Home » Skype for Business » Skype for Business – Is CloudPBX Enterprise Voice?

Skype for Business – Is CloudPBX Enterprise Voice?

With Microsoft’s latest announcement that they are bringing PSTN voice calling to the Office 365 public cloud offering and released tech preview trials in the USA recently has left the industry in a flurry of excitement, rumour and ponder. Partners are hurriedly preparing presentations, marketing material and sales pitches. Customers are beginning to plant the seed for a migration with their finance director and jostling for budget priority. Should we all be in a rush to jump to the cloud? There are a few things that might make you consider your next move. For those of you who read my blog, you may have read this article where I touched on this subject: http://skype4b.uk/2015/04/09/hybrid-or-no-hybrid-skype-for-business/.

Firstly, can we absolutely, without question call CloudPBX Enterprise Voice? Let’s evaluate.

Earlier this week Microsoft announced at WPC 2015 that they would be releasing a new Office 365 subscription plan – E5. This will replace the E4 plan. Details on what this offers you have yet to be published. However I would expect something like:

E3 Plan

  • PSTN Dial-in Conferencing
  • Skype Broadcast Meetings

E5 Plan

  • CloudPBX with PSTN Calling
  • CloudPBX with Local PSTN Calling (Possibly an optional extra)

Firstly, the above licencing options are not official, so please do not use these as gospel. They are what I am expecting, and will update accordingly when we have confirmation. However, let me explain what I mean by PSTN calling and Local PSTN calling.

CloudPBX with PSTN calling means that Microsoft will provide you with the ability to place and receive a call to and from the traditional telephone network using your Skype for Business Online account using a geographical number that represents where you are permanently based. You will also be able to port your existing DDI from you current telephony provider to CloudPBX. This solution is completely hosted within the Microsoft Office 365 datacentres and requires no on premise appliances or infrastructure. In the UK it is looking as though BT and Vodafone are going to be the choice of carriers for CloudPBX and therefore, expect billing to be handled by them. I would imagine that the E5 subscription will not offer inclusive call minutes (maybe some, but not unlimited).

Using CloudPBX in this manner, although gives you the ability to consume and operate the main features of enterprise voice such as call forwarding, hold, transfer and dial tone. Can we actually classify this setup as true Enterprise Voice? In my opinion, no, and here’s why.

When using Skype for Business Online from anywhere, whether it be your company’s head office or your home, your connection is considered to be external. This means that your Skype for Business client will be connecting to Edge servers and reverse proxies in order to consume the features Skype for Business Online offers. So why is this such a big deal and why don’t I see this as Enterprise Voice? In 3 words, “Lack of QoS” (actually its 5 words if you expand the acronym). You cannot guarantee Quality of Service between your Skype for Business client and the Office 365 network because you are connecting to it using consumer grade internet. ADSL, fibre DSL (is slightly better), Business DSL (SDSL), all have bandwidth limitations, peak time congestion and contention using ISP QoS filters to ensure that their exchanges are not overloaded. Your upload speeds are constrained to 50% or less than your download speeds, packet loss due to cabling and congestion, latency due to router hops and ISP filters, increased and variable Jitter. All these are bad news for an audio call. You will also be using the SILK codec which is a great codec by the way, but it does sacrifice some audio quality when networks are bad in order to deliver the data packet to the gateway (SfB FE). So it sacrifices quality audio for almost guaranteed data packet delivery? So what? So, you will experience audio during bad connection times that will sound as though you are hearing the other person talking to you through water, or appear long distance and even sound like Robocop!

Once your data packet reaches Office 365 it is then in a network that can be classed as Enterprise and thus Enterprise Voice can be marketed by Microsoft, but your experience is far from it.

Sure, there will be times where you will experience excellent call quality and you will think I am talking complete garbage. But remember this post during times where the call is so bad, you revert to your home landline, or mobile phone. By definition of the internet connection you have you are unfortunately bound by these and therefore I would not classify this option as true enterprise voice.

CloudPBX with Local PSTN Calling. By this I mean your Skype for Business Online users will be able to place or receive a call to and from the PSTN using you’re existing on premise PSTN gateway. This means you do not have to worry about porting numbers from your existing telephony provider, or get locked into un-negotiable pricing contracts through Office 365 for your calls. Simply connect your gateway to Skype for Business Online using SIP TLS and SRTP and you have enterprise voice in an instant. Or do you?

Again, the connection between your local PSTN gateway and Office 365 will be over a standard internet connection. You may be fortunate to have a 100GB connection to the public internet, but you still cannot guarantee QoS. I admit, with 100GB do you really need it? Maybe, do you know your current peak time throughput?

Taking into account how users connect to Skype for Business Online will not change. They may go down the same internet pipe as the SIP trunk. They place a call and the data packet comes straight back down the same internet connection to your local gateway and out to the PSTN, you could soon find that the connection will get congested. Hopefully, Microsoft will make Media Bypass a feature of CloudPBX so that we can mitigate the congestion by only sending signalling across the internet and all media will be local (when calling from an internal client). External users of course will be first traversing their basic connection to Office 365, down to your PSTN gateway for both signalling and media so that’s a bandwidth consideration to keep in mind.

Based on this evaluation, is CloudPBX with local PSTN calling true Enterprise Voice? – Not quite, but….

There is light at the end of the tunnel. You can have true Enterprise Voice using CloudPBX of any variation with Skype for Business Online. Hooray!! How? Simple, purchase Microsoft Express Route and all your QoS worries will be over. Using Express Route will enable you to direct Office 365 and Azure traffic directly from your WAN to the Microsoft network using an MPLS type connection. Express Route is available at speeds of up to 1GB/s guaranteed, ultra-low latency connectivity that can be fully configured for QoS. Now users from within your WAN can use Skype for Business Online with CloudPBX (any flavour) as true, enterprise voice with the same guarantees as if you were deploying Skype for Business on premise. There is one downside though, it’s hellishly expensive: http://azure.microsoft.com/en-gb/pricing/details/expressroute/ £7K+ per month for 1GB/s premium connection, only the most affluent businesses will be able to afford.

Whilst I do not doubt that CloudPBX will be a massive success for Microsoft and it will be something I would recommend for certain business cases, you should be careful in making this your defacto choice for a Skype for Business Enterprise Voice deployment. Make your customers understand the requirements, understand the limitations and understand the risk. If they accept all these, then CloudPBX is the future, if not, then Skype for Business Hybrid is the way forward.






  1. Thanks, Andrew, whilst I agree with what Microsoft are trying to achieve I think we should be very careful in how we propose that to a customer once we have scraped away all the marketing hype. Probably this post hasn’t done me any favours with Microsoft, but I believe in honesty.

  2. Hi Mark

    Great article, interesting read.

    I work for a German based Cloud Telephony company and we are offering enterprise telephony through Skype for Business with full PBX features. Have a look at our website and happy to talk if you have questions.


Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: