Outbound trunk reference#
Outbound trunk reference explains the fields, values, and states shown on the Outbound Trunks page and in the trunk creation and edit forms.
Main fields#
Field |
Access |
Description |
|---|---|---|
Name |
Editable |
The trunk’s friendly name, shown in this list, matched by the search field, and set under General trunk settings. |
Allowed SIP IPs |
Editable, Credentials & IP-Based only |
The trunk’s allowed signaling SIP IP addresses, configured under Authentication. Blank for authentication methods that do not use IP allowlisting, for example Twilio Account SID. |
24 Hour Limit (USD) |
Editable |
Current spending against the configured maximum for the rolling
24-hour period, shown as spent/limit (for example, |
Editable |
Enables or disables outbound traffic through the trunk. |
|
Editable |
The trunk’s media encryption mode. |
|
Capacity Limit |
Editable |
Maximum number of simultaneous calls through the trunk, or Unlimited when no limit is set, configured under Limits and notifications. |
Editable |
The authentication method configured for the trunk. |
|
Read-only, Credentials & IP-Based only |
Opens the trunk’s Credentials pop-up window. |
Credentials window fields#
Field |
Description |
|---|---|
Auth type |
The authentication method used for the trunk, listed in Authentication method values. |
Username |
The auto-generated SIP digest username. Read-only. It cannot be edited. |
Password |
The generated SIP digest password. Can be revealed or regenerated from the window. Regenerating immediately invalidates the previous password, as described in Credential lifecycle. |
Host(s) |
The regional DIDWW signaling endpoints available to the trunk, or the BGP Anycast and DNS SRV connection options described in Outbound SIP information. |
Allowed SIP IPs |
The trunk’s configured Allowed SIP IP addresses. |
Allowed Voice OUT CLI(s) |
The trunk’s configured Allowed CLI(s) for ordinary outbound calls. |
Emergency calling CLI(s) |
The trunk’s configured Emergency calling CLI(s). |
Status values#
Value |
Description |
|---|---|
Enabled |
The trunk accepts outbound calls that pass its authentication, Caller ID, destination, capacity, and spending controls. |
Disabled |
The trunk blocks new outbound calls. A trunk is also disabled automatically when its rolling 24-hour limit is reached. Active calls are disconnected shortly afterward. Re-enable the trunk manually after reviewing its usage. |
Trunk settings#
The following sections define the fields available when creating or editing an outbound trunk, grouped to match the Create Outbound Trunk and Edit Outbound Trunk forms.
General#
Field |
Access |
Description |
|---|---|---|
Friendly name |
Editable |
Name used to identify the trunk in the DIDWW User Panel and in the Outbound Trunks list. |
Authentication#
Authentication controls which systems can send calls through the trunk, with the security model and recommendations covered in Authentication and security. If your account has multiple trunks, Authentication priority explains how DIDWW matches a request to a trunk.
Field |
Access |
Description |
|---|---|---|
Editable |
The method DIDWW uses to authenticate outbound calls sent through the trunk. Determines which of the fields below apply: Tech Prefix and the Allowed IP address fields apply only to Credentials & IP-Based, and Account SID applies only to Twilio Account SID. |
|
Tech Prefix |
Editable, Credentials & IP-Based only |
Optional code added before the dialed number to help identify and route calls through your trunk. Specification
Example If you set the tech prefix to 123#, it must be added before the dialed number. For example:
Emergency calls must also include the prefix, e.g. |
Allowed SIP IP addresses |
Editable, Credentials & IP-Based only |
Public IP addresses or subnets from which SIP requests are accepted. At least one SIP address is required. Note
|
Allowed RTP IP addresses |
Editable, Credentials & IP-Based only |
Your RTP addresses from which audio packets will be relayed to DIDWW. Note
|
Account SID |
Editable, Twilio Account SID only |
34-character identifier of the Twilio account, in the format |
Read-only, Credentials & IP-Based only |
Authentication and connection details generated for the trunk. View outbound trunk credentials. |
Authentication method values#
Value |
Description |
|---|---|
Credentials & IP-Based |
The default method. DIDWW validates SIP digest credentials and the source IP address. |
IP-Only |
Validates only the source IP address, without digest authentication. Not available for self-service selection. Contact DIDWW Technical Support to request it, as described in Authentication and security. |
Twilio Account SID |
Authenticates the trunk using a Twilio Account SID, for the Twilio BYOC integration. |
phone.systems™ |
