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The Future of Satellite Acceleration
SCPS and Tactical Military Satellite
by Nichols Yuran

Satellite acceleration technologies have been well known to users of military satcom for many years. Performance Enhancing Proxies (PEPs) are now a fixture in today’s tactical satcom equipment suites.

The technology underlying most PEPs is the Space Communication Protocol Standards (SCPS) transport protocol, commonly pronounced “skips”. SCPS is an open-source, TCP variant. The capabilities of the standard transport protocol are extended for adaptation to the rigors of satellite communications. Simultaneously, SSPS must remain fully interoperable with standard TCP implementations.

Mil-Std-2045-44000 is the designation and mandated for use in PEPs by the DoD IT Standards Registry (DISR). SCPS maintains high bandwidth efficiencies while performance loss associated with high round-trip times, channel asymmetry, packet loss, and other environmental impediments common in military satcom, are lessened.

For purposes of standards compliance and interoperability, SCPS is specified as a requirement for most of today’s tactical DoD satcom programs. There are thousands of worldwide implementations currently supporting US tactical military satcom. SCPS is also the standard acceleration technology deployed by DISA, implemented in the Standard Tactical Entry Point (STEP) and Teleport programs to provide accelerated connections to deployed warfighters. As a result, many satellite equipment vendors have been compelled to offer SCPS either as an integrated solution in their product lines, or in the form of a standalone SCPS-based PEP.

With the increasing sophistication of military satellite networks, and the complex architectures and advanced modem technologies deployed in the modern battlefield, many SCPS implementations are strained beyond their original capabilities. Such has forced vendors to reexamine their approaches to the technology.

Traditional PEPs operated under a simple assumption; once the PEP was configured and deployed, the parameters of the satellite channel would remain fixed. The proper acceleration attributes could be applied to the satellite WAN, knowing that neither its speed nor round-trip time would fluctuate over the life of the connections. This practice is known as rate-based acceleration.

However, many of the satcom packages in the military today employ TDMA-based systems. The bandwidth allocated to a specific terminal may be increased or decreased on-demand. What’s more, many of today’s architectures are both mixed-bandwidth. Not every path a connection might travel operates at the same speed, and heterogeneous, meaning networks are often hybridized mixtures of satellite, wire and radio. The effect on the common PEP is confounding.

Because the PEP doesn’t know which of the paths a given connection will travel, it cannot apply optimum acceleration attributes. The PEP is forced to apply the same acceleration criteria to every connection, regardless of the path taken. The results can be catastrophic—dropped packets, large network queues, as well as dramatic degradation of overall network performance.

This problem was quite apparent in the U.S. Army’s JNN network. Comprised of a mixture of FDMA and TDMA satellite, as well as HF line-of-sight radios and tactical fiber connections, the JNN network’s design was truly complex. A variety of media, fluctuating bandwidths, and a mix of environmental conditions, all plagued the network. All traffic had to be routed through a single SCPS-based PEP due to architectural requirements, regardless of which of the media was used.

A customized SCPS implementation from Global Protocols called SkipWare® powered the PEP. Recognizing the network’s complexity, Global Protocols adapted their standard SCPS implementation through inclusion of a unique set of network controls. The PEP could make automatic adjustments to changes in bandwidth allocation without user intervention.

These controls allow the PEP to recognize changes to the network, from redistribution of bandwidth to changes in the media being used. The acceleration attributes for each connection would automatically adjust in response to these changes. This allows for operation in TDMA networks where bandwidth is assigned on a variable basis. Also supported is acceleration in mixed-media networks where connection paths are uncertain.

The benefits these additions to the SCPS standard offered the JNN network were extraordinary. Rather than limited to a single set of acceleration criteria, which improved some connections while degrading others, Global Protocols’ “smart” SCPS is able to learn how to best optimize each individual connection. This optimization is regardless of the media, speed, or environmental conditions.

Today, more than 3,000 turboIPs with SkipWare are in use throughout the Army’s JNN network. Acceleration, error-resistance and bandwidth optimization for thousands of deployed warfighters is provided. The success of turboIPs has influenced other, wide scale deployments of the technology. The USMC’s Satellite Wide Area Network (SWAN) program, the DISA’s STEP and Teleport programs, and several other smaller military programs are prime examples of turboIPs’ success.

SCPS, as a standard, will likely remain a fixture in tactical satcoms for several years, due to its specification for several, large military programs extending beyond 2010. With the many complementary WAN optimization technologies emerging from today’s satellite industry, SCPS is becoming an even stronger, more pervasive technology in tactical satcom. Implementations such as Global Protocols’ SkipWare line are testimony to the adaptability and portability of this technology across the increasingly sophisticated and complex DoD communication architectures.

Nick Yuran is the Director of Sales and Marketing for Global Protocols, Inc. As a founding member of the company, Nick has worked to promote SCPS and other standards through DoD. His focus is on Interoperability in tactical systems. Prior to joining Global Protocols, Nick served as a telecommunication analyst for various U.S. intelligence agencies. He possesses a BA in Slavic Languages from the University of Arizona as well as a MS in Telecommunication from George Washington University.