Everybody uses everybody in the arena of SIP Least Cost Routing (LCR). This spiderweb of interconnected carriers does fantastic things for the cost of communications by driving down the cost of goods for telephone minutes.
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I’ve always said if you look at the declining cost of communications over time and during different technological eras, every time a new innovation in the communications realm becomes more affordable it allows more people to adopt it and our population’s education level increases drastically due wide spread access to information.
Disagree? Look at the affects of the Newspaper, Telegraph, Telephone, Television, The Internet, Cell Phones, I could go on and on. The fact is that when each of these technologies received mass market acceptance, the education level of the populous jumped forward.
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Back to my proposal. Due to the number of carriers in the space (very low) ultimately LCR engines overlap causing loops in call attempts. Example, I send a call to AT&T and they 503 the call due to network congestion or they don’t support the ratecenter I’m calling. I route advance in my LCR, and send to “Bobs CLEC ITSP in a garage”, Garage boy is also interconnected with AT&T and decides that’s the best route to send the call, again resulting in a 503. This illustrates the problem I’m discussing, the fact that Bob’s ITSP didn’t know that I already tried AT&TÂ results in a looping affect.
I’d like to propose an amendment to the SIP RFC 3261 or a new RFC all together that creates a public registration number for each SIP provider, similar to an ASN in the IPv4 space. The RFC would outline support for either a new sip header or an addition to one of the existing headers, that would allow SIP proxies and B2BUAs to populate a list of carrier registration numbers already tried for a particular call attempt, allowing the next carriers’ LCR to filter out those carriers when making the next LCR decision to avoid overlap and looping.
