Inbound SIP Trunk Requirements

This article outlines the requirements for establishing an inbound SIP trunk connection from customer equipment to the Sharpen platform. These requirements apply when customer-side infrastructure — such as a Session Border Controller (SBC) or gateway — will be sending SIP calls into Sharpen.

Customer Requirements The customer must provide between 1 and 3 publicly accessible IP addresses from which Sharpen will accept inbound SIP calls.

Sharpen Inbound Gateway Addresses The following addresses are where customers should direct inbound SIP calls. Contact Strategic Services if you are unsure which set of addresses applies to your account.

FQDN (auto load balancing):

• IZ0: us1-byo-inbound.sipvbx.com

• IZ1: us1-byo-inbound.iz1.sharpen.cx

Manual IP Configuration (if preferred):

IP Whitelisting

• Sharpen will whitelist the customer IP addresses provided in Section 1 to allow an open communication channel to Sharpen's inbound SBCs.

• The customer should whitelist the Sharpen IP addresses listed in Section 1 on their end.

Note: Contact Strategic Services if you wish to use Pre-Shared Key (PSK) authentication instead of IP whitelisting.

Customer-Provided Information

• Provide your SIP and RTP port details to Strategic Services if they differ from Sharpen's default ports listed below.

• Provide expected maximum and average call concurrency estimates to Sharpen.

Sharpen Default Ports

Sharpen accepts inbound voice in the G.711 codec. Support for additional codecs such as G.729 and Opus is on the future roadmap.

Inbound Number Setup Inbound numbers from the customer SIP trunk are manually configured by Sharpen in Admin > Configuration > Inbound Routes, where they are designated as Inbound SIP. The customer must provide the 10-digit numbers that will be sent in the SIP headers and that should be routed through Sharpen Inbound Routes.

SIP Header Requirements Customers should pass the following standard SIP information in their headers:

• Calling Party Number (CID / ANI / Caller ID)

• DNIS (the called/destination number)

Customer-Side Routing Sharpen will accept inbound SIP calls from any of the customer IP addresses provided in Section 1. Any routing strategy is supported, calls may arrive from a single active IP or distributed across all configured IPs in any order.

Sharpen-Side Routing Sharpen will accept SIP calls on all Sharpen IPs listed in Section 1, in any order.

Routing of inbound numbers is managed within Admin > Configuration > Inbound Routes. Once new numbers are configured by Sharpen, they will appear on the customer's Inbound Routes page and can be routed in the same way as native Sharpen voice lines.

• SIP Trunk Limitations

  • SIP trunks support inbound voice calls only. SMS/MMS and fax are not supported over SIP trunks. If native SMS/MMS functionality is required, consider porting the numbers into your Sharpen account.

• Feature Support

  • Certain Sharpen features, such as Q omnichannel SMS/MMS, are not fully supported when using SIP trunks for voice. Limitations may arise from SIP protocol constraints, customer configuration, or the customer's telecom vendor.

• Failover Behavior

  • In active/backup mode, if a remote IP becomes unavailable, callers will hear silence until the next backup IP establishes a connection. Once an IP is marked offline, it will not be retried and calls will proceed normally through the remaining IPs.

• Configuration Updates

  • Changes to Trunk Groups, such as adding, removing, or reordering entries, can take up to 15 minutes to take effect. SIP trunk configurations are cached and refreshed every 15 minutes from the time a call first hits the trunk. Depending on when a change is saved within the refresh cycle, it may take effect anywhere from a few seconds to 15 minutes.