We are directly using the LRZ telephone system, which is based on the Asterisk PBX software. Outgoing calls to non-special numbers are routed via the DFN to its connection with the Telekom in Frankfurt, from where we pay "Ortstarif" for all national calls. International calls are discounted by 80% relative to the normal Telekom end-user rates. Special numbers are routed locally via m"net. In principle the system can also handle pure VoIP connections, however, few commercial VoIP providers allow such connections to their customers (f***ing bastards).
The nice feature of having VoIP-based telephony at the cluster is that it does not matter where in the world the telephone actually is located, as long as it can connect to the LRZ via the Internet. So you can use your office number even if you are at a conference in Brasil, e.g. to make local calls from Garching with no (big) costs. These connection are not encrypted, so if you care, use a VPN tunnel to the LRZ before starting the Softphone.
One thing to keep in mind, though, is that the TUM administration is actively fighting against VoIP on their premises, presumably because of exclusive contracts with Siemens and/or Telekom. Therefore, the fact that we have VoIP at the cluster is a special privilege. Also, we are the first "customers" of this new LRZ service, which they did not intend to offer to the outside yet. Therefore, some things are still in a beta stage, and others need some patience. So, keep in mind that the LRZ is simply being nice to us here.
Analog Backup Line
In case the VoIP telephone system fails, we have two connections to the analog IPP telephone system:
- the fax in the printer room (tel. 3299-4002)
- the fax printer and one telephone in the secretariat (tel. 3299-4003)
The telephone numbers are consequently from the IPP block. Currently the telephone is still missing, to be installed by IPP (contact: Hackl).