Programmable SIP: What You Need to Know When Getting Started

Posted on December 22, 2022

While live chat, text messaging, social media, and email are popular methods for users to engage with an organization, voice is still at the center of many companies’ communications strategies. A survey featured in Forbes found that customers prefer calling a business with a live voice representative rather than interactive voice response (IVR) systems. 

Organizations focusing only on live chat and text channels while neglecting voice may frustrate customers. Integrating high-quality and reliable voice communication into its CRM, systems, apps, and software is essential and can be easy to accomplish using a programmable session initiation protocol (SIP).

A programmable SIP allows a developer to integrate and unify voice communication for an organization or client and provide reliable voice services through systems and software with an API. Using a SIP trunk, users can initiate various forms of communication and have access to security, features, and scalability at a cost-effective price. 

This blog will explore programmable SIP, including what it can accomplish for your company, necessary considerations when getting started with a SIP solution, and how a programmable SIP can help you as a developer.

What Can a Programmable SIP Help Your Company Accomplish?

SIP is a technology that allows IP-based calls to be sent and received over a single trunk line. Calls, videos, faxes, instant messages, and files can be sent and received over the SIP trunk simultaneously if the bandwidth is available. Like HTTP, SIP data is transmitted on the application layer of the network over a transmission control protocol (TCP) or user datagram protocol (UDP) transport layer protocol.

SIP can be used with Public Switched Telephone Networks (PSTN) over a traditional carrier or using Voice over Internet Protocol (VoIP). SIP originates, terminates, and unifies calls and communication on a SIP trunk, while real-time protocol (RTP) carries the voice data in a VoIP system. 

SIP routes calls to and from an endpoint configured on an IP-enabled private branch exchange (PBX), IP phone, mobile device, or software phone. Since the SIP trunk is in the cloud, it can also provide mobility for remote operations and business continuity.

A programmable SIP allows a company to use a SIP trunk to carry its voice, video, instant message, fax, and file traffic between users. A developer can code the SIP into the company’s apps, CRM, or other software. 

As the developer, a programmable SIP with a voice application programming interface (API) can make it easy to implement and configure a voice API and SIP to meet your company or client’s needs. A voice API with SIP provides the ability to port and request phone numbers from a configuration portal. 

In addition, some of the best providers offer Microsoft Teams capabilities that provide access to Teams calling and many features not included in the standard Teams client. They also allow your company or client to bring its own carrier and devices while using the cloud communication solution to provide enterprise-grade features and security.

Related: What Is a Programmable Voice API?

How Does a Programmable SIP Help You as a Developer?

A programmable SIP makes integrating features into your company or client’s phone system easier. Integrating a programmable SIP into a client or company’s software with a voice API reduces your development time to a few lines of code and offers a seamless solution for your company in minutes. 

The API is secured and maintained by the SIP provider, and the ideal provider will have resources for developers to make integrating and configuring the voice API and programmable SIP simple. In contrast, developing the API from scratch can take hours of coding and require extensive resources to maintain, update, and secure.

The ideal programmable SIP provider will have developer resources, including quickstarts for implementing microservices like E911, use case scenarios, articles, and software development kits (SDKs). The resources should allow you to implement and configure the API and microservices as desired using your preferred programming language, including PHP, Ruby, and .NET.

A quality SIP provider will create the voice API using a representational state transfer (REST) architecture. REST APIs can be written in various programming languages and offer excellent compatibility. They use fewer bandwidth resources than other API architectures and rely on simple HTTP operations like “GET” and “PUT.” REST APIs are also compatible with common data formats like JSON and XML, making them ideal for integrating various systems and software.

Related: A Guide for Voice API for Developers

Considerations Before You Get Started With a Programmable SIP

A programmable SIP is a popular solution for organizations looking for scalability and flexibility as part of a unified communications solution. In 2019, a survey of more than 600 companies by Nemertes Research found that 18% of the companies were using SIP, and more than 30% planned to implement SIP within two years. Several considerations will help you get started with a programmable SIP, making integration more manageable and improving your client’s or company’s scalability, features, security, and price.


When you choose a SIP provider, it should offer whatever degree of scalability you need. A cloud-based programmable SIP provides unlimited capacity to send and receive calls and faxes over user datagram protocol (UDP) or transmission control protocol (TCP). The network should also be reliable to ensure unlimited concurrent calls receive high-quality service. 

The SIP provider can dynamically create instances to ensure incoming and outgoing calls are placed. There is no need for the company to build up its infrastructure and resources on-site to respond to user growth, and it can easily scale down if or when the increased SIP channels are no longer necessary.

When your company or client requires new phone numbers or direct inward dialing (DID) numbers, it can provision them from a configuration portal using a scalable cloud-based SIP provider. The cloud-based SIP trunk provider’s payment plan should help your company or client scale up and down quickly.


In general, a programmable SIP can help organizations save money and is typically implemented as a cost-effective solution for communication. It reduces the company’s reliance on costly primary rate interface (PRI) channels from a carrier. It allows incoming and outgoing calls to be routed over the internet, using a DID to reach the correct phone. A cloud-based SIP provider reduces the need for on-site infrastructure and IT resources, saving both the company money and developers time.

A SIP provider may charge a metered or per-minute fee or a monthly flat rate. While a cloud-based provider offers unlimited channels for your SIP trunk, If a traditional PSTN carrier provides your SIP, you may be charged per channel on the SIP trunk. If your company plans to scale your communications, a metered plan can help you scale up and down quickly without paying for minutes your company or organization doesn’t need.


A SIP provider can protect your client or company from fraud and activities that can be costly. Toll fraud monitoring services can protect the SIP trunk from unauthorized calls and track suspicious activity on your company’s trunk. A SIP provider can also enable IP-based authentication to ensure calls are placed to approved outbound IPs and block outbound calls that exceed the maximum rate set by the company from its configuration portal. Providers can identify traffic patterns to identify suspicious spikes and destinations, creating a list of restricted destinations to reduce costs and fraudulent activity.


With the right communications partner, an organization that already uses Microsoft Teams for collaboration can integrate Teams into its SIP. Teams with SIP allows the organization to make calls over the provider’s network, reducing the cost of making calls using Microsoft Teams. It also provides helpful tools and capabilities not accessible in the standard Teams platform.

In addition, an established SIP provider allows the developer to integrate services into the programmable SIP, such as Caller ID options, like CNAM to identify DID phone numbers within the organization and E911 service to identify the caller’s address to emergency services.

A Programmable SIP Makes Integrating and Managing Voice Communications Simple

A programmable SIP can improve your client or company’s communications with an easy-to-integrate, manageable solution. It offers simultaneous and scalable calling and fax services using a SIP trunk on the internet. SIP dynamically routes calls quickly and reliably using DID and provides clear voice service in standard G.711 or compressed G.729 formats. 

As we’ve discussed, the right technology provides security and access to features like Microsoft Teams integration with the SIP for efficient, fully-featured collaboration and communication. Using a metered payment plan, you can get voice SIP at a scalable and affordable price for your client or company.

When you rely on Flowroute for your programmable SIP, you get development resources to help you integrate voice and communication APIs and microservices into your client or company’s software and systems with a REST API. Your client or company can enjoy a reliable and fast connection to their SIP trunk with the Flowroute HyperNetwork™. Its communications will be maintained and secured with instant scalability and configuration through a simple configuration portal. Get started today with a programmable SIP from Flowroute.