IP Packet Filtering And Content Awareness Are Essential
At Comtech EF Data, IP-enabled satellite modems provide advanced FEC technology, end-to-end QoS, payload and header compression, and a wide array of modulation choices. These modems maximize delivery for any content while promoting bandwidth efficiency, while the prioritization of traffic is addressed via a 'Diff Serv' feature as well.
In addition, by using packet-filtering technology to create appropriate flows, the best lossless compression of the payload is achieved. The CDM-570L satellite modem can provide priority treatment for mission critical applications and allow non-critical traffic to use the remaining bandwidth, while the just-released CDD-564L quad demodulator was engineered to maximize IP-over-satellite link efficiency with the integrated router and IP module functionality, which utilize Telnet, HTTP and SNMP.
Comtech EF Data also offers performance enhancement proxy (PEP) products, the turboIP and turboVR, which can alleviate TCP/IP bottlenecks in impaired environments (high bit error rate, high delay) while preserving interoperability with any TCP device.
A sister company, Comtech Vipersat Networks Inc., provides complete solutions that optimize bandwidth utilization for broadband two-way multimedia over satellite networks in the global marketplace. The company's products enable applications such as video teleconferencing, voice, data and Internet/Intranet delivery to a variety of industries. Product features include dynamic bandwidth allocation and switching, data carrier management, single hop on demand, multi-transponder mode and voice prioritization.
Given the importance of content awareness in rich media delivery every step of the way, Comtech EF Data addresses it in a number of ways.
"Content becomes an issue when it causes network congestion. Comtech EF Data addresses content awareness through QoS technology by using session knowledge to differentiate traffic to the appropriate places. QoS automatically recognizes the packet type and directs it accordingly," says Enns. "Complementing our QoS, full IP header compression also optimizes bandwidth allocation, reducing operating expense costs associated with rich media transmission."
"Thales delivers QoS in two ways," says Barouxis. "Thales delivers some QoS at IP level with our Opencast multicast software solution. The Opencast is an excellent companion to the widely deployed Opal IP Encapsulator. The Opal offers statistical IP and adds even more QoS to Thales' end-to-end solutions."
Statistical IP is where a pool of bandwidth is allocated in the overall multiplex output by Opal, according to Barouxis. This fixed pool, called a "virtual channel," is dynamically shared among multiple packet IDs (PID). Each PID has a minimum guaranteed rate and a best effort rate with a priority. The sum of the minimum guaranteed rates has to fit the pool, of course, but at any time - Opal is constantly measuring the IP traffic that each PID has to encapsulate - if a PID uses less than its minimum, the delta between the actual rate and the minimum goes back into the pool as leftover bandwidth that can be used by other PIDs for their best effort rate.
"This, combined with the statistical aspect of the IP traffic and the queuing (First In, First Out or FIFO) for each PID, provides real QoS at the PID level," says Barouxis. "Most recently, Teleglobe has utilized the advanced QoS features of the Opal to provide services to their customers globally. Government agencies around the world have done the same."
While we asked him to outline how Thales addresses interfaces with terrestrial networks including hybrid WANs or WLANs, and what if any challenges are encountered in these architectures, he responded by saying that Thales does not have permission to discuss customers where this has come into play.
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