19.6 Summary

Interactive data is normally transmitted in segments smaller than the maximum segment size . With Rlogin a single byte of data is normally sent from the client to the server. Telnet allows for the input to be sent one line at a time, but most implementations today still send single characters of input.

Delayed acknowledgments are used by the receiver of these small segments to see if the acknowledgment can be piggybacked along with data going back to the sender. This often reduces the number of segments, especially for an Rlogin session, where the server is echoing the characters typed at the client.

On slower WANs the Nagle algorithm is often used to reduce the number of these small segments. This algorithm limits the sender to a single small packet of unacknowledged data at any time. But there are times when the Nagle algorithm needs to be disabled, and we showed an example of this.