What Really makes VoIP Networks Tick?

December 27th, 2007 by Chris Maxwell

VoIP is Tricky. While we’ve come a long way in just a few years and have seen great technological change and mass acceptance happen relatively “overnight” compared to the prior industry changes, we still have a few things to settle.

I spent much of 2007 in a unique position that provided an incredible view into the emerging VoIP Market.. I started a large scale carrier review to find VoIP capacity for the Voxeo Network. Voxeo is a SIP based platform, therefore - it speaks native VoIP. Any other transport medium (TDM) apart from VoIP that terminates into our platform must be converted to VoIP so we can receive and send calls. This is a relatively unique (and fortunate from our perspective) requirement, and it has enabled me to embark upon an epic quest to seek out Carriers of all kinds in an effort to acquire “VoIP Minutes” for our platform.

Essentially, in early 2007 - I began my journey by seeking out every major carrier in an effort to find out where they were with VoIP - and how I could acquire services and minutes from each carrier.

I began with the major players, AT&T, Verizon, XO, Qwest, etc.. and moved on to regional players, “B” grade carriers, Resellers, Garage Telco’s, as well as new and emerging Hybrid and pure VoIP carriers and Peering Players. Some of my exploration has taken my studies overseas to look into the International market.

My Journey was (and still is) filled with drama, adventure, deception, hope and dashed dreams - and of course humor.. in short - it’s been quite a task to really get the true answers on 1. availability. 2. capacity. 3. potential expansion capability. 4. pricing (oh boy - that’s a saga..) 5. platform architectures 6. feature availability and 7. standards and compatibility.

In future blogs I’ll go further into these adventures, but I’d like to begin this saga by describing the exact treasure it is that I have been seeking. Is it minutes? No. Ports? No. Is it concurrent calls? No. Is it Bandwidth or capacity? No.

The real “prize” that allows a carrier accept calls in a robust fashion is something often overlooked by carriers and IP Switch vendors alike. It is “Call Setups Per Second”. In the modern world - automated devices such as the Voxeo hosted network don’t have a problem receiving or making calls, but VoIP resources which receive and handle all these calls - are right now (in 2007-2008) - limited.

Call Setups per Second is the ability of an IP switch to process multiple calls initiations while handling other processing functions required by the device. In short, there are vendors that do this well, and vendors that do not. The ability of a VoIP network to handle vast amounts of VoIP calls often comes down to 1. the device that is handling the traffic and 2. the number of Call Setups per second that this device can process.

There are other variables that affect performance of IP Gateway and IP Switch devices such as call duration, and Codex used, and eventually - final destination of the call. However - the blocking factor of any inbound call to an IP Switch usually comes down to the Call Setup Per Second threshold.

So, CPS is the “Golden Egg” that I’ve been looking for from all of the major VoIP carriers.. Calls per Second. Ultimately - how each of the carriers that I’ve reviewed have responded to the test for this “treasure” has allowed me to measure the capacity, durability and scalability of their VoIP networks.

The big surprise - which brings me back to my opening sentence (VoIP is Tricky) - is that each Carrier has designed and built their network in very different ways, using different technology, and often operating on very different principles of functionality. Sometimes - the big guys got it wrong and the little guys got it right.. sometimes the choices made by “folks in the know” were surprisingly short-sighted and placed very limiting restrictions on future build-out. The fun part of all this, has been figuring out from the the classic analogy of the can of Crisco shortening- that the pie on the front of the can isn’t really what’s inside. ;-)
Chris Maxwell

2 Responses to “What Really makes VoIP Networks Tick?”

  1. Dustin Says:

    Great post Chris. Do you have any preliminary results from your research? We are evaluating vendor switches, add-ons, etc for our premise environment. Our primary concern is cost of course, but your CPS metric will now weigh heavily on our decisions.

  2. Larry Says:

    Interesting. I would have expected that CPS would have at least figured into DOS planning. It certainly makes sense. As my “data” guys keep harping, bandwidth is not an issue (of course, I’m focused more on the LAN environment). Since most of the traffic is peer-to-peer once the call is in progress, so call setup should be the principle load on the IP switch. The limit on the switch would naturally show up in the CPS.

    Simple, once someone shows you the way! ;-) Thanks.

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