Network

BootP

Allocates Ip addresses to devices without storage.

Multilayer Switch

Performs both routing and switching

Well Known Ports

Ports ranging from 0 to 1023; assigned to processes that only the operating system or administrator of the system can access.

Path-Vector Routing

A protocol that uses dynamically updated paths or routing tables to transmit packets from one autonomous network to another.

TFTP

FTP uses the User Datagram Protocol (UDP)and provides no security features. It is often used by servers to boot diskless workstations, X-terminals, and routers. Uses Port 69

Dynamic Ports

Ports ranging from 49152 through 65535; open for use without restriction

ICA

short for Independent Computing Architecture, ICA is a protocol designed specifically for transmitting Windows graphical display data as well as keyboard and mouse input over a network. ICA is one of two technologies used by Citrix servers, the other being WinFrame.

Static Routing

A technique in which a network administrator programs a router to use specific paths between nodes. Because it does not account for occasional network congestion, failed connections, or device moves, static routing is not optimal.

DOCSIS

(Data Over Cable Service Interface Specification) A security technology used for filtering packets and maintaining customer privacy on cable Internet services.

DMZ

(Demilitarized Zone) A computer or small subnetwork that sits between a trusted internal network, such as a corporate private LAN, and an untrusted external network, such as the public Internet. Typically, it contains devices accessible to Internet traffic, such as Web (HTTP ) servers, FTP servers, SMTP (e-mail) servers and DNS servers.

DWDM

(Dense Wavelength Division Multiplexing) A technology that allows multiple streams of information together on an optical fiber using different wavelengths of laser light to carry different signals. Also known as Wavelength Division Multiplexing (WDM).

FTP

(File Transfer Protocol) A set of rules for uploading and downloading files between a client computer and a remote server.FTP ports works on ports 20 and 21.

GBIC

(Gigabit Interface Converter) A transceiver used to convert electrical signals into optical signals and vice versa.

HSPA

(High Speed Packet Access) A family of high-speed 3G digital data services provided by cellular carriers worldwide that use the GSM technology.

HTTP

(Hyper Transfer Protocol) The communications protocol used to transmit Web pages. Uses port 80

HTTPS

(Hypertext Transfer Protocol Secure) A secure version of HTTP that supports e-commerce by providing a secure connection between a web browser and a server. Port 443

IEEE

(Institute of Electrical and Electronics Engineers)--Pronounced I-triple-E; IEEE is an organization composed of engineers; scientists and students. The IEEE is best known for developing standards for the computer and electronics industry.

ISP

(Internet Service Provider) An institution that provides access to the Internet in some form, usually for money.

SMTP

(Simple Made Transfer Protocol) A communication protocol used to send email across a network or the Internet. Uses Port 25

DSL

(Digital Subscriber Line) A method for moving data over regular phone lines.

Bridge Protocol Data Unit

Acronym for bridge protocol data unit. BPDUs are data messages that are exchanged across the switches within an extended LAN that uses a spanning tree protocol topology. BPDU packets contain information on ports, addresses, priorities and costs and ensure that the data ends up where it was intended to go. BPDU messages are exchanged across bridges to detect loops in a network topology. The loops are then removed by shutting down selected bridge interfaces and placing redundant switch ports in a backup, or blocked, state.

AS

An Autonomous System (AS) is a group of networks under mutual administration that share the same routing methodology. An AS uses an internal gateway protocol and common metrics to route packets within the AS and uses an external gateway protocol to route packets to other Autonomous Systems.

Store and forward Switching

Calculates a packets CRC value

SMB

Client Server model to enable computer to communitcate and share resources. Mainly used in Microsoft Networks. Uses Port

FDDI

Fiber distributed data interface (FDDI) is a type of Token Ring network. The implementation and topology of FDDI differs from the IBM Token Ring LAN architecture.

Cut through Switch

Forwards a data packet as soon as it receives it, without processing the packet or checking it for errors.

FHSS

Frequency Hopping Spread Spectrum: Uses a narrowband carrier that changes frequency in a pattern known to both the transmitter and receiver. When synchronized, a single logical channel is maintained. Uses a lower data rate (3 Mbps) than DSSS but can be installed into virtually any location without fear of interference. FHSS = used by Bluetooth standard

FDM

Frequency division multiplexing (FDM) is the process by which the total bandwidth available to the system is divided into a series of non overlapping frequency sub-bands that are then assigned to each communicating source and user pair

GPG

GNU PRIVACY An application that allows you to encrypt and decrypt information, create public and private encryption keys, and use or verify digital signatures.

