A WAN Inter-Working Unit for satellite links

Commercially available protocol implementations often perform well down to a BER of 10^-6. The results presented show that a packet service may tolerate a significant further increase in the tolerated BER allowing operation down to 10^-4 BER using the proposed satellite efficient link protocol implemented in an experimental WAN Inter-Working Unit (IWU). The IWU has two interfaces, one connected to the SATCOM bearer, the other to a WAN (using X.25). Packets from the WAN interface may be routed over the SATCOM bearer using either a standard protocol or one from a selection of satellite efficient protocols. The satellite link protocols transport packets reliably and efficiently between the IWUs using a combination of HDLC-based recovery procedures. The authors describe the selection of these procedures using a comprehensive simulation package (developed in SIMULA) which allowed a comparison of the implementations of the protocols. The same source code was used to construct an operational IWU (X-PC), a pair of which were used during a comprehensive set of experiments connecting two WANs via a SATCOM bearer