delayed exit from telnet session

[ephraimephraim]

When I connect to a nonstop system using telnet, choose OSS, log in, and immediately type 'exit', there's a delay of nearly 15 seconds before the nonstop system closes the connection and telnet exits. If I wait half a minute after logging in, then type 'exit', telnet exits immediately. Packet traces (tcpdump) confirm that telnet always exits as soon as the nonstop system breaks the connection. The delayed exit is purely due to the nonstop not closing promptly.

What's the cause of this delay and how can I avoid it? (Besides using rexec or ssh, which some sites don't have enabled.)