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Robocalls and spoofed caller IDs have become a massive issue. To fight back, the FCC introduced the STIR/SHAKEN framework — a system that lets carriers verify that a call really comes from who it says it does. What do you need to do to ensure your traffic is being signed correctly? If you are an enterprise customer, meaning a customer who is using their service just for their own business communications, you may choose to do nothing, as Sinch will sign calls on your behalf.   However, if you are a service provider, meaning you provide telecom services to other companies, then you are required by the FCC and the TRACED act to sign your own calls.   Enterprise Customer Responsibilities   Enterprises can choose to sign their own calls. When doing so, Sinch will ensure the signing and attestation remains intact as it transits our network. When Enterprises send unsigned calls from Sinch provided numbers (or numbers you have ported to Sinch), Sinch will sign them with an “A” attestation, the highest level of trust possible. Enterprises sending unsigned calls from non-Sinch numbers, will be signed with a “B”. This indicates that while we know who the Enterprise is, we have no knowledge about the calling party number.   Service Providers - You’re Required to Sign Your Own Calls   The FCC requires all voice service providers — including gateway providers and intermediate providers — to sign all outbound IP-based calls using your own STIR/SHAKEN certificate. You should have your own SPC token (from the STI-PA), certificate, and ability to sign calls. Like the enterprises above, any calls that have been signed prior to reaching Sinch will remain as they transit through the Sinch network.   By the same FCC rules, Sinch, as an intermediate provider, is legally required to sign any unsigned calls we receive. Unsigned calls from service providers on EST will be signed with a “C” attestation , meaning we don’t know or can’t vouch for the caller ID, which may increase the likelihood of calls being labeled as “Likley SPAM”.   Have Questions?   We recommend discussing your STIR/SHAKEN strategy with a telecom regulatory advisor or one of the approved certification authorities — but if you have questions about how Sinch handles unsigned calls or would like to talk about Sinch Hosting your certificate on our infrastructure, we’re happy to help. ... View more

Elastic SIP Trunks can be configured with Forwarding / Fallback. Once set, if a call to one of the telephone numbers associated with a trunk cannot be completed over any of your SIP Endpoints (or in the event you have disabled/removed them) the call will immediately forward out to the number you have configured. To forward all calls simply create a trunk without any SIP endpoints, associate phone number(s) and turn on Forwarding. This option can be configured under the Inbound Call Settings on your trunk.     Additionally, once this is enabled the route will display on your SIP Endpoints section.  This provides a visible reminder that it is enabled and will be used as the route of last resort for your telephone numbers.   ... View more

SUBSCRIPTIONS: If you want to subscribe to updates for Elastic SIP Trunking, click the Options menu button in the right-hand-corner of this article and select Subscribe. You will then receive email notifications when this article is updated with new release notes.   Check in here to see information about new releases from Elastic SIP Trunking.   8/4/2025 - Call Blocking   Sinch Elastic SIP Trunking customers may now create rules which will allow them to block incoming or outgoing calls based on pre-configured match criteria. More information on this feature can be found here.   6/24/2025 - Elastic SIP project activation via API   Once your account has been enabled for Elastic SIP Trunking, you are now able to activate any of the projects on your account via the API. API Endpoint documentation for this feature can be found here.   6/24/2025 - G.711 A-law   Elastic SIP Trunking trunks now support G.711 A-law. This codec is already enabled and will be offered in the SDP for Inbound calls. Outbound calls which request it as a priority codec will have it negotiated.   5/2/2025 - Call Forwarding/Fallback   Elastic SIP Trunking trunks may now configure a phone number which all calls will be forwarded to in the event we cannot reach the customer’s infrastructure.     4/16/2025 - Call Detail Record and Reporting Enhancement   Elastic SIP Trunking call records and analytics now include the ability to select multiple projects at the same time.     3/17/2025 - Call Detail Record (CDR) Enhancements    Elastic SIP Trunking call records will now include the calculated MOS (Mean Opinion Score) as well as the transport protocol which was used.     2/27/2025 - Elastic SIP Trunking Expansion to US-West Datacenter   Elastic SIP Trunks can now be configured to use our East coast or our West coast datacenters. There are now additional regional domain names found on your SIP Trunk configuration page which can be used to send your traffic to the datacenter of your choice. Customers using registered trunks should send directly to US-East only using the <customer domain>.us-east.pstn.sinch.com as inbound calls will experience call completion issues over US-West. This will be resolved in an upcoming Maintenance.     2/27/2025 - Packet Captures (PCAPs) are now available for customer calls   Customers can now download a packet capture of their calls from the Sinch Dashboard. Selecting any Call Detail Record in the dashboard will now show an option to download the PCAP. Currently PCAPs are not available for Registered calls, or calls using Encryption. Both will be added soon.     1/17/2025 - Inbound Digest Authentication   Elastic SIP Trunks can now be configured to respond to authentication challenges by the customer infrastructure. ... View more

A Point of Presence (or POP) is the physical location of a network provider's, internet service provider's (ISP), or telecom carrier's network equipment which enables connectivity for their services. It is an access point for users, businesses, and other networks to connect to and use the provider's services and infrastructure. ... View more

All Sinch Elastic SIP Trunks support TLS and SRTP natively. For more information on TLS/SRTP encryption and the benefits of using it, please read more here.   To make encrypted calls with TLS simply send calls to your SIP Trunk FQDN on port 5061.   This port can only be used for TLS, and non-TLS calls will fail.  SRTP must be used when making a TLS call.   To ensure we send calls to your infrastructure using TLS go into your SIP Endpoint on your SIP Trunk and change the transport protocol to “TLS”.  Note, that the port on your SIP endpoint will update automatically to port 5061.  In the event your infrastructure is listening for TLS connections on a non-standard port simply change the port manually to the correct value.     Congratulations, your Sinch Elastic SIP Trunk is now configured to use encryption!  It’s that easy.   Let's Encrypt Certificates   Sinch Elastic SIP Trunking uses TLS certificates secured by Let’s Encrypt.  If your TLS SIP Infrastructure does not already trust certificates from this Certificate Authority you can download the Let’s Encrypt Root Certificate and associate Intermediate certificates here: https://letsencrypt.org/certificates/   Cypher Suite Support   Sinch trusts all well-known Certificate Authorities.  This ensures we will not have any trust issues when your infrastructure presents its certificate on inbound calls.   For negotiation Sinch supports the following Cypher Suites for both TLS and SRTP.   TLSv1.2   TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 TLS_ECDHE_ECDSA_WITH_AES_256_CCM_8 TLS_ECDHE_ECDSA_WITH_AES_256_CCM TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 TLS_ECDHE_ECDSA_WITH_AES_128_CCM TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA   TLSv1.3   TLS_AES_256_GCM_SHA384 TLS_CHACHA20_POLY1305_SHA256 TLS_AES_128_GCM_SHA256 ... View more