Basics terms in Computer Networking

IPTCPUDPFTP

SFTPTFTPSMTPHTTPHTTP

S

Internet ProtocolTransport Control ProtocolUser Datagram Protocol

File Transfer ProtocolSecure File Transfer ProtocolTrivial File Transfer Protocol

Simple Mail Transfer ProtocolHypertext Transfer ProtocolHypertext Transfer Protocol

Secure

POPIMAPSSHICMPARP

RARPIGMP

Post Office ProtocolInternet Message Access Protocol

Secure ShellInternet Control Message

ProtocolAddress Resolution ProtocolReverse Address Resolution

ProtocolInternet Group Management

Protocol

Circuit switchingUses physical path for transmission of data. A physical connection is established between source and destination & then data are sent .Packet switching Data are broken into small parts called packets. Numbered packets may take any shortest route for transmission. virtual connection is made between source and destination.

DTE (Data Terminal Equipment)- Digital device that generates,

transmits and receives messages.- Terminal to show the movement

of messages in and out of the terminal.

- Server and the hosts maintain data and give information to Terminals.Example: ATMs (Automatic Teller Machines)

DCEData Communications Equipment. The DCE provides a physical connection to the network, forwards traffic, and provides a clocking signal used to synchronize data transmission between DCE and DTE devices. DTE.

Twisted pair cable- Up to 7 categories of twisted pair

but Category 3 and 5 twisted pairs are mostly used.

- Category 3 has 2 individually insulated wires twisted together .

- Category 5 is same as 3 with more number of twist per cm. More the number of twists the better the communication medium .

-Leads to less cross talk and better signal transmission over longer distances.

Can infrared be used for transmission?

- The infrared waves - used for short range communication in networking (up to 45 km).

- Wireless communication - no physical medium is required to connect the transmitter and receiver .

- Works on line of sight system.- No government license is

needed till now for this communication.

Satellite and cable medium- Delay in satellite during its transmission - 3 micro seconds per km.- Delay in cable wire is 5 microseconds per km.- Satellite is broadcast media placed in the geo stationary orbit around the earth.- Satellite - wireless communication- Cable - wired communication. On security grounds cable is better than a satellite.

10Base210-Mbps baseband Ethernet specification using 50-ohm thin coaxial cable. 10Base2,which is part of the IEEE 802.3 specification, has a distance limit of 606.8 feet (185 meters) per segment.10Base5, 10BaseF, 10BaseFB, 10BaseFL, 10BaseFP, 10BaseT, 100BaseT, 100BaseTX, 100BaseX,

2G mobile networkSecond generation mobile network. Refers generically to a category of mobile wireless networks and services that implement digital technology. GSM is an example of a 2G mobile network standard.2G+, 3G, 4G

802.xA set of IEEE standards for the definition of LAN protocols.802.1, 802.2, 802.3, 802.5, 802.11

AAAauthentication, authorization, and accounting

AARPAppleTalk Address Resolution Protocol. A protocol in the AppleTalk protocol stackthat maps a data-link address to a network address.

ABR1. available bit rate. QoS class defined by the ATM Forum for ATM networks. Used for connections that do not require timing relationships between source and destination. CBR, UBR, and VBR.2. area border router. Router located on the border of one or more OSPF areas that connects those areas to the backbone network.

access listA list kept by routers to control access to or from the router for a number of services. (to prevent packets with a certain IP address from leaving a particular interface on the router).Acknowledgment (ACK)Notification sent from one network device to another to acknowledge that some eventoccurred (for example, the receipt of a message). NAK.

Address mappingAllows different protocols to interoperate by translating addresses from one format to another. when routing IP over X.25, the IP addresses must be mapped to the X.25 addresses so that the IP packets can be transmitted by the X.25 network.

Address resolutionFor resolving differences between computer addressing schemes. Address resolution usually specifies a method for mapping network layer addresses to data link layer addresses.

ADSLAsymmetric Digital Subscriber Line. One of four DSL technologies. Downstream rates from 1.5 to 9 Mbps. Upstream bandwidth ranges from 16 to 640 kbps. ADSL work at distances up to 18,000 feet (5,488 meters) over a single copper twisted pair. HDSL, SDSL,VDSL.

