01
Registration
A phone, application or platform registers its SIP identity with a server or communications system.
SIP Explained by M5 Technologies
What is SIP? The foundation of modern enterprise communications.
Session Initiation Protocol is the signaling standard used to start, manage and end voice, video and real-time communications over IP networks. SIP powers SIP trunking, cloud PBX, unified communications and Microsoft Teams Direct Routing.
Microsoft Teams Direct Routing Certified SBC
Carrier-Grade Communications
30+ Years of SIP & VoIP Expertise
Made in Canada
How SIP fits into a voice networkEndpoint → signaling control → voice service
SIP signaling architecture
Users and applications
Microsoft TeamsPBXSoftphoneGatewayIP phone
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Microsoft-Certified Sentinel SBC
SIP securityRoutingNormalizationTopology hidingDirect Routing
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Voice services
SIP trunkCarrierCloud PBXPSTNEmergency calling
SIPControls the session.
SDPNegotiates media.
RTPCarries the audio.
Microsoft Teams Direct RoutingSentinel SBCs provide the certified SIP boundary for Teams voice.
SIP TrunkingConnect enterprise voice platforms to carriers over IP.
Legacy ModernizationBridge analog, PBX, PRI and BRI systems to SIP.
SIP SecurityControl signaling, routing, topology and external connections.
Simple definition
SIP tells communication systems how to establish, manage and end a session.
When a user places a call, SIP identifies the caller and destination, selects the route, negotiates session parameters and terminates the call when the session ends. The voice media normally travels separately over RTP or SRTP.
02
Call setup
A SIP INVITE requests a new session between the calling and receiving parties.
03
Media negotiation
SDP identifies codecs, IP addresses, ports and media capabilities.
04
Session control
SIP manages ringing, answer, hold, transfer, updates and call termination.
How a SIP call works
A SIP call is a structured sequence of signaling messages.
SIP EndpointSends an INVITE to request the call
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Sentinel SBCSecures, normalizes and routes signaling
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Carrier or PBXProcesses the route and destination
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RTP / SRTP MediaCarries the voice after the session is accepted
Core comparison
SIP vs VoIP vs RTP vs SBC.
| Technology | Primary role | What it controls | Typical example |
|---|---|---|---|
| SIP | Signaling protocol | Call setup, routing, session state and termination | INVITE, 180 Ringing, 200 OK, BYE |
| VoIP | General communications method | Voice delivered over IP networks | Cloud PBX, SIP trunking, Teams voice |
| RTP / SRTP | Media transport | Audio or video packets after session setup | Voice stream between endpoints |
| Session Border Controller | Security and interoperability control | SIP border, routing, topology, normalization and policy | Microsoft-certified Sentinel SBC |
Protocol comparison
SIP vs H.323 and SIP vs PRI.
| Criteria | SIP | H.323 | PRI / ISDN |
|---|---|---|---|
| Architecture | IP-based signaling protocol | Older multimedia protocol suite | Traditional digital circuit service |
| Flexibility | High for cloud, UC, carriers and hybrid voice | Common in legacy video and telecom systems | Fixed channels and physical telecom circuits |
| Cloud readiness | Strong | More limited in modern cloud environments | Requires gateway migration to IP |
| Microsoft Teams Direct Routing | Core signaling method through a certified SBC | Not the standard Teams Direct Routing method | Requires conversion through gateway and SBC architecture |
| Best fit | Modern enterprise, operator and cloud communications | Legacy systems that still require H.323 interoperability | Existing PBX environments transitioning to SIP |
Gateway vs SBC
A SIP gateway and an SBC solve different problems.
| Criteria | SIP / Media Gateway | Session Border Controller | Combined architecture |
|---|---|---|---|
| Primary function | Converts analog, digital or PBX interfaces to SIP | Protects and controls the SIP border | Interworking plus security and policy |
| Typical products | Mediatrix 4102S, C7 and G7 | Sentinel CS, Sentinel 100 and Sentinel 400 | Gateway plus Microsoft-certified Sentinel SBC |
| Microsoft Teams Direct Routing | Requires a certified SBC | Provides the certified Teams connection | Best for analog, PBX and Teams coexistence |
Microsoft Teams Direct Routing
SIP connects Microsoft Teams Phone to carriers, PBXs and legacy voice through a certified SBC.
Microsoft Teams Direct Routing uses an approved Session Border Controller to connect Teams Phone with SIP trunks and enterprise voice infrastructure. Sentinel SBCs provide the certified SIP boundary, while Mediatrix gateways can preserve analog, PRI, BRI and PBX services behind that architecture.
01
Certified SIP Boundary
Sentinel SBCs provide the Microsoft Teams Direct Routing connection and secure SIP demarcation.
02
Carrier and PBX Integration
Connect Teams to SIP carriers, existing PBXs, contact centers and enterprise voice systems.
