxial cable.

BOOTP (Bootstrap Protocol)

Used for booting diskless nodes.

Bridge

a device interconnecting Local Area Networks (LANs) at the Open Systems Interconnection (OSI) data link layer, and filtering and forwarding frames according to Media Access Control (MAC) addresses.

Broadband

Wide-band technology capable of supporting voice, video and data, possibly using multiple channels.

Broadcast

Data transmission to all addresses or functions

Bus

LAN topology in which all nodes are connected to single cable, considered equal, and receive all transmissions on the medium.

Byte

Data unit of eight bits.

C

CAT-5 (Category 5UTP)

Unshielded twisted pair (UTP) standard cabling, commonly used with fast Ethernet and asynchronous transfer mode (ATM) interfaces for speed cell transmission (more than 50Mbps)

CHAP (Challenge Handshake Authentication Protocol)

Authentication scheme for PPP where password is required to begin connection and during the connection. Failure to provide correct password during login or challenge mode results in disconnect.

Checksum

A computed value which is dependent upon the contents of a packet. This value is sent along with the packet when it is transmitted. The receiving system computes a new checksum based upon the received data and compares this value to the value sent With the packet. If the two values are the same, the receiver has a high degree of confidence that the data was received correctly.

Coaxial Cable

Electrical cable with solid wire conductor at its center, surrounded by insulating materials and an outer metal screen conductor with an axis of curvature coinciding with inner conductor. Examples: standard Ethernet cable and thin wire Ethernet cable.

CODEC (Coder/Decoder)

Electronic circuit converts analog voice signals into digital signals for transmission and switching, and digital signal to analog voice signals so they can be used by telephone.

Collision

Result of two network nodes transmitting on same channel at same time. Transmitted data is not usable.

D

Data Encryption

Transformation of data into unreadable, meaningless data through a cryptographic transformation using key. Decryption turns unintelligible data intomeaningful data using a key

Datagram

A packet or string of bytes carrying and routing data and sufficient information from source to destination.

Data Link Layer

Layer 2 of the Open System Interconnection (OSI) model. Layer 2 is concerned with transmitting units of information or frames, and associated error-checking. It establishes,maintains, and releases data-link connections between elements in a network.

DB (Decibel)

Logarithmic unit describing ratio of two powers

DCE (Data Communication Equipment)

Generic definition of computing equipment that attaches to network via DTE

Digital Certificate

Package of information, digitally signed by trusted authority (usually referred to as a CA or Notary), that binds a public key to owner. Usually consists of identifier field, public key field, serial number (of certificate), activation and expiration date, and signature field.X.509 defines a standard format.

Domain Name

Text name appended to host name to form unique host name across Internets.

Download

Transfer of a file or information from one network node to another. Generally refers to transferring a file from big node, such as server, to a small node, such as terminal or printer.

DTE (Data Terminal Equipment)

Generic definition of external networking interface equipment, such as modem.

E

Encapsulation

Encapsulating data is a technique used by layered protocols in which a low level protocol accepts a message from a higher-level protocol, then places it in the data portion of the lower-level frame. The logistics of encapsulation require that packets traveling over a physical network contain a sequence of headers.

Ethernet

Most popular LAN technology in use today, with configuration rules defined by IEEE standard 802.3. 10 Mbps, CSMA/CD baseband network that runs over thin coax, thick coax, twisted pair or fiber optic cable.

Enterprise Network

An information infrastructure that often combines private and public facilities to cover all of the locations operated by a single company or corporate enterprise with a single Communications fabric.

F

FDDI (Fiber Distributed Data Interface)

An American National Standards Institute (ANSI) standard for fiber-optic links with data rates up to 100 Mbps.

Fiber Optics

A transmission medium consisting of thin glass filaments. Light beams travel through the fiber-optic line, carrying large amounts of data over long distances.

File Server

Computer that stores data for network users and provides network access to that data.

Filtering

Process where an Ethernet switch or bridge reads contents of packet, finds that packet does not need to be forwarded, and drops it. Filtering rate is rate at which device can receive packets and drop them without any loss of incoming packets or delay in processing.

Firewall

System or combination of systems that enforces boundary between two or more networks, controlling access from one to the other.

Firmware

Alterable programs in semi permanent storage, such as some type of read only or flash reprogrammable memory.

Fragment

A piece of a packet. When a router is forwarding an Internet Protocol (IP) packet to a network that has a maximum packet size smaller than the forwarded packet size, it is forced to break up that packet into multiple fragments. These fragments will be reassembled by the IP layer at the destination host.

Frame

A data link layer “packet” that contains the header and trailer information required by the physical medium. Network layer packets are encapsulated to become frames. The terms packet, datagram, segment, and message are also used to describe logical information Groupings.

