UDP vs TCP

Question 1

What is the 3 way handshake?

Answer 1

(TCP) A proposed solution to achieving reliable connection establishment. Senders and receivers exchange info about which sequencing strategy each will use and agree on it before submitting TPDUs

Client sends message to host

Question 2

Does TCP acknowledge bytes or packets?

Answer 2

Bytes.

Question 3

What happens if the networks are overloaded in TCP?

Answer 3

Congestion occurs

Question 4

What layers does congestion affect?

Answer 4

Possibly all

Question 5

Why does TCP impact congestion most significantly?

Answer 5

TCP offers methods to transparently reduce data rate and hence reduce congestion

Question 6

What is the open loop solution?

Answer 6

TCP adopts defensive stance. At connection establishment, suitable window size is chosen by receiver based on buffer size. If sender is constrained to this size, congestion will not occur due to buffer overflow at receiver but may occur due to congestion on network.
Ensure packet lifetimes are bounded

Question 7

What is flow control?

Answer 7

(TCP) Receiver controls sender so sender doesn’t overflow receiver’s buffer by transmitting too much

Question 8

What is window size?

Answer 8

…

Question 9

What is incremental congestion control?

Answer 9

(TCP) When connection is established, sender initialises window to size of max segment in use on the connection and transmits 1 segment. If this is acknowledged before timer expires, sender adds another segment’s worth of bytes to congestion window (now 2 max size segments) and transmits 2 segments. Each time a new segment is acknowledged, congestion window increased by 1 max segment size. Each acknowledgement doubles congestion window, which grows until timeout occurs or receiver’s specified window is reached.

Question 10

What’s flow control?

Answer 10

(TCP) window-based

Sender limits number of outstanding bytes (window size) and receiver window ensures data does not overflow receiver

Question 11

What is congestion control?

Answer 11

(TCP) adapting to packet losses
Congestion window tries to avoid overloading the network (increase if delivery is successful, decrease with loss)
TCP connection starts with small initial congestion window

Question 12

What is role of slow start algorithm within context of TCP congestion control?

Answer 12

Method used to determine congestion window size for transmission based on doubling size of data to be transmitted until a size where no acknowledgements for transmission are received. With certain additions to basic algorithm we can obtain dynamic method to control transmission of data over internet