7 - 3 way handshake process

Question 1

1 - Device (A) wants to telnet to msn.com - next ?

Answer 1

DNS will resolve the name to IP

Question 2

2 - once DNS get the - IP add - what next ?

Answer 2

TCP will see the IP and the port number its trying to reach and it will start to create the 3 way handshake

Question 3

3 - when 3 way handshake is being created what details will go into the header ?

Answer 3

• Source port
• destination port ( telnet 23)
• source ip & MAC add

Question 4

4 - Device will send a SYN request

- what will response be ?

Answer 4

if telnet is not set up (port 23) it will drop the packet
if telnet is set up -

Server will respond with SYN & ACK

Question 5

4b - From a initial TCP SYN request -

why does the server respond with 2 messages

Answer 5

The ACK - is or acknowledgement
The SYN - is for synchronization ( it also wants conirmation)

Since the connection is bidirectional it send both message
known as = SYN - ACK

Question 6

5 - what message will device (A) respond to a

- SYN ACK message ?

Answer 6

Device is has been given the ok form the server in regards to his SYN request

So it too will respond with a single - ACK
to confirm it too is ok with connecting

Question 7

the whole 3 way handshake process is ?

Answer 7

• Deive (A) want to telnt to msn.com
• DNS will resolve the name to ip
• TCP protocol will realise this needs 3 way handshake due to telnet connection and port dest 23
• it will creat a source port ( telnet port is 23 )
• Device will send a Syn request ( can i connect to you )
• The destination or server Acknowledges (ACK) this
• But since it a bidirectional channel ( two way communication ) it will also send its on synchronisation (syn) message
  So it send a (SYN) & (ACK)
• Device a responds with an (ACK)