1. Connecting Networks Repeater: physical layer Bridge: data link layer
Router: network layer
Gateway: network layer and above.

2. Bridge
That connects two or more networks with different types of protocols
Copies frames from one network to another
A Bridge will connect two segments of a LAN, but it also acts as a repeater.
A bridge will read the destination address of a packet of data being transmitted to determine whether to let it across the bridge to the other segment or to keep it within the original segment.
It reads the address of sending and receiving computers
This helps keep the traffic on the network lower by not having packets lost in the wrong segments.
BRIDGE

3. Segment A
Segment B

4. Segmentation
A segment is a run of cable to which are attached a number of workstations
Problem:a large number of computers and heavy traffic can slow down the network so
This problem is solved by segmenting the network into manageable segments by inserting a bridge or router between each network segment.
Traffic is then reduced on each segment, giving better network performance

5. Routers
A Router can do the job of a repeater and a bridge but it also has special software that reads the destination address.
That connects multiple networks using similar or different protocols.
Router is suitable for big Wide Area Network.
It can connect networks of different countries
It send data in less time.
The device then makes a decision as to the best path the data packet must take to get closer to its destination.
A router table database is used to help choose the correct path, but heavy transmission or a fault on a line would be detected by the router and an alternative path would be given.

6. Gateway Operates as a router.
It can convert data according to the protocol.
Can be used to connect a personal computer network to mainframe computer network
Data conversions above the network layer.
A Gateway is an enhanced router, usually used to connect a series of LAN’s to a WAN.
The specialised software on the gateway is used to read different protocols from different operating systems and different hardware an be able to connect them all together.
Conversions:
encapsulation - use an intermediate network
translation - connect different application protocols
encryption - could be done by a gateway

8. Switch A multiport Bridge, functioning at the Data Link Layer
Each port of the bridge decides whether to forward data packets to the attached network
Keeps track of the Mac addresses of all attached devices (just like a bridge)
Similarly priced to Hubs – making them popular
Acts like a Hub, but filters like a Bridge
Each port on a Switch is a collision domain

9. Advantages and Disadvantages of Repeater
Can connect different types of media
can extend a network in terms of distance
does not increase network traffic
Disadvantages – Extends the collision domain
can not filter data
can not connect different network architectures
limited number only can be used in network

10. Advantages and Disadvantages of Hub
Advantages – Cheap
can connect different media types
Disadvantages – Extends the collision domain
can not filter information
passes packets to all connected segments

11. Advantages and Disadvantages of Bridge
Advantages – Limits the collision domain
can extend network distances,
uses MAC address to filter traffic
eases congestion
can connect different types of media
some can connect differing architectures
Disadvantages – Broadcast packets can not be filtered
more expensive than a repeater
slower than a repeater – due to additional processing of packets

12. Advantages and Disadvantages of switch
Limits the collision domain
can provide bridging
can be configured to limit broadcast domain
Disadvantages – More expensive than a hub or bridge
configuration of additional functions can be very complex

13. Advantages and Disadvantages of Router
Advantages – Limits the collision domain
can function in LAN or WAN
connects differing media and architectures
can determine best path/route, can filter broadcasts
Disadvantages – Expensive
must use routable protocols
can be difficult to configure (static routing)
slower than a bridge

14. Modem To do this the computer must be equipped with a modem
(Modulator – Demodulator).
The modem converts digital signals into analogue signals that can be sent along telephone lines.
It can also convert analogue signals it receives back into digital signals the computer can use.

15. Dial up Connection Telephone line Digital signal One Tone ‘1’
represents
Binary ‘1’
‘1’
MODEM
A different Tone
represents
Binary ‘0’
‘0’
Disadvantages
Dial up ties up your telephone line and so it cannot be used for anything else.
It takes a while for the computer to set up a connection i.e many seconds.
Internet Service Providers may charge you by the minute and so a slow link means you pay more.