Adding Pep to the Network

Military systems engineers are adding pep to their networks with a
relatively inexpensive, easy-to-install form of wide area network
optimization technology known as performanceenhancing proxies.

By Adam Baddeley
 

Military systems engineers are adding pep to their networks with a relatively inexpensive, easy-to-install form of wide area network (WAN) optimization technology. As their name suggests, performance enhancing proxies (PEPs) inject a performance-enhancing stimulant to the IP bandwidth stream at the transport layer, delivering improved throughput with neither the need to re-engineer the host systems to integrate new hardware nor the associated costs.

One of the recent recipients of PEP technology is the War fighter Information Network-Tactical (WIN-T) program. General Dynamics C4 Systems and the Army recently selected Expand Network’s Accelerator Operating System (AOS) for the WIN-T increment 2-3 TCP performance-enhancing proxy contract. This tasks the AOS to provide high throughput with low latency to support enterprise-class applications over satellite-enabled communications architectures.

“By implementing a performance-enhancing proxy, the effects of latency on Transmission Control Protocol (TCP) application traffic (individual conversations between Web servers and Web clients) can be mitigated, thereby restoring the wasted bandwidth and accelerating application performance. Expand Networks has chosen to implement a standards-based approach to its PEP that’s robust and scalable by using the Space Communication Protocol Standards (SCPS),” said Howard Teicher, vice president, public sector and satellite markets, for Expand Networks.

Since they are entirely based on software, the introduction of PEPs into military systems requires minimal modification for either party. “The integration of a PEP into systems is generally a very simple process,” Teicher said. “By placing the device in-line between the satellite modem and a switch or router, the PEP is able to see all network traffic and provide TCP optimization.

“For WIN-T increments 2 and 3, the PEP enables the network to maximize the utilization of scarce satellite bandwidth and improves the responsiveness experienced by end user applications. In addition, by maximizing the use of available satellite bandwidth, the network is able to simultaneously support more application traffic,” he continued.

General Dynamics, the prime contractor for WIN-T, uses PEPs on all the WIN-T increments, and more generally, for any network system that uses satellite communications as part of the WAN infrastructure, according to the company.

Satellite on the Move

The WIN-T implementation is just one of several PEP efforts being undertaken by the Department of Defense.

For example, Gerald T. Michael, chief engineer, SATCOM/Space Systems, Army CERDEC Space and Terrestrial Communications Directorate, has undertaken a number of projects in which PEPs have been applied, including satcom-on-the-move (SOTM) applications. He has also helped a PEP provider understand how its product was being used in a fielded system, and identify the limitations and mismatch between its implementation assumptions and how the PEP was actually expected to perform in the field.

Michael pointed out, however, that while PEPs are important to the Army’s goal of maximizing throughput and bandwidth utilization across multiple networks, they are merely one instrument in the toolbox for achieving that goal.

Michael explained some of the drawbacks: “PEPs, by their nature, require access to the TCP header. This means that they have to operate on unencrypted traffic. In some systems this is not an issue. In many systems, this means that multiple PEP instantiations are needed, one for each security level. The determination of the transmission path is made on the encrypted traffic—without feedback to the PEP—and the different transmission paths could have significantly different characteristics.

“Some PEPs assume that they are seeing all of the traffic, and that there is one transmission path, or that the transmission paths all have the same characteristics. Many PEPs incorporate additional optimization features, which may not perform well if there is a mismatch between the PEP optimizations and the actual system architecture,” Michael said.

He continued: “In SOTM applications, both the bandwidth-delay product and packet loss due to link outages caused by blockages between the on-the-move terminal and a geosynchronous satellite are major considerations. TCP has a fundamental bandwidth-delay product issue that limits throughput on satellite links. TCP also considers lost packets to be evidence of network congestion, and so packets lost due to driving by a tree or building—that is, disrupting the terminal-to-satellite link—would result in TCP reducing the transmission rate, which is an inappropriate response under the circumstances. We investigated automatic repeat request, PEP and hybrid approaches to maximizing throughput.”

