Networks DEVICES

Repeater device to amplify or regenerate digital signals received while setting them from one part of a network into another. Works on OSI layer 1.

some time the signal becomes weak or disappears due to the distance that is sent to. Therefore, we need to use repeater. The repeater receives weak signal and then send it after making it stronger.

While Repeater consider as a cheap device that uses to expand LAN networks, it may cause some matters. For example, it does not filtrate bad signal and it cause Broadcast Storm which is accrued when the many packets are sent to all users and reach the maximum capability of the network.

Hub connects multiple Ethernet segments together. When using a hub, every attached device shares the same broadcast domain. It provides bandwidth which is shared among all the objects.

It is used usually in stare networks to connect all nodes together and send signal to all of them. It treats data as electric signals and does not understand IP addresses.

Types of HUBs Active HUB. Passive HUB. Hybrid HUB.

Active HUB The majority of hubs consider as an active hub. They activate signals and they are called sometime multiport repeaters. Also, They require electric power to be used.

Passive HUB: It does not require electric power. It just connect cables and nodes to each others.

Hybrid HUB They are usually used to expand networks. They could be two or more and they are suitable to be connected to different kind of cables.

Switch a device that allocates traffic from one network segment to certain lines (intended destination(s)) which connect the segment to another network segment. So unlike a hub a switch splits the network traffic and sends it to different destinations rather than to all systems on the network. Works on OSI layer 2.

It transmit data depending on MAC Address. It is easy to be installed to a network, and it increases speed of sending data.

We can classify switch in different layers as following: It could be in Physical layer which is named switching hub and deal with bits only. It could be in data link layer which is named LAN switch as it has been described later. It could be in Network layer which is named Routing switch and doing Router jobs.

Bridge: a device that connects multiple network segments along the data link layer. Works on OSI layer 2.

The main role of a bridge is connecting different networks together. Each bridge has a table that contains all nodes addresses, so it allows signal to move on another network if the address is in another one. It does repeater’s job with better performance. It transmit signal depending on MAC address. Also it is worthy to mention that there are internal and external bridges. The internal bridges are usually installed in servers computers.

Local bridges Remote bridges Local bridges connect to networks or more directly by network cables. While Remote bridges connect different networks that are away from each other by phone links. So there should be two bridges at least two modem devices.

Bridge learning: Bridges could realize every addition or cancelation by sending a messages to nodes or recognizing each signal that passes through it.

Router: a specialized network device that determines the next network point to which to forward a data packet toward its destination. Unlike a gateway, it cannot interface different protocols. Works on OSI layer 3.

It has an address table similar to the bridge table but much better. It uses IP Address to reach nodes and has a map to reach different routers and networks quickly.

The main purpose of using routers is to choose the best way to send signal through. Also it links the data link layer devices. The router is considered as a backbone of the networks.

There are two kind of Routers: Static Router Dynamic Router

The static router force networks manager to set convenience tables to transmit data. Also elect the tracks of data that is allowed. While the dynamic router require less attention from the networks manager.

Gateway: A device sit at a network node for interfacing with another network that uses different protocols. Works on OSI layers 4 to 7.