What's the title & publisher? Prof. Tom Lisa, CCAI Community College of Southern Nevada Cisco ATC/Regional Networking Academy
Priscilla Oppenheimer wrote: > John has described the three-way handshake, which is used for session > establishment. Once the session has been established, both sides sequence > their bytes that they send and both sides ACK the other side's bytes. > Remember it's a stream-oriented protocol. Each side has a stream of bytes > it needs to send. > > When a sender sends data, the sequence number that it puts in the packet is > the sequence number of the first byte in the packet. The packet has a > certain number of bytes in it, that is, a length. You should expect the > sequence number in the next packet from this sender to be (seq + length) -1. > > The sender will keep sending as long as it has not gotten to the end of its > send window. Then it must stop and wait for an ACK from the other side. The > sender's send window is based on the recipient's receive window. The > recipient states the size of its receive window in every packet. It is an > indication of how much memory the recipient has for receiving bytes and how > much is used up at this point in time. > > The recipient ACKs every byte, but not explicitly. The recipient sends a > packet with the ACK bit set and the ACK number set to the next byte that > the recipient expects to receive. By stating the next byte it expects to > receive, the recipient acknowledges receiving the bytes before this. > > The recipients is not required to send an ACK the instant it receives data. > In fact, a host can reduce network overhead and increase efficiency by > sending fewer ACKs. This is known as delayed ACKs. The "Host Requirements > RFC" (RFC 1122) states that a TCP implementation should implement delayed > ACKs, but an ACK should not be excessively delayed. In particular, the > delay must be less than 0.5 seconds, and when receiving a stream of > full-sized segments, there should be an ACK for at least every second > segment. Most implementations do not wait a full 0.5 seconds, which would > seem awfully long on modern networks. Upon receipt of a TCP segment, a host > sets an ACK timer. When the timer elapses, the host acknowledges data > received so far. A typical value for the ACK timer is 0.2 seconds. > > One reason for delaying an ACK is that the host may have its own data to > send in the same direction as the ACK. The data can be sent with the ACK, > which avoids extra network traffic caused by so-called empty ACKs. An ACK > that is sent with data is sometimes called a piggyback ACK. > > All of this is best described with an example. However, that would take too > long in this forum. But stay tuned for my new book which will have > examples. I have finished the writing. I'm still waiting for the publisher > to do their business. > > Priscilla > > At 09:21 PM 3/24/02, John Green wrote: > >i know there are many more knowledgeable here but just > >lets get started with this thread. > > > >Source sends a syn packet to the destination and this > >packet contains sequence number(say x) and ACK bit not > >set > >The destination receives it and sends a syn and ack. > >this packet contains its sequence number(say y) and > >ACK bit or flag is set > >Source recieves the syn and ack and sends back an > >ack back to destination. > > > >destination receives the ack and tcp connection is > >established henceforth. > >Refer RFC 793 for further details. (but any tcp/ip > >book would deal with this) > > > >--- Juan Blanco wrote: > > > Team, > > > > > > Do any one knows where I could find any document > > > that explain how calculate > > > the TCP Ack and Seq numbers. Any explanation will be > > > appreciate. > > > > > > Thanks, > > > > > > > > > JB > >[EMAIL PROTECTED] > > > > > >__________________________________________________ > >Do You Yahoo!? > >Yahoo! Movies - coverage of the 74th Academy Awards. > >http://movies.yahoo.com/ > ________________________ > > Priscilla Oppenheimer > http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=39454&t=39393 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
