Abstract
Most transportation agencies and departments have deployed transmission control protocol–Internet protocol (TCP-IP) applications in their offices and are beginning to deploy TCP-IP applications in remote or satellite field offices. Deployment of TCP-IP applications where broadband access is not available can be quite challenging. Satellite-based communication offers an opportunity to provide high-bandwidth connections quickly. However, satellite communications incur significant travel time delay that may result in poor performance of applications designed for a low-latency environment. This paper presents an evaluation of the AASHTO SiteManager software suite with two different satellite broadband providers. SiteManager clients performed poorly in the high-latency environment, in some cases up to 50 times slower than with SiteManager running on a low-latency terrestrial network with equivalent bandwidth. In general, the performance of SiteManager was relatively insensitive to the bandwidth provided by the satellite provider. In most tasks, SiteManager performed better over a 50-kbps dial-up connection than over a 384-kbps satellite connection. In an alternative architecture in which SiteManager was operated remotely via a terminal emulation service over a satellite connection, the performance was observed to be robust. This architecture requires considerably more equipment, software, and technical support. Furthermore, the delay in seeing some key-strokes and cursor movements appear can be somewhat awkward for the user. However, given the extensive bursts of short messages between SiteManager clients and the server, the high-latency constraints of a satellite network make a terminal emulation procedure the only viable method of deploying SiteManager via a commercial satellite IP service.
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