HDLC

High Level Data Link Control. A bit-oriented synchronous data link layer protocol based on SDLC. A protocol that moves data over x.25 or Frame relay.

HIDS

Host Intrusion Detection System - installed on either servers or workstations, monitoring traffic and applications to detect attacks.

IPv6

IPv6 An extended scheme of IP addresses, using 128-bit IP addresses, that allows for more IP addresses than current system, IPv4, which uses 32-bit IP addresses.

Collision Domain

In Ethernet, the network area where data that is being transmitted simultaneously from two or more computers could collide. Repeaters and hubs propagate collisions; LAN switches, bridges and routers do not

ESSID

In computer networking, a service set is a set consisting of all the devices associated with a consumer or enterprise IEEE 802.11 wireless local area network (WLAN). The Service set can be local, independent, extended or mesh.

IGMP

Internet Group Management Protocol. Used for multicasting. Computers belonging to a multicasting group have a multicasting IP address in addition to a standard unicast IP address. IIS - Internet Information Services. A Microsoft Windows web server. IIS comes free with Microsoft Windows Server products.

IIS

Internet Information Services. A Microsoft Windows web server. IIS comes free with Microsoft Windows Server products.

IMAP4

Internet Message Access Protocol 4 allows users to get the email into their inbox or phone straight away without having to login. The emails stay on the ISP server from which they are accessed. Uses Port 143

IPv4

Internet Protocol version 4. Identifies hosts using a 32-bit IP address. IPv4 is expressed in dotted decimal format with decimal numbers separated by dots or periods like this: 192.168.1.1. IPv6 - Internet Protocol version 6. Identifies hosts using a 128-bit address. IPv6 is expressed as eight groups of four hexadecimal characters (numbers and letters), such as this: FE80: 0000: 0000: 0000: 20D4: 3FF7: 003F:DE62.

ARP

Maps Ip and physical addreses.

POP3

Post Office Protocol v3. Used to transfer e-mail from mail servers to clients. POP3 uses port 110.

American Registry for Internet Numbers

Provides services related to the technical coordination and management of Internet number resources Facilitates policy development by its members and stakeholders Participates in the international Internet community Is a nonprofit, community-based organization Is governed by an executive board elected by its membership

Fragment Free Switch

Reads the first 64 bytes (contains the header) Performs error checking; if it is OK then begins transmitting

ICS

Short for Internet connection sharing, a method for connecting multiple computers in a LAN to the Internet through a single connection and a single IP address. ICS typically uses NAT technologies to achieve this and works with most connection technologies, including DSL, cable, ISDN, dial-up and satellite. The device with the modem or broadband interface that establishes the connection to the Internet is called the ICS host, or gateway while the other devices that connect to the Internet via the network and the ICS host are called ICS clients. If the ICS host fails, then all of the ICS clients lose their Internet connection.

TTL

Short for Time to Live, a field in the Internet Protocol (IP) that specifies how many more hops a packet can travel before being discarded or returned.

Hz

The hertz (symbol Hz) is the unit of frequency in the International System of Units (SI). It is defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications, such as the frequency of musical tones. The unit is named for Heinrich Rudolf Hertz, who was the first to conclusively prove the existence of electromagnetic waves.

Link-State Routing

This type of routing is more complex than Distance-Vector Routing. It enables routers to calculate the best routes based on a range of information, instead of using hop count only.

DNS

Translates host names into Ip addresses.

SSH

Uses Port 22

ESP

(1) Short for estimated street price, ESP is a manufacturer or developer's estimated price for a product in a specific region or market sector. The estimated street price is not necessarily the same as the end -user's purchase price. (2) Short for Encapsulating Security Payload, the ESP header is designed to provide a mix of security services in IPv4 and IPv6. ESP may be applied alone, in combination with the IP Authentication Header (AH), or in a nested fashion. The ESP header is inserted after the IP header and before the upper layer protocol header (transport mode) or before an encapsulated IP header (tunnel mode). ESP is used to provide confidentiality, data origin authentication, connectionless integrity, an anti-replay service, and limited traffic flow confidentiality.

Dynamic Host Configuration Protocol

(DHCP) A set of rules that allow network client computers to find and use the Internet address that corresponds to a domain name.

