Trunks vs calls vs call paths: all different right?

I’m trying to get info from a supplier and they are insistent that a trunk is a 1 to 1 with a call:
he said:

A SIP Trunk from any provider is one concurrent call. Simply put a trunk is a call path, so one trunk would always be one call. Now I know there are some providers who package things as to make it seem as though a trunk can provide than one call, but a true trunk is only one call.

Now I’ve got a few providers I’ve worked with where that doesn’t appear to be the case (or maybe I’m reading it wrong, or my terminology is wrong). But IPcomms’ free service is a 2 line trunk. And allows you to set up trunks with up to 25 calls per (so I can set up trunks on two different servers with them, and route to either one). But am I misunderstanding the usage? I believe SIPStation has 1:1. Basically a trunk can have multiple channels (calls), but the trunk is the same, and there only needs to be one.
We work with a lot of places that have 3 phones in active use but need 50 phones around (for guests and occasional conference calls). So we want service that scales- needing to pay for each concurrent call every day of every month makes SIP cost prohibitive with some vendors. But if there is a flex arrangement, then we can make it much more cost effective.

What am I missing? Or do I need a new supplier?

In the VoIP world there is no defined meaning of the word trunk.

As you have seen, some voice service providers call each call path a trunk and charge for that, with others you can have as many concurrent calls as you want on your “trunk” and they charge by the minute or give you a package of call paths and minutes.

That’s all good, just do the math and look at how many call paths you need and how many call minutes per month you will have and then look at different providers.
How they use the word trunk doesn’t really matter.

I’ll bet “Srinagar, the state capital” has more than one phone line. Hard to argue with 15 years of use that a phone “trunk” is explicitly only one “line”, AT&T certainly wouldn’t agree.

The issue I’m running into (and why it does matter) is that the vendor who is supposed to be looking at service options for me doesn’t seem to actually know. So when I tell him I’d like a “multiple call trunk paid by the minute”, and he says “well, you need one trunk per call” we have a disconnect. I know what I want, and the difficulty with the disconnect is that the 1:1 setup requires you pay based on potential needs, not actual needs. If I have one conference call a quarter and need to have 15 external callers, this vendor would say I need 15 “trunks”, and is ignoring the much more cost effective options.

And actually, since you are only setting up the trunk once, what you are probably getting is actually 1 trunk with 15 channels.

I actually went into the FreePBX interface for trunk setup, and it allows you to set the number of channels to limit the number of calls. But I’m guessing that most SIP providers who charge by the trunk are simply setting that number to “1”.

There was recently a thread here (that I can’t find at the moment) started by someone who wanted thousands of trunks, and the conversation shifted “do you mean Trunks or do you mean Calls” along with some other info. I didn’t read it all the way through, but that seemed to support what I’m saying.

@demani I’m not sure where you are located but in US/CA a “trunk” in Telephony is the sames as a trunk in most other senses (like network). A single link between two endpoints that can support multiple “paths”. For the most part T1/PRI’s are trunks. A group of DS0 channels that go between point A and point Z for calls.

SIP sheds the physical limitations of a T1/PRI and thus there are no real “channels” to contend with. Since most LECs/carriers base their pricing how many “channels” and that may or may not be “unlimited” as many still charge for outbound calls. The channels just limit how many of those calls you can have but you’re still charged per minute. In most cases LECs/Carriers still follow that logic because SIP just is the way the calls are delivered. You can still have a “24 Channel” SIP Trunk to replace your PRI/T1 lines.

If you go with a local LEC that’s probably what you’re going to end up with. If you go with a company like Flowroute, Twilio, Vitelity, VoIP Innovations, etc. Those are ITSP’s which deal in SIP only services and don’t care about “channels” (they will give a hard limit to prevent abuse) but they only care about how many minutes you use because that is how they charge you.

Anyone else is most likely a wholesale/resale/MSP still provider and things like 1:1 trunks is probably due to how they get their services delivered from a higher tier or how their systems are set up.

For what you are looking for, look at an ITSP vs a LEC style provider.

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