Authenticates the trunk for calls originated from a phone.systems™ Cloud PBX instance. This is a system trunk: DIDWW creates it automatically when you purchase a phone.systems™ plan, and it is not created manually from the Outbound Trunks page. |
Media#
Field |
Access |
Description |
|---|---|---|
Force Symmetric RTP |
Editable |
Sends RTP to the source IP address and port of the audio DIDWW actually receives, instead of the address negotiated in the SDP offer/answer (also known as COMEDIA mode). Helps when your equipment is behind NAT and its advertised media address is not directly reachable. |
RTP Ping |
Editable |
Sends an empty RTP packet after the call is established to trigger RTP transmission from the remote endpoint. |
RTP Timeout |
Editable |
Disconnects a call when no RTP packets arrive for the configured time, in seconds. Must be between 30 and 600 seconds. |
Editable |
Controls whether and how RTP media is encrypted. |
Media encryption mode values#
Value |
Description |
|---|---|
Disabled |
Does not encrypt media. |
SRTP SDES |
Uses Secure RTP with SDP Security Descriptions key negotiation. The encryption key travels inside the SDP body, so it is only as protected as the signaling transport. |
SRTP DTLS |
Uses Secure RTP with Datagram Transport Layer Security key negotiation, negotiated directly over the media path rather than in SDP. |
ZRTP |
Uses Secure RTP with ZRTP key negotiation, agreed directly between endpoints without relying on the signaling transport for key protection. |
Termination#
Limits and notifications#
Field |
Access |
Description |
|---|---|---|
24 hour limit (USD) |
Editable |
Maximum charge allowed for the trunk during a rolling 24-hour period. When reached, the trunk is disabled, new calls are blocked, and active calls are disconnected shortly afterward. The final charge can slightly exceed the limit. Note The default 24-hour limit is $3000. The minimum limit is $50, and the maximum limit is $10000. |
Capacity limit |
Editable |
Specifies the maximum number of simultaneous calls allowed per trunk. Leave empty for unlimited capacity, shown as Unlimited in the trunk list. |
Voice OUT Trunk usage limit notification |
Editable |
Sends an email when usage reaches 80% of the 24-hour limit. A notification is sent no more than once every 12 hours. |
CLI Settings#
Setting |
Description |
|---|---|
On CLI Mismatch |
A CLI mismatch happens when numbers from other providers are used as the CLI, or when the CLI does not match any numbers acquired via DIDWW.
|
Allow any DID(s) as CLI for Voice OUT |
When this toggle is enabled, all supported numbers are automatically allowed as CLI by default. |
Allow specific DIDs as CLI for Voice OUT |
When this toggle is disabled, only numbers added to the Allowed CLI(s) list can be used as CLI. Numbers are added from Available CLI(s), which can be filtered by CLI, Description, Country, and Region. Lists DIDWW numbers that support outbound trunk calls with local routes. DIDs that support only global outbound routes are not listed. |
Note
The Available CLI(s) list displays only DID numbers that support the Voice OUT feature with local termination. DIDs with the Voice OUT global routes feature are not included in this list.
Destination Dialing Settings#
Setting |
Description |
|---|---|
Allow All |
This method allows calls to all destinations, except those specified in the listed prefixes. Example The configuration below allows calls to all destinations except:
|
Reject All |
This method rejects calls to all destinations, except those specified in the listed prefixes. Example The configuration below rejects calls to all destinations except:
|
Use the shortest prefix that precisely describes the required destination range. Number formatting is covered in Outbound dialing.
Emergency Calling#
Emergency calling requires a DID that supports emergency service and has an active emergency calling service.
The complete trunk-side setup is covered in Configure Outbound Trunks for Emergency Calling.
Field |
Access |
Description |
|---|---|---|
Allow all available DID(s) for emergency calling |
Editable |
When this toggle is enabled, all eligible numbers are automatically allowed as Caller ID for emergency calls by default. |
Emergency calling CLI(s) |
Editable |
When the toggle above is disabled, only numbers added to the Emergency calling CLI(s) list can be used as Caller ID for emergency calls. Numbers are added from Available CLI(s), which can be filtered by CLI, Description, Country, and Region. Lists DIDWW numbers that are registered for emergency calling. DIDs that are not registered for emergency are not listed. |
Note
The Available CLI(s) list displays only DID numbers that are registered for emergency calling. DIDs that are not registered for emergency are not included in this list.