What to Look for in a Direct Routing Provider

Adding calling to Microsoft Teams, by routing Teams to the PSTN, sounds like a relatively straightforward service. There are plenty of providers out there offering it. But take a closer look at the various Direct Routing solutions and you’ll find that not all are created equal. Not all Direct Routing solutions come with the careful design and expert support you need, if you want a hassle-free deployment, reliable service and flexibility to scale in the future. 

Want to make the right choice, first time? Here’s five things you should look for in a Direct Routing provider…  

1. Knowledge of SIP and running a SIP trunking platform  

It might seem obvious but knowledge of the underlying technologies providing the services is key.  I have seen several (and heard of many more) cases where a traditionally Microsoft house with little or no voice experience has put a virtual SBC in a cloud somewhere, hooked it up to Microsoft Teams and a third party SIP trunking provider and got it working.  

That is the easy part. It’s a few hours work if you can follow instructions. It doesn’t mean they fully understand the underpinnings. This will work until there’s a problem that means you have to actually debug the SIP messaging. Suddenly you’re faced with packet traces, obscure error codes that have been badly mapped from PSTN and annoyed customers.

 You should choose a Direct Routing provider that has proven skills in managing a SIP trunking platform… ideally their own. Running any form of voice platform is a very different problem to managing servers, networks or managing an O365 setup for a customer. 

People are generally tolerant if a website doesn’t load first time or an email takes one minute longer to arrive. They’ll hit refresh and get over it. They are generally much less forgiving if they can’t make a phone call. After all, what if it’s the one time they need to call 999? It needs to work first time, every time.  

2. SIP trunking/connectivity to the PSTN  

This goes hand in hand with the above point. If a provider puts an SBC somewhere and connects the Microsoft Phone System with a third party SIP provider there are a few things to consider: 

  • Who is that third party?
  • Are they a stable business?
  • Might they launch their own Direct Routing offering and where would that leave the intermediary provider?  
  • How is your provider connecting to that third party?

Connecting to Microsoft is internet facing, but they do enforce TLS and SRTP for security. It could be your provider is backing your traffic off unencrypted to a third party over the internet. You’re not taking credit card payments over that, right?  

3. Capacity and scale  

Does the provider have the capacity to cope with peaks in demand? Not just yours but everyone else’s too. How quickly can they react to changes in needs?  That demand isn’t just channel capacity (although that is obviously critical). Capacity refers to everything including network bandwidth, physical and virtual resource, skilled staff to deal with provisioning and support cases.  

4. Redundancy/resiliency  

Does your provider have high availability? By that I mean if they lose an SBC will your in-progress calls seamlessly move over to a standby? Are they geo-resilient? What if they lose the physical location their SBCs are hosted in? The above doesn’t just apply to their SBCs. What about their upstream provider and what about theirs? You need to consider the whole chain getting from your Teams client all the way to the PSTN network.   

5. Number porting   

If you want to bring your existing numbers into your Microsoft Teams platform then you need to port them to a provider offering Direct Routing (or to Microsoft direct). 

Number porting in the UK is a minefield. Anyone that has done any quantity of porting within the UK will know it can be a challenge. Unfortunately, the UK porting system is very manual and old fashioned. I don’t think you will find many people compliment it.  

If you want to ensure your number porting goes smoothly you need to know your provider understands the process, can manage the ports, keep you updated and keep the pressure on the upstream carriers. It takes skill and experience to keep ports on track and even more to get them rectified when things go wrong, which they occasionally do.  

Make sure your provider has a number porting team you can actually speak to.    

Why choose N4Engage?

Here at N4Engage we have run our own SIP trunking platform for 13 years. By our own I mean our own hardware, sitting in our own dual powered racks, in our own data centres, running on our own network. With all of the above installed, managed and maintained 24×7 by our own staff.  

SIP knowledge  

We know SIP, we’ve debugged and diagnosed a vast array of problems over those years and gained huge amounts of knowledge in that time. If there’s a SIP problem, we’ve probably seen it. That’s not to say we can always fix it. Sometimes it’s a customer PBX at fault, sometimes it’s an upstream system but I can say with confidence we will be able to work out what’s causing an issue.   


One of the main benefits of having everything owned and managed in house is the capacity we can operate at and flexibility it brings. We don’t have to depend on third party datacentres and third party networks. We can add capacity quickly. We can (and do) deal with complex network integrations and bespoke solutions, all with in-house skill and systems.  


We have redundancy. Lots of it. Another benefit of owning your own datacentres and networks. Each SBC you connect to is actually a highly available (HA) pair that can failover without any one on a call noticing it’s happened. On top of that we have these HA pairs in multiple physical locations so even an issue impacting a physical data centre won’t affect the overall platform.  

Number porting expertise  

Finally, number porting. In the 13 years we’ve been running a SIP platform, we’ve also been  porting. We’ve seen just about everything during that time and know how to handle it. Our dedicated porting team is here to manage your port through and keep you updated at every step of the way.   

Add calling to your Teams platform, without compromising on features or cost. Get started today.