Microsoft Teams Direct Routing: What It Is and When to Use It

What Direct Routing Is

Microsoft Teams Direct Routing connects your organization's Session Border Controller (SBC) directly to Microsoft's SIP gateway, bypassing Microsoft's carrier offerings entirely. Instead of paying Microsoft for minutes or seats through Calling Plans, you contract directly with a carrier for SIP trunk service and manage the SBC yourself (or lease it from a provider).

This architecture gives you three options for voice in Teams:

• Calling Plans: Microsoft acts as your carrier. Simple but expensive ($12–$15/user/month domestic, higher international). Works in ~50 countries. No number porting, instant activation.
• Operator Connect: A certified operator (Ribbon, Comtech, etc.) partners with Microsoft to resell SIP trunks. Middle ground between Calling Plans and Direct Routing. Simpler than Direct Routing but less carrier flexibility.
• Direct Routing: You own the SBC relationship with the carrier. Maximum flexibility, lower per-minute costs if you have call volume, but you manage the complexity yourself.

At its core, Direct Routing requires three pieces:

1. Session Border Controller (SBC): A dedicated appliance (or cloud instance) that sits between your carrier's SIP trunk and Teams. It translates between the carrier's SIP signaling and Microsoft's format, enforces security, and transcodes media if needed.
2. SIP Trunk from your carrier: The actual phone lines. You contract with a carrier for one or more SIP trunks, specifying concurrent call capacity.
3. Teams Phone System license: A $8/user/month Microsoft add-on. This is often overlooked and adds significantly to total cost of ownership.

Direct Routing vs. Calling Plans vs. Operator Connect

For most small businesses, Calling Plans is the right choice. For mid-market and enterprise, the math often shifts in favor of Direct Routing. Here's the comparison:

Factor	Calling Plans	Operator Connect	Direct Routing
Per-user cost	$12–$15 + $8 Phone System	$10–$15 + $8 Phone System	$8 Phone System + carrier SIP (variable)
Carrier choice	None (Microsoft)	Limited (certified operator)	Any SIP-capable carrier
Number porting	Can port in after activation	Can port in	Supported (you manage it)
International coverage	~50 countries only	Varies by operator	Global (if your carrier supports it)
Setup time	Days	1–2 weeks	4–8 weeks
SBC required	No	Operator-managed	Yes (you or hosted provider)
Break-even (100 users)	$2,000/month	$1,800/month	~$1,200/month (if 200+ minutes/user/day)

The key insight: Direct Routing only makes financial sense if you have significant call volume or a large user base. For organizations with 50+ users making 200+ minutes of calls daily, the carrier SIP cost drops to $3–$8 per user monthly. Add the $8 Phone System license, and you're at $11–$16/user—competitive with Calling Plans but with global reach and carrier flexibility.

Session Border Controller Requirements

The SBC is the linchpin of Direct Routing. Microsoft publishes a certified list of SBC vendors, and you must use one from that list. Do not attempt to use an uncertified device—Microsoft's gateway will reject it.

Certified vendors include:

• AudioCodes: Wide range from small to enterprise. Mediant 500 (~$5K) for 20–50 concurrent calls. Hosted AudioCodes ($12–$18/user/month) for cloud-first shops.
• Ribbon: SBC 5000 series (enterprise-grade, $15K–$30K). Offers excellent redundancy and media bypass for bandwidth-constrained WAN links.
• Oracle (NetScaler/ACME): Expensive ($20K+) but robust for massive call volumes (1000+ concurrent calls).
• Cisco (CUBE): If you already own Cisco ISR routers, CUBE can run as a software module. No additional hardware cost, but expertise required.
• Metaswitch/Ribbon SBC Lite: Newer option. Lower cost, still certified.

Hardware vs. Hosted: On-premise SBCs require capital expenditure ($5K–$20K), space, power, and IT management. Hosted SBCs (AudioCodes, some Ribbon offerings) shift to OpEx ($12–$20/user/month) and eliminate on-site management. For most mid-market customers, hosted is simpler.

Sizing: SBCs are sized by concurrent calls, not users. A 100-user organization with average call duration of 5 minutes and 2 calls per person per day needs roughly 15–20 concurrent call capacity. Budget SBC capacity 20% above peak to avoid call failures during surges.

Redundancy: Direct Routing SBCs should be deployed in pairs for high availability. Microsoft's gateway can failover between multiple SBCs. Plan for N+1 redundancy: if one SBC fails, the other carries the load.

Choosing a Carrier for Direct Routing

Not every SIP trunk provider supports Teams Direct Routing. The carrier must:

• Support SIP signaling (many older providers still use proprietary protocols).
• Provide SIP options for your SBC to register against.
• Support Teams-compatible codecs (typically G.711, OPUS).
• Offer concurrent call capacity (not "unlimited" in vague terms).
• Provide SLA guarantees if your organization depends on voice.

US carriers: Twilio, Vonage, Bandwidth, Level3, Lumen, regional carriers like CenturyLink. Most major carriers support Direct Routing.

