Easy to understarnd text file explaining the TCP flags.
1c030f8e8e4c7160a326685f5b35462c47bc4ebc8fda48ecb0cd8500baa9ac8d
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| TCP/IP Flags |
| by: |
| Neon-Lenz® |
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I wrote this small white paper to introduce you to the flags
in TCP headers. I hope you'll gain knowledge from this, and
if not.. bad luck ;-) So let's begin :
The TCP-header contains about 6 fields with one bit for flags.
There are currently 6 flags in a TCP-header and those are :
URG = This flag lets the receiving TCP-module know that the
the field of the Urgent Pointer points to urgent data.
(The TCP-Module needs to process urgent data than any
other data)
ACK = This flag notes that the field ACK-number has a valid
ACK-number. This helps TCP trusting the DATA.
PSH = This flag calls a PUSH. If this flag is on, then the
TCP-module has to send the data from the segment directly
to the target application. Normally, the TCP-Module would
keep the incoming data in a buffer and sends them untill
the target application's buffer is full. The PSH-flag lets
the TCP-Module know that the data of this segment does not
have to arrive in the buffer. Telnet-Applications for example
uses this flag. Because of that, TCP sends the inputted keys
of the user directly to the Telnet-server. This lets the user
see the typed-letters immediately, without lag.
RST = This flag asks the receiving TCP-module to let the connection
recover (reset). TCP sends a msg with this RST-flag if there
are any problems detected with the connection. Most of the
applications stops when they receive this flag, but it's
possible with the help of the RST-flag advanced algorithms
to write which programs can recover from crashes in hardware
or software.
SYN = This flag instructs the receiving TCP-Module to synchronize
sequence numbers. TCP uses this flag to let the receiving
TCP-Module know that the sender wants send new data.
FIN = This flag lets the receiving TCP-Module know that the sender
is finished with sending of data. This flag stops the data-
stream in one-way. The receiving TCP-Module has to send a
msg with the FIN-flag to close the whole connection.
Well that's a short introduction to TCP-Flags, for more information
i would recommend you to read RFC's, and other TCP/IP related books,
text-files and documents.
Spreaded by Neon-Lenz® and The Millennium Hackers Association.
Copyrighted and All Rights Reserved®
E-Mail:neonlenz@hackermail.net
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