Initiating a Telnet Session

Initiating a Telnet Session

1. The client sends a packet with the SYN flag set containing its initial
sequence number (CLT_SEQ)
2. The server responds with a packet with the SYN flag set, containing
its own sequence number (SRV_SEQ), its packet window size
(SRV_WIND), and the sequence number that the client should send
in its next packet (CLT_SEQ+1)
3. The client's response packet will have the ACK flag set, a sequence
number of CLT_SEQ+1, its packet window (CLT_WIND) size and
an expected sequence number for the next packet from the server of
SRV_SEQ+1
Telnet Session Established
Once a connection between the two machines has been established, a
packet is acceptable if the data it contains is either of the following:
• SVR_ACK and SVR_ACK+SVR_WIND from the server.

• CLT_ACK and CLT_ACK+CLT_WIND from the client.
If the sequence number of the packet is outside these limits, it will be
dropped, and the receiving machine will send an acknowledgment
packet containing the correct sequence number. If the sequence number
of the packet is higher than expected, the packet may be stored for later
use (depending on the implementation of TCP), as the stack will
presume that the previous packets were lost during transmission.