1, computer network is the use of communications equipment and lines to geographically different, functionally independent multiple computer systems interconnected to a well-functioning net total software to achieve the network of resources **** enjoyment and information transfer system.
2, on-line system is a central computer connected to a large number of geographically dispersed terminals and constitute a computer system.
3. PDN is a public data network. The network transmits digitized data and is a type of communications subnetwork.
4, OSI is the open systems interconnection reference model. A seven-layer network model developed for ISO (International Organization for Standardization).
5. PSE is packet switching equipment. As an intermediate node of the network, it has the function of storing and forwarding packets.
6. PAD is a packet assembly/disassembly device. In the sender will be large message split into a number of packets, in the receiver will be the same message belongs to the packet and then re-compose the message of the device.
7, FEP is the front-end processor. Set up between the central computer and communication lines, specifically responsible for communication control.
8. IMP is Interface Message Processor, a collective term for intermediate nodes in a network.
Two,
1, data communication: is a computer or other data devices and communication lines, to complete the data encoding signal transmission, transfer, storage and processing of communication technology.
2, data transmission rate: the number of binary bits of information that can be transmitted per second, in B/S.
3, channel capacity: the limit of information transmission data capacity, is the maximum data transmission rate of information.
4, self-synchronization method: is the receiver can be extracted from the data signal waveform synchronization signal method.
5, PCM: called pulse code modulation, is the most commonly used method of encoding analog data into digital signals.
6, FDM: also known as time-division multiplexing technology, is in the channel bandwidth exceeds the required bandwidth of the original signal, the total bandwidth of the physical shutdown is divided into a number of sub-shutdowns with the transmission of a single signal bandwidth is the same as the transmission of a single signal, each sub-information transmission of a signal.
7, synchronous transmission: is a batch of characters as the transmission unit, only in the beginning and end of the addition of synchronization mark, between characters and bits are required to synchronize.
8, error control: refers to the data communication process can be found or corrected errors, the error is limited to the smallest possible allowable range of technologies and methods.
9, FEC: also known as forward error correction, is a method of error control, the receiving end can not only find the error, but also to determine the location of the binary code element error occurs, so as to correct it.
10, signaling: is the electronic or electromagnetic encoding of data.
11, MODEM: also known as modem. Its role is to complete the conversion between digital data and analog signals, so that the media that transmit analog signals can transmit digital data. The sender MODEM will be digital data modulation converted to analog signals, the receiver MODEM and then demodulate the analog signal is restored to the original digital data.
12, the signal transmission rate: also known as the code rate, modulation rate or baud rate, said the number of code elements transmitted through the channel in a unit of time, the unit is recorded as a BAND.
13, baseband transmission: is a direct transmission of digital signals in the line of the electrical impulse, is one of the simplest transmission method, applicable to the local area network (LAN) of the close-range communication.
14, serial communication: data is transmitted bit by bit on a communication line, slower than parallel communication, transmission distance.
15, letter host: communication process to receive and process information in the device or computer.
16, source: the communication process to generate and send information equipment or computer.
17, full duplex: allows data to be transmitted in both directions at the same time, there should be two data channels, the sender and receiver should have independent receive and send capabilities.
18, impact noise: a sudden, often caused by external factors; its noise amplitude may be quite large, can not be avoided by improving the signal-to-noise ratio, is the main error in transmission.
19, ARQ: also known as automatic request for retransmission, is a kind of error control method; requires the receiver to detect errors, it will try to notify the sender to retransmit, until the correct data is received.
20, data: for meaningful entities, it involves the form in which things exist.
Three.
1. network protocol: a collection of rules, or conventions established for the exchange of data in a computer network.
2. Semantics: involves control information used for coordination and error handling.
3. Syntax: the format, encoding and signaling levels of data and control information.
4. Timing: involves speed matching and sequencing, etc.
5. Network architecture: the collection of computer network layers and their protocols.
6. OSI: Open Systems Interconnection, a term used in ISO to refer to hosts in a resource subnet.
7. end open system: is a term used in ISO to refer to hosts in a resource subnet.