Frame Relay

A network interface providing high speed frame or packet transmission with minimum delay and an efficient use of bandwidth.

FTP (File Transfer Protocol)

A protocol that allows a user on one host to access and transfer files to and from another host over a network. FTP is usually the name of the program the user invokes to execute the protocol.

Full Duplex

A circuit or device permitting transmission in two directions at the same time.

G

Gbps (Giga Bits perSecond)

Giga is the prefix representing 109, or one billion. For example, 8 gbps is 8 billion data bits per second.

H

Half Duplex

A circuit or device capable of transmitting in two directions, but not at the same time.

Hardware Address

Every node on network has one or more associated addresses, including at least one fixed hardware address, such as “0F-34-2D-1d-69-E1” assigned by device’s manufacturer. Most nodes also have protocol specific addresses assigned by network manager.

Header

The portion of a packet that precedes the actual data and contains source and destination addresses, error checking, and other fields.

Hop

A term used in routing. A path to a destination on a network is a series of hops, through routers, away from the origin.

Host Table

List of TCP/IP hosts on network along with their IP addresses.

I

ICMP (Internet Control message Protocol)

An extension to the Internet Protocol (IP). ICMP enables the generation of error messages, test packets and informational messages related to Internet protocol. It is defined in STD 5, Request for Comments (RFC) 792.

IEEE (Institute of Electrical and Electronic Engineers)

An international professional society issuing its own standards. The IEEE is a member of the American National Standards Institute (ANSI) and International Standards Organization (ISOs).

IEEE 802.3

Local Area Network protocol suite with 10 Mbps or 100 Mbps throughput. Uses Carrier Sense Multiple Access bus with Collision Detection CSMA/CD media access method and physical and data link layer specifications of local area network. Includes 10BASE2, 10BASE5, 10BASE-FL, and 10BASE-T Ethernet implementations. Allows users to share network cable, but only one station can use the cable at a time. Variety of physical medium-dependent protocols are supported.

IEEE 802.5

Local Area Network protocol suite commonly known as Token Ring. Standard originated by IBM for token passing ring network that can be configured in star topology. Supports Versions 4 Mbps and 16 Mbps.

IGP (Interior Gateway Protocol)

A protocol that distributes routing information to the routers within an autonomous system.

Internet Address

Also known as an Internet Protocol (IP) address. This is a 32-bit hardware-independent address assigned to hosts using the transmission control protocol/Internet protocol (TCP/IP) suite.

Internet Datagram

Unit of data exchanged between pair of internet modules that includes internet header.

Internet Protocol Suite

Official name of TCP/IP, as used in Internet standards documents. See TCP/IP.

Internetwork

Process of connecting two networks together. Result is referred to as an internet.

Internetworking

General term used to describe the industry composed of products and technologies used to link networks together.

Intranet

Closed network of computers that uses similar technology to the Internet, such as Web servers and browsers, to make information available to controlled group of users. May have connection to Internet or may exist on Internet, achieving controlled access through passwords or other means.

Intrusion detection

Detection of break-ins or break-in attempts, manually or via software expert systems that operate on logs or other information available on network.

IOP (Interoperability)

Ability of equipment from different manufacturers (or different implementations) to operate together.

IP (Internet Protocol)

The network layer protocol of the transmission control protocol/Internet protocol (TCP/IP) suite. Defined in STD 5, Request for Comments (RFC) 791.It is a connectionless, best-effort

packet switching protocol.

IP Address (Internet Protocol Address)

A number assigned to each computer’s or other device’s network interface(s) which are active on a network supporting the Internet Protocol, in order to distinguish each network interface (and hence each networked device) from every other network interface anywhere on the network.

ISO (International Standards Organization)

An international organization involved in writing communications standards.

ISP (Internet Service Provider)

Organization offering and providing Internet services to public, with own computer servers to provide services offered.

L

LAN (Local Area Connection)

A data transmission facility connecting a number of communicating devices (computers, terminals and printers) within a single room, building, campus or other limited geographical area.

Load Balancing

A technique that distributes network traffic along parallel paths to maximize the available network bandwidth while providing redundancy

Local Talk

Apple Computer’s proprietary 230 Kbps baseband network protocol. Uses CSMA/CD access method over unshielded twisted pair wire.

M

MAC (Media Access Control)

A protocol that defines the way workstations gain access to transmission media. MAC is most widely used in reference to Local Area Networks (LANs).

MAN (Metropolitan Area Network)

A network that provides regional connectivity within a metropolitan area (such as city). MANs are categorized between Local Area Networks (LANs) and Wide Area Networks (WANs).

