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Don’t Waste Your Money on BYOSBC to Microsoft Teams

At a breakout session in Ignite 2017, Microsoft made reference to a new method of connecting OPCH PSTN to Office 365 which was in development. The current standard offering for OPCH to Skype for Business Online Cloud PBX is Cloud Connector Edition (CCE). CCE is an on-premises hardware appliance (I use the term liberally) that connects one end to your PSTN SBC and the other to Office 365 using Skype for Business Hybrid to all intents and purposes. This solution wasn’t the most elegant and there were many hidden costs involved, such as demanding Windows Server 2012 Datacenter licensing and some beefy hardware to run the full-fat CCE appliance. You also needed to invest in a SBC anyway, although technically CCE could be connected to the likes of Cisco CUCM but that configuration isn’t the most desired from a supportability standpoint. Some vendors like Sonus and Audiocodes came out with various solutions that combined SBC and CCE into one hardware unit. Each solution served a purpose and it was a means to get OPCH connectivity into Office 365. However, as you can imagine the uptake on CCE deployments wasn’t as great as probably Microsoft had hoped for. Coupled with the decision change at Ignite to focus cloud efforts on Microsoft Teams, left many customers looking to move to the cloud, or recently invested into Cloud PBX with CCE in dismay.

Anyway, it was hinted at Ignite that there would be a simpler solution coming in 2018. Rumours were that it would be a BYOSBC solution that removed the dependency on CCE. Well it seems that at various Microsoft Tech Summit’s this year that appears to be the case, that Microsoft will let you connect your SBC directly to Office 365 and more specifically Teams.

As we can see here from this picture of a slide from Tech Summit (Credit Paul Lange), Microsoft have designed a topology that allows this direct SBC connection to the Microsoft Phone System. This is not something new really if I am honest. It’s a similar method that currently allows you to connect your on-premises Cisco / Avaya solution to Exchange Online UM for voicemail boxes.

I don’t have any information on this topology at the moment, but I will bet my house on it that the connectivity will be somewhat similar to what we do for Exchange Online UM and an SBC today, i.e. SIP trunk over TLS to Exchange Online UM public endpoint and using some kind of gateway configuration in Office 365 to tie the SBC to the tenant. In theory any current supported SBC (Sonus & Audiocodes) in Skype for Business should be able to leverage this new service, but this has yet to be confirmed. Furthermore, anyone who has purchased SBC with CCE integrated appliances should be able to continue to use the SBC element, albeit the investment in the CCE element will no longer be leveraged. Again, educated guess, but confident this is accurate going by the above schematic.

So, my advice for those of you with these investments already, hang tight and wait for release. You’ll probably find that your device will support this topology.

However, there may be considerations for hardware. Currently SBCs using CCE don’t have to do any audio transcoding, instead the mediation server on the CCE will perform the transcoding between PSTN codec and Skype Enterprise Voice codecs, unless of course you have taken advantage of Media Bypass in the later versions of CCE. But assuming not, and your relying on the out of the box config, then your SBC may be under powered. Why? Well the above schema does not show an on-premises mediation server. So consider the scenario where you have on site users using Microsoft Teams with PSTN calling. Teams to Teams audio will try all local routes before breaking out back to Office 365. But a PSTN call has to go via a media server. Without Media Bypass, this means the PSTN call’s media will travel from the SBC to Office 365 and then back to the local site where the callee using Teams is located. This is tromboning of the internet is something Microsoft have campaigned hard to avoid with Skype for Business Online and therefore we should expect that when this solution is released, Media Bypass should be the out of the box, preferred solution to prevent this tromboning of the internet.

With Media Bypass, it would allow the Microsoft Teams client to send it’s signalling via Office 365 to the SBC, but the media establishment would be direct between the client and the SBC. This means that we will be expecting the SBC to work harder, transcoding media between Teams and the PSTN, rather than offloading that to the mediation server of old. Media transcoding on a SBC is performed by DSPs or Digital Sound Processors. DSP’s are essentially like CPUs and in the same manner of CPUs, each DSP has a maximum throughput, meaning a maximum number of media streams it can transcode at any one time. With Skype for Business and CCE, this allowed you to buy relatively entry level SBCs with 1 or 2 DSPs, because you didn’t care as Skype would handle it. In the Teams world this might not be the case, and you may have to replace these SBCs as invariably adding DSPs to a chassis is not a field serviceable option.

So why have I titled this “Don’t waste your money”?

Consider the wider picture. Microsoft is allowing direct SIP trunk connectivity to Office 365 that allows you to Bring Your Own Carrier (BYOC). It essentially allows you to choose if you want Microsoft to be in charge of PSTN call delivery and billing, or another provider. If I was a certified SIP trunk provider e.g. Gamma and PureIP for example, I would be working hard to offer direct SIP trunk connectivity to Office 365 as a package deal. This would essentially remove the need for on-premises hardware, risk and maintenance overhead and still allows the company to take advantage of fair market competition, while adopting Cloud Only.

I think this option if it comes to pass is an amazing opportunity, it opens Office 365 to competition and stops the Microsoft Cloud only monopoly of calling plans and allows you to make a decision on which carrier to choose. It also helps Microsoft deliver a global PSTN presence for Office 365, something that they’ve struggled with themselves due to regulations of each country. So instead of waiting for Microsoft to release PSTN calling in Singapore for instance, you potentially could just use a provider in Singapore and hook Office 365 straight up to the PSTN network there and away you go. It’s truly an amazing opportunity that opens the cloud up to coverage, scale and competition. It’s going to be a fantastic market!

Obviously, there are going to be some scenarios where you will have to have OPCH in some of your sites, PRI connections for instance, although, why not move to SIP if you can? Call center integrations or 3rd party PBXs and analog devices.

I am looking forward to seeing how this develops, it makes total sense from my standpoint, and was the first thing I said when CCE was release, was Why? This solution should have been the one deployed from the outset. When this comes in later this year, I expect to see more adoption and less resistance to enterprise voice in the cloud. I can’t wait! All that needs to happen now is for the Microsoft Teams Team to focus on getting enterprise voice feature parity with Skype for Business by the same time and I am sure it will be Microsoft’s finest moment yet. That said, there is no reason why Skype for Business Online users couldn’t leverage the same architecture? But, Let’s wait and see…..

Sorry for the clickbait title…. 🙂


    • Teams should use PSTN friendly codecs G.711. Therefore transcoding may not be needed. But in regions that may not use G711 on the PSTN, transcoding will be needed. Its simply a cost of DSPs not a licencing cost

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