RFC 6913 Support Now In BladeWare (Release 2.6.0)
As you may know, Smart FoIP’s patent-pending technology corrects the two biggest Fax over IP (FoIP) problems inherent in SIP-based carrier networks: no more late-T.38 reINVITE problems; no more PCM clock-sync problems causing G.711 pass-through failures. But what about the third big problem: less-than-optimum call routing by the carriers?
You may be aware that in carrier networks, nearly always a fax call begins as a voice call, typically G.711. Other than V.34 calls, the called gateway is responsible for detecting that the called endpoint is a fax terminal and to send a T.38 reINVITE to the calling gateway or server. Obviously, all of this happens after the call has been routed. So, if you’re a service provider or carrier, how can you take control of the routing to get beyond that “less-than-optimum call routing”? To do so, you must determine which calls are likely to be a fax call, and route the call over an IP-only route if possible, at least until it arrives in the called terminal’s local area. And that’s not always simple since the access provider is rarely responsible for end-to-end routing.
But a good start is for the service provider to provision the subscriber’s fax number for that special routing. Often, a subscriber is more than happy to pay a little more for a FoIP trunk that performs since his alternative is an even-higher-priced POTS line. Another approach is for the service provider to apply a heuristic algorithm to the originating point of inbound calls. (If it looks like a duck and walks like a duck, it’s a fax call.)
Yet another way is to support RFC 6913, which BladeWare now does. It turns out that there are IETF RFCs, such as RFC 3840 and 3841, that allow a caller to express routing preferences to the routing entities by using IANA-registered media-feature tags in the SIP Invite. But there was a problem: there was no media-feature tag for “fax” that could be used in the SIP-INVITE header that was registered with the IANA. The solution is the IETF’s RFC 6913, which defines the “SIP.fax” media-feature tag and registers it with the IANA, allowing the originating SIP entity to declare that it prefers a “fax-friendly” route for the call.
You should use a combination of these techniques since RFC6913 is not widely deployed. And you can take matters into your own hands and only deploy fax servers that support RFC6913, then route those FoIP calls over proven routes.
We would be glad to discuss this and any other FoIP issue with you, simply call Commetrex at 1-770-449-7775, and press 1.