2617Re: Segments with no flags set
- May 30, 2001the ACK bit must be set on all non-SYN packets.
RFC793, p.66, for example:
Any other control or text-bearing segment (not containing SYN)
must have an ACK and thus would be discarded by the ACK
processing. An incoming RST segment could not be valid, since
it could not have been sent in response to anything sent by this
incarnation of the connection. So you are unlikely to get here,
but if you do, drop the segment, and return.
and p. 16:
Acknowledgment Number: 32 bits
If the ACK control bit is set this field contains the value of the
next sequence number the sender of the segment is expecting to
receive. Once a connection is established this is always sent.
cheers, Greg Minshall
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