Satellite Network Performance Enhancers: A Better Way Of Doing Things
by Peter J. Brown
Fortunately, as the Internet started to take off, a number of companies began immediately to devise solutions that enhanced the performance of Internet traffic flowing over satellite networks. Where many saw latency and other obstacles between the point of oirigin and the ultimate destination, these companies saw opportunities.
Working Together In Harmony
The underpinnings of the Internet, specifically TCP/IP, were designed for implementation over static bandwidth where reasonable delay and a reasonable amount of errors would be the rule. In addition, the engine for Internet browsing, HyperText Transfer Protocol (HTTP), for example, was quickly recognized as “a chatty protocol, which is dependent upon a lengthy dialogue.” At least this is how Yair Shapira, vice president of research and development at Israel-based Flash Networks Inc., describes it.
Flash Networks has created the NettGain 1000 and NettGain 2000, and together these represent extremely robust and versatile data optimization and acceleration solutions. Gilat Satellite Networks is an investor in Flash Networks, and among Flash Networks’ recent customers are the two-way Internet via satellite service provider known as Starband, and Thailand-based IPstar, a unit of Shin Satellite.
“The delays encountered in a satellite network impose a very noticeable hardship on TCP/IP. The result is that without some form of data optimization and acceleration, overall throughput does not exceed 30 percent of available bandwidth,” says Shapira. “TCP is not aware of retransmission in the underlying layer. It just sees a two-second delay. The link layer itself performs this retransmission when packet loss occurs in the physical layer.”
Flash Networks’ contribution to enhanced satellite network performance revolves around proprietary protocols, including Boosted Session Transport (BST) protocol and Get All Protocol (GAP). In addition, Flash Networks recommends that satellite network users tap into various compression and decompression techniques or platforms in order to shape content so that, as the data passes through the satellite network, it is more easily and effectively distributed.
“BST is merely TCP redesigned for the satellite environment. On the satellite link, we translate TCP into BST. All this is happening in a way that is completely transparent to the end user one layer below the HTTP or application layer,” says Shapira. “Our client server proxy architecture can be embedded in a modem if necessary. The 1000 and 2000 are both carrier class solutions. In a 1 Gigabit satellite hub, for example, a customer could boost file transfer rates by more than a factor of 10 by adding 12 NettGain-equipped servers.”
Emphasis On Global Networking
Content providers and enterprise network managers are watching as the global dance between satellite and fiber networks goes on. The rule has been for fiber deployments to chase high density and fast growing traffic, while satellite is able to maintain its edge for point-to-multipoint traffic. This does not mean that the point-to-point market for satellite has dried up. However, the trend is unmistakable.
At the same time, outbound data can never know for sure what sort of pipe or pipes it will pass through, unless it is confined to a single hop transmission. As a result, any measures adopted that involve a performance-enhancing additive on the networking side must take this landscape into account.
“In this increasingly global market, content providers must be prepared for their material to traverse multiple networks,” says Bill Steele, president of Stamford, CT-based Kencast Inc. “It is not unusual or uncommon for content to undergo a triple satellite hop, and then pass onto land lines as it moves across the Internet. Instances where content might be required to transit in a multicast then a unicast and then back to a multicast format are not uncommon either, especially for enterprise customers.”
Any performance enhancing mechanism must transition seamlessly across these networks. Kencast embraced the global distribution model years ago, and it is able to readily adapt to a networking environment where the data in question undergoes any reassignment of IP addresses along the way. This is a somewhat normal routine for Kencast, which is now rolling out of Fazzt 6.3. This latest version of Kencast’s digital delivery solution has enhanced features for multicast file delivery and live streaming, according to Steele.
“The main emphasis in Fazzt 6.3 is on encryption and key management. The goal is to deliver the file in question in a single transmission, to prevent its theft, to keep it clean and validate that fact,” Steele says. “We also map it and authorize who can get it. We put our Forward Error Correction (FEC) on the file while it is still in the hands of the content provider, and then we reconstruct and validate the accuracy of the entire file once it reaches the end user.”
The current Fazzt 6.2 offers an enterprise client which has a Web server and caching capability, among other things, and is enabled by the end user’s existing browser. This Fazzt Digital Recorder is powered by what Steele describes as a software version of TiVo for the recording of live streams in all flavors ranging from MPEG 4 to HDTV content, and across all platforms including Microsoft Media Player, Real Video and Cisco IP/TV.
