Data And Computer Communications - Transport Layer Q&A
L11 - Transport Layer: UDP and TCP
(a)
000000
- None of the control bits are set.
- A data segment without ACK.
(b)
000001
FIN
- used in connection termination request
- this signaling segment does not contain any data
©
010001
ACK + FIN
- used in confirmation of connection termination
- this signaling segment does not contain any data
(a) 0632 => Port Number 1586
(b) 000D => Port Number 13
© 001C => 28 bytes
(d) Length of the data = total length - header
28 bytes - 8 bytes = 20 bytes
(e)
If we look at the destination port number, 13 is a well-known port.
meanwhile the source port number, 1586 is a registered port.
So it indicates that A Client is sending a UDP signal to A Server.
The packet directed from a client to a server.
(f)
Port 13 : Daytime
Sequence number (32 bits).
Therefore maximum sequence number =
If the sequence number starts with 7000, it takes to go back to zero.
It takes seconds.
- A SYN segment cannot carry data, but it consumes one sequence number
- A SYN + ACK segment cannot carry data, but does consume one sequence number.
The Acknowledgment of confirmation will not consume 1 sequence number.
- An ACK segment, if carrying no data, consumes no sequence number.
For the ACK, we can label the incremented SN or the unincremented SN.
After this segment, the next segment “->” with Data must be starting with SSN 14535.
(a)
An ACK segment with acknowledgement number 2500 and window size advertisement 5000 is received
(b)
A segment carrying 4000 bytes is sent
Piggybacking
TCP header = 20 bytes
An ACK segment, if carrying no data, consumes no sequence number.
Message Total Length Sequence Number ACK Number 1 50+20 200 650 2(ACK) 20(only header) 650 200+50 3 300+20 250 650 4(ACK) 20(only header) 650 250+300 5 150+20 650 550 6(ACK) 20(only header) 550 650+150
