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Tuesday, December 31, 2013

MS Excel Shortcut Keys


1. F2 Edit the selected cell
2. F3 After a name has been created F3 will paste names
3. F5 Go to a specific cell. For example, C6
4. F7 Spell check selected text or document
5. F11 Create chart from selected data 
6. Ctrl + Shift + ; Enter the current time
7. Ctrl + ; Enter the current date
8. Alt + Shift + F1 Insert new worksheet
9. Shift + F3 Open the Excel formula window
10. Shift + F5 Bring up search box
11. Ctrl + A Select all contents of the worksheet 
12. Ctrl + B Bold highlighted section
13. Ctrl + I Italic highlighted section
14. Ctrl + K Insert link
15. Ctrl + U Underline highlighted section
16. Ctrl + 1 Change the format of selected cells
17. Ctrl + 5 Strike through highlighted section 
18. Ctrl + P Bring up the print dialogue box to begin printing
19. Ctrl + Z Undo last action
20. Ctrl + F3 Open Excel Name Manager
21. Ctrl + F9 Minimize current window
22. Ctrl + F10 Maximize currently selected window 
23. Ctrl + F6 Switch between open work books or windows
24. Ctrl + Page up Move between Excel work sheets in the same Excel document
25. Ctrl + page down Move between Excel worksheets in the same Excel document 
26. Ctrl + Tab Move between two or more open Excel document
27. Alt + = Create a formula to sum all of the above cells
28. Ctrl + ’ Insert the value of the above cell into cell currently selected 
29. Ctrl + Shift + ! Format number in comma format
30. Ctrl + Shift + $ Format number in currency format
31. Ctrl + Shift + # Format number in date format
32. Ctrl + Shift + % Format number in percentage format
33. Ctrl + Shift + ^ Format number in scientific format 
34. Ctrl + Shift + @ Format number in time format
35. Ctrl + Arrow key Move to the next selection on text
36. Ctrl + Space Select entire column
37. Shift + Space Select entire row
38. Ctrl + - Delete the selected column or row 
39. Ctrl + shift + = Insert a new column or row
40. Ctrl + Home Move to cell A1
41. Ctrl + ~ Switch between showing Excel formulas or their values in cells..!! 

Sunday, December 22, 2013

UTP

UTP stands for Unshielded Twisted Pair. It is two or four pair wire medium used in a variety of networks. Lacks shielding and is subject to electrical noise and interference.

UNC

UNC stands for Universal Naming Convention (UNC). It is the standard format for path that include a local area network file server that uses the following syntax:
\\server\share\path\filename

UDP

UDP stands for User Datagram Protocol. It is a connectionless transport layer protocol in TCP/IP protocol stack. UDP is a simple protocol that exchange datagrams without acknowledgments or guaranteed deliery, reequiring that error processing and retransmission be handled by other protocols. 
Delivery is not guaranteed, nor it is guaranteed that datagrams will be delivered in the proper order. UDP is defined in RFC 768.

Type or Service

1. A byte of an IP header that indicates precedence and type of service.
2. Four-bit field within the type-of-service byte in IP header that helps a router select a routing path when multiple paths are available. A source node can specify whether low delay, high throughput, high reliability, or low monetary cost is desired.

Twisted Pair Cable

A type of networking channel cable in which a pair of insulated wires are twisted together. In the Type 1 standard used in the IBM token ring network, each cable supports two twisted pair channels (four wires).

Twisted Pair

A commonly used transmission medium consisting of 22 to 26 gauge insulated copper wire. Can be whether shielded (STP) or unshielded (UTP).

Tunneling Router

It is a router or system capable of routing traffic by encrypting it and encapsulating it for transmission across an untrusted network, for eventual de-encapsulation and decryption.

TFTP

TFTP stands for Trivial File Transfer Protocol. It is a nofrills, unauthenticated protocol used to transfer files. TFTP depends on UDP and often is used to boot diskless workstations.

TTL

TTL stands for Time-To-Live. It is the maximum number of router hops that a datagram of the network layer in TCP/IP protocol can experience on a network before it should be discarded. Used to prevent packets from looping endlessly.

Transport Layer

Layer 4 of the OSI reference model. This layer is responsible for reliable network communication between end nodes. The transport layer provides mechanisms for the establishment, maintenance and termination of virtual circuits; transport fault detection and recovery; and information flow control. Also on the Internet, the layer that implements TCP and UDP over the network layer.

