Throughout the world's satellite communications have become a very well known technology. They provide high quality, flexible and reliable solutions for voice, fax, video and data communications in public, as well as privately owned networks. The dramatic growth of data communication networks, for instance the Internet Protocol (IP)-based Internet, ATM and Frame Relay networks, has led to a growing demand in IP-solutions. With such solutions the consideration of the architectural characteristics of the transport media is one of the key issues for an optimised design, and engineering of Internet and IP-networks.
Today, transport media are very common. They can be accessed through terrestrial cables, microwave signals or satellite communications. Satellite communications offer tremendous advantages over other forms of media. Satellite technology is unrestricted to terrestrial bandwidth limitations, such as E1-T1. The flexible, dynamic, re-configuration of allocated bandwidth allows every combination of receive and transmit speeds, and expands the ISPs (Internet service providers) ability to increase bandwidth as needed. The need to contract an excessive amount of fixed bandwidths, to handle peak traffic, in networks with asymmetric traffic flows, such as the Internet, can be avoided by the use of simplex or asymmetric satellite link configurations thereby eliminating the need for full-duplex terrestrial lines. Satellite communications can be rapidly installed everywhere inside the footprint of a satellite, regardless of the existence of terrestrial infrastructure; in turn, making it possible to extend the internet into rural areas across the world. The price for a satellite link stays nearly constant inside the footprint of a satellite, allowing us to provide a more cost efficient alternative for expensive long distance terrestrial lines. Another major advantage of satellite communications is the broadcast facility. With one transmission via the satellite a large number of recipients can be reached, leading to optimal bandwidth utilisation for more and more upcoming multi-casting and content distribution systems, which are still producing congestion in terrestrial ISP-Backbones. The growth of the internet leads to an increasing amount of content in the network. This content is stored in central servers from where it is being sent to various users requesting specific data. A vast amount of data is frequently asked, causing the same amount of data to be unnecessarily routed via the same path in the internet to local ISPs. To save bandwidth and avoid retransmissions of data most ISPs are using local servers to store the content in small ISP networks, or POPs from where the information can be accessed at a faster pace by the final customer. There are two approaches when feeding the local ISPs with information. The traditional approach is to deliver the content via separate terrestrial internet lines; this requires, for n destinations, n times the bandwidth. Current satellite based content distribution systems push the data from a content Hub and distribute it via the satellite with IP-multicasting to an arbitrary number of receive only stations in the ISP-networks and POPs. Our technology requires only one times the bandwidth to serve an unlimited number of receiving networks, being at the same time both fast and cost-effective. "With a satellite newsfeed the traffic can be transmitted more cost effectively and with less bandwidth consumption." Various applications benefit from a satellite based multicast solution. Traffic is relieved from the terrestrial infra-structure and bypasses the data via a satellite broadcast stream. For example, distribution of Usenet News is now taking approximately 12 percent of the internet traffic, Web cache distribution will take even more. With a satellite newsfeed the traffic can be transmitted more cost effectively and with less bandwidth consumption. Web cache content distribution via satellite is an extremely efficient application to optimise an existing terrestrial ISP infrastructure. Satellite broadcasting is not exclusively used to distribute content on the internet. A further solution to optimise the bandwidth utilisation of ISPs with IP-Broadcasting is the use of a shared IP-Hub-System. Consider the situation which is depicted on the left side of figure three. An ISP has a central IP-Backbone and it serves POPs for its final dial in customers. To provide the highest possible quality of service for our customers, a burst capacity of 2 MB download capacity is necessary for each POP. In this case a terrestrial solution would require the installation of n 2 MB duplex leased lines to each POP. A more efficient way would be the use of a shared IP-Hub broadcasting system (right side of figure 3). One 2 MB broadcast carrier is located at the central ISP backbone, which can serve all POPs with a maximum capacity of 2 MB. Specific filters are located at the receiver sites ensuring that the particular POP destined data is forwarded inside the POP network. To recognise the return channel, 64 K terrestrial lines are installed from each POP to the central backbone. The greatest amount of traffic from the Internet is routed via the satellite broadcast to the POPs. To optimise the delay of time, critical traffic - such as DNS hook-ups and telenet policy routing - can be used at the central uplink to route the critical traffic via the terrestrial lines with more efficiency. DVB (Digital Video Broadcasting) was originally designed to transport video and TV on a less expensive bandwidth, optimised digitally, using MPEG2-compression. The receiver hardware for this technology was developed for a mass consumer market and is therefore relatively low-priced. The DVB-equip-ment was also optimised in terms of the receiver parameters ensuring that inexpensive and small receive-only antennas can be used on the remote sides. Throughout the growth of the IP market it became more and more attractive to integrate IP into DVB. Today, many vendors provide DVB compliant PC cards and set-top boxes for the transport of IP. Currently, operators and ISPs are not only using DVB to deliver high-speed internet access via satellite to the final customer, but is also being used for the extension of their existing ISP infrastructure. Return channels are realised via the PSTN or terrestrial ISP network connections to draw the data from the internet. Since this technical approach benefits from recourse sharing at a central broadcast uplink station, the bandwidth utilisation is optimised and cost-efficient. Additionally, it benefits from the MPEG2-compression and inexpensive receiver hardware developed for a mass consumer market. Internet Access Gateways Internet access gateways are critical to utilisation by ISPs of central access points to major world markets. DeTeSat, for example, has three Internet Access Gateways in Germany and the USA. Connections in Germany are to the respected Deutsche Telekom network, and in the USA to equivalent high calibre linkages. The customers using these gateways are ISPs in Asia Pacific, South America, Africa and Europe, taking advantages of a powerful, direct Internet access to the North American Internet Backbone. Conclusion: Customer Solutions for ISPs T-SkyNet Internet & IP Services offer the full spectrum of customised ISP-solutions, such as dedicated backbone or trunk access, hybrid solutions and specific customer solutions. Uplink equipment fully independent from access gateways can be provided at customer's own locations. Network engineers can help the customer to develop hybrid solutions and integration concepts for his network infrastructure. Service providers offer the opportunity to share infrastructure resources and allow co-location space at the various gateways in the United States and Western Europe, where customers may rent rack space to locate their servers and routers directly to the backbone, also providing remote management access for the co-located equipment. The previously described IP-multicast applications, such as, File, Usenet News, Web cache content and streaming data distribution, are available at many gateways.