8. relay open system: is a term used in ISO to refer to a node machine in a communication subnetwork.
9. DTE: Data Terminal Equipment, a collective term for user-owned network-connected equipment and workstations.
10, DCE: Data Circuit Termination Equipment or Data Communications Equipment, is a collective term for network equipment that provides the user with a point of connection to the network.
11, zero modem: when the RS-232C directly connected to the two near-earth DTE, in order to make the cable ends of the DTE through the cable have seen the parties seem to be DCE, the use of cross-hopping signal cable.
12, V series interface standard: is the interface between the data terminal equipment and modem or network controller, is a more complex interface.
13, X series interface standard: is applicable to the public **** data network in the house circuit termination equipment and data terminal equipment between the interface, it is the development of a later, is a relatively simple interface.
14, 100 series interface standard: is the interface between DTE and DCE without automatic calling equipment (such as modems).
15, 200 series interface standard: is the interface between DTE and DCE with automatic calling equipment (such as network controller).
16. X.21 Recommendation: is a digital interface for how a user computer's DTE exchanges signals with a digitized DCE.
17. Link management: the establishment, maintenance and release of data link layer connections.
18, feedback error control: the method used to enable the sender to confirm that the receiver has correctly received the data information sent by it.
19, ARQ method: also known as automatic request for retransmission, the sender will be sent to send the data frame with a certain redundancy error detection code, the receiver is based on the error detection code for error detection of data frames, if the error is found to return to the request for retransmission of the response, the sender receives the request for retransmission of the answer, then re-transmit the data frame.
20, stop sending method: also known as idle retransmission request, the provisions of the sender to send a frame to stop and wait for the receiver's confirmation of return, only when the sender receives the receiver's confirmation of the correct reception before sending the next frame.
21. go-back-n policy: when the receiver detects an out-of-order frame, it requests the sender to retransmit all unacknowledged frames after the last correctly received frame.
22, selective retransmission strategy: when the receiver detects an error in a frame, it still stores the subsequent correct frames in a buffer and does not submit them to the upper layers, and at the same time requests the sender to re-transmit the frame that was in error; once it receives the re-transmitted frames, it submits them to the upper layers in the correct order, along with the frames stored in the buffer.
23. Transmission window; the boundaries of the serial number queue of frames that have been transmitted by the sender but not yet acknowledged; the upper and lower boundaries are the top and bottom edges of the window, respectively, and the distance between the bottom and bottom edges is the end of the window in inches.
24, asynchronous protocol: character as a separate unit of information transmission, at the beginning of each character begins to synchronize the bits within each character, but the interval between characters is not fixed.
25, synchronous protocol: to multi-byte or multi-bit data block for the transmission of social evening production, synchronized only at the beginning of the frame, the frame to maintain a fixed clock.
26, BSC: character-oriented synchronization control protocol, also known as binary synchronous communication, the use of character-filled first and last delimitations, belonging to the data link layer protocol.
27. Information Frame: also called I-frame, used to transmit valid information and data.
28. Control frames: also called S frames, used for error control and flow control.
29. Unnumbered frames: also called U frames, used to provide link establishment, dismantling, and multiple control functions.
30. HDLC: High-level data link control protocol, a bit-oriented data link layer protocol that uses a bit-filled first place identification method.
31. Virtual Circuit Service: a connection-oriented, reliable data transmission service provided by the network layer to the transport layer that enables all packet sequences to reach the destination system.
32. Blocking: A phenomenon in which too many packets arrive at one part of a communications subnetwork for that part of the network to process, causing a degradation of performance in that part and in the network as a whole.
33. Deadlock: a phenomenon in which a network is blocked so severely that it causes network communication services to come to a standstill.
34, indirect store-and-forward deadlock: between a group of nodes, a node's all buffers are full of packets waiting to be output to the next node, this situation is passed in turn constitutes a cycle, resulting in a deadlock between multiple nodes.