In both the multi-site VSAT environment as well as in point-to-point configurations, content acceleration is key. At Ijamsville, MD-based Viacast Networks Inc., a solution known as Pronto has emerged. Pronto can be either embedded in Viacast’s router/receiver products or used on a standalone basis in a PC-based client version. Either way, according to Viacast president and CEO Mitch Robinson, Pronto combines the best of default gateway architectures in a very small footprint.
“Pronto had to be very small because we had another target in mind,” says Robinson, who adds that Pronto requires servers to be equipped with Windows NT Server 4.0, Windows 2000 or Linux along with 128 MB of RAM. Currently, the server is targeted to be one of Viacast’s family of receivers, like the IP-Companion, Quantum-MSR or Viacast’s new Eclipse caching platform. “Pronto is tightly written to make it not only appealing as a satellite network solution, but also easily ported to a lot of other implementations such as wireless.
“When we developed Pronto, we focused our efforts in keeping the footprint–storage space and run time space–as small as possible since we build embedded network appliances and the environment is so small on real estate to begin with. With a footprint no bigger than 20 Kbytes, Pronto can potentially find its way into handheld devices that need to have TCP/IP acceleration to support a more robust Web experience,” Robinson adds.
Pronto increases outbound performance and simultaneously reduces the return channel bandwidth by reducing TCP acknowledgement traffic. Pronto has been used to increase outbound performance by a factor of seven to eight times and reduce return channel acknowledgments by a factor of 40 times, according to Robinson.
While Robinson describes Microsoft’s Windows as making some headway in large window sizes, he asserts that Microsoft has yet to effectively address the return channel requirements and the effective handling of acknowledgements. “So, the pick up in performance is not as scalable as one that handles both sides of the equation,” Robinson says.
Some companies are focusing their spoofing on the compression of acknowledgements, or a similar form of handling of selective acknowledgements. Spoofing usually entails some sort of process whereby the automatic TCP-based quality control mechanisms of the Internet are tricked into allowing a transmission to flow unimpeded when the actual response by design calls for the IP packet delivery to slow down. Regardless, the brakes are applied to slow the IP data transmission in question.
However, Viacast is focusing it efforts on Enhanced Acknowledgements (EACK), and is engaged in the sophisticated controlling and servicing of acknowledgements with a trickle return channel of only 2.4 kbps, according to Robinson. Pronto supports the EACK protocol that is utilized in Reliable Datagram Protocol (RDP). “Even with this very small return channel, we can achieve 96 to 97 percent efficiency with a nine or 10 Mbps carrier,” Robinson says.
Viacast offers 8PSK with turbo coding, which allows the operator to increase throughput by 1.5 times and utilize the existing antenna. Typically when converting the modulation from QPSK to 8PSK, power must be increased by roughly 3 dB, if not, then the antenna size will have to be increased, according to Robinson.
Current modem technologies are rapidly approaching the theoretical limits of power and bandwidth efficiencies. According to Michael Ready, chief technology officer at Sunnyvale, CA-based Transcendent Technologies Inc., a bandwidth compression solution known as DoubleTalk has been developed.
In a nutshell, DoubleTalk enables the user to achieve 2x bandwidth compression across full duplex links that are operating on loop-back transponders. By transmitting the forward and reverse carriers in the same band, and by operating at the IF level between any up or downconverters and the modems, DoubleTalk has no impact on signal C/N, nor does it care what sort of modulation, FEC or underlying bit stream traffic is involved.
“We are not competing with the modem vendors in this instance. You can use DoubleTalk with any modulation scheme. We are not only very synergistic when it comes to modems, but also completely compatible with other performance enhancing proxies from companies like Mentat and Fourelle Systems,” Ready says. “DoubleTalk gives you the bandwidth efficiency of 16 QAM with the power efficiency and bit error advantages of QPSK. And you can use it with 8PSK, too.
“We realized that any significant gain in the traditional power versus bandwidth tradeoff for satcom signals would require a unique approach,” Ready adds.