ANSIAmerican National Standards Institute. A voluntary organization composed ofcorporate, government, and other members that coordinates standards-relatedactivities, approves U.S. national standards, and develops positions for the UnitedStates in international standards organizations

Application LayerLayer 7 of the OSI reference model. Provides services to application processes (e-mail, file transfer, ..) that are outside the OSI model. Identifies and establishes the availability of intended communication partners, synchronizes cooperating applications, and establishes an agreement on the procedures for error recovery and the control of data integrity.

ARPAddress Resolution Protocol. Internet protocol used to map an IP address to a MACaddress.RARP, Proxy ARP

ARPANETAdvanced Research Projects Agency Network. ARPANET was developed in the 1970s by BBN and funded by ARPA (and later DARPA). It eventually evolved into the Internet.

ASCIIAmerican Standard Code for Information Interchange. 8-bit code for characterrepresentation.

ATMAsynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Takes advantage of high-speed transmission media, such as SONET.

authenticationIn security, the verification of the identity of a person or a process.

authorizationThe method for remote access control.

BER1. bit error rate. Ratio of received bits that contain errors.2. basic encoding rules. Rules for encoding data units described in the ISO ASN.1standard. (SNMP)

BGPBorder Gateway Protocol. Inter-domain routing protocol that replaces EGP. BGP exchanges reachability information with other BGP systems. BGP4, EGPbit rateSpeed at which bits are transmitted, usually expressed in bits per second.

BOOTPBootstrap Protocol. Used by a network node to determine the IP address of its Ethernet interfaces to affect network booting.

Border GatewayA router that communicates with routers in other autonomous systems.

BridgeDevice that connects and passes packets between two network segments that use thesame communications protocol. Bridges operate at the data link layer (Layer 2) of the OSI reference model. In general, a bridge filters, forwards, or floods an incomingframe based on the MAC address of that frame.

BroadcastData packet that are sent to all nodes on a network. Broadcasts are identified by abroadcast address. Broadcast AddressA special address reserved for sending a message to all stations. Generally, a broadcast address is a MAC destination address of all ones.

Broadcast DomainSet of all devices that receive broadcast frames originating from any device within the set. Broadcast domains typically are bounded by routers because routers do not forward broadcast frames.

Broadcast StormAn undesirable network event in which many broadcasts are sent simultaneously across all network segments. A broadcast storm uses substantial network bandwidth causing network time-outs.BrouterConcatenation of “bridge” and “router.” Used to refer to devices that perform both bridging and routing functions.

Bus topologyLinear LAN architecture in which transmissions from network stations propagate thelength of the medium and are received by all other stations. Ring topology, star topology, tree topology.

CATVcable television. A communication system where multiple channels of programmingmaterial are transmitted to homes using broadband coaxial cable. Formerly calledCommunity Antenna Television.

CBRconstant bit rate. QoS class defined by the ATM Forum for ATM networks. CBR is used for connections that depend on precise clocking to ensure undistorted delivery.ABR, UBR, VBR.

CDMAcode division multiple access. A method of dividing a radio spectrum to be shared bymultiple users through the assignment of unique codes. CDMA implements spreadspectrum transmission.CDPCisco Discovery Protocol

CHAPChallenge Handshake Authentication Protocol. Security feature supported on linesusing PPP encapsulation that prevents unauthorized access. PAP.

CIDRclassless interdomain routing. Allows routers to group routes together to reduce the quantity ofrouting information carried by the core routers. With CIDR, several IP networks appear to networks outside the group as a single, larger entity.

Coaxial CableCable consisting of a hollow outer cylindrical conductor that surrounds a single innerwire conductor. Two types of coaxial cable currently are used in LANs: 50-ohm cable,which is used for digital signaling, and 75-ohm cable, which is used for analogsignaling and high-speed digital signaling.

CollisionIn Ethernet, the result of two nodes transmitting simultaneously. The frames fromeach device impact and are damaged when they meet on the physical media.Collision DomainIn Ethernet, the network area within which frames that have collided are propagated.Repeaters and hubs propagate collisions; LAN switches, bridges, and routers do not.

CongestionTraffic in excess of network capacity.

Congestion AvoidanceMechanism by which a network controls the traffic entering the network to minimize delays. To use resources most efficiently, lower-priority traffic is discarded at the edge of the network if conditions indicate that it cannot be delivered.

