2002 - cesnet

5.2.1 IPv6 Network TopologyFor the scheme of the IPv6 backbone network by the end of 2002, including theinternational circuits, see Figure 5.1. Eight nodes of the CESNET2 network arelinked.The logical structure is formed by IPv6 tunnels over IPv4, which, however,copy to a maximum extent the physical topology of CESNET2. In most nodes,the IPv6 router is directly connected to the IPv4 backbone routers and tunnelsusually correspond to the physical circuits of CESNET2, leading from the nodein question. With this arrangement, the transition to an IPv4 and IPv6 network(with dual-stack routers) will be relatively easy – both IPv4 and IPv6 backbonerouters will merge.TeliaÚstí n. L.LiberecPrahaHradec KrálovéPlzeňASN-XS26-6COMOstravaGÉANT6NETČeské BudějoviceBrnoFigure 5.1: Scheme of the IPv6 backbone network topologyAnother principle of the designed topology of the IPv6 backbone network isbased on the requirement for a redundant linking of each backbone router.This is why there are two large circuits within the network: Prague–Plzeň–ČeskéBudějovice–Brno–Prague and Prague–Brno–Ostrava–Hradec Králové–Liberec–Prague, connected in Prague to two different routers, as indicated in Figure 5.1.Both Prague routers are also the terminal point of independent internationalcircuits, which means that even in case of a failure of one router, both internaland external connectivity is maintained.High-speed National Research Network and its New Applications 200265