Ready is fully aware that with DoubleTalk, Transcendent is preparing to compete with others in this space. That list includes companies such as Viasat with its Paired Carrier Multiple Access (PCMA) solution. “We view PCMA as more of component in a turnkey system whereas DoubleTalk is designed as a standalone product. By focusing on the IF level, we are doing something quite different from Viasat here,” Ready says.
“We intend to attract customers in both the point-to-point and star-type VSAT markets. Turbo coded modems are emerging from vendors like Comstream and EF Data. DoubleTalk will allow these modem vendors to go to their customers and say something to the effect of ‘now, you can operate at a lower C/N ratio, and reduce bandwidth leasing costs.’
“DoubleTalk is a fundamental technology which is also ideal for bandwidth recovery on bandwidth-limited transponders. So, it appeals simultaneously to both the end user and the service provider, and as an addition to or alternative to 8PSK,” Ready says.
With the exuberance of the dot.com craze now light years behind us, and with the economy recently jarred by catastrophic events on top of a set of fundamentally weak indicators, the enterprise sector in particular has embraced cost-savings with a vengeance. As a result, Santa Clara, CA-based Fourelle Systems Inc. is ideally situated from the standpoint of offering Venturi, a bandwidth management solution that comes in several flavors.
“Over the past few months, with respect to Venturi, we have concentrated on ROI (return on investment) and payback models that support the changing needs of the enterprise and wireless carrier space,” says Patrick Glenn, chairman and CEO of Fourelle Systems. “Enterprise buyers are consistent and well-known. It is not like demand for satellite services suddenly spiked, although interest and demand for Venturi spiked in the last year as companies strived to align expenses with the revenue line.”
Venturi has always been very content-oriented, according to Glenn. As eXtensible Markup Language (XML) and other new bells and whistles are introduced to the Internet environment as a whole, Glenn sees Fourelle as being well-positioned to take advantage of new opportunities that result from Venturi’s ability to compress, optimize and cache data streams.
“We need proof that there will be a significant market for two-way consumer satellite services. Thus far, we have not seen it. The same is true for realtime video and audio in the streaming sector. No significant market from a demand side perspective has developed here either,” says Glenn. “We see more reasons to be excited by such things as the market for reducing costs and accelerating content delivery, including databases in the enterprise sector.”
Fourelle has incorporated load balancing and prioritization into its combination of Venturi transport protocol and Intelligent Compression. As the trend toward hybrid wireless satellite networking gains momentum, a multiple server strategy and solution is an essential part of the mix.
“If you are roaming or moving around, multiple server balancing based on round trip time becomes a top priority. This is all about accessing the fastest responding server, either because it is the closest or the most regional. We allow for ease of configuration, and this pertains to satellite carriers and ISPs alike where the emphasis is on a regional or global deployment of satellite hubs,” Glenn says.
“This involves an alternative to fixed path routing configurations, whether you are talking about in-service or out-of-service scenarios. You can bet that load balancing with prioritization is bound to be a high visibility item going forward. This all about having the ability to deliver to a specific set of ROI’s, or payback requirements,” he adds.
At Mentat Inc. in Los Angeles, SkyX Protocol lies at the heart of its protocol gateway architecture. In effect, a satellite network operator can deploy an optimization agent such as the SkyX Gateway, which is inserted at transmit and receive sites as a transparent intermediary to overcome the performance problems that are encountered when TCP is delivered via satellite.
With SkyX, a lot of headaches are targeted to go away. As multicast remains an attractive delivery mode in certain circumstances, SkyX simplifies the process enormously by combining a TCP performance enhancement product with optional “Multicast Fan-Out” functionality. However, Mentat executives question how much momentum multicast really enjoys “given the lack of support of multicast by the terrestrial networks and the subsequent lack of multicast tools and applications.” Regardless, with SkyX Client and SkyX Server now joining the SkyX Gateway, a number of new avenues are opening up.
“Mentat is attempting to solve this problem by adding the Multicast Fan-Out functionality to the SkyX Gateway Version 3.0, among other things, so that users can take advantage of the inherent broadcast nature of satellite communications without needing any special multicast tools or applications,” says Jerry Toporek, Mentat’s vice president of engineering.
“One of the major benefits of satellite links is the multicast capability. With the SkyX Gateway, no multicast aware software is required on either clients or servers to take advantage of this capability,” adds Toporek.