EAP

(Extensible Authentication Protocol) An authentication protocol that enables systems to use hardware-based identifiers , such as fingerprint scanners or smart card readers, for authentication.

RIP

(n.) Abbreviated as RIP, an interior gateway protocol defined by RFC 1058 that specifies how routers exchange routing table information. With RIP, routers periodically exchange entire tables. Because this is inefficient, RIP is gradually being replaced by a newer protocol called Open Shortest Path First (OSPF).

Broadcast Domain

A combination of ports on a switch (or multiple switches) that make up a Layer 2 segment. To be able to exchange data with each other, broadcast domains must be connected by a Layer 3 device, such as a router or Layer 3 switch. A VLAN is one type of broadcast domain.

Routing Loops

A condition in which a packet is continuously transmitted within a series of routers without ever reaching its intended destination

Decibels

A dB is a unit of measurement used to express relative difference in power or intensity, usually between two acoustic or electric signals, equal to ten times the common logarithm (an exponent used in mathematical calculations to depict the perceived levels) of the ratio of the two levels.

EDNS

A mechanism to be able to include more information in DNS requests by expanding the size of several parameters. Used by "devices" like Aruba and the Umbrella Enterprise Roaming Client to include information on device ID and enable mapping of device to organization and policy in the OpenDNS system.

Dynamic Routing

A method of routing that automatically calculates the best path between two nodes and accumulates this information in a routing table. If congestion or failures affect the network, a router using dynamic routing can detect the problems and reroute data through a different path. Modern networks primarily use dynamic routing.

IPS

An IPS, or intrusion prevention system is used in computer security. It provides policies and rules for network traffic along with an intrusion detection system for alerting system or network administrators to suspicious traffic, but allows the administrator to provide the action upon being alerted. Some compare an IPS to a combination of IDS and an application layer firewall for protection.

Access control list

An access control list (ACL), with respect to a computer file system, is a list of permissions attached to an object. An ACL specifies which users or system processes are granted access to objects, as well as what operations are allowed on given objects.[1] Each entry in a typical ACL specifies a subject and an operation. For instance, if a file has an ACL that contains (Alice, delete), this would give Alice permission to delete the file.

Asymmetric digital subscriber line

Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line (DSL) technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. It does this by utilizing frequencies that are not used by a voice telephone call.[1] A splitter, or DSL filter, allows a single telephone connection to be used for both ADSL service and voice calls at the same time. ADSL can generally only be distributed over short distances from the telephone exchange (the last mile), typically less than 4 kilometres (2 mi),[2] but has been known to exceed 8 kilometres (5 mi) if the originally laid wire gauge allows for further distribution. At the telephone exchange the line generally terminates at a digital subscriber line access multiplexer (DSLAM) where another frequency splitter separates the voice band signal for the conventional phone network. Data carried by the ADSL are typically routed over the telephone company's data network and eventually reach a conventional Internet Protocol network.

Zeroconfig

Automatically configs IP adresses on network devices.

Challenge Handshake Authentication Protocol

CHAP is a type of authentication in which the authentication agent (typically a network server) sends the client program a random value that is used only once and an ID value. Both the sender and peer share a predefined secret. The peer concatenates the random value (or nonce), the ID and the secret and calculates a one-way hash using MD5. The hash value is sent to the authenticator, which in turn builds that same string on its side, calculates the MD5 sum itself and compares the result with the value received from the peer. If the values match, the peer is authenticated. By transmitting only the hash, the secret can't be reverse-engineered. The ID value is increased with each CHAP dialogue to protect against replay attacks. Contrast with PAP.

Carrier Sense Multiple Access/Collision Detection

CSMA/CD is a set of rules determining how network devices respond when two devices attempt to use a data channel simultaneously (called a collision). Standard Ethernet networks use CSMA/CD to physically monitor the traffic on the line at participating stations. If no transmission is taking place at the time, the particular station can transmit. If two stations attempt to transmit simultaneously, this causes a collision, which is detected by all participating stations. After a random time interval, the stations that collided attempt to transmit again. If another collision occurs, the time intervals from which the random waiting time is selected are increased step by step. This is known as exponential back off. CSMA/CD is a type of contention protocol. Networks using the CSMA/CD procedure are simple to implement but do not have deterministic transmission characteristics. The CSMA/CD method is internationally standardized in IEEE 802.3 and ISO 8802.3.

RARP

Enables nodes to discover their IP adresses.

