# Inbound trunks

Inbound trunks deliver calls received on your DIDWW phone numbers to your
phone system, a mobile or landline number, or the phone.systems(TM) cloud PBX.
Use this section to set up, manage, and monitor inbound call delivery.

## Key features

- Deliver calls to your SIP system, a landline or mobile number, or the
  phone.systems(TM) cloud PBX.
- Use [trunk groups](trunk-groups/index.html) for failover and load balancing.
- Filter unwanted calls with [number lists](number-lists/index.html).
- Set capacity limits to control simultaneous calls through trunks and trunk
  groups.
- Monitor traffic and investigate failed calls with [inbound analytics](analytics/index.html).

## What is an inbound trunk?

A DID number is the phone number that callers dial. An inbound trunk tells
DIDWW where to deliver the calls received on that number. A DID number must be
[assigned to an inbound trunk](../../phone-numbers/my-numbers/how-to-guides/assign-voice-trunk.html#user-panel-assign-trunk) before DIDWW can
deliver its calls.

Multiple DID numbers can use the same trunk and share its delivery settings.
To use several destinations for the same numbers, combine trunks in a
[trunk group](trunk-groups/index.html).

### Choose a trunk type

| Trunk type | Delivers calls to | Best for | What you need |
| --- | --- | --- | --- |
| [SIP trunk](sip-trunks/index.html) | Your IP PBX, SBC, softphone, or voice application, using SIP. | Businesses with their own phone system or voice platform. | A SIP endpoint that DIDWW can reach, or one that registers with DIDWW. |
| [PSTN trunk](pstn-trunks/index.html) | A landline or mobile number, through the DIDWW termination network. | Forwarding calls to a phone without SIP equipment. | A destination phone number. Forwarded calls are charged per minute. |
| [phone.systems(TM) trunk](phone-systems-trunks/index.html) | The phone.systems(TM) cloud PBX, where call flows, IVRs, and users are managed. | Teams that want a hosted PBX without managing equipment. | An active [phone.systems(TM) subscription](../../phone-systems/Getting-started/index.html#ps3-prerequisites). |

## How inbound calls work

When a caller dials your DID number, the public telephone network routes the
call to DIDWW. DIDWW delivers the call through the trunk or trunk group
assigned to that DID number.

```
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  "themeVariables": {
    "fontSize": "14px",
    "actorBkg": "#e0f2fe",
    "actorBorder": "#38bdf8",
    "actorTextColor": "#1f2d3d",
    "actorLineColor": "#38bdf8",
    "signalColor": "#0f766e",
    "signalTextColor": "#1f2d3d",
    "labelBoxBkgColor": "#ccfbf1",
    "labelBoxBorderColor": "#14b8a6",
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    "noteBkgColor": "#fef3c7",
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}}%%

sequenceDiagram
   autonumber
   participant caller as Caller
   participant network as Telephone network
   participant didww as DIDWW
   participant destination as Destination

   caller->>network: Dial DID number
   network->>didww: Route call to DIDWW
   Note over didww: Find the trunk or trunk group<br/>assigned to the DID number
   didww->>destination: Deliver call through the trunk
```

Reliability and failover details

Inbound call delivery is protected at two levels: inside the DIDWW network,
and between DIDWW and your systems. For details, see [Service failover
and load
balancing](sip-trunks/call-handling-and-delivery/service-failover-and-load-balancing.html#inbound-sip-failover-load-balancing).

**DIDWW network redundancy**

- **Multiple Points of Presence (PoPs):** DIDWW receives and delivers calls
  from [PoPs](../../presence/index.html#presence) on several continents. PSTN interconnections
  terminate at more than one PoP. If a PoP or interconnection becomes
  unreachable, traffic for the affected number ranges is diverted to a
  healthy PoP automatically.
- **Redundant SBCs:** Each PoP uses redundant load balancers and session
  border controllers (SBCs). A failed node is removed from service while the
  others continue to handle calls.
- **Resilient connectivity:** Each PoP uses several IP transit providers and
  [direct interconnections](../../presence/index.html#network-interconnection) at major Internet
  Exchanges.
- **24/7 monitoring:** A Network Operations Center monitors the platform and
  responds to incidents.

