EMS HSD series User Manual page 21

Performance considerations of satellite ISDN
The transmission of data over satellite networks differs
from land-based ISDN applications. Satellite
communications experience factors such as transit delay
and bit errors caused by signal fading and blockages.
ISDN protocols are designed specifically for ground-based
ISDN networks. Performance of different ISDN protocols
varies depending on the properties of each application.
Because of these challenges, it is sometimes necessary to
optimize the system to achieve peak performance over the
satellite network.
Optimizing ISDN protocols for satellite networks
ISDN protocols are not designed specifically for use over
satellite communication networks. To improve data transfer
rates most ISDN protocols require minor adjustments.
For best results, consider how the ISDN protocol you intend
on using sends data over the network and adjust the
configuration taking into account the unique operating
environment of satellite network communication.
As examples, consider the ISDN protocols TCP/IP over
PPP and V.120.
As a basic protocol, PPP is typically operated under the
networking protocol TCP/IP. PPP has error checking
properties but does not offer flow control. TCP/IP is
flexible and designed to run over different networks
including the Internet which like satellite networks
experiences high transit delays. Used together, PPP and
TCP/IP protocols perform well over the Inmarsat ISDN
service.
The protocol V.120 includes error correction and flow
control applications. Flow control limits or fixes the amount
of data that can be in transit at any one time and waits for
acknowledgment of receipt from the other end of the
connection before sending more data.
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User's Guide EMS-MN-1110-10048
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