Wednesday, 10 August 2011
66. Cyclic redundancy check (CRC):-
Cyclical Redundancy Check is a type of hash function (one way encryption), which is used to produce a small, fixed-size checksum of a block of data, such as a packet or a computer file. A CRC is computed and appended before transmission or storage, and verified afterwards by the recipient to confirm that no changes have happened in transit.
65. CSU/DSU:-
Channel Service Unit/Data Service Unit. A hardware device that converts a digital data frame from a local area network (LAN) into a frame appropriate to a wide-area network (WAN) and vice versa.
64. CSMA/CD:-
Carrier sense multiple access with collision detection. Media-access mechanism wherein devices ready to transmit data first check the channel for a carrier. If no carrier is sensed for a specific period of time, a device can transmit. If two devices transmit at once, a collision occurs and is detected by all colliding devices. This collision subsequently delays retransmissions from those devices for some random length of time. CSMA/CD access is used by Ethernet and IEEE 802.3.
63. CSMA/CA :-
Collision Sense Multiple Access with Collision Avoidance. A "flavor" of CSMA that includes CA (Collision Avoidance).
62. Crosstalk: -
The effect by which a signal transmitted on one circuit or channel of a wire creates an undesired effect in another circuit or channel.
60. Converge: -
When different intermediary devices exchange information in order to have a consistent viewpoint of the network. We can also use another form of the root word converge in the phrase "converged network". This kind of network aggregates various forms of traffic such as voice, video and data on the same network infrastructure
59. Control data: -
Data that guides a process. A flag in a data-link frame is an example of control data.
58. Console port:-
A port in which we can connect a terminal or computer with a terminal emulator to the network device in order to communicate and configure the network device.
57. Console password: -
A password configured on the console line of the router or switch that requires a user to access the console port only after providing a password.
56. Congestion: -
The state of a network when there is not sufficient bandwidth to support the amount of network traffic.
54. Computer virus:-
A computer virus is a computer program that can copy itself and infect a computer without permission or knowledge of the user.
53. Command Line Interface (CLI):-
A method for interacting with computers using text as input. CLI can generally be considered as consisting of syntax and semantics. The syntax is the grammar that all commands must follow.
52. Collision fragment:-
Collision fragments are the product of a collision on a shared medium. The fragments sizes are less than 64 bytes.
51. Collision domain: -
A network segment where if one particular device sends a frame on a network segment, every other device on that same segment will process that frame. This also means that if two or more devices on that same segment transmit a frame at the same time there will be a collision.
49. Collision: -
In Ethernet, the result of two nodes transmitting simultaneously. The frames from each device impact and are damaged when they meet on the physical media.
50. Collision avoidance (CA):-
Used in multiple access topologies such as wireless LAN networks. When a node wants to transmit, it sends a signal called Request-To-Send (RTS) with the length of the data frame to send. If the receiving station wishes to allow the transmission, it replies the sender a signal called Clear-To-Send (CTS) with the length of the frame that is about to receive. If another node hears the RTS will not transmit in order to avoid conflict with the CTS.
48. Collaborative (information systems):-
Information systems that allow the creation of a document or documents that can be edited by more than one person in real-time.
47. Collaboration tool: -
A collaboration tool is something that helps people work together on a particular file or piece of software. Many people use the term collaboration tool in a software context, for instance, collaboration software such as google docs, Microsoft sharepoint server.
46. Code groups:-
A code group is a consecutive sequence of code bits that are interpreted and mapped as data bit patterns.
44. Coaxial: -
Components that share a common axis. In the case of Coaxial cable there are three different layers of material surrounding the inner conducting material. The outer conductor, the insulator and the protective outer jacket.
43. Cloud :-
The cloud symbol is used to represent network communications without showing specific details of the network architecture. The cloud typically is used to hide the details of Layer 1 and Layer 2.
42. Client/Server model: -
A network architecture that connects a client to a server whereupon the client accesses services provided by the server.
41. Client: -
A client is a computer system that accesses a service on another computer remotely by accessing the network.
40. Classless addressing:-
Ipv4 addressing scheme that uses a subnet mask that does not follow classful addressing rules. It provides increased flexibility when dividing ranges of IP addresses into separate networks.
39. Classful Addressing:-
In the early days of IPv4, IP addresses are divided into 5 classes, namely, Class A, Class B, Class C, Class D, and Class E.
38. Checksum :-
A checksum is a form of redundancy check, a simple way to protect the integrity of data by detecting errors in data that are sent through space (telecommunications) or time (storage). It works by adding up the basic components of a message, typically the asserted bits, and storing the resulting value. Anyone can later perform the same operation on the data, compare the result to the authentic checksum, and (assuming that the sums match) conclude that the message was probably not corrupted
36. CCNA: -
Cisco Certified Network Associate. The associate level certification founded by Cisco Systems.
