TCP Feature!

 

1.   TCP three way handshake

2.   TCP Sequence Number

3.   TCP Flow Control

4.   TCP Windowing

 

TCP Three way handshakes: When a machine wants to communicate with each other machine over the network three processes happen before the actual communication starts.

 

a.    Sync.

b.   Acknowledgement.

c.    Sync acknowledgement.

 

The Source PC first sends a sync message to the destination Machine in order to know if the destination is ready for communication & waits for Acknowledgement message from the destination machine, when destination Machine receives the sync message it reply with yes or no acknowledgement message, finally if the acknowledgment message was yes the source machine

send Sync Acknowledgement message and the communication begins.

 

 

 

 

¤: Here I have made a simple picture which illustrates the three process of three way handshake.

 

The Source PC is named PC1 & the destination PC is named PC2

 

 

What happens when source & destination want to terminate the communication?

 

When both end want to terminate the communication three process take place as shown bellow.

 

 

3 FIN Ack                          

The Source Machine sends a finish message, the destination machine reply an acknowledgement and finally the source machine sends a finish acknowledgement message & the communication gets over.

 

TCP Sequence Number: TCP sequence number and acknowledgment number is one of the features of TCP which adds a number to each packets it sends over the network, when the destination receives the packets it reads the sequence number of received packets and sends an acknowledgement message to

 

 

 

 

the sender of the Packets, if any packet was missing then the TCP automatically resend that packet which Is missing.

 

For example: 10 MB of data is divided into 10 packets (each packet 1 MB), when the packets are about to be sent TCP automatically adds a number which we call sequence number to each packet and when the destination receives the packets it reads the number from 1 to 10 and send acknowledgement back to the sender as it receives them in order to guarantee data delivery. If the destination machine send ok acknowledgement for 1st, 2nd, 4th, 5th and so on but does not send ok acknowledgement for 3rd packet, then the source pc (sender of the packets) automatically resends the missing packet which it has not received ok acknowledgement for.

 

TCP Flow Control: TCP three way handshakes and TCP Windowing Helps the flow control, I think it is better to let you know TCP Windowing first and then I should talk about TCP flow control.

 

TCP Windowing: if data transferring is in process TCP decides the Window size and transfer that. If enough bandwidths are available then TCP increases the size of window in order to transfer more data

 

Window Size= Number of packets sent at a time

 

Each Window has one Acknowledgment message.

 

 

 

 

S            Ack

O

U

R           Ack

C E

 

 

Ack

One Packet

D

 

Tow Packets                        E S

T I N

Four Packets               A T

I O N