CSMA/CDcarrier sense multiple access collision detect. Devices ready to transmit data first check the channel for a carrier. If no carrier issensed for a specific period of time, a device can transmit. If two devices transmit atonce, a collision occurs and is detected by all colliding devices.CSMA/CA

data-link layerLayer 2 of the OSI reference model. Responsible for physical addressing, network topology, line discipline, error notification, ordered delivery of frames, and flow control. IEEE divided this layer into two sublayers: the MAC sublayer and the LLC sublayer.

default routeRouting table entry that is used to direct frames for which a next hop is not explicitly listed in the routing table.

ip route 0.0.0.0 0.0.0.0 next hop IP/exit interface

DHCPDynamic Host Configuration Protocol. Provides a mechanism for allocating IPaddresses dynamically so that addresses can be reused when hosts no longer needthem.

Digital SignatureValue computed with a cryptographic algorithm and appended to a data object in such a way that any recipient of the data can use the signature to verify the data’s origin and integrity.

DLCIdata-link connection identifier. Value that specifies a PVC or an SVC in a FrameRelay network. In the basic Frame Relay specification, DLCIs are locally significant.

DNSDomain Name System. System used on the Internet for translating names of networknodes into addresses.

DQDBDistributed Queue Dual Bus. Data-link layer communication protocol, specified inthe IEEE 802.6 standard, designed for use in MANs.

DTEdata terminal equipment. Device at the user end of a user-network interface. DTE connects to a data network through a DCE device (for example, a modem) uses clocking signals generated by the DCE. DCE.

dynamic routingRouting that adjusts automatically to network topology or traffic changes.

EAPExtensible Authentication Protocol. Framework that supports multiple, optional authentication mechanisms for PPP, including clear text passwords,challenge-response, and arbitrary dialog sequences.

EBCDICextended binary coded decimal interchange code. Any of a number of coded character sets developed by IBM consisting of 8-bit coded characters.

EGPexterior gateway protocol. Internet protocol for exchanging routing information between autonomous systems. RFC 904. EGP is an obsolete protocol that was replaced by BGP.

FDDIFiber Distributed Data Interface. LAN standard, defined by ANSI X3T9.5,specifying a 100-Mbps token-passing network using fiber-optic cable, withtransmission distances of up to 2 km. FDDI uses a dual-ring architecture toprovide redundancy.

firewallRouter or access server, or several routers or access servers, designated as abuffer between any connected public networks and a private network. A firewallrouter uses access lists and other methods to ensure the security of the privatenetwork.

flow controlTechnique for ensuring that a transmitting entity, such as a modem, does notoverwhelm a receiving entity with data. When the buffers on the receiving device are full, a message is sent to the sending device to suspend the transmission until the data in the buffers has been processed.

fragmentationProcess of breaking a packet into smaller units when transmitting over a networkmedium that cannot support the original size of the packet. reassembly.

frameLogical grouping of information sent as a data link layer unit over a transmission medium. Refers to the header and the trailer, used for synchronization and error control, that surround the user data contained in the unit.

Frame RelayIndustry-standard, switched data link layer protocol that handles multiple virtual circuits using HDLC encapsulation between connected devices. Frame relay is more efficient than X.25.

FTPFile Transfer Protocol. Application protocol, part of the TCP/IP protocol stack,used for transferring files between network nodes. FTP is defined in RFC 959.

full duplexCapability for simultaneous data transmission between a sending station and a receiving station. Compare with half duplex and simplex.

full mesha network in which devices are organized in a mesh topology, with each network node having circuit connecting it to every other network node. Full mesh provides redundancy but it can be prohibitively expensive to implement.

Gigabit EthernetStandard for a high-speed Ethernet, approved by the IEEE (Institute ofElectrical and Electronics Engineers) 802.3z standards committee in 1996.

GoodputGenerally refers to the measurement of actual data successfully transmittedfrom the sender(s) to the receiver(s).

GPRSgeneral packet radio service. A service defined and standardized by the European Telecommunication Standards Institute (ETSI). GPRS is an IP packet-based data service for Global System for Mobile Communications (GSM) networks.

