Internet Communication ( 2 ) Flashcards
Why are packets kept their size?
Packets are kept small to ensure that the individual packets do not take excessive time to transfer preventing other packets from moving.
What is a MAC address?
- Media Access Control Address
* Uniquely identifies a physical device with a network interface card
How do MAC addresses differ between devices?
- Each device has a NIC
* Each NIC has a unique MAC address, which is hard coded into the card by the manufacturer
What is a protocol?
Set of rules defining common methods of data communication, or a formal description of the format of digital transmission.
What is a requirement of protocols?
Rules of protocols need to be standard across all devices in order for them to communicate with each other.
What is the purpose of TCP/IP?
• Enables communication with any other computer connected to the internet regardless of location
What is the purpose of a gateway?
• Gateway is required when data is travelling between networks that use different protocols.
What occurs when data passes through a gateway?
Header data are removed and reapplied using the correct format of the new network
What is the TCP/IP protocol stack?
Set of rules used to format a message so it can be sent over a network
What is the purpose of the layers of TCP/IP stack?
- Each layer provides a specific function within the transmission of the message
- At each layer the data to be sent is encapsulated in an envelope containing new packet data s it descends the layers, and is unwrapped at the receiving end
What are the various layers?
- Application Layer
- Transport Layer
- Network Layer
- Link Layer
What occurs at the application layer?
Top of the stack:
• Uses protocols relating to the application being used to transmit data over a network.
• Uses high level protocols that set an agreed standard between communicating end points
• Does not determine how the data is transmitted, specifies only rules of what should be sent.
What is the purpose of the application layer?
- Provide services for applications that want to communicate across a network
- Does not however, determine how the data is transmitted, specifies only rules of what should be sent.
What does the transport layer do?
- Uses transmission control protocol ( TCP ) to establish an end to end connection with the recipient computer.
- Splits data into packets and these are labelled with the packet number, the total number of packets, and the port number through which the packet should route
- At the receiving end this layer confirms that packets have been received and requests any missing packets to be resent.
What is the purpose of the transport layer?
- Establishes end to end connections with the recipient computer
- Ensures that the packets are handled by the correct application on the recipient computer.
Which layer requests missing packets/acknowledges missing packets?
Transport Layer
What does the network layer do?
- Uses internet protocol to address packets with the source and destination IP address
- Adds the source and destination IP addresses
- Routers use IP addresses to forward the packets on to an endpoint called a socket
- Routers use a routing table to instruct the next hop
What layer do routers operate on?
Routers operate on the network layer
How is a socket formed?
Addition of an IP address to the port number
What is the purpose of the socket?
Specifies which device the packet must be sent to and the application being used on that device.
What type of connection does does the link layer operate on?
Physical connection between network nodes
What does the link layer do?
- Adds the unique MAC addresses identifying the network interface cards of the source and destination computers, location where the packets should be sent to based on the IP address
- MAC addresses change with each hop, but the destination MAC address is the destination of the packet, and remains the same
What is the destination MAC address of the packet?
Destination MAC address is that of the device that the packet is being to next, unless the computers are on the same network
What happens to the data at the receiving end?
- The MAC address is stripped off by the link layer which passes the packets on to the network layer.
- IP addresses are then removed by the network layer which passes them on tot eh transport layer to remove the port numbers and reassemble the packets in the correct order
- Resulting data is passed to the application which presents the data for the user.
