TCP and UDP Transport Layer Protocols

Study Notes

TCP is a transport layer protocol that establishes a connection, transmits data in byte order, and closes the connection.
It verifies connections between sending and receiving hosts.

UDP is a transport layer protocol that provides a datagram delivery service.
It does not verify connections between sending and receiving hosts.
Applications that transport small amounts of data use UDP because it eliminates the processes of establishing and validating connections.

This layer is analogous to the transport layer of the OSI model.
It is responsible for end-to-end communication and error-free delivery of data.
It shields upper-layer applications from the complexities of data.
Three main protocols present in this layer are:
- HTTP and HTTPS: used for managing communications between web browsers and servers.
- SSH: used for secure terminal emulations and encrypted connections.
- NTP: used for synchronizing clocks on computers to a standard time source.

Packet switching: data is processed at all intermediate nodes, including the source system; delay between data units is not uniform; less wastage of resources; no physical path between the source and destination; call setup is not required; requires complex protocols for delivery; latency is high.
Circuit switching: data is processed at the source system only; delay between data units is uniform; more wastage of resources; physical path between the source and destination; call setup is required; requires simple protocols for delivery; latency is low.

Packet switching is a method of transferring data to a network in the form of packets.
Routers play a crucial role in packet switching networks.

Two ways to define the end of the frame and the beginning of the next frame:
- Length field: introduce a length field in the frame to indicate the length of the frame.
- End Delimiter (ED): introduce a pattern to indicate the end of the frame.

Simple Parity Check: adds an extra bit to a data transmission to make the total number of 1's even.
Two-dimensional Parity Check: calculates parity check bits for each row and column, and sends them along with the data.
Checksum: introduces redundancy bits to provide additional information.
Cyclic Redundancy Check (CRC): detects errors by adding redundancy bits to the data.

Multiple-bit error: occurs when more than one bit in a data transmission is affected.
Burst error: occurs when several consecutive bits are flipped mistakenly in digital transmission.

CSMA/CD: used in wired networks, stations can terminate transmission of data if a collision is detected.
CSMA/CA: used in wireless networks, uses collision avoidance by introducing interframe space and contention window to avoid collisions.