Tracing routines

Routines to aid the programmer in following the logical of a program during the execution of the program.

Top-Down Network Design

It is a network design methodology  that calls for analyzing business and technical requirements and developing a logical design, including a topology and protocols, before selecting products and devices to implement the physical design.

Token Ring

Token-passing LAN developed and supported by IBM. Token ring runs at 4 or 16 Mbps over a ring topology. Token ring was standardized in the IEEE802.5 specification. A network system that uses a ring logical topology and a token channel access method. Examples include FDDI and Token Ring.

Token Passing

It is a access method by which network devices access a physical medium in an orderly fashion based on possession of a small frame called token.

Token

It is a channel access control method in which a token is passed between the nodes on the network., any station with the node at any particular time can then use the network channel. Also frame that contains control information. Possession of the token allows a network device to transmit data onto the network.

TDM (Time Division Multiplexing)

It is a method of sharing a communication channel in which the total time available in the channel is divided between several users and each user of the channel is allotted a time slice during which it may transmit a message. The channel capacity is fully utilized by interleaveing a number of data streams belonging to different users into one data stream. TDM is fast because it does not do error checking. Data are transparent to it. It just provides the slots for the data. TDM works well enough for applications that need continuous slots on the channel, such as voice and video.

Telecommunications

Transmission of data between computer system and/or terminals at different locations through telephone facilities.

Time Division Multplexer (TDM)

TDM stands for Time Division Multplexer. It is a device implements time division multiplexing.

TCP/IP

It is a protocol stack, designed to connect different network on which the Internet based. The suite includes protocols for remote login (Telnet), file transfer (FTP), E-mail (SMTP), etc. TCP/IP can work with any hardware or operating system.

Saturday, December 21, 2013

Synchronous Optical Network

It is a family of fiber-optic transmission rates from 51.84 Mbps to13.22 Gbps, created to provide the flexibility needed to transport many digital signals with different capabilities and to provide a design standard for manufacturers. It is an optical interface standard that allows internetworking of transmission products from multiple vendors.

Switches

Switches constantly monitor the traffic that comes across them and remote their internal connections automatically to provide the most efficient operation for the network. With the sophisticated layer-3 switches rapidly getting accepted in the market, the router market is getting considerable displaced. Layer-3 switching has significant price/performance advantages over routers on account of their topological flexibility. A packet-by-packet layer-3 switching facilities high speed routing and is interoperable with legacy routers. It also facilitates routing table construction and maintenance and investigates packets to determine their destination before forwarding them. Layer-3 switching is rapidly emerging as a standard for centralised networking. Also a network device that filters and forward frames based on the destination address of each frame. It is and advanced form of hub. Switches can provide dedicated bandwidth at each node. Due to this, the network traffic passing through one node does bot effect another node. A switch isintelligent and can turn on and off specific ports using software controls. Due to this, switches automate network configuration and hence increase network availability abd capability. Theswitch operates at the data link layer of the OSI model.

Switched Virtual Circuit (SVC)

SVC stands for Switched Virtual Circuit. It is a temporary virtual circuit that is set up and used only as long as data is being transmitted. Once the communication between the two hosts is complete, the SVC disappears. In contrast, a permanet virtual circuit (PVC) remains available at all times.

Subnetwork

In IP networks, a network sharing a particular subnet address. Subnetworks are networks that are arbitrarily segmented by a network administrator in order to provide a multilevel, hierarchical routing structure while shielding the subnetwork from the addressing complexity of attached networks.

Subnet address

Portion of an IP address that is specified as the subnetwork by the subnet mask.

Stream

A source from which input data can be obtained or a destination to which output data can be sent.

STP

STP stands for Shielded Twisted Pair. It is two or four-pair wiring medium used in a variety of networks. STP cabling has a layer of shielded insulation to reduce noise and interference.

Store And Forwarding Switching

It is a frame switching technique in which frames are completely processed before being forwarded out the appropriate port. This processing includes calculating the CRC and checking the destination address. In addition, frames must be temporarily stored until network resources such as an unused link are available to forward the frame.

Source Route

A route identifying the path a datagram must follow, determined by the source device.

SONET

SONET stands for Synchronous Optical Network. High speed up to 2.5 Gbps synchronous network specification developed by Bellcore and designed to run on optical fiber. STS-1 is thebasic building block of SONET. Approved as an international standard in 1988.

