Outbound trunks#
An outbound SIP trunk connects your customer system to DIDWW termination routes so you can place calls to local and international destinations. Each trunk controls authentication, media, Caller ID, allowed destinations, capacity, and spending.
Important
Outbound trunks are not enabled automatically. Request access before creating a trunk or placing outbound calls.
Key features#
Control simultaneous call capacity and rolling 24-hour spending limits.
Choose from supported authentication methods and restrict signaling and media by IP address where applicable.
Configure Caller ID numbers and allow or block destination prefixes.
Use SIP over UDP, TCP, or TLS, with optional encrypted media.
Place calls through local or global routes and use emergency calling in supported countries.
Review per-trunk call records, statistics, and reports.
Use redundant network infrastructure and customer-side failover options.
How outbound calls work#
Your customer system sends a SIP INVITE to DIDWW. DIDWW identifies and
authenticates the outbound trunk according to its configured authentication
method, applies Caller ID and dialing rules, and routes the call to the
destination network for delivery to the called party.
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"actorLineColor": "#38bdf8",
"signalColor": "#0f766e",
"signalTextColor": "#1f2d3d",
"labelBoxBkgColor": "#ccfbf1",
"labelBoxBorderColor": "#14b8a6",
"labelTextColor": "#1f2d3d",
"noteBkgColor": "#fef3c7",
"noteBorderColor": "#f59e0b",
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sequenceDiagram
autonumber
participant system as Customer System
participant trunk as DIDWW
participant network as Destination network
participant callee as Called party
system->>trunk: SIP INVITE
Note over trunk: Authenticate the trunk<br/>Apply Caller ID and dialing rules
trunk->>network: Route call
network->>callee: Deliver call
See Authentication and security for authentication methods. See Call-flow examples for complete Credentials & IP-Based and IP-Only SIP exchanges.
Reliability and failover details
Outbound call delivery uses several layers of redundancy across the DIDWW network and your customer system’s connection:
DIDWW provides network redundancy across multiple Points of Presence (PoPs), termination carriers, load balancers, and session border controllers (SBCs).
DIDWW maintains resilient connectivity through multi-homed IP transit and direct interconnections at major Internet Exchanges.
Use DNS SRV or BGP Anycast for customer-side failover, or create multiple outbound trunks to distribute traffic.
For signaling, network architecture, and failover details, see Outbound SIP information.
Get started#
Choose the path that matches your account:
Start here if outbound trunks are not enabled on your account.
Create your first trunk after outbound trunk access is enabled.
Configure, manage, and monitor outbound calling#
Edit, enable, disable, or delete trunks, and manage trunk credentials.
Understand authentication methods and controls that reduce unauthorized use and toll fraud.
Configure number formats, local routes, call forwarding, and destination restrictions.
Configure the calling number and Caller Name Delivery (CNAM OUT).
Review outbound call logs, statistics, and reports, and isolate common configuration problems.
Trust and compliance#
Understand DIDWW attestation and customer-generated Identity header relay.
Understand call labeling and applicable US robocall compliance requirements.
Technical references#
Find signaling endpoints, transports, media networks, codecs, encryption, registration, and SIP header details.
Find definitions, values, and status behavior for every field on the Outbound Trunks page and in the trunk creation and edit forms.