What is a SIP phone system?

A SIP phone system successfully transmits voice data over the internet, enabling unified communications, greater reliability, and secure remote working. As an enabler for VoIP (Voice over Internet Protocol) services, SIP can support everything from voice calls and video conferencing to instant messaging and media distribution. This breadth of choice can vastly improve the customer experience while enabling greater flexibility for your users. While a SIP phone system can be installed by a variety of providers, there are few who can deliver a tailored voice IP service that meets your needs effectively. At Nasstar, we have developed our experience in the industry and have direct and established relationships with multiple carriers, ensuring you get the best connectivity price. Our SIP voice IP service can be delivered as a fully managed service, letting you get on with the stuff that matters.

What's the difference between SIP and VoIP?

SIP, or Session Initiation Protocol, is a protocol used to set up and disconnect VoIP calls and send multimedia messages over the internet. VoIP, or Voice over Internet Protocol, is an umbrella term for a group of technologies that enables voice to be sent over the internet. In essence, SIP describes how VoIP calls are established , maintained, and disconnected, so it’s a subprotocol that enables VoIP.

What are the benefits of migrating to SIP-enabled voice services?

There are several reasons why businesses choose to move to SIP-enabled voice services from traditional ISDN or analogue lines, with the main one being to get ahead of the PSTN switch-off coming in 2027. Other benefits of moving to SIP include: - Greater resilience with services carried over the internet instead of physical lines - Cost savings with predictable monthly costs - No additional hardware investment - No physical infrastructure to build or maintain - Enabler for remote working with unified communications - Greater network consolidation - Immediate ROI

How does the multi-carrier network benefit my business?

Having a multi-carrier network can benefit your business by avoiding reliance on a single carrier. At Nasstar, we work with several carrier partners to ensure there are multiple options for receiving and delivering your call traffic. Should one carrier experience service or capacity issues, we can easily route your calls to another to avoid downtime. Another benefit of multiple carriers is that we can choose the optimal route for your needs, which is also often the most cost-effective

How does Nasstar’s SIP-enabled voice service ensure business continuity and quality?

Before your SIP-enabled voice service is installed, our presales team will work with you to understand your security, quality, and business continuity requirements in depth. We will then design the resilience of the solution to accurately meet those needs. Our teams can offer solutions that meet a variety of requirements, from efficient site transfers in case one goes down, or full resilience over multiple sites.

Services/Secure Networks/SIP-enabled Voice

SIP-enabled Voice

Q: What is SIP-enabled voice?

S ession I nitiation P rotocol ( SIP ) -enabled voice is an IP-voice service that is highly flexible and designed to future-proof your business’ voice solutions. It helps to maintain call quality and business continuity with a much lower price point than traditional ISDN lines.

Voice that works the way you do

ISDNandPSTNhadagoodrun,butold-schoolphonelinesareontheirwayout,andSIP-enabledvoiceisreadytotakeover.

Session Initiation Protocol (SIP) enabled voice transforms how you connect. It enables unified communications across platforms and devices, while cutting operational costs and boosting flexibility. From voice to video, it adapts to your workflows and meets the demands of a modern, distributed workforce.

We provide a fully managed, end-to-end voice service, supported by resilient multi-carrier networks and real-time optimisation. With Nasstar, you’re not just staying connected, you’re staying ahead.

Whatourexpertsays...

We have a lot of experience helping customers navigate complex needs. Especially in the fast-moving world of communications. Our SIP-enabled voice solution has been developed to keep you moving forward, ensuring a future-proof voice solution that keeps pace with advancements yet to come.

Rada SookramanienVoice Product Manager, Nasstar

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Case studies

We’ve partnered with a range of businesses on their SIP voice service transformations. 

Retail

The Works

Public sector

Accent Housing

What others have to say...

"With the ambition to have 600 stores by next year, we needed to know we had a reactive partner that could provide a seamless and scalable IT solution to match. A trustworthy partner who has the experience and expertise to fulfil our requirements and support our expansion plans. Nasstar is exactly the right fit for our business. Their support enables us to move forward as a business and remain ahead of the game in the competitive retail sector."

Tom Scott

IT Director

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The Works

Why choose Nasstar?

We don’t just deliver SIP voice solutions, we design them around your business, build them to scale, and back them with trusted carrier relationships for better performance and pricing.

We’ve delivered SIP solutions across industries, and we know what works. From streamlined setups to bespoke designs, we tailor your system to meet your exact needs around performance, security, and growth. You’ll have the infrastructure to scale fast and the reliability to never miss a beat.

Change is constant, so we build for what’s coming. Our SIP-enabled voice systems are resilient by design and ready to meet tomorrow’s communication challenges. As your strategy, workforce, and customer expectations shift, we’ll make sure your SIP solutions are built to move with you.

The future of communication starts with the right partners. We’ve cultivated strong relationships with multiple carriers to give you the best connectivity options available, while our tailored approach ensures your voice infrastructure is built around you.

Once you go live, we don’t disappear. We’re here 24/7 to keep your SIP service running smoothly. Things will stay sharp with real-time monitoring, ongoing support, and regular check-ins. Our teams are on hand to support you through your ISDN to SIP migration and onboarding, as well as afterwards through our managed service offering.

FAQs

Session Initiation Protocol (SIP)-enabled voice is an IP-voice service that is highly flexible and designed to future-proof your business’ voice solutions. It helps to maintain call quality and business continuity with a much lower price point than traditional ISDN lines. 