EGP

Exterior Gateway Protocol: Used for an inter-autonomous system routing, that is, routing between autonomous systems

FQDN

FQDN is a abbreviation for the term "Fully Qualified Domain Name". This refers to the full domain name of a URL. It is "fully qualified" because it is completely defined separate from the IP address where it is located.

AAA protocol

In computer security, AAA commonly stands for authentication, authorization and accounting. It refers to a security architecture for distributed systems for controlling which users are allowed access to which services, and tracking which resources they have used. Two network protocols providing this functionality are particularly popular: the RADIUS protocol,[1] and its newer Diameter counterpart

FM

In telecommunications and signal processing, frequency modulation (FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. (Compare with amplitude modulation, in which the amplitude of the carrier wave varies, while the frequency remains constant.)

Advanced Encryption Standard

AES is based on a design principle known as a substitution-permutation network, and is fast in both software and hardware.[8] Unlike its predecessor DES, AES does not use a Feistel network. AES is a variant of Rijndael which has a fixed block size of 128 bits, and a key size of 128, 192, or 256 bits. By contrast, the Rijndael specification per se is specified with block and key sizes that may be any multiple of 32 bits, both with a minimum of 128 and a maximum of 256 bits. AES operates on a 4×4 column-major order matrix of bytes, termed the state, although some versions of Rijndael have a larger block size and have additional columns in the state. Most AES calculations are done in a special finite field. The key size used for an AES cipher specifies the number of repetitions of transformation rounds that convert the input, called the plaintext, into the final output, called the ciphertext. The number of cycles of repetition are as follows: 10 cycles of repetition for 128-bit keys. 12 cycles of repetition for 192-bit keys. 14 cycles of repetition for 256-bit keys. Each round consists of several processing steps, each containing four similar but different stages, including one that depends on the encryption key itself. A set of reverse rounds are applied to transform ciphertext back into the original plaintext using the same encryption key.

Address Resolution Protocol

ARP, a network layer protocol used to convert an IP address into a physical address (called a DLC address), such as an Ethernet address. A host wishing to obtain a physical address broadcasts an ARP request onto the TCP/IP network. The host on the network that has the IP address in the request then replies with its physical hardware address. There is also Reverse ARP (RARP) which can be used by a host to discover its IP address. In this case, the host broadcasts its physical address and a RARP server replies with the host's IP address.

Asynchronous Transfer Mode

ATM is a network technology based on transferring data in cells or packets of a fixed size. The cell used with ATM is relatively small compared to units used with older technologies. The small, constant cell size allows ATM equipment to transmit video, audio, and computer data over the same network, and assure that no single type of data hogs the line. Some people think that ATM holds the answer to the Internet bandwidth problem, but others are skeptical. ATM creates a fixed channel, or route, between two points whenever data transfer begins. This differs from TCP/IP, in which messages are divided into packets and each packet can take a different route from source to destination. This difference makes it easier to track and bill data usage across an ATM network, but it makes it less adaptable to sudden surges in network traffic. When purchasing ATM service, you generally have a choice of four different types of service: constant bit rate (CBR): specifies a fixed bit rate so that data is sent in a steady stream. This is analogous to a leased line. variable bit rate (VBR): provides a specified throughput capacity but data is not sent evenly. This is a popular choice for voice and videoconferencing data. available bit rate (ABR): provides a guaranteed minimum capacity but allows data to be bursted at higher capacities when the network is free. unspecified bit rate (UBR): does not guarantee any throughput levels. This is used for applications, such as file transfer, that can tolerate delays.

Application Service Provider

Abbreviated as ASP, a third-party entity that manages and distributes software-based services and solutions to customers across a wide area network from a central data center. In essence, ASPs are a way for companies to outsource some or almost all aspects of their information technology needs. They may be commercial ventures that cater to customers, or not-for-profit or government organizations, providing service and support to end users.

ISDN

Abbreviation of integrated services digital network, an international communications standard for sending voice, video, and data over digital telephone lines or normal telephone wires. ISDN supports data transfer rates of 64 Kbps (64,000 bits per second). There are two types of ISDN: Basic Rate Interface (BRI) -- consists of two 64-Kbps B-channels and one D-channel for transmitting control information. Primary Rate Interface (PRI) -- consists of 23 B-channels and one D-channel (U.S.) or 30 B-channels and one D-channel (Europe). The original version of ISDN employs baseband transmission. Another version, called B-ISDN, uses broadband transmission and is able to support transmission rates of 1.5 Mbps. B-ISDN requires fiber optic cables and is not widely available.