SkyX Multicast Fan-Out transparently converts a standard unicast TCP connection from FTP or any other TCP-based application into a reliable multicast file transfer over the satellite link. Mentat President Kay Guyer describes this as ideal for things like caching applications, software updates, database synchronization, and main video server to local video server content delivery.
“This allows our customers to get files simultaneously to all remote sites via any normal FTP client,” says Toporek.
“Our intent here is not to compete with others in the multicast market. We are not selling software to make machines multicast-enabled, rather this is just one more benefit of SkyX,” says DC Palter, Mentat’s vice president of sales and marketing.
For expansions and multi-link flexibility, SkyX Gateway Version 3.0 allows the SkyX Gateway XR10 to support up to four separate outbound links, while the SkyX Gateway XR45 can support up to 32 individual links. A new quality of service feature on 3.0 is ideal for implementing the guaranteed bandwidth required to set up and maintain private virtual circuits as well.
Wildblue Communications Inc. will use SkyX Gateway in an integrated modem along with its Ka-band spotbeams starting next year. Radyne Comstream demonstrated SkyX Gateway at NAB 2001, combined with its modular SCPC system known as IPSat. IPSat Plus uses a TDMA burst return channel as part of its bi-directional bandwidth-on-demand IP over satellite solution. Because Version 3.0 includes a Simple Network Management Protocol (SNMP)-based solution, the managing of dynamic rate adjustment and bandwidth-on-demand transmissions can be easily configured and readjusted.
Constructive Link Routing
In Europe, a concerted effort to improve the Internet’s performance in the sky has been underway for years. One area of development involves a platform built to support routing protocols known as Unidirectional Link Routing (UDLR). It mimics a conventional bi-directional transmission so that routers transfer their routing information seamlessly and smoothly atop a unidirectional link.
A back channel from a receiver to a feed is required so that all traffic that cannot be sent over the unidirectional link can be exchanged nonetheless via so-called “IP tunnels.”
Antoine Clerget, chief technical officer at UDcast in Paris, France, credits Eutelsat and INRIA–France’s national telecom engineering institute–for, among other things, propelling UDLR along at the Internet Engineering Task Force (IETF). Last March, a UDLR protocol emerged, and interoperable UDLR implementations are already running on products from companies like Sony, Hitachi and Thomcast, according to Clerget.
“UDLR is implemented below the IP layer where it is transparent to IP and all IP protocols such as TCP, UDP and ARP (Address Resolution Protocol),” says Clerget. “It transforms the satellite network into a LAN. Any local ISP, wired or wireless, can be used for the return path.”
Clerget believes that developments like UDLR will gradually draw the satellite industry away from proprietary solutions designed for specific applications. “With the arrival of DVB-S boards from several vendors, you might say our timing is excellent,” says Clerget.
Hybrid wireless satellite networks in Europe and elsewhere will also be well served by UDLR. “GPRS in Europe carries wireless IP. If the satellite router in question also has a GPRS board, the operator can use a UDLR-equipped forward channel via satellite,” says Clerget.
He sees multicasting via satellite as one of the chief benefactors of a derivative of UDLR known as UDRouteCast (UDRC), an optimization technique for IP multicasting protocols. “The objective is to not have the network collapse under the weight of the control traffic. We can use UDRC to limit the traffic exchange between neighboring routers, and do it while interoperating with standard protocols,” Clerget says.
“Now you have the ability to leverage satellite and attain true scalability. You also have the ability to put all applications on satellite in a seamless fashion. At the same time, you can use the satellite network for distributing any sort of content with a very large number of routers,” Clerget adds.
Get It There Fast On The First Try
This roster of companies encompasses some of the best talent anywhere when it comes to ensuring that content and data distribution over satellite performs in the best way possible. When expectations are high, and a global agenda is on the table, the satellite path is often the optimal route.
As readers watch the steady emergence of new and updated versions of performance enhancing software, they know the challenge is still there for the talent pool that has been attracted to this arena. The fact that so many adept players are immersed in the ongoing attempt to fashion the next best thing for both the users and providers of high performance satellite networking services alike is proof that the evolution of satellite technology is by no means a thing of the past.
Peter J. Brown is Via Satellite’s Senior Multimedia Editor. He lives on Mount Desert Island, ME.