Answers about SIP, softphones and Teams calling

SIP, the Session Initiation Protocol, is the signalling that sets up, changes and ends voice and video calls over IP. It negotiates who is calling whom and how, while the audio itself travels separately over RTP.

VoIP, voice over IP, is the umbrella term for carrying calls over the internet. SIP is the most common protocol used to set those calls up, so most VoIP calls are SIP calls.

A Session Border Controller sits at the edge between networks and secures, normalizes and controls SIP and media. It is how providers protect a PBX, traverse firewalls, stop fraud and connect to platforms like Microsoft Teams.

NAT and corporate firewalls hide devices and block media paths. STUN, TURN, ICE and a media proxy solve it. Spanvox relays over 443, so if a device can reach HTTPS, it can make calls.

Mobile operating systems suspend backgrounded apps, which kills the SIP connection so the PBX can no longer reach the device. The fix is a server-side registration plus a VoIP push that wakes the app and rings it through CallKit or ConnectionService.

On an incoming call, the platform sends an APNs or FCM notification that wakes the softphone, which then presents the native call screen. It removes the need to keep a battery-draining socket open.

Yes. With a white-label softphone the app carries your brand and ships under your own Apple and Google accounts and push identity, so your customers never see the underlying vendor.

Register an endpoint to your PBX exactly like a softphone. Spanvox does this server-side and hands users a branded app, so calls route through your existing PBX with no trunk, no dialplan change and no firewall edit.

No. A registration bridge uses dual SIP registration, not a trunk, so there is nothing to provision as a trunk and no inter-PBX routing to configure.

Any SIP PBX, including Asterisk, FreePBX, FreeSWITCH, 3CX, BroadWorks, FusionPBX, Kamailio and OpenSIPS. If it speaks SIP and accepts a registration, it bridges.

Direct Routing connects Teams Phone to any carrier through a certified SBC, the bring-your-own-carrier path, so you keep your numbers and routing instead of buying Microsoft Calling Plans.

Operator Connect is simple if your carrier is already a listed operator. Direct Routing wins when you own your PSTN, need PBX integration or global reach, and want to keep your carrier and margin.

Yes, Microsoft only supports Direct Routing with certified SBCs holding a valid TLS certificate. Delivered as a service, the SBC and certificates are run for you.

It can be, and should be. Signalling runs over TLS or WSS and media over SRTP, terminated on hardened SBCs, with credentials encrypted at rest and never exposed to the device.

Toll fraud is abuse where attackers place expensive calls on a compromised account. It is contained with per-endpoint concurrency caps, registration rate-limiting and automatic IP banning before it reaches a bill.

STIR/SHAKEN is a framework that cryptographically signs and verifies caller ID to fight spoofing and robocalls. A good platform passes the identity through untouched so verified calls stay verified.

Carrier-grade platforms run a pool of redundant nodes across regions with GeoDNS failover and a 24/7 NOC, so a single node or region failing does not take your customers down.