LAN Devices And Switch Types Computer Science Essay

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LAN devices is very important stations in restaurant control, which is switch, router, and modem. switch is device that reduce data packet collision, and increase transmission speed switch establishes a connection between two pc s so when we want to send packets to pc 2 the switch save the address in temporary memory called (buffer) reading the Mac address and compare it with a list of addresses in look up table .

switch methods:

switch uses one of three ways:

Cut-through :when switch receives the packet it start to save 6 bytes that shows the address information and start to send it. even though the packet is not fully send to switch.

Store and forward :that means switch save the whole packets and check the packets for an error if there are the packet not send if not the switch compare the Mac address with addresses in look up table .

Fragment-free :like cut-through which is saving the 64 bytes before sending the packets because error and collision happens during these initial 64bytes.

Switching type:

Shared-memory: The switch saves all packets in a memory buffer that share all the switch ports. Then, the switch sends the packets from correct port to the destination node.

Matrix: has inner grid which is the I/O ports cross each other. When the switch receive a packet on the input port, the switch check the MAC address in the lookup table to find the right output port. The two port then are intersect.

Bus-architecture: has internal transmission path using time division multiplexer access to shared all ports. to dedicates a memory buffer to each port.



Router is hardware device use to send information to another computer or system.

How it works? when you want to send an e-mail to another PC at remote network .i.e.( any computer that is not on same local network). To default router or "gateway" This router contains all the data with different destination addresses to the computer network .


In fact . router is a very fast machine . It has a memory, processor , software and inputs outputs connection to communicate with other computers. To keep things simple we will take router with minimum connections required. Which is an WAN port (Wide Area Connection)and port Ethernet ,The PC that you want to send an e-mail to Needs to be connect to Ethernet interface. This e-mail will be redirected by the WAN interface to WAN port on the destination (router),since each destination add is saved individually in the memory of the router.


In restaurant network we need router to connect local network to any network that manager can see the work remotely.

What is Modem:

To understand the modem take this example when you want to send information(video e-mail) along telephone line you need modem. Why? because computer understand digital information and the signal transmitted along telephone line is analog. So the modem convert between them for that it short for modulate demodulate.


Types of modem:

External modem.: have own power supply ,connect with a computer's serial port. By cable and socket for telephone line connection and Because it has own power supply, you can turn off the modem to break an online connection. Also does not drain any power from the computer unlike internal modem and you can see modems connection activity by watching lights.

Internal modem: comes inside computer system. Activated when run a communications program and turned off when exit the program.

How it works:

When modem first connect to telephone line you will hear screeching sound these digital signals being modulated into analog signal. Higher tone represent the digit 1 and lower tone represent the digit 0. The receiving modem demodulate signal to digital and send it to distention address . The modems knows the incoming data and outgoing by the type of tones they use. also allows to compress digital

signals before modulating them and decompressing them after demodulating the signals. This make data travel more efficient. To establish a speed network in restaurant we have to balance the data flow through cable with speed of network devices .so we decided to connect the network to desktop server with speed 10\100Mbps Ethernet ,switch 8 ports10 /100 mbps speed

Switch feature



Ethernet ports




Easy plug and play

Plug and play


Fast store and forward

Fragment free


10.97 $


For router we need 10/100Mbps Ethernet ports:

Router features

EBR-2310 router

D link DGL-4100 router

Ethernet ports

10/100 Mbps






1-Diagnose physical cable problems.

2-Ideal for pc/network speed.

1-Firewall feature.

2-Ideal for pc/network speed.




To connect the internet we need fast modem with 56k speed

Modem feature







1-Makes communication fast.

2-Remote management server applications.

1-Connect to internet easily.

2-Take incoming call while online.



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