IP Telephony Accounting and WAN Deployment Experience Sven Ubik

CESNET A not-for-profit organization for development and operation of Czech NREN 2.5 Gb/s backbone (CESNET2 network) Member of Géant and TERENA Partner of Internet2 Gigabit network testing laboratory

Project goals Interconnect PBXs of largest universities on CESNET2 network Create VoIP testbed (e.g., for QoS for VoIP tests on a real WAN network) Reduce cost of telephone calls between interconnected universities and to PSTN Develop means for statistical measurement of VoIP traffic allowing optimization of PSTN / mobile phone gateway locations Phase 2: QoS tests, IVR applications

Pilot project

Current VoIP network

16000 users 11 voice gateways (Cisco) 9 PBXs (Erricson, Siemens, Alcatel, Matra) PSTN / mobile phone network gateway Connection to CERN, Switzerland (Bremen and Hannover, Germany) Mostly H.323

Statistical measurement - features Flexible accounting plans and using multiple accounting plans in parallel Output at different levels of aggregation Modular architecture - using multiple protocols for gathering call data Based on open software Resilience against network configuration changes Recovery from broken and lost call data

Statistical measurement - design 3 layers: Call data gathering (e.g., RADIUS, syslog) Data processing Presentation Where to account calls?

Statistical measurement - architecture Linux MySQL database LDAP authorization

Call legs

Using RADIUS messages Predefined set of attributes (RFC2865, RFC2866) does not contain some important information (e.g., start and end time of a session) 2 solutions: Vendor-specific attributes Overloading of AcctSessionId attribute

Using RADIUS messages (cont.) Vendor-specific attributes h323-gw-id=AS2-OV.ten.cz h323-conf-id=4776D8CD B9A DBD1 74 h323-call-origin=answer h323-call-type=VoIP h323-connect-time=16:17: MET Mon Jan h323-disconnect-time=16:17: MET Mon Jan h323-disconnect-cause=10 h323-remote-address= /10:08: MET Thu Nov /Voice-OV.ten.cz/ D A66029F 042FD97B4/answer/Telephony/ 10:08: MET Thu Nov /10:08: MET Thu Nov /10/ Overloading AcctSessionId attribute

Caching legs Unneeded legs (may be needed later) Broken legs (may be replaced by other legs)

Statistical measurement - summary Using multiple accounting plans in parallel Recovery from broken and lost call data Output at different levels of aggregation Based on open software

Specification of accounting parameters

Example listing

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