Stuff Flashcards
(50 cards)
What are the 7 layers of the OSI Model?
- Application
- Presentation
- Session
- Transport
- Network
- Data link
- Physical
What are the 4 layers of the TCP/IP Model?
- Application
- Transport
- Internet
- Network Interface
Roughly which layers of the OSI model does Layer 1 of the TCP/IP Model cover?
1 and 2
Roughly which layers of the OSI model does Layer 2 of the TCP/IP Model cover?
3
Roughly which layers of the OSI model does Layer 3 of the TCP/IP Model cover?
4
Roughly which layers of the OSI model does Layer 4 of the TCP/IP Model cover?
5, 6, 7
TCP/IP
What is the purpose of the network interface layer?
Define details of how data is physically sent through the network
Determines how bits are electrically or optically signaled by hardware
TCP/IP
Ethernet, Token Ring, FDDI, X.25 and Frame Relay are protocols in which layer?
1 - Network interface layer
What does CSMA/CD stand for?
Carrier Sense Multiple Access/Collision Detection
What is the purpose of CSMA/CD?
To prevent data collision in shared media.
How does CSMA/CD work?
Listens to the media to see if there is any current transmission. If so, wait then listen again. If not, send the data. If the data then collides it will need to be retransmitted so wait and listen again.
TCP/IP
What is the purpose of the Internet layer?
It packs data into packets known as IP datagrams and ensures they reach the correct destination host
TCP/IP
What information does an IP datagram contain?
Source and Destination address, headers and the actual data itself
TCP/IP
What is the purpose of the Internet layer?
Routing data to the correct destination through the shortest path
Transmitting data to the network interface layer
Handling errors, fragmentation, and reassembling of packets
TCP/IP
IP and ICMP are protocols operating in which layer?
2 - Internet layer
TCP/IP
What is the purpose of the Transport layer?
To transfer data to and from the correct application using port numbers and transport layer protocols
TCP/IP
What are the two Transport Layer Protocols?
TCP (Transmission Control Protocol)
UDP (User Datagram Protocol)
What is the purpose of reference models such as OSI and TCP/IP?
It allows manufacturers of different systems to let their products interoperate.
Same model used everywhere so Software and Hardware can integrate
Makes solutions more portable
Briefly describe the operation of TCP
Header contains source/dest port, seq number, ack number, other info, then the data section
Establishes a connection between two hosts and allows exchange of data.
Keeps track of packet sequence so that if a packet is lost it can be resent
Guaranteed delivery - detects errors in transmission or the packet itself
Packets arrive in the correct order thanks to sequence number
Briefly describe the operation of UDP
Header contains source and destination port, length of data, checksum
UDP is unreliable - there is no guarantee the packet will reach it’s destination, and packets are not ordered.
TCP/IP
What is the purpose of the application layer?
Includes the applications running on the host which send and receive packets. Each application has port numbers assigned for sending and receiving.
What is POP3, and what is it’s purpose?
Post office protocol (version 3)
Retrieves emails from a remote mail server, using TCP
On which port does POP3 listen?
110
What is the purpose of HTTP?
Hyper Text Transfer Protocol allows a client to request data from a server, and the server to respond to a request.
Used most commonly in web browsers for unencrypted transmission of data such as websites, images etc.
Headers are used to transmit information about a request or response. e.g. a 200 header response from the server means the request qas successful, while 404 means the file asked for by the request could not be found.
