Stora datanät och OSI-modellen Flashcards
What is an upside with packet switching instead of circuit switching?
- Greater efficiency thanks to dynamic routing.
- Can perform data rate conversions.
- The communication slows down at heavy traffic loads but does not completely stop.
- Packets can have different priority.
What are the two switching techniques?
- A datagram approach
- A virtual circuit approach
What is the datagram approach?
Every packet is treated individiually and can thus take different routes to reach the destination. To restore the message, the packets have to be reordered and the data reconstructed.
What is the virtual circuit approach?
The packets are sent along a pre-planned “virtual circuit”. Routing decisions are made only once.
Why are packets broken up into smaller packets?
Firstly, not all networks have the same limit of maximum packet size.
Secondly, the transmission time increases as the packet can not be sent until it has been processed.
What are the upsides to:
- Circuit switching
- Virtual circuit packet switching
- Datagram packet switching
In terms of performance.
A circuit switching is slow at startup since the connection has to be made, afterwards the transmittion is quick.
A virtual circuit is similiar but also has node delay.
A datagram switching network is quick for shorter exchanges since the packets themselves experience node delay.
Give examples of a few ways a wave could be modulated in order to convert digital data to analog form.
Examples:
Amplitude modulation, high or low amplitude.
Angle modulation:
Frequency modulation: high or low frequency.
Phase modulation: Specific phase, 0 or Pi.
What is the purpose of DHCP?
(dynamic host configuration protocol)
It is an IP which enables dynamic allocation of IP-addresses to hosts. It was invented to deal with the issue of IP shortages for IPv4.
Unused addresses are free to used and are managed by a DHCP server.
What is HTTP used for?
(On the 7th layer, application layer)
Hyper text transfer protocol is the foundation protocol of the WWW. Used for transmitting information needed for hypertext jumps, aka images, texts, sound etc.
What is an HTTP request message/response message?
A request message is from a client to a server.
The response message is from the server to the client.
Where are the transport protocols used?
They are used for end to end transportation of data that shields the user from the details of the underlying communications systems.
On the transport layer, the fourth layer between application and network layer.
What is NAT?
What is QUIC?
Network Address Translation:
Translates the private IP address to a public IP address. Works on the 3rd, network, layer.
QUIC is a general purpose transport protocol (4th layer) like UDP developed by Google.
