2002 - cesnet

the GSR 12016 routers in GigaPoP form an interface between the sparse modefor the backbone and the dense mode, used for the connection of customers.The division of the backbone network into more separate domains enablesmore effective control over the multicast operation within the backbone networkand the restriction of undesirable operation (e.g., filters at the level of theMSDP protocol restrict the Novell NDS traffic, ImageCast, etc.).R44LiberecHradec KrálovéR45PardubiceOstravaR48R32Ústí n. L.R46R32ZlínSW28R50OlomoucSW21PrahaR40R41R42R43BrnoIMBGP RR1R84R21IMBGP RR2R85TeliaR53NIX.CZGÉANTPlzeňR52České BudějoviceRendezvous PointMSDP Mesh-groupDense Mode (MSDP)IBGP, IMBGP, MSDPIBGP, IMBGP, MSDPMBGP, MSDPMSDPFigure 3.4: Logical topology of multicastWithin the backbone network, we make use of the iMBGP protocol with thesame topology as iBGP (we have route-reflectors configured on R84 and R85),together with the iMSDP protocol within the full-mesh topology among all RP(full-mesh iMSDP is configured on all border routers in GigaPoPs). The full-meshconfiguration of iMSDP enables the exchange of SA messages (Source Active)among all iMSDP routers, irrespective of the mechanism of the RPF check.The application of this mechanism with iMSDP was the main cause of multicastrelated problems on the backbone. The core routers lack the routing informationfrom iBGP, concerning the network availability, so the RPF check blockedsending SA messages to other routers.22 High-speed National Research Network and its New Applications 2002