35, direct store-and-forward deadlock: two nodes each other all buffers are full of packets waiting to be output to each other, resulting in two nodes can neither receive nor send packets.
36, network quality of service: is seen between the transport connection points of certain characteristics of the transport connection, is a measure of the performance of the transport layer, reflecting the quality of transport and the availability of services.
37. Abstract syntax: is a description of the general structure of the data and is a description of the data structure by the application layer entities.
38. Contextual relationship: the correspondence between the abstract syntax and the transport syntax, called the contextual relationship.
39. Resynchronization: the session layer requests the sender to retransmit after it has already answered the sender's correct reception and an error is found in post-processing.
40, FTP service: a protocol for accessing remote machines, using a client/server model that allows users to perform operations related to file transfers between the local and remote machines.
41. Simple Mail Transfer Protocol: is an application layer protocol that is simple text-based, reliable and efficient data transfer protocol.
42. Address Relay Protocol ARP: A protocol that translates IP addresses into corresponding physical network addresses at the network layer.
Four.
1. Token: A special mountain of frames that can control the media possessed by a site to distinguish data frames and other control frames.
2, carrier listening: that is, the sending site in the frame before sending, first listen to the channel whether there are other sites to send carrier signals, if there is no
other carriers, you can send the signal; otherwise, delay sending the frame.
3, conflict detection: that is, the transmitting station should listen to the channel while transmitting data, if listening to the channel has an interference signal, it means that a conflict has arisen, so we must stop transmitting data.
4, time slot: a fixed-length binary bit string, corresponding to a specific time slice, each station can only send data within the time slice.
5, Service Access Point: referred to as SAP, is a hierarchical system of the interface between the upper and lower layers of communication, N layer of SAP is N + 1 layer can access the N layer of services.
6, LAN operating system: is in the LAN low-level data transmission capabilities provided on the basis of high-level network users to provide *** enjoy resource management and other network service functions of the LAN system software.
7. Transmission delay: the total time it takes for a station to send a data frame from the beginning to the end of the data frame, or the total time it takes for a receiving station to receive a data frame.
8. Local Bridge: A bridge that interconnects networks within the allowable length of the cable.
9, bit ring length: when the transmission delay of the data frame is equal to the signal propagation delay in and on the ring, the number of bits of the data frame is the ratio of the measure of the ring length.
V.
1, ISDN: is the evolution of the integrated digital telephone network from the development of a communications network, it provides end-to-end digital connectivity to support a wide range of services, support for voice and non-voice communications services, it provides a small number of users to connect to the network of a small set of standard multi-purpose network interface.
2. Digital Bit Pipeline: refers to the interface that transmits the bit stream between the user equipment and the ISDN switching system. Bidirectional transmission of bit stream in the pipe is formed by the use of time-division multiplexing of bit streams from a number of independent channels.
3, the signal element: ATM's signal element is a frame with a fixed length, *** 53 bytes. Among them, 5 bytes is the header, 48 bytes is the information segment. Information segment can be all kinds of services in the user data, the beacon header contains a variety of control information.
4, Frame Relay: is a new type of fast packet switching, it inherits the characteristics of X.25, after simplifying its network layer protocol function and development.
5. ISP: Internet Service Provider.
6, URL: that is, the Uniform Resource Locator, each page on the WWW in the URL format named unique address.
7, subnet mask: is a 32-bit binary number, corresponding to the IP address of the subnet host identification area is all "0", the rest of the whole "1". Used for two hosts whether in the same subnet.
8, the World Wide Web: also known as WWW, is the Interner on the text, sound, images, video and other multimedia information in one of the global information resources network, is an important part of the Internet.
9, intranet: represents a group of interconnected networks used within the scope of a particular organization, they follow the Internet protocol, using a client/server structure, also known as the Intranet.
10, firewall: is a kind of software installed on the inter-network connection equipment, in the protected intranet and the Internet between the firm erected a security barrier, used to enhance the security of the intranet.