Computer Networking Notes
(Delhi University First Year 2021)
What are Unicasting, Anycasting, Multicasting and Broadcasting?
If the message is sent from a source to a single destination node, it is called Unicasting. This is
typically done in networks.
If the message is sent from a source to any of the given destination nodes. This is used a lot in
Content delivery Systems where we want to get content from any server.
If the message is sent to some subset of other nodes, it is called Multicasting. Used in the
situation when there are multiple receivers of the same data. Like video conferencing, updating
something on CDN servers which have a replica of same data.
If the message is sent to all the nodes in a network it is called Broadcasting. This is typically used
in Local networks, for examples DHCP and ARP use broadcasting.
What are layers in OSI model?
There are a total of 7 layers
1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer
What is Stop-and-Wait Protocol?
In Stop and wait protocol, a sender after sending a frame waits for an acknowledgment of the
frame and sends the next frame only when acknowledgment of the frame has received.
What is Piggybacking?
, Piggybacking is used in bi-directional data transmission in the network layer (OSI model). The
idea is to improve the efficiency. Piggyback acknowledgment (of the received data) is hooked on
the data frame (to be sent) instead of sending a separate frame.
Differences between Hub, Switch and Router?
Hub Switch Router
Physical Layer Device Data Link Layer Device Network Layer Device
Connects devices within a Can connect multiple sub- Connect multiple LANS and
single LAN LANs within a single LAN WANS together.
Simply repeats signal to all Doesn’t simply repeat, but Routes data based on IP
ports filters content by MAC or LAN address
address
Collision domain of all Switch divides collision It divides both collision and
hosts connected through domain, but broadcast domain broadcast domains,
Hub remains one. i.e., if of connected devices remains
signal sent by any two same.
devices can collide.
Network Devices (Hub, Repeater, Bridge, Switch, Router, Gateways and
Brouters)
Network Devices: Network devices, also known as networking hardware, are physical devices
that allow hardware on a computer network to communicate and interact with one another. For
example Repeater, Hub, Bridge, Switch, Routers, Gateway, Brouter, and NIC, etc.
1. Repeater – A repeater operates at the physical layer. Its job is to regenerate the signal over
the same network before the signal becomes too weak or corrupted to extend the length to which
the signal can be transmitted over the same network. An important point to be noted about
repeaters is that they do not amplify the signal. When the signal becomes weak, they copy it bit
by bit and regenerate it at its star topology connectors connecting if original strength. It is a 2-port
device.
2. Hub – A hub is a basically multi-port repeater. A hub connects multiple wires coming from
different branches, for example, the connector in star topology which connects different stations.
Hubs cannot filter data, so data packets are sent to all connected devices. In other words, the
collision domain of all hosts connected through Hub remains one. Also, they do not have the
intelligence to find out the best path for data packets which leads to inefficiencies and wastage.
Types of Hub
(Delhi University First Year 2021)
What are Unicasting, Anycasting, Multicasting and Broadcasting?
If the message is sent from a source to a single destination node, it is called Unicasting. This is
typically done in networks.
If the message is sent from a source to any of the given destination nodes. This is used a lot in
Content delivery Systems where we want to get content from any server.
If the message is sent to some subset of other nodes, it is called Multicasting. Used in the
situation when there are multiple receivers of the same data. Like video conferencing, updating
something on CDN servers which have a replica of same data.
If the message is sent to all the nodes in a network it is called Broadcasting. This is typically used
in Local networks, for examples DHCP and ARP use broadcasting.
What are layers in OSI model?
There are a total of 7 layers
1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer
What is Stop-and-Wait Protocol?
In Stop and wait protocol, a sender after sending a frame waits for an acknowledgment of the
frame and sends the next frame only when acknowledgment of the frame has received.
What is Piggybacking?
, Piggybacking is used in bi-directional data transmission in the network layer (OSI model). The
idea is to improve the efficiency. Piggyback acknowledgment (of the received data) is hooked on
the data frame (to be sent) instead of sending a separate frame.
Differences between Hub, Switch and Router?
Hub Switch Router
Physical Layer Device Data Link Layer Device Network Layer Device
Connects devices within a Can connect multiple sub- Connect multiple LANS and
single LAN LANs within a single LAN WANS together.
Simply repeats signal to all Doesn’t simply repeat, but Routes data based on IP
ports filters content by MAC or LAN address
address
Collision domain of all Switch divides collision It divides both collision and
hosts connected through domain, but broadcast domain broadcast domains,
Hub remains one. i.e., if of connected devices remains
signal sent by any two same.
devices can collide.
Network Devices (Hub, Repeater, Bridge, Switch, Router, Gateways and
Brouters)
Network Devices: Network devices, also known as networking hardware, are physical devices
that allow hardware on a computer network to communicate and interact with one another. For
example Repeater, Hub, Bridge, Switch, Routers, Gateway, Brouter, and NIC, etc.
1. Repeater – A repeater operates at the physical layer. Its job is to regenerate the signal over
the same network before the signal becomes too weak or corrupted to extend the length to which
the signal can be transmitted over the same network. An important point to be noted about
repeaters is that they do not amplify the signal. When the signal becomes weak, they copy it bit
by bit and regenerate it at its star topology connectors connecting if original strength. It is a 2-port
device.
2. Hub – A hub is a basically multi-port repeater. A hub connects multiple wires coming from
different branches, for example, the connector in star topology which connects different stations.
Hubs cannot filter data, so data packets are sent to all connected devices. In other words, the
collision domain of all hosts connected through Hub remains one. Also, they do not have the
intelligence to find out the best path for data packets which leads to inefficiencies and wastage.
Types of Hub