Modem

Modulator-demodulator device for changing transmission signals from digital to analog for transmission over phone lines. Used in pairs, one at each end of line.

Multiplexer

Device that allows several users to share single circuit. Funnels different data streams into single stream. At other end of communications link, another multiplexer reverses process by splitting data stream back into original streams.

N

Name Server

Software that runs on network hosts charged with translating (or resolving) text-style names into numeric IP addresses.

Native Address

Address that matches one of given node’s summary addresses

NetBIOS/NetBEUI

Microsoft’s networking protocols for its LAN Manager and Windows NT products.

NetWare

Novell-developed Network Operating System (NOS). Provides file and printer sharing among networks of Personal Computers (PCs). Each network must have at least one file server, and access to other resources is dependent on connecting to and logging into file server. File server controls user logins and access to other network clients, such as user PCs, print servers, modem/fax servers, and disk/file servers.

Network

Interconnected system of computers that can communicate with each other and share files, data, and resources.

Network Address

Every node on network has one or more associated addresses, including at least one fixed hardware address, such as “ae-34-2c-1d-69-f1” assigned by device’s manufacturer. Most nodes also have protocol specific addresses assigned by network manager.

Network Layer

A layer in the Open System Interconnection (OSI) reference model. The network layer provides address resolution and routing protocols. Address resolution enables the network layer to determine a unique network address for a node. Routing protocols allow data to flow between networks and reach their proper destination.

Network Management

Administrative services for managing a network, including configuring and tuning, maintaining network operation, monitoring network performance, and diagnosing network problems.

NFS (Network File System)

The recognized standard protocol for accessing files over a network as if they were on local disks. Defined in Request for Comments (RFC) 1094.

NIC (Network Interface Card)

Adapter card inserted into computer that contains necessary software and electronics to enable station to communicate over network.

NOS (Network Operating System)

Software for network that runs in file server and controls access to files and other resources from multiple users. Provides security and administrative tools.

P

Packet

An ordered group of data and control signals transmitted through a network as a subset of a larger message.

PAP (Password Authentication Protocol)

Authentication scheme for PPP links. Password can be specified for both Devices on remote link. Failure to authenticate results in dropped connection prior to start of data transmission.

Parity Bit

An additional non-information bit added to a group of bits to ensure that the total number of bits in the character is even or odd.

Physical layer

Layer 1 of the Open System Interconnection (OSI) model. Layer 1 is concerned with electrical, mechanical and handshaking procedures over the interface connecting a device to the transmission medium.

Physical Address

Address identifying a single node.

PPP (Point-to-Point Protocol)

Provides a standard means of encapsulating data packets sent over a single-channel Wide Area Network (WAN) link. PPP is the standard WAN encapsulation protocol for the interoperability of bridges and routers over synchronous or asynchronous circuits.

Presentation Layer

The Open System Interconnection (OSI) layer that determines how application information is represented or encoded while in transit between two end systems.

Protocol

A formal set of conventions governing the formatting and relative timing of message exchange between two communicating systems.

Proxy

Software agent that acts on behalf of user. Generally accepts connection from user, makes decision whether or not user or client IP address is permitted to use proxy, may perform additional authentication, and completes connection on behalf of user to remote destination.

PSTN (Public Switched Telephone Network)

The telecommunications network commonly accessed by standard telephones, key systems, Private Branch Exchange (PBX) trunks and data equipment.

Q

QoS (Quality of Service)

A group of service classes that define the performance of a given circuit. For an Asynchronous Transfer Mode (ATM), there are a number of different QoS parameters

R

RAM (Random Access Memory)

Computer’s direct access memory that can be accessed very quickly and overwritten with new information. Loses its content when power is turned off.

Remote Access

Access to network resources not located on same physical Ethernet (entire site network topology).

Remote Control

Form of remote access where device dialing in assumes control of another network node. All remote keystrokes translated into keystrokes on network node. Used primarily with IPX protocol.

Remote Node

Form of remote access where device dialing in acts as peer on target network. Used with IP and IPX protocols.

Repeater

A device that automatically amplifies, restores, or reshapes signals before retransmission to compensate for distortion and/or attenuation.

RISC (Reduced Instruction Set Computing)

Computer processing technology in which microprocessor understands few simple instructions, providing fast, predictable instruction flow.

ROM (Read-only Memory)

Memory device that retains its information even when power is off. ROM version of network device does not need to download as contains entire executable code, so never needs to reload it. Frequently provided as “flash ROM”, which can be reprogrammed by downloading if user chooses.

Route Server

Physical device that runs one or more network layer routing protocols and uses route query protocol to provide network layer routing forwarding descriptions to clients.