Socket

A bi-directional pipe for incoming and outgoing data that enables an application program to access the TCP/IP protocols.

SNAP

SNAP stands for SubNetwork Access Protocol. It is version of the IEEE local area network (LAN) logical link control (LLC) frame similar to the more traditional data link level transmission frame that lets you use non-standard higher level protocols.

SNA

SNA stands for Systems Network Architecture. Large, complex, feature-rich network architecture developed in the 1970s by IBM for communication between terminals and mainframes.

Single Mode Fiber

Fiber optical cabling with a narrow core that allows light to enter only at a single angle. Such cabling has higher bandwidth than multimode fiber, but requires a light source with a narrow spectral width, for example a laser.

Simulation

To represent and analyze properties or bahavior of a physical or hypothetical system by the behavior of a system model.

SGSN

SGSN stands for Serving GPRS Support Node. It mediates access to network resources on behalf of mobile subscribers and establishes a link with GGSN for GPRS data transfer.

Session layer

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

Service Program

Service programs are commonly used in all computer centers for providing better service to users. They include programs to prepare object programs for execution, to store programs on a magnetic disk, sort data stored on secondary storage devices, etc. They are part of the operating system.

Server

Server is a Node or a software program that provides services to clients. Also a main high capacity computer where all the information is stored. Also a system that shares resources with one or more workstations on a network.

SLIP

SLIP stands for Serial Line Internet Protocol. It is a TCP/IP protocol for trans \mitting IP datagrams over serial lines, such as phone lines. With SLIP, personal computer users can connect to the Internet and still function in their native environment instead of having to deal with a character based UNIX environment.

Segmentation

A method of providing virtual memory. A multidimensional linear address space implementation differentiates this from paging.

Security

The issuses of protecting data from unauthorized use, tampering, or destruction are collectively referred to as security issues.

Secure Socket Layer (SSL)

SSL stands for Secure Socket Layer. It is a security layer sandwiched between the application and transport layers. SSL transparently protects application layer protocols (like HTTP, for which it was originally conceived) and data, with little effort on the part of the application developer. Also, public security protocol developed by Netscape. It can create a secure link between the Web server and the browser, thereby facilitating e-transactions.

Screening Router

A router configured to permit or deny traffic based on a set of permission rules installed by the administrator.

Screened Subnet

A subnet behind a screening router. The degree to which the subnet may be accessed depends on the screening rules.

Screened Host

A host on a network behind a screening router. The degree to which a screened host may be accessed depends on the screening rules in the router.

Friday, December 20, 2013

RTT

RTT stands for Round Trip Time. Time required for a network communication to travel from the source and generate a reply.

RTP

RTP stands for Real Time Protocol. It is IETF protocol that provides end-to-end network transport functions for applications transmitting real-time data, such as audio, video, or simulation data, over multicast or unicast network services. RTP provides services such as payload type identification, sequence numbering, time stamping and data delivery.

RTCP

RTCP stands for Real Time Control Protocol. It is a protocol that monitors the Qos of an RTP connection and conveys information about the on-going session.

RSVP

RSVP stands for Resource Reservation Protocol. It is a protocol that supports the reservation of resources across an IP netwrok. Applications running on IP network. Applications running on IP end systems can use RSVP to indicate to other nodes the nature (bandwidth, jitter, maximum burst and so on) of the packet streams they wish to receive. Defined in RFC 2205.

Routing Metrics

Method by which a routing algorithm determines that one route is better than another. This information is stored in routing tables. Metrics include bandwidth, communication cost, delay, hop count, load, MTU, path cost, and reliability. Sometimes referred to simply as a metric.

RNC

RNC stands for Radio Network Controller. It is a network component.

RMON-2

It is defined by RFC 2021. This is an extension of RMON-1. RMON-2 provides netwrok statistics from MAC layer to application layer. It extends the network segment view to end-to-end global view of the network.

RMON-1

It is defined by IETF RFC 1757 for token-ring. It specifies the method for an SNMP-based network management station to remotely gather, the network segment statistics at MAC layer to application layer. It extends the network.

Ring Network

A computer network in which there is no host computer for controlling other computers and in which all stations are equal.

Remote Job Entry (RJE)

A particular type of batch procesing, where the input and output devices are located away from the central computer facility. The equipments for a RJE station can include terminals, card reader, card punching devices, printers etc.