GSMglobal system for mobile communication. A second generation (2G) mobilewireless networking standard defined by ETSI.Uses TDMA technology and operates in the 900-MHz radio band.

guard bandAn unused frequency band between two communications channels that providesseparation of the channels to prevent mutual interference.

half duplexCapability for data transmission in only one direction at a time between a sendingstation and a receiving station.HDLChigh-level data link control. Bit-oriented synchronous data link layer protocoldeveloped by ISO.

HFChybrid fiber-coaxial. Technology being developed by the cable TV industry toprovide two-way, high-speed data access to the home using a combination of fiberoptics and traditional coaxial cable.

HMACHash-based Message Authentication Code. HMAC is a mechanism for messageauthentication using cryptographic hash functions. HMAC can be used with anyiterative cryptographic hash function for example, MD5, SHA-1.

hopPassage of a data packet between two network nodes (between two routers). hop countRouting metric used to measure the distance between a source and a destination. RIP uses hop count as its sole metric.

HTTPHypertext Transfer Protocol. The protocol used by Web browsers and Web servers totransfer files, such as text and graphic files.

hubA device that serves as the center of astar-topology network.Device that contains multiple independent but connected modules of network and internetwork equipment.

IANAInternet Assigned Numbers Authority. IANA delegates authority for IP address–space allocation and domain-name assignment to the InterNIC and other organizations.

ICMPInternet Control Message Protocol. Network layer Internet protocol that reports errors and provides other information relevant to IP packet processing. RFC 792.ICMP floodDenial of service attack that sends a host more ICMP echo request packets than the protocol implementation can handle.

IEEE 802.1 – Spanning Tree AlgorithmIEEE 802.12 – Physical Layer & MAC sublayer of MACIEEE 802.2 – LLC sublayer of MACIEEE 802.3 – EthernetIEEE 802.4 – Token busIEEE 802.5 – Token RingIEEE 802.6 – DQDB

IGMPInternet Group Management Protocol. Used by IP hosts to report their multicastgroup memberships to an adjacent multicast router.

IMAPInternet Message Access Protocol. Method of accessing e-mail or bulletin board messages kept on a mail server that can be shared. IMAP permits client e-mailapplications to access remote message stores as if they were local without actually transferring the message.

Internet Protocol (IP, IPv4)Network layer for the TCP/IP protocol suite. Internet Protocol (version 4) is aconnectionless, best-effort packet switching protocol.

Inverse ARPInverse Address Resolution Protocol. Method of building dynamic routes in anetwork. Allows an access server to discover the network address of a deviceassociated with a virtual circuit.

IP address32-bit address assigned to hosts using TCP/IP. An IP address belongs to one of five classes (A, B, C, D, or E) and is written as 4 octets separated by periods. Each address consists of a network number, an optional subnetwork number, and a host number.

IP multicastRouting technique that allows IP traffic to be propagated from one source to a number of destinations or from many sources to many destinations.

IP spoofingIP spoofing attack occurs when an attacker outside your network pretends to be atrusted user either by using an IP address that is within the range of IP addresses foryour network.

IPSecIP Security. A framework of open standards that provides data confidentiality, data integrity, and data authentication between participating peers.

ISDNIntegrated Services Digital Network. Communication protocol offered by telephone companies that permits telephone networks to carry data, voice, and other source traffic.

ISPInternet service provider. Company that provides Internet access to other companies and individuals.

KerberosDeveloping standard for authenticating network users. Kerberos offers two keybenefits: it functions in a multivendor network, and it does not transmit passwords over the network.

LANlocal-area network. High-speed, low-error data network covering a relatively smallgeographic area. LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited area.MAN, WAN

LAN switchHigh-speed switch that forwards packets between data-link segments. Most LANswitches forward traffic based on MAC addresses.

Layer 3 SwitchingLayer 3 switching technology that integrates routing with switching to yield very high routing throughput rates in the millions-of-packets- per-second range.

link-state routing algorithmRouting algorithm in which each router broadcasts or multicasts informationregarding the cost of reaching each of its neighbors to all nodes in the internetwork.Link state algorithms create a consistent view of the network and therefore are notprone to routing loops.

load balancingIn routing, the capability of a router to distribute traffic over all its network ports that are the same distance from the destination address.

loopRoute where packets never reach their destination, but simply cycle repeatedlythrough a constant series of network nodes.