**Failover to your systems**

- **DNS SRV:** Publish several SIP servers behind one host name. DIDWW tries
  another server when one does not respond. See [DNS SRV
failover](sip-trunks/call-handling-and-delivery/service-failover-and-load-balancing.html#inbound-sip-dns-srv-failover).
- **Trunk groups:** Combine SIP and PSTN trunks. DIDWW tries the next trunk
  when a call attempt fails, or spreads calls between trunks. See
  [Trunk group failover](sip-trunks/call-handling-and-delivery/service-failover-and-load-balancing.html#inbound-trunk-group-failover-load-balancing).
  For SIP or PSTN destinations, prepare the member trunks, then
  [create a trunk group](trunk-groups/how-to-guides/create-trunk-group.html)
  and [assign the group to your DID
number](../../phone-numbers/my-numbers/how-to-guides/assign-voice-trunk.html#user-panel-assign-trunk)
  instead of an individual trunk.

---

## Get started

Prepare your DID number and call destination, then assign the trunk and test
incoming calls.

### 1. Get a DID number

Start by finding an available number you want to buy. You can also review
the payment methods before purchasing.

**Search and buy numbers**

Search available numbers, review prices and service options, and buy
one if you need a new DID number.

[How to buy numbers](../../phone-numbers/buy-numbers/how-to-buy.html#user-panel-purchase)

**Add a payment method**

Choose a payment method and add funds if your prepaid balance is
insufficient for the purchase.

[Payment Methods](../../billing/payment-methods/index.html#billing-payment-methods)

### 2. Choose your call destination

Choose one option based on where you want to receive calls.

**SIP endpoint**

Create a SIP trunk for your PBX, SBC, softphone, or application.

[Create a SIP trunk](sip-trunks/how-to-guides/create-sip-trunk.html)

**Telephone number**

Create a PSTN trunk to forward calls to a landline or mobile number.

[Create a PSTN trunk](pstn-trunks/how-to-guides/create-pstn-trunk.html)

**phone.systems(TM) PBX**

Use the trunk named **phone.systems**, created automatically with an
active subscription.

[phone.systems(TM) trunks](phone-systems-trunks/index.html)

### 3. Assign and test

Assign first, then complete your destination setup and test an incoming call.

**Assign the trunk to your DID**

Assign the prepared trunk or trunk group to your DID number.

[Assign a voice trunk](../../phone-numbers/my-numbers/how-to-guides/assign-voice-trunk.html#user-panel-assign-trunk)

**Test and view call logs**

After assignment and destination setup, call your DID number and
confirm the test call in Inbound Call Logs.

[Inbound Call Logs](../../logs-analytics/call-logs/inbound-logs.html#inbound-cdr-logs)

---

## Configure, manage, and monitor inbound calls

**SIP trunks**

Deliver calls to your SIP infrastructure, choose a routing method, and
configure call handling.

[SIP trunks](sip-trunks/index.html)

**PSTN trunks**

Forward calls to a landline or mobile number.

[PSTN trunks](pstn-trunks/index.html)

**phone.systems(TM) trunks**

Deliver calls to the phone.systems(TM) cloud PBX.

[phone.systems(TM) trunks](phone-systems-trunks/index.html)

**Trunk groups**

Combine trunks for failover and load balancing.

[Trunk groups](trunk-groups/index.html)

**Number lists**

Allow or reject calls by calling number or prefix.

[Number lists](number-lists/index.html)

**Preferred server routing**

Select the DIDWW Points of Presence used for SIP call delivery.

[Configure Preferred Server routing](sip-trunks/how-to-guides/configure-preferred-server-routing.html)

**Dialing formats**

Find the formats callers dial to reach toll-free numbers and UIFNs.

[Dialing formats](dialing-formats.html)

**Analytics**

Review inbound call logs, SIP response codes, statistics, and reports,
and export or stream call records.

[Analytics](analytics/index.html)

**Troubleshooting**

Identify why an inbound call failed and find troubleshooting guidance.

[Troubleshooting](troubleshooting.html)

## Technical references

**Inbound trunks reference**

Look up the tabs, filters, fields, values, and actions on the Inbound
Trunks page.

[Inbound trunks reference](reference.html)

**SIP connectivity reference**

Find signaling addresses, media addresses, codecs, and firewall
requirements.

[SIP connectivity reference](sip-trunks/sip-connectivity-reference.html)

## Related resources

**Outbound trunks**

Create and manage outbound trunks for placing calls.

[Outbound trunks](../outbound-trunks/index.html)

**My numbers**

Manage the DID numbers on your account and their assigned trunks.

[My Numbers](../../phone-numbers/my-numbers/index.html)

**Capacity**

Understand and add channels for concurrent inbound calls.

[Capacity](../../phone-numbers/capacity/index.html)

**Integrations**

Configure trunks and endpoints for PBX systems, contact center
platforms, and AI voice agents.

[Introduction](../../integrations/index.html)

**Download pricelists**

Download public or account-specific pricelists.

[Download pricelists](../../phone-numbers/buy-numbers/download-pricelists.html#services-coverage-pricing-access-pricelists)

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