Remote Access Server

A Microsoft server component that allows remote users to dial in to the network. This is an ulternative to expansive hardware like routers, and terminal servers if the traffic is not too high.

Remote Access

Accessing a computer from a distant station using communication facilities.

Remote Access Server

It is a communication server that connects remote nodes or LANs to an internetwork. Generally supports standard terminal services, such as Telnet, as well as remote-node, protocol-translation, and asynchronous routing services.

Tuesday, December 17, 2013

Prototyping

A working system to explore implementation or processing alternatives and evaluate results.

Protocol Data Unit (PDU)

PDU stands for Protocol Data Unit. It is the technical term for Datagram. PDUs are generated at all levels of the OSI Model, and are distinguished from one another by a prefix that indicates from witch layer or sub layer the PDU originates. For example, an SNMPv1 (Sub-Network Access Protocol Version 1) message consists of a message header and a PDU which contains specific commands and operands tha indicate the object instances involved in the transaction.

Protocol Analyser

It is a specialized real time computer software that connects to a network and analyzes the network traffic. A good protocol analyser can record and display the data from data link layer to application layer. It helps in detection, tracking down and fixing the network problems. It has features of real time traffic analysis, packet capturing, decoding and retransmission.

PRI

PRI stnads for Primary Rate Interface. Is is ISDN (Integrated Service Digital Network) interface to primary rate access. Primary rate access cnsists of a single 64-Kbps data (D) channel for signaling, plus 23 (T1) or 30 (E1) bearer (B) channels for user data.

Presentation Layer

Layer 6 of the OSI reference model. This layer ensures that information sent by the application layer of one system is readable by the application layer of another.

Preprocessor

A part of the compiler that manipulates the program text before compiling is done. Three important tasks of the preprocessor are 1. To replace each #inclue directive with the contents of the designated file. 2. To replace each escape sequence with the designated character. 3. To process macro definitions and expand macro calls.

PPS

PPS stands for Packet Per Second. It is a measure of how quickly a switch or router can forward data.

POP

POP stands for Post Office Protocl. It is a protocol that specifies how a personal computer can connect to a mail server on the Internet and download E-mail.

Portability

The capability of a program to run on different types of machines with minimum modification.

PPP

PPP stands or Point-to-Point Protocol. It is a TCP/IP protocol, similar to SLIP (Serial Line Internet Protocol), for transmitting IP datagrams over serial lines such as phone lines. With PPP, PC users can connect to the Internet and still function in their native environment instead of having to deal with a character based Unix environment. PPP was designed to work with several network layer protocols, such as IP, IPv6, IPx and AppleTalk.

Pinging

It is a technique to identify networks problems, A LAN message is sent to a remote LAN node. The node, in turn, formulates an echo reply and returns it to the original sender. Successful receipt of echo reply implies that the major components of transport systems are functioning.

PIM

PIM stands for Protocol Independent Multicast. It is the Multicast routing architecture that allows the addition of IP multicast routing on existing IP networks. PIM does not require a specific unicast routing protocol, and can be operated in two modes: dense mode and sparse mode.

Physical layer

Layer 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.

Phased Replacement

A system Changeover method in which the complete changeover to the new system takes place incrementally over a period of time. The new system is gradually implemented part by part and the old system is gradually phased out.

Phase Modulation

A form of modulation in which two binary values of digital data are represented by the shift in phase of the carrier signal. That is a sine wave with phse = 00 represents a digital 1 and a sine wave with phase = 180 degree represents a digital 0.

Phantom Router

In HSRP (Hot Standby Router Protocol), two or more router shares the same virtual IP address and virtual MAC address thus creating a third, non-physical router, called the phantom router.

PVC

PVC stands for Permanent Virtual Circuit. It is a fixed communication circuit, created and maintained even when no data is being transmitted. The only difference between a PVC and a Switched Virtual Circuit (SVC) is that an SVC must be reestablished each time data is to be sent. Once the data has been sent, the SVC disappears. PVCs are more efficient for connections between hosts that communicate frequently. PVCs play a central role in Frame Relay networks. They're also supported in some other types networks, such as X.25.

Password

A code by which a user gains access to a computer system. It is used for security purpose.

Partial Mesh

Term describing a network in which devices are organized in a mesh topology without requiring that every device have a direct connection to every other device.

Parity Bit

An extra bit added to a string of bits that enables the computer to detect internal errors in the transmission of the binary data.

