The Generic Gateway Reference Implementation
The Generic Gateway (GG) is an ENUM driven PSTN ==> VoIP gateway. Generic in this case means, that it supports various protocols and various number ranges.
Supported Protocols IP:
- H.323 (E2U+voice:h323, E2U+h323, h323+E2U)
- SIP (E2U+voice:sip, E2U+sip, sip+E2U)
- SMTP (E2U+ifax:mailto)
Supported Protocols PSTN:
- ISDN (Primary Rate E1)
- G3 Fax
Supported Number Ranges:
- Any number range that you can route to the gateway (on the ISDN side)
The GG works as shown in the following figure: Calls from the PSTN will be routed to the ISDN interface of the GG. The GG performs an DNS lookup and looks for NAPTR records for the corresponding phone number. If it finds a supported service, it sets up the call to the destination found in the NAPTR.
The GG consists of the following components:
- one or more Cisco AS53000 (or newer Cisco VoIP gateways like 1750, ...)
- one or more Linux PCs
There is no SIP proxy or H.323 gatekeeper necessary. All the VoIP signaling will be done by the gateway. The Linux PC will be used to bypass the limitations of the Cisco ENUM implementation and for storing the accounting CDRs produced by the Cisco gateway.
The following figure shows the “inside” of the GG:
The dnsproxy will rewrite the DNS responses to transform the NAPTRs from RFC 3761 style to the obsolete RFC 2916 style, which will be used by the Cisco gateway as shown in the following figure:
Software:
Most of the software is open source – please refer to the licenses of the corresponding software. The scripts and codes which were developed by us are copyright © Internet Privatstiftung Austria and licensed under the GPL license.
Further documentation:
Generic Gateway Concept (slides, pdf)
Files:
Interoperability Tests:
The Gateway was tested with various VoIP devices to ensure interoperability. There are test protocols for the following devices:
Alcatel OmniPCX Enterprise 6.0 (SIP, pdf)
Although there are no test protocols available, the GG was tested succesfully with the following clients: Netmeeting (H.323), Cisco 7960 (SIP), SNOM 200 (SIP), Xlite (SIP), Windows Messenger 5.1 (SIP)
If you have questions about the generic gateway or ENUM, or if you have comments, please feel free to contact me: klaus.darilionREMOVEME@enum.at