Networking 1

Question 1

Switch

Answer 1

• A switch is a device that connects computers on a network together.
• Many computers can be connected to the switch, and the switch will receive all data on the network and decide which cable to send the data through, based on which computer the information is destined for.

Question 2

Hub

Answer 2

• A hub is similar in function to a switch, in that it connects computers on a network together.
• Unlike a switch, it isn’t ‘smart’. It receives data, but it doesn’t know which computer to send it to, so it sends it to every computer connected to the hub.
• It is then up to the computer to receive that data and decide if it was intended to receive that data or if it should discard it.
• Wireless Access Point = Wireless Hub

Question 3

Router

Answer 3

• A router is a device that connects two networks together.
• Most commonly this will be connecting the LAN to the internet, but it can be used to connect any networks together.
• The router will make the decision about which piece of data needs to go to which network.

Question 4

Network Interface Card (NIC)

Answer 4

• A piece of hardware attached to a computer, which allows the computer to interface with a network
• A computer with an Ethernet port has a NIC inside of it, which provides the means to connect to a network.
• It is also possible to connect an external NIC to your computer via USB; this can be useful when your computer does not have Ethernet or wireless capability.

Question 5

IP Addresses

Answer 5

• Identifies your computer on the network and allows other computers on the network to find your computer.
• Each NIC (Network Interface Card) is assigned an IP address when it connects to a network.
• Two types: public/private or external/internal
  e. g. 192.168.0.77

Question 6

Private IP Addresses

Answer 6

• A private IP address is one assigned to your computer on the local network (LAN).
• Private IP addresses have to fall within certain ranges and are only accessible to computers on the same LAN.
• People on a different LAN cannot access your computer using the private IP address.
• Must be unique on a LAN.

Question 7

Public IP Addresses

Answer 7

• A public IP address is internet facing. In most home and small business network setups, the entire LAN will have only a single public IP address, which is shared by all computers on the LAN.
• The ability to share an IP address is handled by something called Network Address Translation (NAT).

Question 8

Media Access Control (MAC) Address

Answer 8

• An address that is burned into the NIC when it is produced.
• MAC addresses are meant to be globally unique; no two NICs are supposed to have the same MAC address. In practice it’s hard to verify the claim but the likelihood of two computers on the same local network having the same MAC address is so small it’s almost irrelevant.
• MAC addresses are used to identify computers on a local network. They enable a switch to know which cable to send information down, in order to send data to a particular computer.
• They are used together with private IP addresses, but the difference is that private IP addresses can change, while MAC addresses are meant to stay the same.
  e. g. 34:13:65:76:09:86.

Question 9

Packets

Answer 9

• A data packet is a unit of data, which can be transmitted over the network.
• All data must be placed into (encapsulated into) packets before it can be transmitted.
• Packets are typically quite small pieces of data, so any large piece of data must be split up into several packets before it can be transmitted over the network.
• Typically you will see a maximum packet size of about 1500 bytes - 65535 bytes (64 KiB).

Question 10

Transmission Control Protocol (TCP)

Answer 10

• A protocol designed with the reliable delivery of data in mind. That makes it perfect for the majority of common tasks on the internet
  1. The protocol involves a connection setup, called the ‘TCP handshake’, which prepares two computers to talk to each other.
  2. Once the handshake is performed, the data is sent between computers.
  3. After the TCP connection is done, the TCP teardown closes the connection.

The TCP protocol includes measures to re-transmit data that was lost in transit, or corrupted en route to the destination.

Question 11

Ports

Answer 11

• A port is a communications channel for applications running on the operating system to listen to.
• Ports are numbered, between 0 and 65535.
• No two applications on the computer can listen to the same port.
• Once an application is listening on that port, it is known as being bound to that port.

Question 12

User Datagram Protocol (UDP)

Answer 12

• The UDP is key to many applications that require fast data transmission at the expense of reliability.
• Unlike TCP, UDP does not need a connection handshake. It also does not detect if a data packet is missing, it never asks about re-transmission, and if the data it gets is corrupt, it will just ignore it instead of asking for it to be re-sent.
• You will frequently see it being used in video chats, for example, when it doesn’t make sense to wait on a single dropped frame to be re-transmitted when the user will not notice 1 out of 30 frames missing in that one second.