03
Legacy Voice Migration
Use Mediatrix gateways to preserve analog, PRI, BRI and legacy endpoints during Teams adoption.
SIP use cases
Where SIP is used across modern communications.
01
SIP Trunking
Connect enterprise PBX and UC platforms to carriers over IP.
02
Microsoft Teams Voice
Connect Teams Phone to carriers through a Microsoft-certified Sentinel SBC.
03
Cloud PBX
Deliver hosted voice and unified communications over SIP infrastructure.
04
POTS Replacement
Move compatible analog phones, fax, alarms and elevators to SIP transport.
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PBX Modernization
Bridge legacy PBX systems to SIP carriers and cloud communications.
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Contact Centers
Route enterprise calling between carriers, platforms and customer-service systems.
07
Critical Infrastructure
Support secure and resilient voice for airports, utilities, government and public safety.
08
OEM Communications
Embed SIP into devices, gateways, applications and specialized platforms.
M5 SIP portfolio
Products that secure, connect and modernize SIP environments.
Migration roadmap
Move from legacy voice to secure SIP in controlled stages.
1
Inventory
Document PBXs, trunks, carriers, numbers, analog devices and sites.
2
Classify
Separate standard voice from fax, emergency, alarm and critical services.
3
Design
Select SBC, gateway, carrier, Teams and failover architecture.
4
Validate
Test call flows, codecs, DTMF, fax, security and emergency calling.
5
Deploy
Migrate users and sites with monitoring, rollback and support plans.
Why M5 Technologies
Deep SIP expertise across software, gateways and certified SBC infrastructure.
01
Microsoft Teams Direct Routing
Certified Sentinel SBC architecture for enterprise Teams voice.
02
Carrier-Grade SIP
Security, interoperability and routing for enterprise and operator networks.
03
Legacy-to-IP Migration
Mediatrix gateways for analog, PRI, BRI, PBX and POTS modernization.
04
30+ Years of Expertise
Long-standing experience in SIP, VoIP, embedded voice and communications infrastructure.
SIP FAQ
Common questions about SIP, SBCs and Teams Direct Routing.
What does SIP stand for?
SIP stands for Session Initiation Protocol. It is used to establish, manage and terminate real-time communication sessions over IP networks.
Is SIP the same as VoIP?
No. VoIP is the broader method of carrying voice over IP. SIP is one of the main signaling protocols used to control VoIP sessions.
What is RTP?
RTP carries the audio or video media after SIP establishes the session. SRTP is the secure version used to encrypt media.
What is SDP?
Session Description Protocol communicates media capabilities such as codecs, addresses and ports during SIP session negotiation.
What is SIP trunking?
SIP trunking connects a PBX, UC platform or SBC to a telecom carrier over IP instead of traditional PRI or analog circuits.
What is a Session Border Controller?
An SBC protects and controls SIP traffic between trusted systems and external networks. It provides routing, normalization, topology hiding and security policy.
What is a SIP gateway?
A SIP gateway converts analog, digital or PBX interfaces into SIP so legacy systems can connect to modern IP voice infrastructure.
Does Microsoft Teams use SIP?
Microsoft Teams Direct Routing connects Teams Phone to carriers through a Microsoft-certified SBC using SIP-based enterprise voice architecture.
Why does Teams Direct Routing require an SBC?
The SBC provides the certified connection, secure SIP border, routing, interoperability and media control between Teams and enterprise voice systems.
Can Mediatrix gateways connect to Microsoft Teams?
Yes. Mediatrix gateways integrate with Teams Direct Routing through a Microsoft-certified Sentinel SBC.
Can SIP be encrypted?
Yes. SIP signaling can use TLS, while media can use SRTP when supported by the connected systems and architecture.
Why is SIP security important?
Exposed SIP can be targeted by scanning, fraud, malformed traffic, denial-of-service attempts and topology discovery.
What is the difference between SIP and PRI?
SIP uses IP networks and scalable virtual routing. PRI uses fixed digital circuits and channel-based telecom infrastructure.
What is the difference between a gateway and an SBC?
A gateway performs interface conversion. An SBC protects and controls SIP signaling and media at the network boundary.
Which M5 product should I choose?
Sentinel SBCs fit secure SIP and Teams Direct Routing, while Mediatrix 4102S, C7 and G7 gateways fit analog, PBX, PRI and BRI migration.
SIP architecture assessment
Turn SIP knowledge into a secure migration plan.
Provide a high-level overview of your environment. M5 can help identify the right Sentinel SBC, Mediatrix gateway, SIP trunking and Microsoft Teams Direct Routing architecture.
- PBX, Microsoft Teams, UC and contact-center platforms
- SIP carriers, trunks, numbers and routing requirements
- Analog, PRI, BRI and POTS modernization
- Security, high availability and disaster recovery
- Sentinel SBC and Mediatrix gateway selection