Datasheet
Functions and their Configuration INSYS ETHERNET 5.X
46
Nov-06
Collect data from
RS232: block A
ethernet
transmission
Output data via
RS232: block A
Modul#1
Modul#2
Collect data from
RS232: block B
Collect data from
RS232: block C
Output data via
RS232: block B
Output data via
RS232: block C
ethernet
transmission
ethernet
transmission
For some application protocols, this pipeline effect can not be utilized in the best possible
way. When data blocks are sent in the serial protocol of the end application and con-
firmed by the remote terminal (the next block is sent afterwards, etc. ...), the following
scenario might possibly occur:
The application sends a data block (e.g. 1400 bytes) in series to the INSYS Ethernet, where
the data is collected and forward by Ethernet after the block forming time has extended.
The second INSYS Ethernet receives the packet and sends the data in series to the remote
terminal of the application. The application itself will not forward the data, however, be-
cause it first needs to have the last 1400 bytes confirmed from its remote terminal. The
pipeline effect is not utilized and the data is on the way twice as long (+ block formation
time).
Collect data block A
Transmit data block
A
TX
RX
ACK v.
remote
station
Collect data block B
Transmit data block
B
ACK v.
remote
station
ethernet
transmission
In this case, the maximum block size could be reduced with AT#MSS=<n> to be able to
use the pipeline effect at least partly. A maximum block size of 1/4 of the application
data packet to be expected (example: AT#MSS=350) would reduce the transmission time
roughly from factor 2.0 to 1.25. However, for too small IP block sizes the achieved pipe-
line effect on the serial interface is destroyed by the increased overhead (IP header for
each packet = high amount of data) on the Ethernet side. The optimum for each applica-
tion depends on several factors and can only be found through actual tests.
A1
TX
RX
ACK A
A2 A3
A3
A4
A4
B1
ACK B
B2 B3 B4
B4
ethernet
transmission
IP block formation when a trigger byte occurs