MAC addressData link layer address -required for every port or device that connects to a LAN. Other devices in the network use these addresses to locate specific ports in the network and to create and update routing tables and data structures. MAC addresses are 6 bytes long. Hardware address, MAC layer address, and physical address.

MANmetropolitan-area network. Network that spans a metropolitan area. Generally, aMAN spans a larger geographic area than a LAN, but a smaller geographic area thana WAN.

man-in-the-middleForm of active wiretapping attack in which the attacker intercepts and selectivelymodifies communicated data to masquerade as one or more of the entities involved in a communication association.

masquerade attackType of attack in which one system entity illegitimately poses as (assumes theidentity of) another entity.

MD5Message Digest 5. A one-way hashing algorithm that produces a 128-bit hash.

MPLSMultiprotocol Label Switching. Switching method that forwards IP traffic using alabel. This label instructs the routers and the switches in the network where toforward the packets based on preestablished IP routing information.

MTUmaximum transmission unit. Maximum packet size, in bytes, that a particularinterface can handle.

NATNetwork Address Translation. Mechanism for reducing the need for globally uniqueIP addresses. NAT allows an organization with addresses that are not globally unique to connect to the Internet by translating those addresses into globally routable address space.

network layerLayer 3 of the OSI reference model. Provides connectivity and path selection between two end systems. The network layer is the layer at which routingoccurs.

OSI reference modelOpen System Interconnection reference model. Network architectural modeldeveloped by ISO.

OSPFOpen Shortest Path First. OSPF features include least-cost routing, multipath routing, and load balancing. OSPF was derived from an early version of the IS-IS protocol.

PAPPassword Authentication Protocol. Authentication protocol that allows PPP peers to authenticate one another. The remote router attempting to connect to the local router is required to send an authentication request. PAP passes the password and the host name or username in the clear.

PDUprotocol data unit. OSI term for packet.PGPPretty Good Privacy. Public-key encryption application that allows secure file andmessage exchanges.

physical layerLayer 1 of the OSI reference model. The physical layer defines the electrical,mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems.

piggybackingProcess of carrying acknowledgments within a data packet to save networkbandwidth.pingpacket internet groper. ICMP echo message and its reply. Often used in IP networks to test the reachability of a network device.

POP1. point of presence. a physical location where an interexchange carrierinstalled equipment to interconnect with a local exchange carrier (LEC).2. Post Office Protocol. Protocol that client e-mail applications use to retrieve mailfrom a mail server.

port1. Interface on an internetworking device (such as a router).2. In IP terminology, an upper-layer process that receives information from lower layers. Ports are numbered, and each numbered port is associated with a specific process. A port number is also called a well-known address.

port address translationTranslation method that allows the user to conserve addresses in the global addresspool by allowing source ports in TCP connections or UDP conversations to betranslated.

PPPPoint-to-Point Protocol. Successor to SLIP that provides router-to-router andhost-to-network connections over synchronous and asynchronous circuits. Whereas SLIP was designed to work with IP, PPP was designed to work with several network layer protocols, such as IP, IPX.

presentation layerLayer 6 of the OSI reference model. This layer ensures that information sent by theapplication layer of one system will be readable by the application layer of another.

propagation delayTime required for data to travel over a network from its source to its ultimatedestination.

Proxy ARPproxy Address Resolution Protocol. Variation of the ARP protocol in which anintermediate device (for example, a router) sends an ARP response on behalf of an end node to the requesting host.

QoSquality of service. Measure of performance for a transmission system that reflects its transmission quality and service availability

queuing delayAmount of time that data must wait before it can be transmitted onto a statistically multiplexed physical circuit.

random early detectionCongestion avoidance algorithm in which a small percentage of packets are droppedwhen congestion is detected and before the queue in question overflows completely.

RARPReverse Address Resolution Protocol. Protocol in the TCP/IP stack that provides amethod for finding IP addresses based on MAC addresses.

