The document provides a detailed study of various network devices, including repeaters, hubs, switches, bridges, routers, and gateways, along with their functions and characteristics. It explains how these devices operate at different layers of the OSI model and their roles in enhancing network performance and connectivity. Additionally, it discusses the role of firewalls in managing network security and controlling traffic flow.

1. Study of Network Devices in Detail
1.Repeater:
Basic knowledge,Feature and Services:
>> A repeater is a device that operates only at the Physical layer.
>> A repeater can be used to increase the length of network by elemenating the effect
of attenuation on the signal.
>> It connects two segments of the same network, overcoming the distance
limitations of the transmission media.
>> A repeater forwards every frame; It has no filtering capability.
>> A repeater is a regenerator not an amplifier.
>>Repeaters can connect segments that have the same access method.
(CSMA/CD,Token Passing, Polling etc.)

2. 2. Hub:
Basic knowledge,Feature and Services:
>> A hub is used as a central point of connection among media segments.
>> It works at Physical layer of the OSI model.
>> It cannot filter data. Data packets are sent to all connected devices and there is no
intelligence to find out the best path for data packet which then leads to inefficiencies
and wastage.
>> Cables from network devices plug in to the port on the hub.
>> Types of hubs :
Passive hub: A passive hub is just a connector. It connects wires coming from
different branches. The signal pass through a passive hub without regeneration
or amplification.
Active hub: They regenerate or amplify the signal before ther are
retransmitted. It is known as Multiport repeater also.
>> Hubs are used on a small networks where data transmission is not very high.

3. 3. Switch:
Basic knowledge,Feature and Services:
>> A network switch is a computer networking devices that is used to connect
devices together on a computer network by performing a form of packet switching.
>> Types of Switch :
Two layer switch : It operates at Physical and data link layer. eg. Bridge.
Three layer switch : It operates at network layer. eg. Router.
>> It is considered more advanced than a hub because a switch will only send a
message to the device that need or requests it, rather than broadcasting the same
message out of its ports.

4. 4. Bridge:
Basic knowledge,Feature and Services:
>> Operates in both the PHYSICAL and the data link layer.
>As a PHYSICAL layer device, it regenerates the signal it receives.
>As a data link layer device, the bridge can check the PHYSICAL/MAC
addresses (source and destination) contained in the frame.
>> Types of Bridges :
Transparent Bridge – Also called learning bridges. Build a table of MAC
addresses as frames arrive. Ethernet networks use transparent bridge.
Source Routing Bridge – Used in Token Ring networks. Each station should
determine the route to the destination when it wants to send a frame and
therefore include the route information in the header of frame. A Frame
contains not only the source and destination address but also the bridge
addresses.
>> A bridge has a table used in filtering decisions. It can check the destination
address of a frame and decide if the frame should be forwarded or dropped. If the
frame is to be forwarded, the decision must specify the port.
>> A bridge has a table that maps address to ports.
>> Limit or filter traffic keeping local traffic local yet allow connectivity to other
parts (segments).

5. 5. Router:
Basic knowledge,Feature and Services:
>> Routes packets based on their logical addresses.(host-to-host addressing)
>> A router normally connects LANs and WANs in the Internet and has a routing
table that is used for making decision about the route.
>> Types of Routers:
There are several types of routers in the market. eg. Broadband Routers,Wireless
Routers, Brouters, Edge Router, Subscriber Edge Router, Inter-provider Border
Router, Core Router, Wired and Wireless Routers etc.
>> The routing tables are normally dynamic and are updated using routing protocols.
>> Provide sophisticated routing, flow control, and traffic isolation.
>> Configurable, which allows network manager to make policy based on routing
decisions.

6. 6. Gate Way :
Basic knowledge,Feature and Services:
>> Connect two networks above the network layer of OSI model.
>> Are capable of converting data frames and network protocols into the format
needed by another network.
>> Types of Gateways :
Transport Gateway- Make a connection between two networks at the
transport layer.
Application Gateway- Connect two parts of an application in the application
layer. eg. Sending email between two machines using different mail formats.
Broadband-modem-router Gateway- It combines the functions of a DSL or
cable modem, a hub or switch, and a firewall. Broadband routers attempt to
combine all of the essential features of home networking in one integrated,
easy-to-use package. Differentiators for home "residential gateways" include
specific features, reliability, cost, speed, and vendor reputation.
>> Provide for translation services between different computer protocols.

7. Ans to the ques no: 04
Firewall: An entity that prevents a specific type of information from moving between
outside world (untrusted network) and inside world (trusted network).
Perform and process of Firewall:
Firewall can limit network exposure. It can prevent the dangers of the Internet from
spreading into a LAN (e.g. DdoS). It can keep one (more vulnerable) segment of a
LAN from another. A firewall can log Internet activity. Since all traffic passes
through the firewall, the firewall is a good place to collect information about system
and network use or misuse. Based on this view I will block the access of
FACEBOOK (https://www.facebook.com) under network in Bangladesh.
I will apply this Firewall at Gateway hardware which I described above.