Basics of network devices

Letting the network work smoothly, efficiently and the ability to connect to other network systems requires the use of dedicated network devices. These network devices are diverse and rich in types but are based on basic devices such as Repeater, Hub, Switch, Router and Gateway.

This article will help readers get a basic understanding of the network devices mentioned above:

Repeater

On a LAN, the limit of the network cable is 100m (for CAT 5 UTP network cable type - the most commonly used cable), because the signal is attenuated on the transmission line so it cannot go further. Therefore, in order to be able to connect the devices further away, the network needs devices to amplify and re-signal the signal, allowing the signal to travel far beyond this limit.

Repeater is a device in layer 1 (Physical Layer) in OSI model. Repeater plays the role of amplifying the physical signal at the input and provides power to the signal at the output to be able to reach the next path in the network. Telegraph, telephone, fiber optic communication . and the need for far-away signaling need to use Repeater.

Hub

The hub is considered a multi-port Repeater. A Hub has from 4 to 24 ports and may be even more. In most cases, Hub is used in 10BASE-T or 100BASE-T networks. When the network configuration is Star topology, the Hub acts as the center of the network. With a Hub, when information enters from a port and will be taken to all other ports.

Hub has 2 types: Active Hub and Smart Hub. Active Hub is a commonly used Hub, needs to be powered when operating, used to amplify the incoming signal and output signals to the remaining ports, ensuring the required signal level. Smart Hub (Intelligent Hub) has the same function as Active Hub, but with integrated chip that automatically detects errors - very useful in case of detecting and detecting errors in the network.

Bridge

Bridge is a network device of layer 2 of the OSI (Data Link Layer) model. Bridge is used to pair 2 networks to form a single large network. Bridge is commonly used as a bridge between two Ethernet networks. Bridge observes packets on every network. When you see a packet from one computer on this network transferring to another network computer, Bridge will copy and send this packet to the destination network.

The advantage of Bridge is transparent operation, computers of different networks can still send information to each other simply without knowing the "interference" of Bridge. A Bridge can handle many network traffic like Novell, Banyan . as well as IP addresses at the same time. The disadvantage of Bridge is that connecting only the same networks and using Bridge for fast-functioning networks will be difficult if they are not physically close to each other.

Switch

Switches are sometimes described as a multi-port bridge. While one The bridge has only two ports to connect the two network segments together, the Switch is able to connect multiple segments together depending on the number of ports on the Switch. Like Bridge, the Switch also "learns" the information of the network through the packets it receives from computers on the network. The switch uses this information to build up the Switch panel, which provides information to help the packets arrive at the correct address.

Today, in data communications, Switch has two main functions: to transfer data frames from source to destination, and to build Switch panels. Switches operate at much higher speeds than Repeater and can provide more functions such as the ability to create virtual LANs (VLANs).

Router

Router is a layer 3 network device of OSI model (Network Layer). Routers connect two or more IP networks together. Network computers must "be aware" of a router's participation, but for IP networks, one of the rules of IP is that every computer connected to the network can communicate with the router.

Router Advantages: Physically, the router can connect to other types of networks together, from high-speed local Ethernet to low-speed long-distance phone lines.

Disadvantages of Routers: Routers are slower than Bridge because they require more computation to figure out how to route packets, especially when the networks connect to each other not at the same speed. A fast-functioning network can broadcast packets much faster than a slow network and can cause network congestion. Therefore, the router may require the computer to send the packets more slowly. Another problem is that routers are protocol-specific - that is, the way a computer connects to an IP router is different from how it communicates with a Novell or DECnet router. Currently this problem is solved by a network that knows the path of any known network type. All commercial routers can handle a variety of protocols, usually at the extra cost for each protocol.

Gateway

Gateway lets you join two types of protocols together. For example, if your network uses IP protocol and someone's network uses IPX, Novell, DECnet, SNA . or a protocol, Gateway will switch from one protocol to another.

Through Gateway, computers in networks using different protocols can easily "talk" to each other. Gateway not only distinguishes protocols but can also distinguish applications like how you send e-mail from one network to another, convert a remote session .