Choosing the Right Microsoft Teams Direct Routing Solution

I have spent the last 2 years deploying Direct Routing for Microsoft Teams to different customers. This has involved a myriad of solutions and integrations across the globe, from local telco, direct routing as a service, calling plans and private direct routing.

With the increase in companies offering direct routing solutions to their customers, I wanted to share the experiences I have had with my clients using different types of solutions so that you can make an informed decision on what combination works for you.

First and foremost, do not automatically think that choosing a single Direct Routing solution (whether that is a service or self-managed) is the complete answer to your organisational needs. Invariably, my customers use a mixture of solutions that together create a robust and integrated voice solution optimised for cloud and their business requirements.

Here I am going to walk through each option and what use cases they are good for and the ones that aren’t.

Calling Plans

Calling Plans are the quickest and easiest route to Teams telephony services for your business. These aren’t Direct Routing solutions. Instead, Microsoft provide you all the connectivity you need to make and receive a phone call within Microsoft 365 for a monthly subscription (or Calling Plan). You can acquire phone numbers directly from Microsoft, or port your own inclusive of the monthly fee.

Typically there are two types of calling plans available. Domestic and Domestic & International, each with their own inclusive minute package.

Availability of these calling plans is limited to about 9 or 10 countries. Tip: Download the Excel workbook – its easier to read!

Features of Calling Plans
Inclusive minute packages for each plan type. Some countries have different usage profiles (low (120 mins), medium (1200 mins) & high (3,000mins)
n x 1.1+10 phone numbers for every calling plan purchased. Confused? If you purchase 10(n) calling plan licenses you get 21 numbers to use. More here. You can acquire geographic, non-geographic numbers for both users & service numbers and toll-free for just service numbers
You can port your existing number ranges to Microsoft
All features of Microsoft Teams Phone System
Calling plan minutes are pooled together and consumed as a single pot per-sku and per-region. More on this later…

The below columns look at the main advantages and disadvantages of using a calling plan


  • Swipe card solution. From none to fully featured telephony in a matter of minutes
  • 100% cloud delivery without IT burden
  • Scalable up or down on demand without worrying about capacity or infrastructure limitations
  • Plain, simple dial tone for the common worker
  • Microsoft are the single point for solution support. No annual maintenance contracts or complicated demarcations


  • Limited country availability
  • Numbers may not be available in your required area code
  • Unused minutes are lost at the end of the month
  • No integration with other PBX systems
  • Not all types of domestic or international numbers are included in the calling plan. Additional pre-paid credit license required for out of plan charges

Why you should use a calling plan?

There is a lot of anti-calling plan rhetoric out there in cyber space. The common theme used to discredit them is their availability and expense. Even I think they are expensive. But when the use case fits, they are by far the best solution to work with.

For me, there are two key components that need to fall in place for calling plans to work for you.

  1. The user of the calling plan has very simple dial tone needs. They just need to be able to make and receive a phone call.
  2. They work at a site (or home office) that has cheap local internet provision and SDWAN.

Calling plans are cloud optimized for a cloud optimized worker. Requiring them to route their calls over a mixture of public and private network connections to a centralised datacenter somewhere is complicated to manage and support as well as invariably giving a net poorer experience to the user.

Microsoft have invested heavily in their global Azure network so that almost everyone in the world can reach it within 2 or 3 hops from their office router. It makes sense that in cases of the remote / SDWAN user for them to get to that network as fast as possible and not have to leave it to come back on-prem somewhere else (a datacenter is on-prem when you’re standing in it ;)).

All in, when faced with the alternative of standing up infrastructure, whether that is telephony or underlying technology to support it, the calling plan, if available is a compelling option to consider, especially when project timelines and intra-departmental budgets are concerned.


There are a couple of gotchas for calling plan users. They aren’t major, but they should play a part in your decision making process.

Minute Pools

Calling plan minutes are pooled at tenant level, but it can be easy to misunderstand the intricacies of this statement. There are different calling plans in different countries and only the same type of calling plan are pooled together.

