![]() ![]() We called it ENUMER - a portmanteau of ENUM and Emer.Ĭryptocurrencies are in vogue these days, but some of them just try to ride the fad. To overcome the above challenges, we have built a decentralized ENUM implementation based on the Emercoin blockchain. We have seen this happen with, which first forwarded toll-free calls to its PSTN partners, then started sending empty responses, and finally dropped the business altogether, taking all the databases with it. Because “it’s only metadata,” you know?įinally, an outage of the central service results in the whole network’s going down at once. Today it works as intended,and tomorrow it starts forwarding your calls to interesting locations - say, an intermediate VoIP node that can do anything to your data. It doesn’t help that the algorithm and criteria for query resolution are completely unknown. In other words, the credibility of such an ENUM system is limited by the credibility of the organization running it. Indeed, the centralization makes ENUM dependent on the central node, which creates and maintains ENUM records, as well as the DNS server resolving ENUM queries. The above failures are of both organizational and technical nature and come from the service’s centralized nature and the obscurity of the way it resolves queries. This results in denials and delays of service and makes the server infrastructure pretty costly. Despite caching by intermediate DNS servers, the load is still high for a server that has to serve all the PBXs around the world. Last but not least, an ENUM server experiences a huge load, having to respond to each IP PBX call.Of course, failures in the DNS system also result in the denial of service for ENUM. As the classic, centralized ENUM system uses DNS transport, it is vulnerable to all kinds of attacks on the DNS infrastructure, including spoofing, hijacking, and the like. ![]() During the last month of its existence, the service stopped giving ENUM responses at all, although it still did contain correct data (we checked). Naturally, this deprived toll-free number owners of any incentives to use it. For example, despite having registered toll free numbers, it landed VoIP data to its partner PSTN providers instead of its subscribers’ IP PBXs, resulting in corresponding landing charges. During its last 2 years of operation it had stability issues and resorted to foul practices. The second issue is ENUM’s critical dependence on a central service, which might work incorrectly or not work at all. ![]() The former use it to provide each other with landing data for their networks, but the latter have no access to it. Some ENUM servers, such as e164.arpa, do linger on, but they are more of an “inter-carrier node” for large and mutually trusted VoIP providers rather than IP PBX owners. Previously there were and, but the former has long gone offline, and the latter has ceased operations in November 2016. ![]() The first problem with ENUM is that there is simply no place for a usual IP PBX owner to register their number(s) and SIP URI(s).Issues with existing ENUM implementations: Seamless and automatic operation with minimum IP PBX configuration efforts.Īlthough ENUM is simple, lightweight, effective, and supported by all the most popular IP PBXs, it did not catch up due to several organizational and economical reasons.Free toll-free calls for the called party,.No risk of service denial due to network overload,.No volume or time limits imposed by the PSTN operator,.Higher data transfer speed and reliability,.Better signal, thanks to direct connection,.If not, it uses the conventional PSTN way and pays the landing fee,ĮNUM favors both the calling and the called party, providing: If such a shortcut exists, Acme’s PBX uses it.During the call, Acme’s IP PBX makes a query to ENUM, trying to find a “shortcut” to Globex bypassing the PSTN network,.Globex registers their IP PBX with ENUM,.In our example above, ENUM works as follows: The ENUM protocol (see rfc6116) acts as a distributed address book that allows finding the path to a certain IP PBX by a telephone number serviced by it. That’s why IETF has developed ENUM - a network protocol that translates phone numbers to paths, or URIs. Of course, knowing all the paths - that is, the whole map of all possible direct IP connections, - is not a cakewalk. This would also improve call quality and reliability, as there would be fewer middle links and hence fewer re-codings of the voice data. ![]()
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