At 02:45 PM 3/25/02, Tom Lisa wrote: >What's the title & publisher?
Troubleshooting Campus Networks (with Joseph Bardwell, who wrote the wireless and Windows chapters). The publisher is Wiley (though I still recommend Cisco Press books too.) You can order it at Amazon today. &;-} Thanks for asking. >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 ________________________ Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=39482&t=39393 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