35. Carrier Sense Multiple Access (CSMA):-
A protocol in which a node wishing to transmit listens for a carrier wave before trying to send. If a carrier is sensed, the node waits for the transmission in progress to finish before initiating its own transmission.
34. Carrier :-
Electromagnetic wave or alternating current of a single frequency, suitable for modulation by another, data-bearing signal.
33. Cache: -
A temporary storage where data that is accessed frequently can be stored. Once the data is stored in the cache, accessing the cached copy instead of accessing the original data, so that the average access time is lower. For example a proxy server that has a cache.
32. Burned-in-address:-
The MAC address of a network interface card. It is called burned-in because the address cannot be changed.
31. Broadcast domain:-
A logical network composed of all the computers and networking devices that can be reached by sending a frame to the data link layer broadcast address.
30. Broadcast address:-
An address that is meant to represent a transmission from one device to all devices based on the specified broadcast address.
29. Broadcast :-
A form of transmission whereupon one device transmits to all devices within the network or on another network.
28. Bridging :-
The process of forwarding frames from one port to another port or from segment to segment.
27. Bridge table :-
The table that the bridge creates that associates mac addresses with the outgoing port.
26. Bridge :-
A layer 2 device that connects multiple network segments at the data link layer of the OSI model.
25. Bits :-
A bit is a binary digit, taking a value of either 0 or 1. Binary digits are units of information storage and communication in computing.
24. Bit time :-
The time it takes for one bit to be transmitted from a NIC operating at some predefined standard speed. The time is measured between the time the logical link control layer 2 sub layer receives the instruction from the operating system until the bit actually leaves the NIC.
21. Benchmarks :-
A standard by which something can be measured or judged. A benchmark is usually used when testing network performance and comparing it to the performance results of the benchmark.
20. Bandwidth :-
The amount of data that can be transmitted in a certain amount of time. For digital bandwidth, it is usually expressed in bits per second (bps). For analog bandwidth, it is expressed in cycles per second, or Hertz (Hz).
19. Backoff algorithm :-
When a collision is detected each sender will delay before retransmitting. Each sender chooses a random delay between 0 and d (d is some standard delay value). If another collision occurs, each computer doubles the range from which the delay is chosen, that means, the random delay will now be between 0 and 2d. If another collision occurs the range will be between 0 and 4d and so on. After each collision the range of the random delay increases.
18. Backoff :-
The (usually random) retransmission delay enforced by contentious MAC protocols after a network node with data to transmit determines that the physical medium is already in use.
17. Aux port :-
17. Aux port :- Auxiliary port of a router. Is used for out of band connectivity with the router. It is usually used to get dial-in access to the router.
15. Authentication :-
A process whereupon a person must prove that they are legitimate users of that certain resource.
13. Asynchronous transmission mode:-
Term describing digital signals that are transmitted without precise clocking. Such signals generally have different frequencies and phase relationships. Asynchronous transmissions usually encapsulate individual characters in control bits (called start and stop bits) that designate the beginning and end of each character.
12. ARP table:-
A cache in which a device keeps a table of MAC addresses and their associated layer 3 address.
11. ARP poisoning:-
The sending of fake ARP messages to an Ethernet LAN. These frames contain false MAC addresses that "confuse" network devices, such as switches. As a result frames intended for one node can be mistakenly sent to another node. Also known as ARP spoofing.
9. ARP:-
Address Resolution Protocol. A host wishing to discover another host's MAC address broadcasts an ARP request onto the network. The host on the network that has the IP address in the request then replies with its MAC address.
7. AND:-
A Boolean operation used to combine search terms and find a result. If x = 1 and y =1 then z = 1. If x = 1 and y = 0 then z = 0. If x = 0 and y = 1 then z = 0. If x = 1 and y = 0 then z = 0.
6. American National Standards Institute (ANSI):-
American National Standards Institute. private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States.
5. Administratively scoped addresses:-
Administratively scoped addresses are also called limited scope addresses. These addresses are restricted to a local group or organization.
4. Address Resolution Protocol (ARP):-
Address Resolution Protocol (ARP). The method for finding a host's hardware address when only its network layer address is known. Primarily used to translate IP addresses to Ethernet MAC addresses.
2. Acknowledgment:-
Acknowledgments are sent by receiving stations to sending stations to confirm receipt of data.
1. ACK:-
In TCP ACK is used in the initial 3 way handshake to acknowledge the sending station's sequence number and in the actual sending of data the ACK is used to acknowledge sent segments.
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