Common Address Redundancy Protocol

Acronym for Common Address Redundancy Protocol. CARP is a free alternative to the Virtual Router Redundancy Protocol (VRRP) and the Hot Standby Router Protocol (HSRP). Its primary purpose is to allow multiple hosts on the same network segment to share an IP address. CARP works by allowing a group of hosts on the same network segment to share an IP address. This group of hosts is referred to as a redundancy group. The redundancy group is assigned an IP address that is shared among the group members. Within the group, one host is designated the master and the rest as back-ups. The master host is the one that currently holds the shared IP. It responds to any traffic or ARP requests directed towards it. Each host may belong to more than one redundancy group at a time.

Amplitude modulation

Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength (amplitude) of the carrier in proportion to the waveform being sent. That waveform may, for instance, correspond to the sounds to be reproduced by a loudspeaker, or the light intensity of television pixels. This contrasts with frequency modulation, in which the frequency of the carrier signal is varied, and phase modulation, in which its phase is varied, by the modulating signal. AM was the earliest modulation method used to transmit voice by radio. It remains in use today in many forms of communication; for example it is used in portable two way radios, VHF aircraft radio and in computer modems. "AM" is often used to refer to mediumwave AM radio broadcasting.

Content Switch

Analyzes the content of data packets in real time, and assesses factors like criticality and request type. Used for load balancing among server groups, web caching and application redirection. Aka 4-7 switches because they also operate on Layers 4-7.

Authentication Header

Authentication Header (AH) is a member of the IPsec protocol suite. AH guarantees connectionless integrity and data origin authentication of IP packets. Further, it can optionally protect against replay attacks by using the sliding window technique and discarding old packets (see below). In IPv4, the AH protects the IP payload and all header fields of an IP datagram except for mutable fields (i.e. those that might be altered in transit), and also IP options such as the IP Security Option (RFC-1108). Mutable (and therefore unauthenticated) IPv4 header fields are DSCP/ToS, ECN, Flags, Fragment Offset, TTL and Header Checksum.[9] In IPv6, the AH protects most of the IPv6 base header, AH itself, non-mutable extension headers after the AH, and the IP payload. Protection for the IPv6 header excludes the mutable fields: DSCP, ECN, Flow Label, and Hop Limit.[9] AH operates directly on top of IP, using IP protocol number 51.[15] The following AH packet diagram shows how an AH packet is constructed and interpreted:[

Border Gateway Protocol

BGP is an exterior gateway routing protocol that enables groups of routers (called autonomous systems) to share routing information so that efficient, loop-free routes can be established. BGP is commonly used within and between Internet Service Providers (ISPs). The protocol is defined in RFC 1771.

DSU

Data service unit. Device used in digital transmission that adapts the physical interface on a DTE device to a transmission facility such as T1 or E1. The DSU is also responsible for functions such as signal timing. Often referred to together with CSU, as CSU/DSU. See also CSU.

LDAP

Determines how a client shares directory info on a server.

DSSS

Direct-Sequence Spread Spectrum. A transmission technique in which a signal's bits are distributed over an entire frequency band at once. Each bit is coded sot hat the receiver can reassemble the original signal upon receiving the bits. used on original 802.11 standard and in the 802.11b standard

DDoS

Distributed denial-of-service. An attack on a system launched from multiple sources intended to make a computer's resources or services unavailable to users. DDoS attacks are often launched from zombies in botnets. DDoS attacks typically include sustained, abnormally high network traffic. A performance baseline helps administrators detect a DDoS. Compare to DoS.

HIPS

Host-based intrusion prevention system. An extension of a host-based IDS. Designed to react in real time to catch an attack in action.

HSRP

Hot Standby Router Protocol. Provides high network availability and transparent network topology changes. HSRP creates a Hot Standby router group with a lead router that services all packets sent to the Hot Standby address. The lead router is monitored by other routers in the group, and if it fails, one of the standby routers inherits the lead position and the Hot Standby group address.

ICANN

ICANN (Internet Corporation for Assigned Names and Numbers) is the private (non-government) non-profit corporation with responsibility for IP address space allocation, protocol parameter assignment, domain name system management, and root-server system management functions.

