Transport Layer Flashcards
What is UDP?
User Datagram Protocol: Connectionless (“send and forget”), no acks.
What is TCP?
Transmission Control Protocol: Connection-oriented, reliable
Client-server use sockets to create enpoints.
Provides control flow and retransmission
What is the 3-way handshake of TCP connection establishment?
- SYN - Open connection with random sequence number (client)
- SYN-ACK - Server confirms connection.
- ACK - Connection confirmed by client.
Why are sequence numbers used for TCP packets?
To detect and identify repeat and lost packets.
Discard and transmit respectively.
What is the process for TCP video streaming?
Connection opens.
Video data sent to client.
Client stores data in buffer (fast links can buffer ahead of playback) for playback.
If the link is slow, the video “buffers”, not suitable for live streaming.
What is the process of UDP live streaming?
UDP packets sent to client at fixed transmission rate.
No buffering, if packets are lost, glitches appear in video rather than pausing (buffering).
What are sockets?
Communication enpoints for TCP connections.
They contain a port and IP address.
Can be used to uniquely identify applications in subsequent data transmissions.
How do TCP and UDP handle flow control?
UDP does not handle flow control.
TCP provides flow and congestion control.
What is the Sliding Window Protocol?
Controls the sending rate of segments depending on the available buffer size of the receiver in order to prevent time being wasted by having to retransmit segments.
What is the process for the Sliding Window Protocol?
- Sender sends segment with sequene numbe and starts timer.
- Receiver responds with ack, window size and next expected sequence number.
- If windowSize == 0, sender can send 1-byte probe to get new window advertisment.
- Otherwise, sender sends next segment/s according to window size and sequence number.
What 2 windows are used for TCP congestion control?
Congestion Window
Receiver Window
