Redundancy and reliability PRI vs SIP

We have numerous issues lately with TimeWarner/Spectrum’s PRI. But, all the research I’ve done, and what sales & technical people tell me is that a PRI is still more reliable than SIP. I wanted to ask everyone here what they experience and what they recommend ?

Today the issue is inbound DID is not working - and it’s definitely on the provider’s end.

TW sells you a PRI over SIP over a cable modem.

Thanks a lot of hardware to make PRI work. SIP is simple. can you ping
Yes, Then you have dial-tone

How much will it cost you have a backup PRI from TW. 300.00 or more a month.


I didn’t give all the details.
The first issue we had in April, was a ‘nation-wide’ PRI issue with many (all) of TW/Spectrum customers. so inbound & outbound was not working.

today, the issue is just us (that I know of), with inbound DID numbers only - it’s a simple programming error on their end - but it’s taking them forever to fix it.

PRI technology is ultra reliable…but reliability of the provider is a different story.

There are trade-offs on every aspect of a setup like this. Price, for example, is an order of magnitude higher with PRI (cards, setup, monthly), but it generally considered a superior connection. On the other hand, you are limited to 23 inbound + outbound connections at a time. Adding additional capacity comes at a price, as does the ability to call long-distance.

On the other hand, VOIP (in general, and SIP is included in that) is generally cheaper. In many markets, VOIP is delivered on cable TV or on a DS1 (24 channels of data service on, effectively, a PRI). How the service is delivered to your demark will be the determining factor for how much you have to spend. Internet service delivered over a PRI/DS1 line will be the most expensive and be limited to 1.5Mbps. It will also be the most reliable. From there, the delivery system and speed can vary widely, with similarly wide variations in price and reliability.

The other thing to consider is that, if you are using PRI, your phone service provider is the guy that sold you the cable. With VOIP, you can access an entire marketplace of vendors trying to sell you VOIP services over your Internet connection (or connections). The reliability of these guys varies crazily from vendor to vendor. Their ability to provide high quality services is limited by their expenditure on equipment and their access to higher level PSTN vendors.

I just finished up a project for a company here - I told them I’d cut their bill in half and they scoffed. Their $1000+ a month phone bill went down to about $200 a month, and now they can make more than four phone calls at a time. They, like you, were concerned about reliability, so we put in two cable provider’s Internet and set them up with two VOIP providers. If any one of those goes down, everything automatically rolls over to the other. They have a single server that backs to a “warm” backup that they can turn on and replace their live server in a short few minutes.

So, it all depends on what you’re looking for. If you’re a 911 call center, you just have to build in layers of support and choose your technologies carefully. There’s an old saying: “Fast, Cheap, Reliable - pick two.”

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We have Spectrum SIP, and have had them for about 2yrs. We also have them for our broadband. Before that we had MegaPath (Speakeasy when we first started)

For SIP, Spectrum (TW at the time) brought in a separate cable drop and cable modem. This connects to a session border controller that they provided and that is the DMARC. If we were in a Fiber area they would have had a dedicated fiber connection for SIP at the same price, at least that’s what I was told; and our SIP is supported by the Fiber Support team but our cable broadband connection is not.

I like the fact that Spectrum’s DMARC is on our premise and the connection between them and our PBX is on our network. It’s also nice not having to share a connection between “voice” and “data”.

As far as reliability, the first and only issue we’ve had was back in April, and it may be the same overall issue you were talking about. Inbound and outbound calls were spotty for about an hour. I’d say 50% would go through.

On the PRI side, I know someone with an AT&T PRI (several probably) and they had a serious outage in late April / early May that lasted for most of a day.

In your case you most likely will have zero advantage with a PRI vs SIP.

That’s because TWC’s PRI is SIP backbone, which means that with PRI they are giving you nothing but a SIP trunk to a PRI gateway at your site. That’s their demarc.

So on their end the technology is identical, they are just giving you a PRI handoff instead of Ethernet.
Spectrum PRI would then only make sense for legacy, non SIP capable PBXs or if you prefer PRI pricing model over SIP, cause they can differ very much.

Haven’t talked to TWC since they became Spectrum, but last I did this was the case, at least in my area.
Ask them if their PRI is SIP backbone or not. If that’s the case, no advantage for you with one or the other technology when it comes to reliability.

Of course there are still other providers out there still sell true traditional PRI, but that’s becoming rare.

So if your problems lie with the provider, you should have the same problems even if you had SIP trunks with them.

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we have 200 DIDs at one building for voice.
maybe we should consider, having more than one provider, and putting half of DIDs on each, and maybe also splitting up the outbound trunks between 2 or more providers ?

I know with local DIDs, it seems cheaper to NOT port them to internet based SIP providers, so maybe keep the DIDs on 2 of the local CLECs on PRIs, and use SIP for outbound ?

just thinking of various options.

PRI much more reliable as long as you get a TRUE PRI. The only folks that can provide this at least in my area is the phone company. Even then you still have to make sure they are quoting you a traditional REAL copper PRI.

SIP provides more flexibility and is very reliable as long as you have a quality provider that has redundancy. I would suggest 2 internet connections at your servers location to provide yourself redundancy.

Get SIPSTATION. TW PRI is garbaggio. Usually not even true. It’s way more reliable and better quality.

Don’t agree with that statement and doesn’t make much sense comparing apples and oranges.

The quality of Sipstation or any other VoIP provider will also depend on the reliability of the circuit they’re running on, your ISP, and what’s that gonna be, Time Warner?

I have found TWC business class products to be fairly ok. I rarely have call quality issues.