confused with TCP and 3 way hand shake

This is a discussion on confused with TCP and 3 way hand shake within the Networking/Device Communication forums, part of the General Programming Boards category; Hello . I am not sure that I have undrestood a TCP concection or not . can u plz correct ...

  1. #1
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    Nov 2003
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    confused with TCP and 3 way hand shake

    Hello .
    I am not sure that I have undrestood a TCP concection or not . can u plz correct my mistakes .
    station A(requester) wants to send one byte data , it sends segment1 then recieves segment2 and send segment3 and so on
    is it right to say?
    segment1 :
    syn-flag=1,ACK-flag=0, seqnr. = m,acknr.=not important ------>
    segment2:
    <--------- syn=1, ack=1, seqnr. = n, acknr. = m + 1
    segment3:
    syn=0,ack=1, acknr. = n + 1,seqnr.=not important ------>
    segment4:
    syn=0,ack=1, seqnr. = p, acknr. = q, 1 byte data ------>
    segment5:
    <--------- syn=0,ack=1, seqnr. = q, acknr. = p + 1
    segment6:
    syn=0,fin=1, ack=1, seqnr. = s, acknr. = t ------>
    segment7:
    <----- syn=fin=0,ack=1,acknr.=s+1,seqnr.= not important
    segment8:
    <--------- syn=0,fin=1, ack=1,seqnr. = t, acknr. = s + 1
    segment9:
    syn=fin=0,ack=1,acknr.=t+1,seqnr.=notimportant ----->

    and also in a TCP packet , what is 13th byte
    is Hlen(data offset) somthing linke legth in UDP ?
    length(UDP)=UDP header + UDP data //(in byte)
    is
    Hlen=(TCP Header + TCP Data)/4 ??????
    it is just 4 bytes , is it like IP lenght that the NO. is divided by 4 ?

    thank you

  2. #2
    ~viaxd() viaxd's Avatar
    Join Date
    Aug 2003
    Posts
    246
    it looks correct, as for the tcp header:
    The header length(Data offset) gives the length of the header in 32-bit words. This is required because the length of the options field is variable. With a 4-bit field, TCP is limited to a 60-byte header. Without options, however, the normal size is 20 bytes.
    :wq

  3. #3
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    is there different form of TCP connection ? for example
    if station A sends data and station B just sends ACK in a session , can I say :
    station A(requester) wants to send 1 byte data to station B .
    3-way hand shake :
    (1)-segment1:requester sends a packet with
    SYN flag = 1
    ACK flag = 0
    seq-NO = m
    ACK-no = not important
    (2)-segment2:requester recieves a packet with
    SYN flag = 0
    ACK flag = 1
    seq-NO = not important
    ACK-no = m+1
    (3)-segment3:requester sends a packet with
    SYN flag = 0
    ACK flag = 0
    seq-no = not important
    ACK-no = not important
    segment4:then A sends 1byte data in a new packet with
    SYN flag = 0
    ACK flag = 0
    seq-no = p
    ACK-no = not important
    segmen5:recieved ACK
    SYN flag = 0
    ACK flag = 1
    seq-no = not important
    ACK-no = p+1
    segment6:after sending 1 byte station A requests to close the connection
    Fin flag = 1
    SYN flag = 0
    ACK flag = 0
    Seq-no = s
    ACK-no = not important
    segment7:
    Fin flag = 0
    SYN flag = 0
    ACK flag = 1
    Seq-no = not important
    ACK-no = s+1

    ----------------------------------and
    If I want to send a packet that has no option , is padding necessary ? can I put my data after urgent pointer ?


    THANK YOU

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