For instance, take the UK. There are 120, 240 & 1200 minute plans for domestic

If you purchased 5 x 120 minute calling plans you would have 600 minutes you can use between the 5 users who are assigned these exact calling plans.

If you then purchased 10 x 240 minute calling plans you would have 2,400 minutes to use but only to users who you’ve assigned these plans to.

In other words you cannot mix and match minutes between plans in a single pool. If your 10 240 minute users consume 2,400 minutes in three weeks and the 120 minute users had 400 minutes left, the 240 users could not use that allocation as overflow.

Out of Country Plan Usage

It is not supported to use a US (or other) calling plan license SKU in any other country. In other words, you cannot buy a 3,000 minute domestic calling plan from the US and make 3,000 minutes of calls to UK destinations because your user is license location is set to UK.

But you can assign a calling plan to a user with a license location outside of the calling plan supported geography. Essentially that user will be able to place calls to supported destinations by that plan. e.g. assign a US domestic plan to a UK person. They will be able to call US numbers at national rate.

However, this is not a pstn replacement service and therefore, they will not be able to call UK emergency services or any UK destination.

Domestic & International Calling Plans

Domestic and International Calling plans are complex. However, they allow you to make a total of either X amount of domestic minutes OR Y amount of international minutes.

When you see the UK Domestic & International plan you have 1200 minutes of Domestic OR 600 minutes of international. Which ever you hit first is the deciding factor on when your minute pool is exhausted. This means that you could spend 10 hours on a single phone call to the US on Monday and your plan will be used up for the rest of the month. Or you could spend 1,199 minutes on domestic calls and 599 minutes on international before your plan is used…

These plans are not pooled with domestic only minutes, so you cannot add the domestic side of the plan to your comparable 1200 minute domestic only calling plan pool.

You do not have enough credit to make this call

What happens if you have consumed all your pooled minutes in a license category? Simply put, outbound calling stops except for emergency numbers.

Tenant admins are alerted in advance if a pool is under threat of reaching capacity. They can choose to purchase more plans in that category (they don’t have to be assigned) or load communication credits.

Communication credits is a pre-paid account where you pay for outbound calls per minute using the Microsoft rate card.

Direct Routing as a Service

Direct Routing as a Service (DRaaS) is gaining a lot of traction. Microsoft have made it really easy for service providers to bring telephony services to their customers. It is a highly competitive market and a race to the bottom in terms of costs.

I’ve seen providers go head to head bidding for contracts to provide telephony for Microsoft Teams. Invariably, it comes down being able to provide the bare minimum for the cheapest price. This is what happens when customers focus on a price war vs looking at the bigger picture and choosing the right service and coverage they need. They end up with a solution that does not meet all their use cases and invariably is very hard to adapt.

I have been known to call out DRaaS providers and ask that they do more to consult with their customer to capture the real requirements so that a solution can be properly tailored for them. But this only works if the customer is properly focused on their objectives, not just the bottom line on a quote sheet.

DRaaS is where the provider provisions the telephony connectivity in order for your Teams clients to make and receive calls. This means that all infrastructure is supplied by them in terms of SBCs and all the customer has to do is purchase a Phone System license for each voice user.

There are two ways in which a provider can integrate their Direct Routing Solution into your tenant

  1. Dedicated SBC
  2. Derived / Super Trunk

Dedicated SBC

This is where the provider will provision an SBC in their cloud and supply you with the FQDN of that SBC for you to pair with your tenant as an Online PSTN Gateway.

These are generally used for customers with either volume demand, need a little more flexibility without ownership or looking to de-risk performance impact by using a shared service.


