This preview shows page 1. Sign up to view the full content.
Unformatted text preview: 14) [12/09/2001 14.47.18] Chapter 19. TCP Interactive Data Flow Figure 19.1 One possible way to do remote echo of interactive keystroke.
Normally, however, segments 2 and 3 are combined-the acknowledgment of the
keystroke is sent along with the echo. We describe the technique that combines these
(called delayed acknowledgments) in the next section.
We purposely use Rlogin for the examples in this chapter because it always sends one
character at a time from the client to the server. When we describe Telnet in Chapter 26,
we'll see that it has an option that allows lines of input to be sent from the client to the
server, which reduces the network load.
Figure 19.2 shows the flow of data when we type the five characters date\n. (We do
not show the connection establishment and we have removed all the type-of-service
output. BSD/386 sets the TOS for an Rlogin connection for minimum delay.) Line 1
sends the character d from the client to the server. Line 2 is the acknowledgment of this
character and its echo. (This is combining the middle two segments in Figure 19.1.) Line
3 is the acknowledgment of the echoed character. Lines 4-6 correspond to the character a,
lines 7-9 to the character t, and lines 10-12 to the character e. The fractional second
delays between lines 3-4, 6-7, 9-10, and 12-13 are the human delays between typing each
Notice that lines 13-15 are slightly different. One character is sent from the client to the
server (the Unix newline character, from our typing the RETURN key) but two
characters are echoed. These two characters are a carriage return and linefeed (CR/LF),
to move the cursor back to the left and space down one line.
Line 16 is the output of the date command from the server. The 30 bytes are composed
of the following 28 characters file:///D|/Documents%20and%20Settings/bigini/Docum...i/homenet2run/tcpip/tcp-ip-illustrated/tcp_int.htm (2 of 14) [12/09/2001 14.47.18] Chapter 19. TCP Interactive Data Flow Sat Feb 6 07:52:17 MST 1993
View Full Document
This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.
- Spring '12