[VoiceOps] Geographic redundancy

David Birnbaum davidb at pins.net
Wed Aug 12 08:56:26 EDT 2009

I think perhaps we're using "interconnection" differently.

Obviously, you can SIP peer and "interconnect" via various IP<->SS7 gateways for 
the purposes of exchanging signaling traffic.  As you point out, there's a whole 
pile of technologies available with various pros and cons.

However, if you want to connect directly to the tandems for the purposes of 
owning number blocks, registering an LRN, porting numbers natively, etc. there 
is no way to do that with IP.  If you buy media gateways to do the TDM -> IP 
conversion, then you are now in the TDM world with all that implies; I don't 
prejudice against running an "IP backplane" with distributed media gateways vs. 
a more traditional DMS or 5E.  That's how I run my network, after all, but 
that's semantics from the PSTN perspective.  One man's "media gateway" is 
another man's switch.  The SS7 call control and the PSTN interconnection are 
already separate.

If you peer with another carrier who does the IP/TDM interconnection at the 
tandems on your behalf, you are still beholden to the actual CLEC that owns your 
numbers.  To me, that's the true difference (which is both technical as well as 
regulatory) between a CLEC and a facilities-based reseller. This may change at 
some point (actually, I'm sure it WILL change at some point) but that's at least 
a couple of years out, I'm guessing.




On Wed, 12 Aug 2009, Alex Balashov wrote:

> David Birnbaum wrote:
>> I don't believe it's possible to interconnect with IP anywhere as a CLEC 
>> since the PSTN infrastructure doesn't exist outside of the SS7 environment 
>> for all practical purposes.  (Obviously, you can peer with IP but that's 
>> not the same as interconnection from a PSTN perspective).
> Sure it is.  That's basically what SIGTRAN is;  SS7 mapped onto IP.
> I don't know if VeriSign still offers their interconnection product (forget 
> what it was called), but it used to be until very recently that you could get 
> them to take your point codes and send you the signaling out the back side as 
> SIGTRAN, over Internet VPN.
> I've seen many DIY switches built that way, usually for cheap CLECs created 
> to support the back side of some VoIP product who don't want to shell out for 
> a real switch.  Common technique there is to purchase a SIGTRAN to 
> H.248/MEGACO and/or MGCP signaling gateway and drive media gateways with that 
> controller.  So, your physical bearer IMTs can come from the local ILEC to 
> your MGWs but your SS7 can come from somewhere else over the Internet 
> indirectly.
> Squire makes a product that does this 
> (http://www.squire-technologies.co.uk/), and I'm sure there are others.  Last 
> I heard none of them do TCAP/LNP yet, though, which is obviously going to be 
> something of a crippling factor if you're interconnecting in a pooling area 
> (most markets at this point).  And I understand them to have other problems, 
> as well.  Nevertheless, it is possible.
> Level3 famously built their own signaling gateway for the Lucent TNT Max via 
> H.248 in their pre-Viper platform, although I do not know whether the other 
> side of that was SS7 or ISDN Q.931 or whatnot.  But it did work.
> -- Alex
> -- 
> Alex Balashov
> Evariste Systems
> Web     : http://www.evaristesys.com/
> Tel     : (+1) (678) 954-0670
> Direct  : (+1) (678) 954-0671

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