SIP Trunking Basics

Posted on: 2016-08-01 | Categories: SIP SIP Trunking

SIP trunking is quickly becoming a great alternative to the PSTN based for enterprises, both big and small. SIP trunks offer lower costs, better efficiency and enhanced reliability. These are advantages that businesses cannot afford to ignore any longer. While some organizations prefer hosted VoIP services, SIP trunks can be the more suitable alternative under certain circumstances.

What are the SIP Trunking Basics?

To put it simply, SIP trunks are one to one equivalents for the more traditional PRI lines. Just like those enterprise cable, SIP trunks serve as the conduit for enterprise calls. The only difference is that instead of copper lines carrying analog sound signals, SIP trunks transmit voice that has been converted to data packets.

Deploying SIP Trunks

Before deploying SIP trunks, the enterprise data network may need some preparation or maintenance. All the SIP trunking basics are founded on solid Internet connectivity. Even if the corporate LAN is sufficient for the current workload, additional capacity may have to be added to handle the extra traffic. VoIP is especially sensitive to dropped packets, jitter and delays. So optimizing necessary hardware should be a priority. Enterprises may even need to increase the speed of the internet connection to handle VoIP.


The SIP trunking basics define two common architectures – centralized or distributed implementations. Both have their pros and cons and are suitable for different scenarios. Centralized SIP trunks reduce financial expenditure, improve reliability and make it easier to track down bugs or troubleshoot problems in VoIP calls. But they also introduce a single point of failure – if the central data center goes down, then it takes the entire business phone system with it.

Distributed architecture reduces the risk of failure that plagues centralized architectures and does not require as much advance planning. However it can be more expensive as each location will need its own SIP trunk. Tracing bugs can be time consuming and reliability can be an issue. Peak demand may also overwhelm the trunk, degrading quality. Unlike centralized deployments, sessions can’t be pooled and used across SIP trunks so individual locations will need to plan for peak traffic in advance.


Moving over to SIP trunks from PRI lines can introduce new vulnerabilities into the system that were absent before. Although PSTN calls can also be subject to toll fraud, combining the data and voice networks brings with it a whole new world of risks. The same ills that plague business data networks can put voice calls at risk too. Corporate calls can be eavesdropped on, data stolen and even fraudulent charges racked up, unknown to the business. Such fraud can result in bills of thousands of dollars for which the company is on the hook.

Thus securing SIP trunks should be a top priority, rather than an afterthought. Encryption is just one tool that can help enterprises protect their networks. Monitoring and recording software can also be just as helpful in detecting the first hints of intrusion by outsiders, hackers or otherwise unauthorized users. However basic security practices like securing account credentials, not revealing passwords to anyone etc should also be emphasized.

Costs of SIP Trunking

SIP trunks require more investment that simply purchasing hosted services but that investment can also yield significant returns over time. Companies often underestimate the total costs of deploying them. They assume that the only costs involved is paying for the trunks and paying for desk phones. But in reality there is so much more to take into account.

Having on premise SIP trunks means that the company needs to have expert personnel on hand to configure and maintain the system. In addition, VoIP or UC related software may require payment such as licensing or subscription fees. Apart from that, conference systems, cameras for video calls, speakers, headsets etc can also rack up the bills. Fortunately the tremendous cost savings can more than make up for the initial investment.

Finding A SIP Trunking Provider

Selecting and committing to one vendor can appear to be a daunting task. There are a plethora of vendors in the marketplace and finding the right fit can take some time. But there are no shortcuts and it is never a good idea to settle for the first vendor you look at. Past experience and expertise matter a lot when it comes to SIP trunking. A vendor that supports SIP standards, does not require contracts and who goes the extra mile for customer service are just some aspects that you should look out for.

SIP trunking basics are not that difficult to grasp but there are hidden intricacies when it comes to individual deployments. What works for one organization may not necessarily work for another, even if their requirements appear similar on the surface. Costs can also vary significantly between deployments. But at the end of the day, SIP trunks offer great potential for efficiencies and cost savings over older technologies that simply can’t keep up with the latest workflows.