Pitfalls of Least-Cost Routing for SIP Trunking

SIP trunking can provide cost savings for telephony customers, but pricing should be only one part of the equation when choosing a telecom provider. Any business looking for a new VoIP solution should also consider factors such as reliability and call clarity.

Buyers should be particularly wary of any provider that promises least-cost routing (LCR) to deliver lower prices. LCR works by being carrier-agnostic. For each call, carriers are ranked from lowest to highest price, and the call is attempted over the lowest-cost network. If the call can’t be completed over the lowest-cost carrier, the call is then attempted over whatever carrier ranks as having the next-lowest cost.

While LCR can make SIP trunking pricing appealing and works for some businesses, some LCR users pay in the form of lower overall call quality, because not all carriers provide the same level of service. It’s important to understand how a SIP service provider balances the two key factors of cost and call quality.

The challenges of using LCR

If a SIP trunking provider uses LCR, its calls may be routed to whatever network provides the lowest rate for a particular time and location, regardless of connection quality. By focusing only on cost, LCR users may experience challenges such as:

1. Audio cut-out: Since SIP trunking providers that use LCR don’t factor in quality, calls might be routed over networks that experience audio cut-outs, known as “jitter,” in which phone calls sound jittery or where words seem to be coming in out of order. SIP trunking providers route calls over the internet and the actual voice sound is transmitted as packets of data, so if a connection is unreliable, some data packets might come in out of order or not at all, which leads to jitter.
2. One-way audio: Similar to jitter, those who are on calls made via LCR can experience one-way audio if voice packets aren’t properly transmitted. When this occurs, it can result in only one party being able to hear the call, while the other party hears nothing and might think that the call dropped or the other person hung up.
3. Dropped calls: Again, by not prioritizing quality, those who are on calls made via LCR can find their calls dropped by unreliable networks.
4. Latency: Have you ever experienced a delay between the time someone on a call says something and the time the other person hears it? It makes having a conversation difficult, and it’s a problem that can occur with LCR when networks don’t transmit data fast enough. With good carrier quality, there should be no delay.  
5. High post-dial delay: LCR providers may try to connect over a network that’s at capacity and have to try again over the next-lowest-cost network. While this happens relatively quickly behind the scenes, you don’t want to waste precious seconds waiting for calls to connect every time, particularly at high-volume call centers.
6. Lack of support for automated operating systems: LCR providers may not be able to connect to a number that uses dual-tone multi-frequency (DTMF) signaling for interactive voice response (IVR), such as an automated operating system at a customer service call center that asks callers to enter information using a Touch-Tone keypad so calls can be routed to the appropriate department. Some LCR systems pick carriers based only on cost, rather than looking into whether the underlying carrier can support DTMF.
7. Lack of Caller ID retention: Calls transmitted using LCR don’t always retain calling line identification (CLI), which means the recipient might get a call from a number that displays as “Unknown.” As we all know, calls from an “unknown” number rarely gets answered. Even if the call displays a number, it may be a random number, not the one that the caller wants to display. That means that if a customer tries to call back based on the number displayed by the LCR carrier, they may not reach the original caller.

Selecting the right carrier

To avoid these pitfalls that accompany LCR, companies should look for SIP trunking providers that have these five attributes:

1. Media and signalling PoPs near where you make calls: Having points of presence (PoP) available close to the regions where you intend to make calls helps ensure that calls connect clearly and quickly, without the latency issues that can plague LCR.
2. Multiple local carrier connections: Similar to the benefits of having strong PoP coverage, having multiple local carrier connections improves routing efficiency because it eliminates latency and call routing.
3. Guaranteed DTMF support: To avoid the problems that can occur with an LCR that can’t connect to automated operating systems that use DTMF, look for a carrier that guarantees DTMF support.  
4. CLI retention: Make sure your carrier provides CLI retention so you can avoid the problems that can stem from not displaying the right phone number.
5. High availability with promised uptime: What good is a carrier if you can’t make calls due to network downtime? Look for a SIP trunking provider that can deliver consistently. Zentrunk, for example, promises 99.95% uptime.

Quality should be the priority

While LCR provides the benefit of cost savings, both SIP trunking pricing and SIP trunking quality need to be considered together, with quality coming first. That’s because “saving money” on ineffective calls often isn’t really saving money at all, due to lost productivity and missed opportunities from unreliable calls.

One benefit of a cloud-based SIP trunking provider like Plivo is that we work with multiple local carriers and can route your calls efficiently. Rather than ranking carriers solely by cost and routing accordingly, our intelligent routing system measures call quality and creates a quality score to reorder the priority of carriers and make calls through the highest-quality carrier available. Using self-learning algorithms, Plivo continuously searches for the best-quality route for calls.

Focusing on highest quality rather than the lowest cost helps ensure that SIP trunking as a whole is worthwhile for your business.

To better understand how to select the right SIP trunking provider beyond looking just at SIP trunking pricing, see our blog post on 10 factors to consider. To learn more about SIP trunking and see how Zentrunk can help with your communications needs, get in touch with our team.