Challenge-Response Authentication Mechanism- Message Digest 5

In cryptography, CRAM-MD5 is a challenge-response authentication mechanism (CRAM) based on the HMAC-MD5 algorithm. As one of the mechanisms supported by the Simple Authentication and Security Layer (SASL), it is often used in email software as part of SMTP Authentication and for the authentication of POP and IMAP users, as well as in applications implementing LDAP, XMPP, BEEP, and other protocols. When such software requires authentication over unencrypted connections, CRAM-MD5 is preferred over mechanisms that transmit passwords "in the clear," such as LOGIN and PLAIN. However, it can't prevent derivation of a password through a brute-force attack, so it is less effective than alternative mechanisms that avoid passwords or that use connections encrypted with Transport Layer Security (TLS).

IGP

Interior Gateway Protocol, used to exchange routing information with routers in the same autonomous system (AS) examples include RIP, EIGRP, OSPF, and IS-IS

IANA

Internet Assigned Numbers Authority (IANA) is the organization responsible for passing out IP addresses to ISPs.

ICMP

Internet Control Message Protocol. Used for diagnostics such as ping. Many DoS attacks use ICMP. It is common to block ICMP at firewalls and routers. If ping fails, but other connectivity to a server succeeds, it indicates that ICMP is blocked.

ISAKMP

Internet Security Association and Key Management Protocol, a protocol defined by RFC 2408 for establishing Security Associations (SA) and cryptographic keys in an Internet environment.only provides a framework for authentication and key exchange and is designed to be key exchange independent

IDS

Intrusion detection system. A detective control used to detect attacks after they occur. A signature-based IDS (also called definition-based) uses a database of predefined traffic patterns. An anomaly-based IDS (also called behavior-based) starts with a performance baseline of normal behavior and compares network traffic against this baseline. An IDS can be either host-based (HIDS) or network-based (NIDS). In contrast, a firewall is a preventative control that attempts to prevent the attacks before they occur. An IPS is a preventative control that will stop an attack in progress.

Registered Ports

Ports ranging from 1024 to 49151; accessible to network users and processes that do not have special administrative privileges.

Automatic Private IP Addressing APIPA

Short for Automatic Private IP Addressing, a feature of later Windows operating systems. With APIPA, DHCP clients can automatically self-configure an IP address and subnet mask when a DHCP server isn't available. When a DHCP client boots up, it first looks for a DHCP server in order to obtain an IP address and subnet mask. If the client is unable to find the information, it uses APIPA to automatically configure itself with an IP address from a range that has been reserved especially for Microsoft. The IP address range is 169.254.0.1 through 169.254.255.254. The client also configures itself with a default class B subnet mask of 255.255.0.0. A client uses the self-configured IP address until a DHCP server becomes available. The APIPA service also checks regularly for the presence of a DHCP server (every five minutes, according to Microsoft). If it detects a DHCP server on the network, APIPA stops, and the DHCP server replaces the APIPA networking addresses with dynamically assigned addresses. APIPA is meant for nonrouted small business environments, usually less than 25 clients.

Basic Rate Interface

Short for Basic-Rate Interface, the basic ISDN configuration, which consists of two B-channels that can carry voice or data at rate of 64Kbps, and one D-channel, which carries call-control information. Another type of ISDN configuration is called Primary-Rate Interface (PRI), which consists of 23 B-channels (30 in Europe) and one D-channel.

British Navel Connector

Short for Bayonet Neill Concelman connector, (sometimes erroneously called a British Naval Connector or Bayonet Nut Connector,a type of connector used with coaxial cables such as the RG-58 A/U cable used with the 10Base-2 Ethernet system. The basic BNC connector is a male type mounted at each end of a cable. This connector has a center pin connected to the center cable conductor and a metal tube connected to the outer cable shield. A rotating ring outside the tube locks the cable to any female connector. BNC T-connectors (used with the 10Base-2 system) are female devices for connecting two cables to a network interface card (NIC). A BNC barrel connector allows connecting two cables together. BNC connectors can also be used to connect some monitors, which increases the accuracy of the signals sent from the video adapter.

Channel Service Unit

Short for Channel Service Unit/Data Service Unit. The CSU is a device that connects a terminal to a digital line. Typically, the two devices are packaged as a single unit. The dSU is a device that performs protective and diagnostic functions for a telecommunications line. You can think of it as a very high-powered and expensive modem. Such a device is required for both ends of a T-1 or T-3 connection, and the units at both ends must be set to the same communications standard.

