2002 - cesnet

Figure 4.3: Situation concerning the regional network in South-Eastern Europe4.2.1 Generic Network StructureThe generic network structure is a model defining the basic types, functionsand methods of router interconnection, within the range of CESNET competences– i.e., routers which are its property or have been leased, lent, etc.Backbone StructureThe backbone is formed by several rings, each with 3–4 backbone nodes(P routers). The number of backbone nodes is limited, particularly due to thehigh price. The access abroad and to CZ.NIX is provided from Prague, where apair of backbone routers is installed in order to increase the reliability.P routers are “dumb”. They ensure just the basic routing functionality, withoutany complicated features. On the other hand, they are very fast and able tocope with a considerable data load.Access InterfaceThe access to the backbone is provided exclusively through PE routers – localor remote (approx. up to 300 km). One PE router can be connected to more thanone P router (if necessary and economically feasible). It is possible to connectthe PE router to P routers on different rings.PE routers provide the “smart” network services, e.g., virtual private networks,packet filtering, etc. They identify datagrams with MPLS tags and prepare themfor fast transmission through P router network.44 High-speed National Research Network and its New Applications 2002