International: Vonage, Bandwidth, and Orange Business Services offer global SIP trunking. Pricing varies wildly by region—get quotes for your specific countries.

Pricing models: Most carriers bill per concurrent SIP channel (call). A 50-channel trunk typically runs $500–$1,200/month depending on region and service level. Some offer per-minute pricing ($0.03–$0.08 outbound, $0.01–$0.05 inbound) if you have very low call volume.

What to ask in the carrier agreement:

• Uptime SLA (should be 99.5%+ excluding your network).
• Emergency backup routing if primary fails.
• Number porting timeline and fees (usually $1–$5 per number).
• Setup fees (typically $0–$500 depending on complexity).
• Early termination fees (negotiate these down; 30-day notice is ideal).

Implementation Complexity: Timeline and Ownership

Direct Routing implementation is not a weekend project. Plan for 4–8 weeks for a mid-size organization (100–500 users).

Pre-implementation (Week 1–2):

• Order SBC hardware or sign up for hosted SBC. Lead time: 2–4 weeks if hardware.
• Sign carrier SIP trunk agreement. Confirm concurrent call capacity, FQDN registration details, IP ranges.
• Confirm all users have Teams Phone System licenses assigned.
• Audit your current phone numbers and dial plan rules.

DNS and Network (Week 2–3):

• Configure DNS SRV records for your SBC (sip.yourdomain.com).
• Obtain and install TLS certificates for your SBC (Teams requires valid certs; self-signed will fail).
• Open firewall rules: SBC to Microsoft gateway (SIP port 5061 outbound, RTP media ports 49152–57500).
• Configure QoS rules if your WAN is bandwidth-constrained (media traffic should be prioritized).

SBC Configuration (Week 3–4):

• Register SBC against both carrier SIP trunk and Microsoft Teams gateway.
• Configure dial plan rules: how Teams phone numbers map to PSTN numbers, how incoming calls route to Teams users.
• Set up media transcoding if carrier and Teams use different codecs.
• Enable call logging and monitoring.

Number Porting (Week 2–6, overlapping):

• Submit Letter of Authorization (LOA) to your current carrier and new carrier.
• Porting typically takes 2–4 weeks depending on carrier and country.
• Plan a cutover window (usually nights/weekends) when incoming calls switch from old carrier to new.

Pilot and Testing (Week 5–6):

• Assign Direct Routing to 10–20 pilot users; test inbound/outbound, call quality, forwarding rules.
• Run call quality analyzer (Teams built-in tool) to verify MOS (Mean Opinion Score) is 4.0+.
• Test emergency calling (911 in US); ensure location routing is configured.

Full Rollout (Week 7–8):

• Migrate remaining users in cohorts (by department or region).
• Provide support for user questions (call forwarding, voicemail, transfer rules).

Who owns it? This requires cross-functional collaboration:

• Network team: Firewall, DNS, QoS, WAN.
• IT/Cloud team: Teams administration, licensing, Azure AD groups for rollout.
• Telecom/Voice engineer: SBC configuration, carrier coordination, dial plans, emergency calling.
• Business owner: Approve number porting, manage cost trade-offs.

Hidden Costs Often Overlooked

Beyond the obvious (SBC, SIP trunk, Phone System license), budget for:

• SBC Software Licensing: If using a hosted SBC, anticipate $12–$18 per user per month on top of carrier costs. For on-premise, expect annual support/maintenance at 15–20% of hardware cost ($750–$4,000/year for a $5K SBC).
• SBC Hardware (on-premise only): $5K–$20K upfront depending on vendor and capacity. Replace every 5–7 years (~$1K–$3K/year amortized).
• Number Porting: $1–$5 per number being ported. For 100 users, budget $100–$500.
• Carrier Setup Fees: Usually $0–$500 depending on complexity and carrier willingness to negotiate.
• Professional Services: If you use a partner (like ITG) to design and implement, expect $5K–$20K depending on complexity and head count.
• Ongoing Management: Plan 0.5–1 FTE for continuous SBC monitoring, OS updates, certificate renewals, and carrier relationship management. If outsourced, $1K–$3K/month.
• Emergency Calling: Some regions charge for E911 routing ($0.50–$2/user/month). US doesn't, but UK and Canada do.
• Call Quality Monitoring Tools: If you want real-time alerts, third-party tools like Cisco Webex Cloud Connected UC or Ribbon Insights run $500–$2K/month for mid-market.

For a 100-user organization, realistic total monthly cost breakdown:

• Teams Phone System: $800 (100 users × $8)
• SIP Trunk (carrier): $800 (50 channels at $16/channel)
• Hosted SBC: $1,400 (100 users × $14)
• Total: $3,000/month or $30/user/month

Versus Calling Plans at $20/user/month ($12 Calling Plan + $8 Phone System) = $2,000/month for 100 users. Direct Routing wins by $1,000/month for this organization—but requires staff expertise to manage the SBC.

Frequently Asked Questions