Deutsches Elektronen-Synchrotron DESY
Sergey F. Berezhnev, Dmitry A. Avdeyev
Nuclear Physics Institute, Moscow State University
A combined satellite/microwave network has been set up between three High Energy Physics institutes in the Moscow region and DESY. 2 Mbps microwave links are used for Moscow local loops. The hub is connected to DESY via a 256 Kbps satellite channel .
A combined satellite/microwave network has been set up between three High Energy Physics institutes in the Moscow region and DESY.
Previously, access from these institutes (ITEP - Institute of Theoretical and Experimental Physics, the Lebedev Physics Institute of the Russian Academy of Science, and NPI MSU - the Nuclear Physics Institute of Moscow State University) was only possible through a terrestrial line running at 12 kbps.
The Radio-MSU network (Fig. 1) uses a Russian satellite to link up DESY and NPI MSU at 256 kbps. The tower of Moscow State University is used as a radio tower for three microwave links running at 2 Mbps to ITEP, Lebedev, and the Lebedev campus at Troitsk. The end points of the microwave links were chosen in such a way that they act as distribution centers of middle and low speed terrestrial connections. This hierarchical scheme avoids the "last mile problem" since terrestrial connections can be implemented as direct electrical connections within one telephone exchange which permits line speeds up to 38.4 kbps using cheap Russian modems.
At the DESY end, traffic is split between DESY, European HEPnet via CERN, and the rest of the world via DFN (the German Research Network).
All backbones (satellite and microwave) are connected via cisco AGS+ routers (there are 5 of them). Terrestrial lines are linked via Telebit Netblazer rout-ers. The TCP/IP stack is the main network protocol, with RIP, OSPF, and BGP as routing protocols. The network registered domain is Radio-MSU.NET.
Two types of Russian made microwave equipment are used:
Except for the US made satellite modems (Fairchild 2900), Russian made equipment is used:
The Moscow microwave links became operational on October 25, 1993. Satellite channel tests were started on December 14, 1993. Regular operation of the satellite link commenced on March 25, 1994, after the German certification procedures for the DESY ground station were completed.
The satellite modems use Viterbi encoding which produces corrected bit error rates normally below 10 . This is an improvement of at least 3 orders of magnitude over the raw bit error rates. The error rates of the digital microwave links are already below 10 " without forward error correction.
Satellite and microwave link quality as well as IP connectivity between selected networks is monitored continuously by a management station at NPI MSU.
Geostationary satellite links exhibit a minimum round trip time of 500 milliseconds. This should be taken into account by all applications which are normally written/configured for terrestrial environments. Touch typing skills are very helpful for interactive work, especially since round trip times show very little variation.
FTP accounts for the third largest number of bytes transferred, right after netnews and mail. It should be noted that the maximum 16 bit TCP window size introduces a throughput limit for FTP transfers independently of the bandwidth: with a round trip time of half a second, a single TCP connection cannot use up more than roughly 1 Mbps.
At the current link speed of 256 kbps, ftp transfer rates of 16..18 Kbytes/s are observed. This is due to hosts using less than the maximum window size.
The project consists of two stages:
Further development will be pursued in three directions:
This project (*) was funded by the German Ministry of Research and Technology. DESY and DFN (the German Research Network) were tasked with the implementation, with NPI MSU acting as subcontractor in Russia.
Special thanks go to the administration of Moscow State University for making possible the use of the university tower for the microwave distribution system.
-------------------------------------------------------- (*) "Pilotvorhaben zur Verbindung von Wissenschaftseinrichtungen im Grossraum Moskau mit DESY und WiN", TK596-001.