1 Transport Control Protocol

2 Header Identifies the port number of a source application program. Used by the receiver to reply. (16-bit). Identifies the port number of a source application program. Used by the receiver to reply. (16-bit).

3 Header Identifies the port number of a destination application program. (16-bit). Identifies the port number of a destination application program. (16-bit).

4 Header Specifies the sequence number of the first byte of data in this segment. (32-bit). Specifies the sequence number of the first byte of data in this segment. (32-bit).

5 Header Identifies the position of the highest byte received. If the ACK control bit is set, this field contains the value of the next sequence number that the receiver is expecting to receive.(32-bit).

6 Header This indicates where the data begins. 4-bit field which shows the number of 32 bit words in the header. Also known as the Data Offset field or Header size. The minimum size header is 5 words (0101) 2.

7 Header Reserved bits for future use; In RFC-3540: 3-bit In RFC-3168: 4-bit In RFC-793:6-bit Reserved bits for future use; In RFC-3540: 3-bit In RFC-3168: 4-bit In RFC-793:6-bit

8 Header The meaning of Connection Oriented Protocol is that, before any data can be trans, a reliable connection must be obtained and ack. Control Bits govern the entire process of connection estab, data trans & connection term.

TCP Flag 9 FINNo more data from sender SYNSynchronize sequence numbers. Only the first packet sent from each end should have this flag set. Some other flags change meaning based on this flag RSTReset the connection PSHPush function. Asks to push the buffered data to the receiving application. ACKIndicates that the Acknowledgment field is significant. All packets after the initial SYN packet sent by the client should have this flag set. URGIndicates that the Urgent pointer field is significant ECEECN-Echo indicates.(SYN=1:TCP peer is ECN capable, SYN=0:Congestion Experienced flag in IP header) CWRCongestion Window Reduced (CWR) flag is set by the sending host to indicate that it received a TCP segment with the ECE flag set and had responded in congestion control mechanism NSECN-nonce concealment protection

10 Header Specifies the amount of data the destination is willing to accept. (16-bit)

11 Header The checksum field is used for error- checking of the header and data.(16-bit)

12 Header Indicates data that is to be delivered as quickly as possible. This pointer specifies the position where urgent data ends.(16-bit)

13 Header End of Option List Indicates the end of the option list. It is used at the final option, not at the end of each option individually. This option needs to be used only if the end of the options would not otherwise coincide with the end of the TCP header. Stop looking for further options. End of Option List Indicates the end of the option list. It is used at the final option, not at the end of each option individually. This option needs to be used only if the end of the options would not otherwise coincide with the end of the TCP header. Stop looking for further options.

14 Header No Operation Indicates boundaries b/w options. Can be used b/w other options; e.g., to align the beginning of a subsequent option on a word boundary. There is no guarantee that senders will use this option, so receivers must be prepared to process options even if they do not begin on a word boundary. No Operation Indicates boundaries b/w options. Can be used b/w other options; e.g., to align the beginning of a subsequent option on a word boundary. There is no guarantee that senders will use this option, so receivers must be prepared to process options even if they do not begin on a word boundary.

15 Header Maximum Segment Size Indicates the maximum segment size TCP can receive. This is only sent in the initial connection request. Does not include TCP header. Maximum Segment Size Indicates the maximum segment size TCP can receive. This is only sent in the initial connection request. Does not include TCP header.

Connection Established 16 ClientServer SYN =1 SYN=1, ACK=1 ACK =1 Active Request Connection Established SYN = 0, ACK=1 Server want to Established connection Server do not want to Established connection Acknowledge to Client Connection Established Passive Open Wait for Active Req. Normal Operation

Connection Established 17 ClientServer SYN =1 SYN=1, ACK=1 RST=1, ACK =1 Active Request Connection Reject Server want to Established connection Received SYN After Timeout Connection Reject Passive Open Wait for Active Req. Delayed SYN

Connection Established 18 ClientServer SYN =i SYN=j, ACK=i ACK =j New SYN Send Connection Established SYN = k, ACK=p New SYN accept Connection Established Old SYN arrived Delayed SYN, ACK RST =1, ACK=k Old SYN Reject New SYN accept Old SYN Reject

Connection Termination 19 InitiatorReceiver FIN =1 FIN =1, ACK=1 ACK =1 Connection Established Connection Closed FIN = 0, ACK=1 Receiver want to Terminate connection Receiver do not want to Terminate connection Acknowledge to Receiver Connection Closed Connection Established