2002 - cesnet

4.2.2 User InterfaceSubscribers (members and directly connected participants or their branches)connect to PE routers or CE routers. CE routers may not provide full services(e.g., VPN) and are connected to a single PE router. More CE routers may beconnected to the same PE router. CE routers may be connected to PE routerseither locally or at longer distances (approximately up to 100 km).4.2.3 Changes in Generic StructureThe generic structure is a stable characteristic of the network. Changes in thegeneric structure are considered a significant intervention in the network topology,hardware and software, and must therefore be designed sufficiently inadvance (e.g., one year). The following modifications are not considered aschanges in the generic structure: increase in the number of CE routers, PE routers,deploying multiple accesses for PE routers, increase in the number of backbonerings or an increase in the number of P routers (however, not exceedingfour in one ring). The acceptability of such changes is particularly an economicaspect.4.2.4 Application of R&D ResultsThe generic structure makes it possible to evaluate new types of routers, circuitsand other devices (e.g., optical amplifiers) in the real operation. This ispossible in nodes connected via an alternate route. Particular procedures arespecified according to an agreement of the operating staff and researchers.4.3 Deployment of Generic StructureAfter reaching an agreement concerning the generic structure of CESNET2, wealso agreed on the procedures for its deployment. For the target stage to bereached in 2003, see Figure 4.4.The aforesaid modifications of the topology may be carried out using the existingGSR 12016 routers as backbone routers, and without having to purchase anymore costly OC-48 cards. The backbone lines to Ústí n. L. will be based on theGigabit Ethernet.High-speed National Research Network and its New Applications 200245