Networks Flashcards
What is a network?
A network is a set of devices that commuicate to each other via a physical transmission medium. It consists of nodes (each representing a connection point) and edges (connection links).
What is a router?
A router is a device connecting two or more packet-switched networks. Its job is to manage the connections so data packets can be sent and received in an efficient manner.
Describe the 7-layer OSI network model.
Physical - Converts data bits into electrical impulse signals.
Data Link - Packets are (de)encoded into bits, providing a node-to-node data transfer.
Network - Transfers data from one node to another.
Transport - Transfers data between nodes and confirms its success.
Session - Manages node connections(establish, coordinate, exchange, terminate).
Presentation - Transforms data into a form acceptable to the application layer.
Application - The front-end layer the user interacts with.
What is TCP/IP? Describe its structure.
The TCP/IP (Transmission Control Protocol / Internet Protocol) model is designed for transmitting data from one node to another in a reliable fashion. It consists of 4 major layers:
Application - Provides application with some exchange protocol (HTTP, FTP, SMTP).
Transport - Maintains comms with communication protocol (TCP, UDP).
Network - Connects/transports data packets across different networks (IP, ICMP).
Data Link - Operates on a link, interconnects different nodes (Ethernet, LAN, ARP).
TCP/IP works by first establishing a connection to another node with a 3 way handshake that operates like so:
- SYN - Synchronise message sent to alert server that client will start communication.
- SYN + ACK - Server responds with own sync and acknowledge that the first message was received.
- ACK - Client sends own acknowledge message back, and can start data transfer.
Transmitted data is split into smaller packets that are sent. As these packets may take varying routes, they may arrive out of order. It is the protocols responsibility to then reassemble the packets in the correct order.
What is UDP? Describe its structure.
UDP (User Datagram Protocol) is similar in concept to TCP/IP, but omits many of the latter’s checks. It is a connectionless protocol - it does not establish a connection with the destination node first before sending packets. It also does not guarantee the delivery or order of the packets being sent.
These properties make UDP significantly faster, but less reliable than TCP/IP.
What are the differences between TCP/IP vs UDP? Where might you use each?
TCP/IP requires a connection, UDP does not.
TCP/IP guarantees packet order, delivery and error checking, UDP does not.
TCP/IP is slower with large packets, UDP is faster with smaller packets
TCP/IP would typically be used for applications where correct delivery is important. These include web pages, email, file transfer (HTTP, SMTP, FTP).
UDP would be used for applications where speed is more important. This includes domain name lookup, video and audio streaming (DNS, RTP).
Give a brief description of the following network protocols:
IP (Internet Protocol)
FTP (File Transfer Protocol)
SSH (Secure Shell)
SSL (Secure Sockets Layer)
TELNET (Teletype Network)
SMTP (Simple Mail Transfer Protocol)
POP3 (Post Office Protocol)
IMAP (Internet Message Access Protocol)
HTTP (HyperText Transfer Protocol)
SIP (Session Initiation Protocol)
NTP (Network Time Protocol)
PPP (Point-To-Point Protocol)
IP - Intenet networking using IP address for each computer.
FTP - File transfer between hosts over TCP/IP network.
SSH - Cryptographic for secure data communication.
SSL - Security by allowing apps to encrypt sent data.
TELNET - Bidirectional network communication, unencrypted.
SMTP - Mail transfer, understood by most computers.
POP3 - Mail download from server.
IMAP - Another mail access protocol.
HTTP - Enables transfer of data across the internet.
SIP - Signalling for multimedia comms. (e.g. VoIP).
NTP - Synchronizes clocks between computer systems.
PPP - Establishes a direct connection between two nodes.
Give a brief description of the following network area types:
LAN (Local Area Network)
PAN (Personal Area Network)
WLAN (Wireless Local Area Network)
CAN (Campus Area Network)
WAN (Wide Area Network)
VPN (Virtual Private Network)
LAN - Connections within a small region (e.g. home network).
PAN - Connections within a single person (e.g. bluetooth).
WLAN - Wireless connections in a small area, less secure but more flexible. -
CAN - Connections within a medium area (office, campus, company networks).
WAN - Connections not restricted by geographical area (e.g. company remote).
VPN - Provides a stable and secure connection exclusive from others.