Investigations into SOTM applications for PEP were primarily done with Lincoln Laboratory and Boeing.

“My group has worked directly with Global Protocols, and we have some experience with devices from Mentat Packeteer and Circadence. I know of other groups here that have worked with Expand Networks, and there is an awareness of Xiplink,” Michael said.

Military Tuned Protocol

Global Protocols was the first company to market a satellite accelerator based on the SCPS, and this has been a major factor in its successful penetration of the U.S. market, according to Nick Yuran, the company’s vice president of business development.

SCPS is an open-source DoD standard that replaces standard TCP with a specialized transport protocol that has been tuned to withstand the rigors of satellite communications, such as delay and error. Yuran said, “Because SCPS is non-proprietary and fully interoperable with standard TCP, it has been broadly deployed throughout the U.S. military, allowing for cross-program interoperability between different networks and different military branches.”

The Global Protocols’ implementation of SCPS, SkipWare, has been expressly developed for the military environment. “It is tuned to work with the DoD’s most commonly deployed modem technologies and most complex military network architectures,” Yuran said. “It has a very small footprint, which allows it to be easily ported to any number of different networking devices, and consumes very little computing resources on its host device.

“As a result, you can put SkipWare on anything from a router to a modem to a laptop without disrupting the network. Ultimately, we see SkipWare running on everything in the network-centric battlefield, including handhelds, sensors, UAVs and terrestrial wireless devices—anything that suffers from operational and environmental stresses,” he predicted.

Yuran attributed much of the appeal of SkipWare to the fact that it is based on open-source technology. But while the adoption of open-source technology as the basis for software development is advantageous is many ways, it imposes its own rigor.

“Our engineers are constantly coming up with new and innovative ways to improve the technology, but we can’t do anything to the technology that might render it proprietary and inhibit interoperability. So, the challenge for us is always going to be finding ways to improve and extend SkipWare while remaining true to the open standard that our customers value so much,” he said.

Yuran pointed in particular to the use of SkipWare in the Defense Information Systems Agency (DISA) Standard Tactical Entry Point (STEP) and Teleport programs. STEP and Teleport are the primary satellite bandwidth provision services of DoD, and have standardized on SkipWare product for their acceleration solution.

As a result, the thousands of warfighters who subscribe to STEP and Teleport bandwidth are also encouraged to use SkipWare to accelerate their satellite connections. “SkipWare was selected after a lengthy competitive process, where multiple vendor technologies were tested under a broad set of operational scenarios, and evaluated for both straight throughput performance and their degree of interoperability,” Yuran said. “SkipWare outscored the competing technologies and has powered the STEP and Teleport programs since 2003. This in turn has influenced the many other organizations throughout DoD that consume DISA bandwidth services to likewise adopt SkipWare as their acceleration standard.”

SkipWare was selected last fall for the DISA STEP Phase II upgrade, with 115 units replacing the company’s legacy 15 Mpbs turboIP PEPs with a 45 Mpbs version turboIP at each STEP site worldwide.

Trojan SPIRIT

The software is being used in a number of tactical military programs, primarily in the Army and Marine Corps, and has also been implemented by DoD integrators such as General Dynamics C4 Systems, Datapath, CACI and Booz Allen Hamilton.

The most recent was the Army’s Trojan SPIRIT program, where SkipWare is being implemented in the special purpose integrated remote intelligence terminal used for direct intelligence dissemination for both fixed and vehicular applications. The number of licenses is expected to reach 500 in 2008.

“This was a somewhat unique award, in that it required us to adapt our software to a much smaller platform than we had ever operated on before. The mobility requirements of the program were such that the host hardware had to be in a significantly reduced form factor, so we had to modify our software to run on this smaller platform with its reduced resources. The success of this program was very gratifying to us, since it validated the high degree of flexibility and portability of our technology,” Yuran said. ♦