Router

An interconnection device that connects individual Local Area Networks (LANs). Unlike bridges, which logically connect at Open System Interconnection (OSI) Layer 2, routers provide logical paths at OSI Layer 3. Like bridges, remote sites can be connected using routers over dedicated or switched lines to create Wide Area Networks (WANs).

Routing Protocol

General term indicating protocol run between routers and/or route servers to exchange information used to allow computation of routes. Result is one or more forwarding descriptions.

S

Server

Computer that provides resources to be shared on network, such as files (file server) or terminals (terminal server).

SLIP (Serial Link Internet Protocol)

An Internet protocol for host dial-up connection. SLIP frames are encapsulated Internet protocol (IP) datagram in which SLIP adds just a few bytes of control data.

SMTP (Simple Mail Transfer Protocol)

A protocol, defined in STD 10, Request for Comments (RFC) 821, used to transfer electronic mail between computers. It is a server-to-server protocol, so other protocols are used to access the messages.

SNMP (Simple Network Management Protocol)

The network management protocol of the Transmission Control Protocol/Internet Protocol (TCP/IP) suite.

STP (Shielded Twisted Pairs)

General term for shielded cabling systems that are designed specifically for data transmission. Also means Spanning Tree Protocol, a routing protocol that eliminates routing loops in a network.

Subnet

A portion of a network, which may be a physically independent network segment, which shares a network address with other portions of the network. It is distinguished by a subnet number.

Switch

Multiport Ethernet device designed to increase network performance by allowing only essential traffic on attached individual Ethernet segments. Packets are filtered or forwarded based upon their source and destination addresses.

Synchronous Transmission

Transmission in which data bits are sent at a fixed rate, with the transmitter and receiver synchronized.

T

TCP (Transmission Control Protocol)

An Internet standard transport layer protocol defined in STD 7, Request for Comments (RFC) 793. It is connection oriented and stream-oriented, as opposed to User Datagram Protocol (UDP)

Telnet

The virtual terminal protocol in the Internet suite of protocols. It lets users on one host use the Internet to access and work as terminal users of a remote host.

TFTP (Trivial File Transfer Protocol)

A simplified version of the file transfer protocol that transfers files but does not provide password protection or user directory capability.

Thick wire

Half-inch diameter coax cable.

Thin wire

Thin coaxial cable similar to that used for television/video hookups.

Throughput

Rate of data transmitted between two points in given amount of time (e.g., 10 Mbps).

Token Ring

Developed by IBM, this 4 or 16 Mbps network uses ring topology and token passing access method

TTL (Time to Live)

A field in the Internet Protocol (IP) header that indicates how long this packet should be allowed to survive before being discarded. It is primarily used as a hop count.

Tunneling

Refers to the encapsulation of protocol A within protocol B, such that A treats B as though it were a data link layer.

Twisted-Pair Cable

Inexpensive, multiple-conductor cable comprised of one or more pairs of 18 to 24-gauge copper strands twisted to improve protection against electromagnetic and radio frequency interference. May be either shielded or unshielded. Because of narrow bandwidth, used in low-speed communications, as telephone cable only.

U

Uplink

Connectivity from border node to upnode.

Upnode

Border node’s outside neighbor in common peer group. Must be neighboring peer of one of border node’s ancestors.

V

VBR (Variable Bit Rate)

Traffic containing bursts but centered around an average bandwidth.

VC (Virtual Channel)

A connection established between end users, in which packets are forwarded along the same path and bandwidth is not permanently allocated until it is used.

VCI (Virtual Channel Identifier)

A 16-bit value in the asynchronous transfer mode (ATM) cell header that provides a unique identifier for the Virtual Channel (VC) within a Virtual Path (VP) that carries that particular cell.

Virtual Circuit

A network service that provides connection-oriented service regardless of the underlying network structure.

Virus

Self-replicating code segment. Viruses may or may not contain payloads, attack programs, or trapdoors.

VLAN (Virtual Local Area Network)

A network architecture that allows geographically distributed users to communicate as if they were on a single physical Local Area Network (LAN) by sharing a single broadcast and multicast domain. Asynchronous Transfer Mode (ATM) forum LAN emulation supports virtual Local Area Networks (VLANs).

VPN (Virtual Private Network)

Public network service in which a customer is provided a network that appears as though it were a private network. The advantage of VPNs over the dedicated private networks is that the VPNs allow a dynamic use of the network resources and offer very reliable, high-speed and less expensive communications.

W

WAN (Wide Area Network)

A network that typically spans nationwide distances and usually utilizes public telephone networks.

Workgroup Switching

Configuration in which numbers of users are connected to Ethernet network via switch that allows each user to get greater throughput than would be available through hub