Classless inter domain routing

Short for Classless Inter-Domain Routing, an IP addressing scheme that replaces the older system based on classes A, B, and C. With CIDR, a single IP address can be used to designate many unique IP addresses. A CIDR IP address looks like a normal IP address except that it ends with a slash followed by a number, called the IP network prefix. For example: 172.200.0.0/16 The IP network prefix specifies how many addresses are covered by the CIDR address, with lower numbers covering more addresses. An IP network prefix of /12, for example, can be used to address 1,048,576 former Class C addresses. CIDR addresses reduce the size of routing tables and make more IP addresses available within organizations. CIDR is also called supernetting.

ESD

Short for Electronic Software Distribution, a system for selling software over a network. ESD systems provide secure communications that customers use to download and pay for software. These systems can operate over the Internet or on a direct modem -to-modem connection. ESD systems can also allow users to use software for a trial period before purchasing. (1) Short for electrostatic discharge, the rapid discharge of static electricity from one conductor to another of a different potential. An electrostatic discharge can damage integrated circuits found in computer and communications equipment.

IPSec

Short for IP Security, a set of protocols developed by the IETF to support secure exchange of packets at the IP layer. IPsec has been deployed widely to implement Virtual Private Networks (VPNs). IPsec supports two encryption modes: Transport and Tunnel. Transport mode encrypts only the data portion (payload) of each packet, but leaves the header untouched. The more secure Tunnel mode encrypts both the header and the payload. On the receiving side, an IPSec-compliant device decrypts each packet. For IPsec to work, the sending and receiving devices must share a public key. This is accomplished through a protocol known as Internet Security Association and Key Management Protocol/Oakley (ISAKMP/Oakley), which allows the receiver to obtain a public key and authenticate the sender using digital certificates.

InterNIC

Short for Internet Network Information Center, a registered service mark of the U.S. Department of Commerce and now a defunct entity. InterNIC began as a collaborative project between AT&T and Network Solutions, Inc. (NSI) supported by the National Science Foundation. When active, the project offered four services: InterNIC Directory and Database Services -- online white pages directory and directory of publicly accessible databases managed by AT&T. Registration Services -- domain name and IP address assignment managed by NSI. Support Services -- outreach, education, and information services for the Internet community managed by NSI. Net Scout Services -- online publications that summarize recent happenings of interest to Internet users (managed by NSI). The InterNIC is currently an informational Web site established to provide the public with information about domain name registration. ICANN now oversees the domain name registration industry.

IP

Short for Internet Protocol. IP specifies the format of packets, also called datagrams, and the addressing scheme. Most networks combine IP with a higher-level protocol called Transmission Control Protocol (TCP), which establishes a virtual connection between a destination and a source. IP by itself is something like the postal system. It allows you to address a package and drop it in the system, but there's no direct link between you and the recipient. TCP/IP, on the other hand, establishes a connection between two hosts so that they can send messages back and forth for a period of time. The current version of IP is IPv4. A new version, called IPv6 or IPng, is under development.

OSPF

Short for Open Shortest Path First, an interior gateway routing protocol developed for IP networks based on the shortest path first or link-state algorithm. Routers use link-state algorithms to send routing information to all nodes in an internetwork by calculating the shortest path to each node based on a topography of the Internet constructed by each node. Each router sends that portion of the routing table (keeps track of routes to particular network destinations) that describes the state of its own links, and it also sends the complete routing structure (topography). The advantage of shortest path first algorithms is that they results in smaller more frequent updates everywhere. They converge quickly, thus preventing such problems as routing loops and Count-to-Infinity (when routers continuously increment the hop count to a particular network). This makes for a stable network. The disadvantage of shortest path first algorithms is that they require a lot of CPU power and memory. In the end, the advantages out weigh the disadvantages.

DoS

Short for denial-of-service attack, a type of attack on a network that is designed to bring the network to its knees by flooding it with useless traffic. Many DoS attacks, such as the Ping of Death and Teardrop attacks, exploit limitations in the TCP/IP protocols. For all known DoS attacks, there are software fixes that system administrators can install to limit the damage caused by the attacks. But, like viruses, new DoS attacks are constantly being dreamed up by hackers.

EMI

Short for electromagnetic interference, a naturally occurring phenomena when the electromagnetic field of onedevice disrupts, impedes or degrades the electromagnetic field of another device by coming into proximity with it. In computer technology, computer devices are susceptible to EMI because electromagnetic fields are a byproduct of passing electricity through a wire. Data lines that have not been properly shielded are susceptible to data corruption by EMI.

