Tcp Sender Sequence Number Space

Sequence Number Space SeqNum field is finite sequence numbers wrap around 0, 1, , S-1, 0, 1, , S-1, 0, 1, Main concern In out-of-order channels, an old packet carrying the same sequence number confused with a packet of current concern. 10192005 CSC 257457 - Fall 2005 4 TCP Overview connection-oriented

Lecture 17 -TCP in detail Peter Steenkiste Fall 2010 Sequence Number Space Each byte in byte stream is numbered. 32 bit value Receiver can only return a single quotackquot sequence number to the sender. Acknowledges all bytes with a lower sequence number

So it maintains a cwnd congestion window of the maximum number of bytes it can send from first unacked sequence number. The value of cwnd is determined by congestion control algorithms. As long as there is space in cwnd, sender keeps sending TCP segments of size MSS. ACKs will help in clearing space in cwnd, and also increase and decrease cwnd.

3 sequence numbers allowed for new data transmission 4 future sequence numbers can't be seen but may be queued 5 sender app is put to sleep when sequence number of buffered data reaches here Send Sequence Variables SND.UNA send unacknowledged value of last ack received SND.NXT send next next sequence number to be

TCP endpoints consume sequence number space each time a segment is formed and entered into the network output queue at a source host. if active and the remote socket is specified, issue a SYN segment. An initial send sequence number ISS is selected. A SYN segment of the form ltSEQISSgtltCTLSYNgt is sent. Set SND.UNA to ISS,

sender sequence number space source port dest port sequence number acknowledgement number checksum rwnd urg pointer outgoing segment from sender. 5 TCP seq. numbers, ACKs User TCP sender events Managing a single timer data rcvd from app create segment with seq seq is byte-stream number of first data byte

Sequence Numbers. It is essential to remember that the actual sequence number space is finite, though very large. This space ranges from 0 to 2 32 - 1.. Since the space is finite, all arithmetic dealing with sequence numbers must be performed modulo 2 32.This unsigned arithmetic preserves the relationship of sequence numbers as they cycle from 2 32 - 1 to 0 again.

The TCP Sequence Number field is always set, even when there is no data in the segment. For example, the sequence number for this packet is X. The length for this packet is Y. If this packet is transferred to another side successfully, then the sequence number for the next packet is XY. The sequence number is the first byte of the outgoing

TCP sequence numbers, ACKs Sequence numbers byte stream quotnumberquot of first byte in segment's data source port dest port sequence number With sufficiently large seq number space, sender's window does NOT overlap with receiver's window. 36 Backup slides. 37 TCP retransmission scenarios lost ACK scenario

Go-Back-N doesn't have this issue since the sender pushes n packets up to window size which is at max n-1 and never slides the window until it gets cumulative acks up to n. And those two protocol have different max size windows. Note For Go-Back-N, the maximum window size is maximum number of unique sequence numbers - 1.