2002 - cesnet

Canarie622 MbpsESNET622 MbpsGÉANT/GTRN622 Mbps2.5 Gbps2.5 GbpsUKATGÉANTITNrouterAbilene2.5 GbpsDEFigure 3.2: Interconnection of GÉANT and North American research networks3.2 Current Situation concerningCESNET2 and its Development in2002We made a change in the physical topology of our backbone network, fromthe star-type to a ring network. All GigaPoPs are now connected with at leasttwo lines. In addition, the number of leased fibres increased. For the currentsituation concerning the physical topology and a summary of the types of datacircuits, see Figure 3.3.The basic transport protocols are POS/SDH (2.5 Gbps) and a Gigabit Ethernet(1 Gbps). As regards the 2.5 Gbps circuits, we make use of leased SDH circuits(Aliatel, Český Telecom), or leased optical fibres, fitted with the Cisco ONS15104 regenerators. We operate the circuits of the Gigabit Ethernet using leasedfibres. In order to increase the operating distance, we are using two differenttechnologies: EDFA amplifier or intermediate L2 switch (Catalyst 3524), fittedwith GBIC-ZX, with a range of 70 km.The use of an intermediate L2 switch is relatively inexpensive; however, itbrings in trouble concerning the switching to the backup line in case of a circuitfailure (this needs to be solved on layer 3). It is therefore not suitable as acommon solution. It seems promising to use EDFA amplifiers at the line ends(without a need for an active element along the line), the use of which is alsoprotocol transparent (POS/SDH STM-16/OC-48 and GE).Along the Prague–Pardubice and Prague–Ústí nad Labem lines, we have beenverifying the use of Keopsys amplifiers, available for reasonable prices. The useHigh-speed National Research Network and its New Applications 200219