  • Allows customer to use inbound and outbound number translations so they can manipulate as needed
  • Performance analytics in Teams Admin Center on SBC health, call quality and call statuses e.g. response codes
  • Control advanced options such as PIDF-LO, PAI etc.
  • Integrate with on-prem PBX**
  • Extended coverage


  • Customer required to own the initial pairing of the gateways and voice routes in their tenant
  • Any call flow not supported by the service provide standard service agreement will not work

** Service provider dependant. Not everyone allows this. Check with your provider

Derived / Super Trunk

This is where the provider asks the customer to activate a sub domain within their Microsoft 365 tenant. Once activated, all the provisioning is done by the service provider. Instead of having to pair PSTN Gateways, you simply add the domain as a voice routing destination and the rest is taken care of.

Using this method service providers are able to provision direct routing for customers with zero touch. Many have tried to distinguish themselves by providing portals and provisioning tools that do all the voice routing provisioning needed inside the customer tenant and provide a robust calling solution within minutes.

On the face of it, it does seem like a match made in heaven. But the price paid by the customer is that they loose everything that a dedicated paired SBC gave them and this method can be better represented as a 3rd party calling plan offering.


  • Black box & hands off solution for customers wanting basic dial tone
  • Competitive calling plans vs Microsoft or local alternatives
  • Extended coverage


  • No gateway side analytics in the Teams admin center. Customer unable to see if the service is functional
  • No ability to modify inbound or outbound numbers at trunk level
  • No ability to integrate with other on-prem PBXs

To compensate for the lack of analytics and manipulations, some derived trunk providers have created their own portals and software to manage and view this directly in their cloud whilst the call is within their realm. There are some providers that allow you to build quite complex call flows that enrich the native Teams call offering that could be a compelling reason for you to choose that model over others. Check out Zapappi, SIPPIO & Fuse2

Why should you use a DRaaS Provider?

The most common reason will be coverage. Service providers will be able to provide pstn replacement services in a lot more locations than Microsoft. In addition they are also able to generally be more competitive on call rates offering a standardised global rate.

They also take care of a lot of the complexity of traditional site based telephony. You won’t need to consider least cost routing for instance, where you need a complex dial plan and routing design to switch calls between specific voice gateways to achieve the most optimal call rate. All that is done with the provider.

You also don’t have to worry about infrastructure, licenses or software maintenance for SBCs. Neither do you have to find people that understand the technology to support them once the integrator has left. DRaaS is a compelling solution for many companies and the defacto starting position in most cases.


These will depend greatly on the provider you choose. I have listed the most common I have come up against here.


Be aware that when a service provider claims they have global SIP coverage, that doesn’t mean they have global pstn replacement. The two are different and can be easily confused.

  1. Global SIP coverage means that the provider has the ability to provide you DDI in a lot of countries (but not all). DDI is not PSTN replacement. It means they can give you a phone number in a country but cannot provide emergency services. This means that you will need to have something else at that site, e.g. POTS or mobile for emergency services.
  2. PSTN replacement means that they can fully support all telephony services in that country including emergency services.

Typically, you will see headline claims “Global SIP coverage in over 200 countries”. But what you really need to look at is PSTN replacement countries. Typically these are around the 40 to 60 mark.

Inter Range Routing

A lot of these services are sold as a single service funnel. That means if you are porting a range of phone numbers, lets say a block of 1,000. All those numbers will be routed to Teams via the DRaaS solution.

This is great is all 1,000 numbers are supposed to terminate in Teams. However, is some numbers should route to non-Teams PBXs e.g. on-prem PBX, analog, intercoms etc. then Teams cannot be used to inter-trunk route.

This means that you need to have another solution that allows the re-routing of select numbers away from DRaaS to these phone systems.

This can get very complicated, very quickly. How you do this depends greatly on how the other phone system is connected and what your DRaaS provider can support.

You might:

  1. Have to take out a new PSTN contract for local SIP/PRI that terminates to the other phone system and use new DDIs with carrier number forwards in place
  2. Look at providing your own interconnect between these systems and your DRaaS provider i.e. dedicated SBC and/or Analog to SIP converters
  3. Using Teams accounts as resource accounts to manage forwards
  4. Move to e-Fax services for fax devices

It can be easy to walk into a DRaaS contract without understanding this initially as invariably this only comes out of the woodwork when you get to each site and they come out with their requirements, or there is a hardware delivery issue.

