ND SatCom SKYWAN IDU 1070, Manual

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20 Network Design and Engineering Guide 2010-10-26
General Carrier Design
Data and Voice Networking Overview
Within the task A2 Carrier Design the network efficiency / TDMA overhead will be determined.
The average TDMA overhead is 15%. But as the overhead range is between 5% and 30% it
will be worth to elaborate and downsize such ’nasty peanuts’. With some experience you can
start with a good guess about the carrier sizes and feed the ’
Sky WAN
®
TDMA Calculation Tool’
to prove your guess.
2.2 Data and Voice Networking Overview
To send data and voice applications traffic over satellite the end user equipment is connected
to an IP or Frame Relay input port of the
Sky WAN
®
IDU.
Figure 2-2 SkyWAN
®
Networking at a Glance
The figure 2-2 represents a brief overview of the supported data networking protocols; depicted
is an IP connection. On the ethernet port (interface 1)
Sky WAN
®
supports the Internet Protocol
(IP) routing functionality. On the serial ports 2-5 (interfaces 2-5) the Frame Relay (FR) switch-
ing functionality is supported.
a)
Both types of data packet protocols are transported over the satellite link layer interfaces (mod-
ulator port Tx Out and demodulator port(s) Rx In) using an efficient proprietary Satellite Link
Layer (SLL) encapsulation.
During forwarding the ethernet packets will have their header stripped. The remaining IP packet
will be encapsulated in an SLL frame which includes a 2 Byte SLL header and a 4 Byte CRC
check sum. Frame Relay frames will be encapsulated in a similar SLL frame. The SLL frames
will be put into a
Sky WAN
®
TDMA container. If the frame sizes are larger than the remaining
space in such a container, the SLL frames will be fragmented. A TDMA header will be added
to the container. Finally the complete gross container will be encoded and modulated.
a. Note that to use the Frame Relay serial ports a run-time license is required on the IDU.