Programmable SIP: What You Need to Know When Getting Started

Posted on October 16, 2023

As organizations adapt to distributed remote workforces in recent and upcoming years, cloud-based calling becomes an ideal choice for scalable and cost-effective voice service. Voice over internet protocol (VoIP) service is one way to make calls, but organizations looking for a more cohesive approach to communication can benefit from programmable SIP (Session Initiation Protocol). A SIP allows you to meet your business or client’s voice, texting, chat, and video conferencing requirements.

According to Globe Newswire, the VoIP market is expected to grow by an annual compound rate of over 10% within the next decade. Voice SIP constitutes a significant portion of overall VoIP growth, with its enterprise-grade hosted features that enable enhanced business communications. As a developer, integrating a SIP into your business or client’s software can be simple, using a SIP API (application programming interface) from a reputable cloud-based communication platform.

A SIP API allows a developer to integrate and unify voice communication for an organization and provide reliable voice services through systems and software. Using SIP trunking, companies can cost-effectively maintain various forms of communication and have access to security, connectivity features, and scalability.

In essence, SIP APIs can seamlessly enhance business communications. It’s critical to consider what you need when getting started with SIP to implement the configuration your business or client requires.

What Can a Programmable SIP Do for Your Company or Client?

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 with VoIP service. 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 a company’s 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 provide improved 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-sharing traffic between users. A developer can code the SIP into the company’s apps, CRM, or other software. 

As the developer, you can easily implement a SIP with a voice API and configure the technology to meet your company or client’s needs. A reputable SIP platform allows the company to port and request phone numbers from a configuration portal. 

In addition, some of the best providers offer Microsoft Teams capabilities that grant access to Teams calling and many features not included in the standard platform. They also allow your company or client to bring its own carrier and devices while using the cloud communication solution with enterprise-grade features and security. Administrators can choose whether certain users can access the SIP, Teams, or both in a hybrid configuration.

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 SIP into software with a voice API reduces your development time to a few lines of code and offers a seamless solution for the organization in minutes. 

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

Related: What Is a Programmable Voice API?

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

An ideal 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.

What Advantages Can a SIP Implementation Provide Businesses?

Now that you’ve seen what SIP can do for organizations and developers, let’s take a look at the potential advantages that your client or company can gain.

Reliability and Business Continuity

Implementing a cloud-based SIP can deliver reliable communication to an organization. Users connect to the SIP over the internet, ensuring consistent communication from anywhere with a stable internet connection. When a business receives incoming voice calls, the SIP dynamically increases calling capacity to ensure calls are received and delivers outbound calls on the shortest path for optimal reliability and call quality.

Cloud-based voice SIP can also be integral to an organization’s business continuity and disaster recovery strategy. Its ability to provide seamless communication to remote and distributed workforces means your company or client can continue to use its voice SIP when users need to relocate to another office or work from home. Features like remote call forwarding ensure that calls reach the correct recipient on different devices, like a mobile or software phone.

Scalability and Flexibility

SIP provides near-unlimited scalability to an organization’s communications. Your client or company can dynamically scale to meet inbound call demands without investing in new onsite infrastructure or systems. Unlike primary rate interfaces (PRIs) used in traditional voice communications, cloud-based SIP offers an unlimited number of voice channels, based on your client or company’s internet connection. When the company needs to scale back down, the elasticity of the cloud allows its communications to return to normal levels without any financial consequences.

Cloud-based SIP also allows the business to scale worldwide, with rate centers to provide consistent calling over the Internet regardless of location. Your client or company’s users are no longer limited to using the SIP in the office. Authorized users can access it wherever they go, providing improved flexibility for remote workforces.

Cost Effectiveness

SIP provides a cost-effective means of communication for businesses of every size. Your client or company can implement SIP without costly onsite infrastructure or devices as long as it already has a stable internet connection. In most cases, it can use existing devices and PBX systems with the cloud-based SIP.

With a considerably lower investment, SIP allows small and growing businesses to enhance voice communications affordably. Inbound and outbound calls can be made at a fraction of the cost using a SIP compared to traditional carrier options.

Considerations Before You Get Started With a SIP

SIP is popular for organizations looking for scalability and flexibility as part of a unified communications solution. Several considerations will help you get started with a SIP API, making integration more manageable and improving your client’s or company’s scalability, features, security, and price.


A cloud-based SIP can be implemented using an API, giving your client or company access to its communication solution in minutes. There is no need to wait for carriers to install physical lines if the business already has a suitable internet connection. The organization can also port numbers to the SIP quickly and assign users and phone numbers using a simple web portal.

The API allows you to program the SIP to meet the company’s needs and provide the features it demands, such as E911, remote call forwarding, and CNAM (Caller ID name). It makes setting up communications for remote or distributed workforces as simple as downloading an app.


When you choose a SIP provider, it should offer the scalability your business or client requires. A cloud-based programmable SIP provides unlimited capacity to send and receive calls over the Internet. 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. The company will not need to build up its infrastructure and resources on-site to respond to user growth, and it can easily scale down if the increased SIP channels are no longer necessary.

Related: Voice SIP: How Reliable Voice Calling Solutions Can Impact Your Business

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 payment plan should help your company or client scale up and down quickly.


A SIP provider can protect your client or company from fraud and unwanted calls in the following ways.

  • Toll fraud monitoring services can protect against unauthorized calls and track suspicious activity on your company’s trunk.
  • When enabled, IP-based authentication can 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.
  • Analyze traffic patterns to identify suspicious spikes and destinations, creating a list of restricted destinations to reduce costs and fraudulent activity.

Since an API is facing the public internet, it has become a critical vector for malicious actors to gain access to data. It is vital to evaluate the security of your SIP API to ensure communications are safe. A survey from Salt Security reported a 400% increase in API attacks during the first quarter of 2023. The security needs of APIs are expected to grow in the coming years, so selecting a secure and reputable API provider for your organization’s SIP is essential.


In general, a programmable SIP is a cost-effective solution for business communication. It reduces the company’s reliance on costly 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 onsite infrastructure and IT resources, saving time and money.

A SIP provider may charge a metered or per-minute fee or a monthly flat rate. 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. For scaling your organization’s communications, a metered plan can help you scale up and down quickly without paying for minutes they don’t need.

Integration Features

With the right communications partner, an organization using 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 overall cost of using Microsoft Teams. It also provides helpful tools and capabilities inaccessible in the standard Teams platform.

In addition, an established SIP provider allows the developer to integrate services into the SIP. Features include 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, messaging, 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. 

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 SIP, you get development resources to help you integrate communication APIs and microservices into your client or company’s software and systems with a REST architecture. They can enjoy a reliable and fast connection to their SIP trunk with the Flowroute HyperNetwork™. Communications will be maintained and secured, with instant customization through a simple configuration portal. Get started with resilient and unified communications for business over a SIP trunk from Flowroute.