Network Layers Flashcards
What are the layers in ascending order in the OSI model ?
Physical Layer, Link Layer, Network Layer, Transport Layer, Session Layer, Presentation Layer, Application Layer
What services does the link layer provide and how are they provided ?
Framing, fragmentation, Link access, reliable delivery
Framing, this is the encapsulation of the frames sent from the datagrams with a header and a trailer
Fragmentation, if a frame is too large it will be broken down into smaller frames and sent off
Link access, MAC protocol is used at this stage
Reliable delivery, MAC protocol used to ensure this
What error handling methods are there in the link layer ?
This is the MAC protocol, this is done through handshaking, flow control by using the take in turn, random access protocol, or channel partitioning
What protocols are there in the link layer ?
MAC protocol
What services does the network layer provide ?
Fragmentation, encapsulation, logical addressing, error handling
What error handling methods are there in the link layer ?
MAC protocol once a collision has occurred there will be a time where they will back off and have a random time where they will refire their packets
What does ICMP stand for ?
Internet control message protocol
What is a PDU and what does it stand for ?
Protocol data unit
What protocols are there in the transport layer ?
TCP/IP UDP, windowing
What is TCP/IP ?
TCP is an extension of the IP protocol that uses acknowledgments, flow control, congestion control and windowing to ensure the reliable delivery of segments as well as multiplexing
What is multiplexing ?
Combining multiple signals into one complex signal
Where is multiplexing used ?
In the transport layer
What is ICMP?
This is a error handling protocol in the link layer, that provides feedback to the user in case of the errors
What is packet loss ?
Where a packet is either dropped during transmission because it has surpassed the time to live, or has been dropped because the router buffer is full
What is a subnet ?
A subnet is a network within a larger network
What are the benefits of using a subnet ?
Manageable, more secure, extension of space, more IP addresses and more space for people
What are the issues with IPv4 ?
There is a limit to the amount of IP addresses to use
What are the error checking methods used in the link layer ?
Checksum, Cyclic redundancy check, parity checking
What is the checksum check within the link layer /
The entire frame will be placed into a 16 bit sequence, this is then sent once recieved it will be checked against the sent form.
What is CRC and how does it work ?
The bits of data will be added to to with a bit string pattern, the entire frame will then be divided by 2, if it can be then there is no error else then there is an error
What is partiy checking ?
They will store the amount of 1’s there are, once recieved if this has changed then there has been an issue
What is the address resolution protocol and which layer is it used in ?
This is used within the network layer, because IP delivery isnt reliable the delivery of packets is used with the devices MAC address.
What is CSMA/CD and what does it stand for ?
This is a collision detection system that will detect colliisons within the network, Carrier sense multiple access with collision detection
