EMS Technologies Canada Ltd. HSD-400 Manuale Utente
Page 2–19
25 June 2008
EMS SATCOM
SYSTEM DESCRIPTION, INSTALLATION, AND MAINTENANCE MANUAL
eNfusion™ HSD-400 High-speed Data Terminal
(1) Mobile ISDN versus MPDS
Deciding which service type to use depends how you intend on using your data
connections. For more information about optimizing network usage, refer to the
eNfusion® HSD High-speed Data Terminal Developer’s Guide (MN-1252-13005).
connections. For more information about optimizing network usage, refer to the
eNfusion® HSD High-speed Data Terminal Developer’s Guide (MN-1252-13005).
(2) Connecting to Inmarsat Mobile ISDN Service
This section provides tips for connecting to the Inmarsat Mobile ISDN service (M4
Circuit-Switched Service). The transmission of data over satellite networks differs from
land-based ISDN applications. Factors inherent in satellite communications (signal
fading, latency, and transmission blockages) can cause data transit delays and bit
errors.
Circuit-Switched Service). The transmission of data over satellite networks differs from
land-based ISDN applications. Factors inherent in satellite communications (signal
fading, latency, and transmission blockages) can cause data transit delays and bit
errors.
Because of these challenges, it is sometimes necessary to optimize the system to
achieve peak performance over the satellite network.
achieve peak performance over the satellite network.
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 to use sends
data over the network.
networks. To improve data transfer rates most ISDN protocols require minor
adjustments. For best results, consider how the ISDN protocol you intend to use sends
data over the network.
As examples, consider the protocols TCP/IP (over PPP) and V.120. As a basic
protocol, PPP operates under the networking protocol TCP/IP. PPP has error checking
properties but does not offer flow control.
protocol, PPP operates 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). When used together,
PPP and TCP/IP protocols perform well over the Inmarsat network.
(which like satellite networks experiences high transit delays). When used together,
PPP and TCP/IP protocols perform well over the Inmarsat network.
Improve the performance of TCP/IP (over PPP) for Mobile ISDN by changing the
default parameters. Increase the maximum size of data allowed in transit at one time
to a value up to approximately 255,552 bytes.
default parameters. Increase the maximum size of data allowed in transit at one time
to a value up to approximately 255,552 bytes.
The V.120 protocol includes error correction and flow control applications. Flow control
limits 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.
limits 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.
The default parameters of V.120 limit the maximum transit size of the data package
to approximately 1764 bytes, causing poor performance results over satellite ISDN
networks. Improve the performance of V.120 over Mobile ISDN by changing the
default parameters. Increase the maximum size of data allowed in transit at one time
to a value up to approximately 8000 bytes. (Some applications of V.120 permit the
user to change the “window size”.)
to approximately 1764 bytes, causing poor performance results over satellite ISDN
networks. Improve the performance of V.120 over Mobile ISDN by changing the
default parameters. Increase the maximum size of data allowed in transit at one time
to a value up to approximately 8000 bytes. (Some applications of V.120 permit the
user to change the “window size”.)
Both the HSD-400 terminal ISDN and Ethernet (x2) interfaces support connections
to Inmarsat's Mobile ISDN service.
to Inmarsat's Mobile ISDN service.