Parallel Operation

A system changeover method whereby data is processed by both the odd and new system until the performance of the new system is verified satisfactorily.

Parallel Adder

An adder in which all the bits of the two operands are added simultaneously.

PAP

PAP stands for Password Authentication Protocol. It is an authentication protocol that allows PPP (Point-to-Point Protocol) peers to authenticate one another. Unlike CHAP (Challenge Handshake Authentication Protocol), PAP passes the password and host name or username in clear text (unencrypted).

Packet Switching

A method of communication between computers in a network in which blocks of messages to be transmitted are formed into packets and placed on the channel. Each packet contains source and destination addresses, synchronizing, error correction and control bits. The packets are routed using the source and destination addresses.

Packet Switching Network

A telecommunication network based on packet switching technology, where in a trasmission channel is occupied only for the duration of the transmission of the packets.

Packet

Logical grouing of information that includes a header containing control information and usually user data. Packets are most often used to refer to network layer units of data.

Sunday, December 15, 2013

OSPF

OSPF stands for Open Shortest Path First. Link state hierarchical interior routing algorithm proposed as a successor to RIP in the Internet Community. OSPF features include least cost routing, multipath routing and load balancing. Defined in RFC2178.

Optical Carrier (OC)

OC stands for Optical Carrier. It is a series of physical protocols (OC-1, OC-2, OC-3 and so on) defined for SONET optical signal transmissions. OC signal levels put STS frames onto fiber optic lines at a variety of speeds. The base rate is 51.84 Mbps (OC-1), each signal level thereafter operates at a speed divisible by that number (thus, OC-3 runs at 155.52 Mbps).

Node

An end point of branch in a network, or a common junction of two or more network branches.

Network to Network Interface

NNI stands for Network-to-Network Interface. It is the ATM forum standard that defines the interface between two ATM switches that are both located in a private network, or are both located in a public network.

Network Management System (NMS)

NMS stands for Network Management System. It is a system that responsible for managing a network. A NMS is generally a powerful and well-equipped computer such as an engineering workstation. NMSs communicate with agents to help keep track of network statistics and resources.

NLSP

NLSP stands for Netware Link Service Protocol. It is a link state routing protocol based on IS-IS used in Novell Networks.

Netware Loadable Module (NLM)

NLM stands for Netware Loadable Module. It is a individual program that can be loaded into memory on a Netware server and function as part of the Netware network operating system.

NHRP

NHRP stands for Next Hop Resolution Protocol. Protocol used by routers to dynamically discover the MAC address or other routers and hosts connected to a NBMA network. These systems can then directly communicate without requiring traffic to use an intermediate hop, thus increasing performance in ATM, Frame Relay, and SMDS environments.

Network Monitor

A relatively inexpensive computer device that is attached to a network segment and monitors all or a selected portion of network traffic. It examines frame-level information in each packet and compiles statistics on network utilization, packet type, number of packet errors and other significant information.

Network Layer

Layer 3 of the OSI reference model. This layer provides connectivity and path selection between two end systems. The network layer is the layer at which routing occurs.

NIC

It is a chip based circuit board used to connect the PC to a network or a server. The card is activated by loading software on the PC. Network Interface Card is a printed circuit board that is installed in a vacant slot in a computer I/O bus. The back of the card conatains a physical interafec for connectivity between a computer's internal resources and external resourcess connected to the network.

Network File System (NFS)

NFS stands for Network File System. Network File System (NFS) is an open operating system designed by Sun Microsystems that allows all network users to access shared file stored on computers of different types. NFS provide access to shared files through and interface called the Virtul File System (VFS) that runs on top of TCP/IP. Users can manipulate shared files as if they were stored locally on the user's own hard disk. With NFS, computers connected to a network operate as clients with while accessing remote files, and servers while providing remote users access to local shared files.

Network Downtime

It is the time duration during which the network is down or degraded.

Network Address

Network layer address referring to a logical, rather rather than a physical , network device. Used by the network layer.

Network Level Firewall

A firewall in which traffic is examined at the network protocol packet level.

Network

An of systems and/ or pheripheral devices with carriers and data communication devices for the purpose of exchanging data and information.

Netware

Popular distributed networking operating system developed by Novell. Provides transparent remote file access and numerous other distributed network services.

NetFlow

A Cisco Systems optimization technique that identifies traffic flows and speeds the forwarding of traffic for a flow. When a flow is identified, the switching, security, QoS and traffic measurement services required for the flow are used to built an entry in a NetFlow cache. Subsequent packets in the flow and handled via a single streamlined task that references the cache.

