1. TCP Interactive Data Flow
miyu

2. What’s talk about? Transfer of data using TCP Delayed acknowledgments
Interactive data |bulk data
Delayed acknowledgments
Nagle algorithm
Window size advertisement

3. Bulk data || Interactive data
ftp, electronic mail, Usenet news…
Tend to be full sized(normally 512 bytes)
Interactive data
telnet,rlogin…
Much smaller (90 % of packets less than 10bytes)

4. Interactive Input client server data byte keystroke server
ack for data byte
echo of data byte
echo
display
ack of echoed byte

5. Flow of data typed “date\n”
1 0.0 bsdi.1023 > svr4.login: P 0:1(1) ack 1 win 4096
(0.0165) svr4.login > bsdi.1023: P 1:2(1) ack 1 win 4096
(0.1235) bsdi.1023 > svr4.login: . ack 2 win 4096
(0.3181) bsdi.1023 > svr4.login: P 1:2(1) ack 2 win 4096
(0.0163) svr4.login > bsdi.1023: P 2:3(1) ack 2 win 4096
(0.0656) bsdi.1023 > svr4.login: . ack 3 win 4096
(0.2746) bsdi.1023 > svr4.login: P 2:3(1) ack 3 win 4096
(0.0165) svr4.login > bsdi.1023: P 3:4(1) ack 3 win 4096
(0.1090) bsdi.1023 > svr4.login: . ack 4 win 4096
(0.2512) bsdi.1023 > svr4.login: P 3:4(1) ack 4 win 4096
(0.0164) svr4.login > bsdi.1023: P 4:5(1) ack 4 win 4096
(0.1323) bsdi.1023 > svr4.login: . ack 5 win 4096
(0.3407) bsdi.1023 > svr4.login: P 4:5(1) ack 5 win 4096
(0.0173) svr4.login > bsdi.1023: P 5:7(2) ack 5 win 4096
(0.0420) bsdi.1023 > svr4.login: . ack 7 win 4096
(0.0599) svr4.login > bsdi.1023: P 7:37(30) ack 5 win 4096
(0.1403) bsdi.1023 > svr4.login: . ack 37 win 4096
(0.0042) svr4.login > bsdi.1023: P 37:44(7) ack 5 win 4096
(0.1958) bsdi.1023 > svr4.login: . ack 44 win 4096

6. Delayed Acknowledgments1
PSH 0:1 ack 1 (d)
0.0 2
PSH 1:2 (1) ack 1 (echo d)
(0.0165)
Delayed ack{
ack 2
(0.1235)* 3
(0.3181) 4
PSH 1:2 (1) ack 2 (a)
PSH 1:2 (1)ack 2 (echo a)
(0.0163) 5
Delayed ack{
(0.0656)* 6
ack 3
(0.2746)
PSH 2:3 (1) ack 3 (t) 7 8
PSH 1:2 (1)ack 2 (echo a)
(0.0165)
Delayed ack{
ack 4
(0.1090)* 9

7. Nagle algorithm
RFC 896
solution of tinygrams congestion on wide area networks(Simple and Elegant)

8. Nagle algorithm
Have only one outstanding small segment that has not yet been ackonwleged
Small amounts of data are collected by TCP
sent in a single segment when the acknowledgement arrives
Self-clocking
The faster the ACKs come back,the faster the data is sent…
On a slow WAN(desired to reduce the number of tinygrans),fewer segments are sent

9. When the RTT incleases…

10. Disabling the Nagle algorithm
When small message(and mouse movements) must be deliverd
ex)X Windows System server
Typing one of the terminal’s special function keys during an interactive login
Normally generate multiple bytes of data
Often beginning with “ESC” (ASCII)

11. type F1 type F2 F2 F1 F2echo F1echo N I ESC M [ ESC N [ ESC M [ ESC
PSH 1:2 (1)ack 2
type F1
PSH 2:3(1)ack2
PSH 3:4(1)ack 2
PSH 2:5(3)ack 3
lost
PSH 5:6(1)ack 4
ack 2
Timeout and retransmisson
PSH 2:6(4)ack 4
ack 6
PSH 4:5(1)ack 6
type F2
PSH 5:6(1)ack 6
PSH 6:7(1)ack 6
F F1
PSH 6:8(3)ack 5
F2echo F1echo
PSH 6:8(1)ack 7
ack 10
N I ESC M [ ESC
N [ ESC M [ ESC
^ [ [ M ^ [ [ N

12. Window Size Advertisements
Why Segment 5 advertises a window of 4095 bytes?
Still 1 byte in the TCP buffer for the application to read.
When the client TCP sends the buffered data…
Clienthad a chance to read the data from the server
Client’s advertised window is less the 4096

13. Summary
Interactive data
Nagle algorithm
Disabling the Nagle algorithm

14. END
Va bena?