ReassemblyThe putting back together of an IP datagram at the destination after it has been fragmented either at the source or at an intermediate node.

repeaterDevice that regenerates and propagates electrical signals between two networksegments.replay attackAttack in which a valid data transmission is maliciously or fraudulently repeated,either by the originator or by an adversary who intercepts the data and retransmits it.

repudiationDenial by a system entity that was involved in an association (especially anassociation that transfers information) of having participated in the relationship.

ring topologyNetwork topology that consists of a series of repeaters connected to one another byunidirectional transmission links to form a single closed loop. Each station on thenetwork connects to the network at a repeater.

RIPRouting Information Protocol. The most common IGP in the Internet. RIP uses hop count as a routing metric.routerNetwork layer device that uses one or more metrics to determine the optimal path along which network traffic should be forwarded. Routers forward packets from one network to another based on network layer information.

routing protocolProtocol that accomplishes routing through the implementation of a specific routing algorithm. routing tableTable stored in a router or some other internetworking device that keeps track ofroutes to particular network destinations and, in some cases, metrics associated with those routes.

RTTround-trip time. Time required for a network communication to travel from the sourceto the destination and back. RTT includes the time required for the destination to process the message from the source and to generate a reply.

SANstorage area networking. A data communication platform that interconnects servers and storage at Gigabaud speeds.

segment1. Section of a network that is bounded by bridges, routers, or switches.2. In a LAN using a bus topology, a segment is a continuous electrical circuit thatoften is connected to other such segments with repeaters.3. Term used in the TCP specification to describe a single transport layer unit ofinformation.

session layerLayer 5 of the OSI reference model. This layer establishes, manages, and terminates sessions between applications and manages the data exchange between presentation layer entities.

simplexCapability for transmission in only one direction between a sending station and a receiving station. Broadcast television is an example of a simplex technology.

SMTPSimple Mail Transfer Protocol. Internet protocol providing e-mail services.SNMPSimple Network Management Protocol. Network management protocol usedexclusively in TCP/IP networks.

socket1. Software structure operating as a communications end point within a network device.2. Addressable entity within a node

SOHOsmall office, home office. Networking solutions and access technologies for offices that are not directly connected to large corporate networks.SONETSynchronous Optical Network.

star topologyLAN topology in which end points on a network are connected to a common central switch by point-to-point links.static routeRoute that is explicitly configured and entered into the routing table. Static routes take precedence over routes chosen by dynamic routing protocols.

stub networkNetwork that has only a single connection to a router.subnet mask32-bit address mask used in IP to indicate the bits of an IP address that are being used for the subnet address.

SwitchingProcess of taking an incoming frame from one interface and delivering it throughanother interface. Routers use Layer 3 switching to route a packet, and Layer 2switches use Layer 2 switching to forward frames.

throughputRate of information arriving at, and possibly passing through, a particular point in a network system.tracerouteProgram available on many systems that traces the path a packet takes to a destination.

transport layerLayer 4 of the OSI reference model. Responsible for reliable networkcommunication between end nodes. Provides mechanisms for the establishment, maintenance, and termination of virtual circuits, transport fault detection and recovery, and information flow control.

Trojan horseComputer program that appears to have a useful function but also has a hidden andpotentially malicious function that evades security mechanisms.

UDPUser Datagram Protocol. Connectionless transport layer protocol. Simple protocol that exchanges datagrams withoutacknowledgments or guaranteed delivery, requiring that error processing andretransmission be handled by other protocols.

VLANvirtual LAN. Group of devices on one or more LANs that are configured (usingmanagement software) so that they can communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments.

VLSMvariable-length subnet mask. Capability to specify a different subnet mask for thesame network number on different subnets. VLSM can help optimize availableaddress space.

VoIPVoice over IP. The capability to carry normal telephony-style voice over an IP-based internet with reliability, and voice quality. VoIP enables a router to carry voice traffic over an IP network.

VPNVirtual Private Network. Enables IP traffic to travel securely over a public TCP/IPnetwork by encrypting all traffic from one network to another. A VPN uses“tunneling” to encrypt all information at the IP level.

wildcard maskA 32-bit quantity used in conjunction with an IP address to determine which bits inan IP address should be ignored when comparing that address with another IPaddress. A wildcard mask is specified when setting up access lists.

wildcard maskA 32-bit quantity used in conjunction with an IP address to determine which bits inan IP address should be ignored when comparing that address with another IPaddress. A wildcard mask is specified when setting up access lists.