User's Manual

Page 2–47
18 September 2007
SYSTEM DESCRIPTION, INSTALLATION, AND MAINTENANCE MANUAL
eNfusion™ HSD-128 High-speed Data Terminal
Because of these challenges, it is sometimes necessary to optimize the system to
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. Adjust the configuration taking into account the unique
operating environment of satellite network communication.
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.
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.
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.
The protocol V.120 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.
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”.)
When choosing an ISDN protocol for satellite ISDN networks, consider a flexible
solution that allows for modifications to the operating parameters to suit the unique
environment of satellite communications.
Both the HSD ISDN and Ethernet interfaces support connections to Inmarsat’s Mobile
ISDN service. Ethernet is available for HSD transceivers, PNs 1110-A-0150 and
1110-A-0160 and HSD transceivers with Service Bulletin 1110-SB-0004
accomplished. All HSD-X transceivers support the Ethernet interface.
(a) Using the ISDN Interface
The basic requirements for using the HSD ISDN interface to access Swift64
Mobile ISDN services over the satellite network are listed below:
• A EURO ISDN terminal adapter or router
• An account with an Inmarsat Service Provider
• A computer
• Dial-up Networking capabilities
The following sections describe the three main components required for Swift64
Mobile ISDN service using the ISDN interface (terminal adapters – ISDN
modems, ISDN protocols, and ISDN line).