My doubt cn

Question

Can anyone explain in details why those options are right...??? i am not getting it properly...

Thanks in advance

Comments

https://networkengineering.stackexchange.com/questions/38805/why-is-the-last-ack-needed-in-tcp-four-way-termination

Read Edit 2:

At some point timer gets expire and in the end sends reset signal. Its all depends on timer. There is also probability that after sending fin for certain number of times and on no notification it will reset connection.

---

@Swapnil Naik .....I have gone through the above details previously... and i have understood those cases..but my doubt is

...suppose server sends the fin segment to client and client sends ack to server and goes to timewait state ...now this ack is lost to server....so sever sends again a fin segement to client within client's timewait time...and client sends ack to server....and now will the client reinitialize its timer and go in time wait again because it may happen that the ack is lost again and server will again send the fin segment....if this reinitialization of timer happens then this will go many times...that is ack is getting lost and server sending fin segment again ....will this process continue till server gets the ack or it has some way of termination to avoid this process again and again ....please tell me??

Thanks in advance...

---

I gone through various links and finally come to conclusion that-

• If fin is lost then server will keep on sending fin until it receives acknowledgement for sure.

• If final ack is lost, server sends fin again, now client will resend ack back. At this point it will restart timer, and will send ack again,but Time-wait state value remains the same(usually its valid till 2 min, timeout may occur many times=> ack may get sent many times from client but), once the 2 minutes are over client will directly terminate connection irrespective of whether ack is reached or not. The whole purpose of time-wait state is to manage connections and avoid duplicate packets from previous connection when another connection is established by the client on same server. Hence the time is 2 MSL. It makes sure that all packets will die by that time.

• Now what happens after 2 min, server will get message Reset because client is closed now.

brother this is the best possible explanation from my side.

References:

https://networkengineering.stackexchange.com/questions/19581/what-is-the-purpose-of-time-wait-in-tcp-connection-tear-down

http://www.pcvr.nl/tcpip/tcp_conn.htm

http://www.dcs.gla.ac.uk/~lewis/networkpages/m07s03TCPoperation.htm

[releasing connection part]

There were so many links, I found above very helpful.

Answer 1

S1: True. Because, the basic thing in connection oriented protocol is whenever one send data it expects ack from other side. So, when server send FIN segment, it expects ACK. If it's lost the time out will be on server side and it send FIN segment again . The client able to receive  it because  this is the reason it is waiting in TIME_WAIT state as to resend ack if lost.

S2:This is straight forward. For clear understanding of change of this states confusion, refer this.

https://www.geeksforgeeks.org/computer-network-tcp-connection-termination/

S3: False, because, incase if ack from server lost, anyway after sometime server send FIN packet with with same ack.no which lost previously. So, client can proceed further without any problem.