[VoiceOps] Geographic redundancy

Alex Balashov abalashov at evaristesys.com
Wed Aug 12 02:14:07 EDT 2009

Kenny Sallee wrote:

> On a curiosity note - why would you even need to interconnect with SS7 
> to the PSTN when you can SIP peer to all the major carriers?  There can 
> be an argument for backup to SIP peering that makes sense.  Maybe it's 
> cheaper?  But outside of those what other benefits are there (don't 
> misread my tone here - I'm really asking)?

If you're just an ITSP, you may not need to, strictly speaking.  But if 
you're a CLEC, you do, and the original question seemed to be heavily 
concerned with making CLEC facilities redundant.

Beyond that, it's a matter of opinion.  My experience has been that SIP 
peering isn't terribly mature;  reliability and interop issues abound. 
I've had a number of high-volume customers that gave up and went to TDM 
access circuits after they realised that their top tech people spend 90% 
of all days dealing with SIP issues from their O/T providers.

It's the usual litany of crap.  formatting differences (E.164 vs. 
ten-digit), buggy in-band DTMF, very buggy RFC2833 (out-of-band) DTMF, 
caller ID and CNAM (From vs. Remote-Party-ID vs. P-Asserted-Identity), 
QoS, one-way audio, dropped calls, DSP bugs in ISDN<->VoIP gateways, 
etc.  When they move to TDM these problems seem to magically go away.

But I have other customers that just don't seem to have a lot of these 
problems, either.  It's a coin toss.

Alex Balashov
Evariste Systems
Web     : http://www.evaristesys.com/
Tel     : (+1) (678) 954-0670
Direct  : (+1) (678) 954-0671

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