NetBIOS

NetBIOS stands for Nerwork Basic Input/Output System. API (Application Program Interface) used by application on a LAN to request services from lower level network processes. These services include session establishment and termination, and information transfer. NetBIOS is used by network operating systems such as LAN Manage, LAN server, Windows for Work-groups and Windows-NT.

NBP

NBP stands for Name Binding Protocol. It is the Appletalk protocol that translates a character string name into the network layer address of the corresponding client.

NBMA

NBMA stands for NonBroacast MultiAccess. It is a term describing a multiaccess network that does not inherently support broadcasting, for example ATM.

Network Address Translation (NAT)

NAT stands for Network Address Translation. It is a mechanism for reducing the need for globally unique IP addresses. NAT allows an organization with addresses that are not globally unique to connect to the Internet by translating those addresses into globally routable addresses.

Narrowband Channel

It is the communication channels that handle low valumes of data, typically from 45 to 300 baud. They are used mainly for telegraph lines and low speed terminals.

Multistation Access Point (MAU)

MAU stands for Multistation Access Unit. It is a hub in a IBM token Ring network. Each multistation access unit or MAU supports up to eight workstations, servers, or combinations. MAUs can be connected to create larger networks.

Multiplexing

The method of dividing a physical channel into many logical channels so that a number of independent signals may be simultaneously transmitted on it. Also scheme that allows multiple logical signals to be transmitted simulteneously across a single physical channel.

Multimode Fiber

Optical fiber supporting propagation of multiple frequencies of light.

Multicast

Message that is sent to a subset of nodes on a network.

Mean Time Between Failure (MTBF)

MTBF stands for Mean Time Between Failure. It is the average time that elapses between network or system failures.

Multi Service Provisioning Platform (MSPP)

MSPP stands for Multi Service Provisioning Platform. These devices provide the conversion of T1/E1 to EVC service.

Mobile service Switching Center (MSC)

MSC stands for Mobile service Switching Centre. This is the interface between the radio system and the public switched telephone network (PSTN). The MSC performs all signalling functions that are necessary to establish calls to and from mobile stations.

Message Handling Service (MHS)

MHS stands for Message Handling Service. It is a popular E-mail protocol for storage, management and exchange, especially in corporate offices, licensed by Novell.

Message Oriented Middleware (MOM)

MOM stands for Message Oriented Middleware. It is a middleware that uses messages and queues to exchange information. MOM allows application to continue processing before a remote service call is complete. MOM is suitable for slower networks such as WANs and the Internet.

Mesh Topology

Network topology in which device are organised with many, often redundant, interconnections strategically placed between network nodes.

MCDV

MCDV stands for Maximum Cell Delay Variation. In an ATM network, the maximum two point CDV objective across a link or node for the specified service category.

MBS

MBS stands for Maximum Burst Size. Parameter defined by the ATM forum for ATM traffic management. MCR is defined for VBR transmissions.

MAN

MAN stands for Metropolitan Area network. A network that spans a metropolitan area. Generally, a MAN spans a larger graphic area than a LAN, but a smaller geographic area than a WAN.

MAC Address

MAC (Media Access Control) Address is a unique number assigned to each network interface adapter on a network. This layer works at the physical layer of the OSI reference model. NIC (Network Interface Card) manufacturing companies have to get unique MAC address block from IEEE. Two network cards in the world can never have the same MAC address. Also standardized data link layer address that is 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. MAC addresses are six bytes long and include a 3-byte vendor code that is controlled by the IEEE. Also referred to as a hardware address, MAC-layer address or physical address.

MAC

MAC stands for Media Access Control. Lower of the two sublayers of data link layer defined by the IEEE. The MAC sublayer handles access to shared media, such as whether token passing or contention will be used.

Tuesday, December 10, 2013

Link-State Advertisement

LSA stands for Link-State Advertisement. Multicast packet used by link-state protocols that contains information about neighbors and path costs. LSAs are used by the receiving routers to maintain their routing table.

Long-haul Service

Communication networks such as public telephone that permit computer networking over extended geographical distances.

Logical topology

The geometric arrangement of the nodes and links of a network as they function to support  information transfer in the network.

Logging

The process of storing information about events that occurred on the firewall or network.

