Networks Flashcards
what are packets?
Packets are segments of data.
what are the 3 main things a packet contains?
Header
Payload
Trailer
What are the things that are present in the header of a packet?
○ Sender and recipient IP addresses
○ Protocol being used
○ Order of the packets
○ Time To Live / Hop Limit
What is the purpose of having a sender and recipient IP addresses in the header ?
The sender and the recipient’s IP addresses act like a postcode,
allowing the packet to be delivered to the correct destination and
enabling the recipient device to trace where the packet came from
What is the purpose of having a protocol in the header?
The protocol allows the recipient computer to understand how to interpret the packet.
What is the purpose of having an order of packets space in the header?
Upon arriving at the recipient device, packets are reconstructed in the appropriate order as specified in the header
What is the purpose of having an TTL / Hop Limit ?
The Time To Live (TTL), tells the packet when to expire so that it does
not travel forever.
What does a payload contain?
A payload contains raw data to be transmitted
What does a trailer contains?
Trailer contains checksum, or cyclic redundancy check that is used to detect whether any errors have
occurred during transmission.
There are two techniques using which networks exchange data:
circuit switching and
packet switching
Describe how and what packet switching is and works.
Packet switching is a method of communication in which data is communicated using packets across a network. In this method of communication, packets are sent across the most efficient route, which can vary for each packet.
What are the advantages of using packet switching
Multiple methods to ensure data arrives intact eg. checksums and cyclic redundancy checks.
Multiple routes can be used between devices, so if one path breaks, another can be used.
Packets can be transferred over very large networks to allow communication globally.
What are the disadvantages of using packet switching
Time is spent deconstructing and reconstructing the data packets
Must wait for all packets to arrive before data can be received.
Describe what and how circuit switching is and works.
Circuit switching is a method of communication where a direct link is created between two
devices. This direct link is maintained for the duration of the entire conversation between
devices. Circuit switching requires the two devices to transfer and receive data at the
same rate.
What are the advantages of using circuit switching
Data arrives in a logical order which results in a quicker reconstruction of the data.
Enables two users to hold a call without delay in speech.
What are the disadvantages of using circuit switching
Bandwidth is wasted during periods of time in which no data is being sent.
Devices must transfer and receive data at the same rate.
Using switches means electrical interference may be produced which can corrupt or destroy data.
Ties up sections of the network which cannot be used by others data until transmission has been completed.
what does TCP/IP stands for
Transmission Control Protocol/Internet Protocol
What is TCP/IP stack
a set of networking protocols that work together as four connected layers
The 4 connected layers in a TCP/IP stack are
Application Layer
Transport Layer
Network Layer
Link Layer
What is layering
it is the process of breaking a complex process into several processes or layers in a particular order.
Describe the nature of the application layer
sits at the top of the stack and uses protocols relating to the application being used to transmit data over a network.
Describe the nature of the transport layer
This uses the TCP to establish an end to end connection with the recipient computer.
Data split into packets and labelled with packet number and port number.
If any packets from the collection are missing the transport layer requests that part of the packet again.
