LAN Technologies | Computer Networks - Computer Science Engineering (CSE) PDF Download

Local Area Network (LAN) Technologies

A local Area Network (LAN) is a data communication network connecting various terminals or computers within a building or limited geographical area. The connection among the devices could be wired or wireless. Ethernet, Token Ring and Wireless LAN using IEEE 802.11 are examples of standard LAN technologies.

Ethernet 

Ethernet LANs consist of network nodes and interconnecting media or links. The network nodes can be of two types:

Data Terminal Equipment (DTE):

Generally, DTEs are the end devices that convert the user information into signals or reconvert the received signals. DTEs devices are: personal computers, workstations, file servers or print servers also referred to as end stations. These devices are either the source or the destination of data frames. The data terminal equipment may be a single piece of equipment or multiple pieces of equipment that are interconnected and perform all the required functions to allow the user to communicate. A user can interact with DTE or DTE may be the user.

Data Communication Equipment (DCE)

DCEs are the intermediate network devices that receive and forward frames across the network. They may be either standalone devices such as repeaters, network switches, routers or maybe communications interface units such as interface cards and modems. The DCE performs functions such as signal conversion, coding and maybe a part of the DTE or intermediate equipment.

Ethernet networks can be divided into three categories depending upon their speed:

1. Fast Ethernet

Fast Ethernet refers to an Ethernet network that can transfer data at a rate of 100 Mbit/s.

2. Gigabit Ethernet

Gigabit Ethernet delivers a data rate of 1,000 Mbit/s (1 Gbit/s).

3. 10 Gigabit Ethernet
10 Gigabit Ethernet is the recent generation and delivers a data rate of 10 Gbit/s (10,000 Mbit/s). It is generally used for backbones in high-end applications requiring high data rates.

ALOHA

The Aloha protocol was designed as part of a project at the University of Hawaii. It provided data transmission between computers on several of the Hawaiian Islands involving packet radio networks. Aloha is a multiple access protocol at the data link layer and proposes how multiple terminals access the medium without interference or collision.

There are two different versions of ALOHA:

1. Pure Aloha

Pure Aloha is an un-slotted, decentralized, and simple to implement the protocol. In pure ALOHA, the stations simply transmit frames whenever they want data to send. It does not check whether the channel is busy or not before transmitting. In case, two or more stations transmit simultaneously, a collision occurs and frames are destroyed. Whenever any station transmits a frame, it expects the acknowledgement from the receiver. If it is not received within a specified time, the station assumes that the frame or acknowledgement has been destroyed. Then, the station waits for a random amount of time and sends the frame again. This randomness helps in avoiding more collisions. This scheme works well in small networks where the load is not much. But in largely loaded networks, this scheme fails poorly. This led to the development of Slotted Aloha.
To assure pure aloha: Its throughput and rate of transmission of the frame to be predicted.
For that to make some assumptions:
i) All the frames should be the same length.
ii) Stations can not generate frames while transmitting or trying to transmit frames.
iii)The population of stations attempts to transmit (both new frames and old frames that collided) according to a Poisson distribution.

2. Slotted Aloha

This is quite similar to Pure Aloha, differing only in the way transmissions take place. Instead of transmitting right at demand time, the sender waits for some time. In slotted ALOHA, the time of the shared channel is divided into discrete intervals called slots. The stations are eligible to send a frame only at the beginning of the slot and only one frame per slot is sent. If any station is not able to place the frame onto the channel at the beginning of the slot, it has to wait until the beginning of the next time slot. There is still a possibility of collision if two stations try to send at the beginning of the same time slot. But still, the number of collisions that can possibly take place is reduced by a large margin and the performance becomes much well compared to Pure Aloha.

The document LAN Technologies | Computer Networks - Computer Science Engineering (CSE) is a part of the Computer Science Engineering (CSE) Course Computer Networks.
All you need of Computer Science Engineering (CSE) at this link: Computer Science Engineering (CSE)
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FAQs on LAN Technologies - Computer Networks - Computer Science Engineering (CSE)

1. What is a Local Area Network (LAN)?
Ans. A Local Area Network (LAN) is a network that connects computers and other devices within a limited area, such as an office building or a campus. It allows the devices to share resources, such as files and printers, and enables communication between them.
2. What is Ethernet?
Ans. Ethernet is a commonly used LAN technology that defines the standards for the physical and data link layers of the network. It uses a packet-switched architecture and provides a reliable and efficient means of transmitting data over a LAN.
3. What is a Data Communication Equipment (DCE)?
Ans. Data Communication Equipment (DCE) refers to the devices that provide the interface between the data terminal equipment (DTE) and the communication link. In the context of LAN technologies, DCE includes devices such as modems, routers, and switches.
4. What is ALOHA LAN?
Ans. ALOHA LAN is a LAN technology that was developed at the University of Hawaii in the 1970s. It is a simple and decentralized network access method that allows multiple devices to transmit data over a shared medium. However, it suffers from low efficiency and high collision rates.
5. How does LAN technology benefit Computer Science Engineering (CSE) students?
Ans. LAN technology provides numerous benefits for Computer Science Engineering (CSE) students. It allows them to easily share files and resources with other students and faculty members within the same LAN. It also enables collaborative projects and facilitates communication among CSE students for knowledge sharing and learning. Additionally, LAN technology provides a practical environment for CSE students to gain hands-on experience in network configuration, troubleshooting, and security.
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