EUMETCast Terrestrial Service

Created by Ben Loveday
Last updated: 19 Aug 2021 by Klaus Peter Renner
2 min read

EUMETCast Terrestrial Service

EUMETCast Terrestrial Service

The dissemination of multicast data through terrestrial networks – instead of uplinking to satellites - currently relies on the infrastructure provided by GÉANT and providers of national research networks (NRENs) globally, GÉANT network in Europe and the global connectivity of GÉANT to other continents. The worldwide connectivity offers the possibility to an extensive geographical reach of the EUMETCast terrestrial service. The overall principle for EUMETCast Terrestrial is to have a single data source where files are encoded into a multicast stream and then transported to the user via a multicast-enabled dedicated network based on Source-Specific Multicast (SSM) service model.

The terrestrial service will re-use components familiar to users of the EUMETCast satellite service and then, as for EUMETCast satellite, subscribes to the related multicast channels to receive the data (figure 7a).

EUMETCast Terrestrial mainly relies on native multicast. However, in those special cases where an NREN has not yet enabled native IP-multicast support, GEANT is able to provide GRE tunnel concentrators located within their infrastructure to which the end-users can initiate a GRE tunnel connection from their EUMETCast client.

The GRE (Generic Routing Encapsulation) tunnelling protocol was developed by Cisco Systems for encapsulating a wide variety of network layer protocols inside virtual point-to-point links over an IP network. GRE tunnels are used here to encapsulate the IP-multicast streams and transport them over a routed IP-unicast connection.

GRE tunnels build point-to-point TCP connections from the GEANT concentrator directly to the reception station. GRE tunnels are also used as a backup path to address temporary loss of native multicast to end-users and overcome islands of non-multicast enabled networks. The back-up GRE tunnel is manually activated when a temporal loss of multicast is detected.

 

More detailed information can be found via the links below;

Figure 7a: EUMETCast NREN GÉANT data flow

 

Figure 7b: GÉANT Global connectivity

Figure 7c: The European Network connectivity of GÉANT 1

Credit GÉANT for images, full resolution network maps are available at https://www.geant.org/Resources#maps