Local acknowledgment

Method whereby an intermediate network node, such as a router, responds to acknowledgments for a remote end host. Use of local acknowledgments reduces network overhead and therefore the risk of time-outs.

Logical Link Layer (LLC)

LLC stands for Logical Link Layer. The Logical Link Layer provides addressing and control of the data link. It specifies which machanisms are to be used for addressing stations over the transmission medium and for controlling the data exchanged between the originator and recipient machines.

Link

A communication path between two nodes or channel. Also communication network channel consisting of a circuit or a transmission path and all related equipment between a sender and a receiver.

Least Privilege

Designing operational aspects of a system to operate with a minimum amount of a system privilege. This reduces the authorization level at which various actions are performed and decreases the chance that a process or a user with high privileges may be caused to perform unauthorized activity resulting in a security breach.

Leased Line

Transmission line reserved by a communication carrier for the private use of a customer.

Layer 3 Switch

Switch that filters and forwards packets based on MAC addresses and network addresses.

Latency Time

In case of disk storage, the time taken for the desired record to come under the read/write head positioned over that track. Maximum Latency time equals the time taken by disk to rotate once.

Latency


1. Delay between the time a device requests access to a network and the time it is granted permission to transmit.

2. Delay between the time a device receives a frame and the time that frame is forwarded out to the destination port.

LANE

LANE stands for Local Area Network Emulation. LANE enables ATMLAN clients to access the use existing LAN application through a software layer added to the emulating devices. This software layer becomes an integral part of that device's ATM protocol Stack.

Local Area Network (LAN)

LAN stands for Local Area Network. High speed, low error data networking covering a relatively small geographical area up to a few thousand meters. LANs connect workstations, peripherals, terminals and other devices in a single building or other geographical limited area. Also a digital communication system capable of interconnecting a large number of computers, terminals and other pheripheral devices within a limited geographical area, typically within 1km. 

kerberos

An authentication system that provides user-to-host security for application layer protocols such as FTP and Telnet.

Keepalive Message

Message sent by one network device to inform another network device to inform another network device that the virtual circuit between the two is still active.

Jitter

Communication line distortion caused by the variation of a singal from its reference timing positions.

ISP

ISP stands for Internet Service Provider. Company that provides Internet access to other companies and individuals.

ISO Protocol

A communication protocol to interconnect geographically dispersed heterogenous computers. This protocol has been standardized by the International Standards Organization (ISO).

ISO 9000

Set of International quality management standards defined by ISO. The standards, which are not specific to any country, industry or product allow companies to demonstrate that they have specific processes in place to maintain an effective quality system.

ISO

ISO stands for International Organization for Standardization. International organization that is responsible for a wide range of standards, including those relevant to networking. ISO developed the OSI reference model, a popular networking reference model.

ISA BUS

Abbreviation for industry Standard Architecture. It is an unofficial designation for the bus design of the IBM PC/XT, which allows various adapters to be added to the system by means of inserting plug-in-cards into expansion slots.

IP Spoofing

An attack whereby a system attempts to illicitly impresonate another system by using its IP network address.

IP splicing or Hijacking.



An attack whereby an active, attacker. IP Splicing attacks may occur after an authentication has been made, permitting the attacker to assume the role of an already authorized user. Primary protections against IP splicing rely on encryption at the session or network layer.

IP Multicast

Routing technique that allows IP traffic to be propagated from one source to a number of destinations. Rather than sending one packet to each destination, one packet is sent to a multicast group identified by a single IP destination group address.

IP Address

32-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 four octets separated by periods (dotted dicimal format). Each address consists of a network number and a host number.

Intrusion Detection

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

Internetworking

General term used to refer to the industry and technologies devoted to connecting networks together. Also collection of networks interconnected by routers. 

IPX

IPX stands for Internet work Packet eXchange. Novell's NetWare networl layer protocol that specifies addressing, routing and switching packets between a server and workstations and across interconnected LANs. Encapsulated IPX packets can be carried by Ethernet packets and token ring frames.

Internet Telephony

Generic term used to describe various approaches to running voice traffic over IP networks, in particular, the internet.

Interface

The point in which independent systems or diverse groups interact. It consists of the devices, rules or conventions by which one components of a system communication with another. It is also the point of communication between a person and a computer. 

Interactive Mode

Used to enter commands directly from the keyboard.

Thursday, December 5, 2013

Inter Process Communication

The topology provided by an operating system to allow concurrent processes to communicate with each other.