Ideally, you want to work with a DRaaS provider that supports Bring Your Own Trunk so they can help route numbers accordingly.

Interop with PBX

Many customers, especially large enterprises will retain multiple phone systems to make their business operate. When introducing Teams, even if you are migrating a lot to Teams you may still require Teams users to call other endpoints within the organisation and vice versa.

Consider a factory scenario. Office workers can use Teams, but there will be factory lines with analog phones on shop floors. There will be overhead paging (loud ringer), intercoms and even DECT radios. All of these workers will need to be contactable no matter what platform they use.

More often than not it is isn’t acceptable for the site to maintain a legacy PBX infrastructure and more importantly phone lines to service these systems. Instead they will look to consolidate their needs to a single carrier solution. The problem is that some DRaaS solutions out there do not allow organisations to connect these other systems directly to their SBCs.

This is not a criticism, the DRaaS solution should not support this because it would be an absolute mine field for the provider and also require private network connections adding costs to the solution. Instead, for these scenarios, private Direct Routing used in conjunction with generic SIP trunking from the same provider is the most sensible solution.

The reason this is a gotcha is mainly down to customer interpretation of the DRaaS solution. Often they think it is buying a SIP trunking service and it can be used for whatever their needs. In reality, it is a SIP trunking service, but just for Teams. You’ll need a complimenting solution for everything else.

Private Direct Routing

This method uses the same principles as DRaaS, except you are responsible for the SBC infrastructure and configuration. This will involve purchasing an SBC, installing it and connecting it to Teams, a generic SIP trunking or PRI service with your provider and any other SIP connections you need to work with to provide a telephony solution to your users.

This offers the most flexibility to you when creating your voice solution. You can integrate with multiple systems and carriers to create a bespoke topology that 100% fits your business needs without compromise. However, it comes at increased costs as you take on maintenance, support and service management.


  • Ultimate flexibility and control of telephony services
  • Can be deployed anywhere in the world
  • Supports cloud or on-prem deployments
  • Virtual or physical hardware
  • Can integrate Teams with any SIP based system
  • Maintain user dial plan habits including extension dialling or short dial codes


  • Most expensive solution (total cost of ownership)
  • Customer owns the support / SLA or has to outsource
  • Application / hardware lifecycle
  • Dead Admin (the person who knows the system inside out leaves, exposing the business to service risks)

Why should you use Private Direct Routing?

As a result of the disadvantages, it is often best to use this sparingly and where appropriate to keep costs optimised. Situations where you would use this:

  • At sites in countries where your DRaaS provider or Microsoft cannot support full pstn replacement services e.g. Russia, China, India, UAE, Macedonia etc. and you need local ISDN or SIP circuits with a local provider
  • To support integration with other phone systems like Analog phones, intercoms, DECT radios, PBXs etc. and Teams

For everything else, you really should be looking at a managed solution.


Media Optimisations

Out of the box Direct Routing uses transport relays in Microsoft to connect client with SBC. So, where you have deployed a local SBC to a site, the call flow will be from client –> to internet –> Microsoft –> to internet –> client site –> SBC –> PSTN.

In countries with good connectivity like the US, Europe & UK, this call flow is generally acceptable, even if media is taking the long way round. However, in more challenging geographies where either connectivity is an issue or Microsoft do not have a transport relay in region (South Africa for example, the closest relay is Amsterdam), you’ll need to deploy media bypass and / or local media optimisation to shorten the media path to maintain good voice quality.


In summary, your perfect direct routing solution for Microsoft Teams will invariably consist of at least 2 if not all 3 of the above variations. Hopefully this article will help you understand the services on offer and help guide you to making an informed choice for planning, design and purchase so that you don’t make expensive mistakes.

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