LOCAL NETWORKING BASICS

Basic Local Networks technologies

Architecture Ethernet technologies can be divided into two generations. The first generation of architecture are providing low and high data transfer rate: Ethernet 10 Mbit /s), Token Ring (16 Mbit /s) and ARC net (2,5 Mbit /s). To transmit data, these technologies use cables with copper wire. Second generation technologies are modern high-speed architecture: FDDI (100 Mbits / s), ATM (155 Mbit /s) and upgraded version of the first generation architectures (Ethernet): Fast Ethernet (100 Mbit /s) and Gigabit Ethernet (1000 Mbit/s). An improved version of the first generation architectures are calculated as the use of cables with copper conductors and fiber-optic data transmission. New technologies (FDDI and ATM) focused on the use of fiber-optic data transmission and can be used for simultaneous transmission of different types of information (video, voice and data). Network technology - a minimum set of standard protocols and implementing their software and hardware, enough to build a computer network. Network technology known as basic technology. Currently, there are a huge number of networks with different levels of standardization, but widespread such well-known technologies such as Ethernet, Token-Ring, Arcnet, FDDI.

Basic Network access method

Ethernet is a multiple access technique with listening carrier and resolution of conflicts (conflicts). Before transmitting each workstation determines the channel is free or busy. If the link is idle, the station starts transmitting. Conflicts result in actual lowering speed network only when the work stations 80-100. Access Method Arcnet. This access method is widespread mainly due to the fact that the equipment Arcnet cheaper than equipment Ethernet or Token -Ring. Arcnet is used in local area networks with "star" topology. One of the computers creates a special marker (special report), which was subsequently transferred from one computer to another. If a station has to send a message that it received the token generates a packet, complete addresses of the sender and destination. When the packet reaches the destination station, the message "disengaged" from the marker and passed the station. Access Method Token Ring. This method was developed by IBM; it is designed pa ring topology network. This method resembles Arcnet, as also uses the token transmitted from one station to another. Unlike Arcnet with Token Ring access method provides the ability to assign different priorities to different workstations.

Basic technologies of Local Area Networks (LANs)

Ethernet technology is now the most popular in the world. In classical Ethernet network with standard coaxial cable two species (thick and thin). However, more-spread version of Ethernet, is used as a transmission medium twisted pairs, since their installation and maintenance much easier. Apply topology "tire" and type "passive star." The standard defines four basic media type.

1. 10BASE5 (thick coaxial cable);
2. 10BASE2 (thin coaxial cable);
3. 10BASE-T (twisted pair);
4. 10BASE-F (fiber optic cable).

Fast Ethernet - high-speed kind of network Ethernet, transmission speed of 100 Mbit / s. Fast Ethernet network compatible with networks supported by standard Ethernet. Basic network topology Fast Ethernet - passive star.

1. The standard defines three types of transmission media for Fast Ethernet:
2. 100BASE-T4 (Quad twisted pair);
3. 100BASE-TX (dual twisted pair);
4. 100BASE-FX (fiber optic cable).

Gigabit Ethernet - high-speed network variety of Ethernet, transmission speed of 1000 Mbps /s. Standard Gigabit Ethernet network currently includes the following media types:

1. 1000BASE-SX - segment on multimode fiber optic cable with a wavelength of 850 nm light signal.
2. 1000BASE-LX - segment on multimode and single-mode fiber optic cable with a wavelength of 1300 nm light signal.
3. 1000BASE-CX - segment on the electric cable (shielded twisted pair).
4. 1000BASE-T - a segment on the electric cable (quadruple unshielded twisted pair).

Due to the fact that the networks are compatible, it is easy and simple to connect segments of Ethernet, Fast Ethernet and Gigabit Ethernet in a single network. Token-Ring network offered by IBM. Token-Ring designed for networking of all types of computers manufactured by IBM (from personal to large). Token-Ring Network has a star-ring topology. Network Arcnet - this is one of the oldest networks. As the topology of the network uses Arcnet "bus" and "passive star." Arcnet network enjoyed great popularity. Among the main advantages Arcnet network can be called high reliability, low cost and flexibility adapters. The main disadvantage is the low speed network transmission (2.5 Mbit / s). FDDI (Fiber Distributed Data Interface) - a standardized specification for network architecture, high-speed data over fiber optic lines. Speed ​​- 100 Mbit / s. Main technical characteristics of the FDDI network as follows:

1. The maximum number of subscribers - 1000.
2. The maximum length of the ring network - 20 km
3. Maximum distance between network subscribers - 2 km.
4. Transmission media - fiber optic cable
5. Metod access - marker.
6. The data transfer speed - 100 Mbit /s.

NETWORKING BASICS

NETWORKING BASICS CONCEPT

Computer network-a set of stand-alone computers for joint solution of information, computing, and other tasks. Two computers are related if they can exchange information. The requirement of autonomy here is used to exclude from consideration of the decentralized system (one computer can control the other force). System with one control device and are not multiple managed network. In a distributed system, there are numerous independent PV rsonal′nye computers is transparent (invisible to other users). Users of such a system, setting the team, unaware of the existence of several processes execute the given command. In computer networking, the user must explicitly register on one machine and explicitly specify the remote setting. The simplest type of network is a peer-to-peer, which link personal computers of end users and enables you to share printers, files, drives. More advanced network in addition to end-user computers (workstations) include dedicated computer servers. Server is a computer that performs specific functions in the network services to other computers on the network.

USE of COMPUTER NETWORKS 

The use of computer networks:

1.  sale of air and railway tickets; 
2.  access to information in computer databases and databanks; 
3. exchange of information between the slave. a teacher and a servant. places pupils. The use of computer networks:

1. In organizations:

• resource sharing cat provide access to programs that are given to any user regardless of NAT. the location of the resource and the user;
• ensure high reliability through the use of alternative sources of information;
• opportunity cost savings;
• scalability;
• the possibility of rapid communication between remote employees.

2. individuals:

• Remote access to information;
• Communication;
• interactive games, video, TV;
• e-business.

  Networks Architecture «Client Server Types» Server types:

• print server — attach the printer to the network via a specialized node processing print jobs;
• DB server is a shared database;
• file server is the data store;
• communication server-manages access to remote resources, provides a channel of communication with global figures. network;
• application server-run specialty computing jobs (handling graphics);
• Web Server — provides access to Web pages.

Very popular today and extremely promising technology of information processing in the network name.«client-server». In the function «client» includes:

• providing a user interface for certain production duties and powers;
• query to the server;
• analysis of server responses to and bring them to the user.

The primary function of the server is to perform a specific action at the request of the client (for example, the solution to a difficult mathematical problem, search data in the database, your connection with another client, etc.); the server itself does not have any interactions with the customer. If the server to which the client has failed to solve the problem of a lack of resources, then ideally they find another, more powerful server and transfers the task of it, becoming, in turn, by the client, but not informing the primary client unnecessarily.