IDF

Short for intermediate distribution frame, a cable rack that interconnects and manages the telecommunications wiring between an MDF and workstation devices. Cables entering a building run through a centralized MDF, then each individual IDF and then on to specific workstations. For example, an enterprise that encompasses a building with several floors may have one MDF on the first floor and one IDF on each of the floors that is connected to the MDF.

E1

Similar to the North American T-1, E1 is the European format for digital transmission. E1 carries signals at 2 Mbps (32 channels at 64Kbps, with 2 channels reserved for signaling and controlling), versus the T1, which carries signals at 1.544 Mbps (24 channels at 64Kbps). E1 and T1 lines may be interconnected for international use.

Gbps

Stands for gigabits per second. Approximately a thousand million bits can be transmitted through the media in one second.

Boot Protocol / Bootstrap Protocol

The Bootstrap Protocol (BOOTP) is an obsolescent computer networking protocol used in Internet Protocol networks to automatically assign an IP address to network devices from a configuration server. The BOOTP protocol was originally defined in RFC 951. When a computer that is connected to a network is power up and boots its operating system, the system software broadcasts BOOTP protocol messages onto the network to request an IP address assignment. A BOOTP configuration server assigns an IP address based on the request from a pool of addresses configured by an administrator. BOOTP is implemented with the User Datagram Protocol (UDP) as transport protocol, and operates on IPv4 networks only.

IKE

The Internet Key Exchange (IKE) protocol is a key management protocol standard that is used in conjunction with the IPSec standard. IKE enhances IPSec by providing additional features, flexibility, and ease of configuration for the IPSec standard. IPSec can however, be configured without IKE. Benefits provided by IKE include: Eliminates the need to manually specify all the IPSec security parameters in the crypto maps at both peers. Allows you to specify a lifetime for the IPSec security association. Allows encryption keys to change during IPSec sessions. Allows IPSec to provide anti-replay services. Permits Certification Authority (CA) support for a manageable, scalable IPSec implementation. Allows dynamic authentication of peers.

Convergence Time

The period between a network change which prompts routers to update their router tables, and the time when the routing info on the routers reaches a steady state once again - known as a converged state.

STP

a link management protocol that is part of the IEEE 802.1 standard for media access control bridges. Using the spanning tree algorithm, STP provides path redundancy while preventing undesirable loops in a network that are created by multiple active paths between stations. Loops occur when there are alternate routes between hosts.

Carrier Sense Multiple Access/Collision Avoidance

a network contention protocol that listens to a network in order to avoid collisions, unlike CSMA/CD that deals with network transmissions once collisions have been detected. CSMA/CA contributes to network traffic because, before any real data is transmitted, it has to broadcast a signal onto the network in order to listen for collision scenarios and to tell other devices not to broadcast.

Bit Error Rate Test

a procedure or device that measures the bit error rate of a transmission.

Distance Vector Routing

a route discovery method in which each router tells every other router what networks and routes it knows about and the distance to them

Canonical Name

also referred to as a CNAME record, a record in a DNS database that indicates the true, or canonical, host name of a computer that its aliases are associated with. A computer hosting a Web site must have an IP address in order to be connected to the World Wide Web. The DNS resolves the computers domain name to its IP address, but sometimes more than one domain name resolves to the same IP address, and this is where the CNAME is useful. A machine can have an unlimited number of CNAME aliases, but a separate CNAME record must be in the database for each alias. Usage Note: While CNAME is short for canonical name, use of the abbreviated term implies that one is referring to the canonical name record, not simply the canonical name.

EIGRP

enables routers to exchange information more efficiently than earlier netowrk protocols using neighbors to help determine routing information...keep copies of neighbors routing information and query these tables to find the best possible rout for transmissions to follow...uses DUAL to determine best route to destination

Data Link Control

the second lowest layer in the OSI Reference Model. Every network interface card (NIC) has a DLC address or DLC identifier (DLCI) that uniquely identifies the node on the network. Some network protocols, such as Ethernet and Token-Ring use the DLC addresses exclusively. Other protocols, such as TCP/IP, use a logical address at the Network Layer to identify nodes. Ultimately, however, all network addresses must be translated to DLC addresses. In TCP/IP networks, this translation is performed with the Address Resolution Protocol (ARP). For networks that conform to the IEEE 802 standards (e.g., Ethernet ), the DLC address is usually called the Media Access Control (MAC) address.