CAPI is an interface for ISDN-applications which is very popular and widely deployed within Europe. Initially CAPI offers a simplified and standardized interface to the ISDN protocol software and hardware below. ISDN and H.323 Call Control are very similar. Both of them are based on the Q.931 protocol of the ITU-T. These common features and ikons experience gained in numerous telecommunication projects, build up the basics for the development of the VoIP-CAPI.
VoIP-CAPI offers to the application the usual CAPI 2.0 interface and appears like a virtual ISDN card for the application, but the transmission of the data (voice, fax) is handled over the IP-Network (LAN,WAN) by relaying on the VoIP standard protocol H.323.
As a result already existing CAPI based voice and fax applications are now able to migrate to VoIP without requiring any changes at the applications itself. The protocol below (ISDN, H.323, etc.) becomes a black box for the application.
Even for the development of new applications the integration of VoIP-CAPI offers crucial benefits. The development process and hence the important time to market are reduced enormously.
VoIP-CAPI offers to the application a CAPI 2.0 interface. CAPI based applications should be able to communicate to VoIP-CAPI without requiring any changes. By attending the VoIP-CAPI partnership program, we guarantee that your application supports the promised CAPI features in IP-networks too.
VoIP-CAPI supports the basic features like connection setup and teardown for voice connections, as well as supplementary features like Call Transfer and Line Interconnect according to the CAPI 2.0 specification.
The VoIP-CAPI additionally supports Real Time Fax over IP according to the ITU-T Recommendation T.38. Thus VoIP-CAPI is the first choice of migrating to VoIP and FoIP, especially in the field of Unified Messaging and fax server applications.
Currently Windows NT, Windows 2000 and Windows XP are supported.
Linux-support for VoIP-CAPI is planned.
Generally VoIP-CAPI does not require gateways from specific vendors. The gateways just have to support the standard VoIP protocol H.323. If real time fax transmission is a requirement the gateway needs to support T.38 too. Currently the VoIP-CAPI passed interoperability-tests with gateways from Cisco and innovaphone among others.
No, VoIP-CAPI is hardware independent. It connects to TCP/IP and UDP/IP ports via sockets. These ports are already provided by the operating systems being supported (cf. above mentioned OSs). The only hardware required is a usual Network Interface Card. ISDN hardware and even expensive VoIP specific hardware are no longer needed.
Yes, please find below a short extract of reference installations. Some of them are already running for more than a year. Our partner Servonic uses a special adaption called "H.323 Connecting Modul".
Company |
Partner/Software |
VoIP environment |
Cema AG, Frankfurt |
Servonic |
Cisco |
Ciba Vision, Grossostheim |
CAE |
Cisco |
EVO-Elektroheizungen, Mietingen |
Colima |
innovaphone |
Getronics, Zürich |
CAE |
Cisco |
Hochschule Bremerhaven |
Shamrock |
innovaphone |
Tebis AG, Martinsried |
Servonic |
Cisco |
Windmöller & Hölscher, Lengerich |
Telindus/Shamrock |
Cisco |
Wolfburg AG, Wolfsburg |
CAE |
Cisco |
Currently the mostly spread standard H.323 is supported including real time fax transmission according to T.38. But even competing VoIP protocols are kept in mind too. If SIP for example should become more and more important the VoIP-CAPI will support SIP as well in the future.
Let us have a short look how migration to voice and fax over IP is done in the conventional way.
The traditional migration of ISDN-applications to VoIP/FoIP causes considerable costs.
First, the costs for the protocol software have to be taken into account (H.323 protocol stack for voice and T.30/T.38 Subsystem for fax transmission).
Second, the protocols have to be integrated and the interface to the application has to be modified for H.323. Up to now application vendors were used to the simplified CAPI interface. Now, for integrating an H.323 stack, additional knowledge of protocol stacks is required. The integration time as well as the Time-to-Market is prolonged, the costs rise.
Third, the migration to VoIP/FoIP causes two interfaces which have to be supported. On one hand the CAPI, to support ISDN applications, on the other hand the H.323 and fax interfaces, to support Voice and Fax over IP.
VoIP-CAPI leads to considerable cost savings, because
In this case the CAPI offers vendor specific extensions (so called Manufacturer Requests). These extension can also be used for future VoIP-CAPI extensions. Especially customer specific extensions can be realized in this way too.
Very simple answer: because it works!
The implementation as a system service based on a user mode process is simpler and therefore the probability of making errors is smaller. If however an error occurs then the system service normally may be restarted as the operating system itself keeps on working. This fault tolerant behaviour guarantees a high system availability.
On the other hand there are no practical disadvantages regarding voice and fax transfer caused by the chosen implementation. At this time our customers operate systems with up to 60 channels which work excellent even when using the Line Interconnect feature. In our laboratory we measured a CPU load of less than 5% running our test application with 100 parallel connections on a 2.0 GHz Pentium 4.
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last update: July-30-2007 |
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© 2007 by ikon GmbH, Ulm |