Is Call Quality up to Scratch on VoIP Phone Systems?

Do we take call quality for granted in modern VoIP systems?

As you may have noticed recently, voice over IP telephony has become something of an industry standard. ISDN is looking like it’s on its last legs and most businesses these days don’t think too hard about choosing a SIP- based phone system over an old analogue or digital one. But is it that simple?

I have had a lot of conversations about the benefits of VoIP versus ISDN telephony in the last few years. It used to be commonplace to discuss call quality. Potential customers would be wary of poor call quality when using voice over IP and would usually have some anecdotes about colleagues who had tried it and were getting all sorts of problems. As a big believer in VoIP as a technology I’ve always found this frustrating. Instead of talking about call quality, I wanted to talk about about the great features on offer; the mobility, the cost savings, the easy disaster recovery, and so on.

These days I have this conversation a lot less. But you know, it is still a really vital component of a good phone system and taking call quality for granted on a VoIP system is still potentially a big mistake. When I do have this conversation these days, I can speak from a lot of experience on how to ensure that VoIP call quality is just as good if not better than ISDN, but that’s not to say that it can’t go wrong if you don’t pay attention to the basic requirements of VoIP.

These days, with the ubiquity of IP telephony, the chances are that even if you are not using VoIP, you have been on a call with someone who is, and you might well have experienced this issue. The people on the other end of these calls have moved to VoIP to get nice new features, to make their work more convenient and to save money, but now you are suffering because of their poorly implemented IP phone system. So how can you make sure that you don’t fall into to the common pitfalls when implementing VoIP?

If it doesn’t get what it wants, it will let you know straight away with a poor call quality tantrum.

When it comes to dealing with VoIP traffic on a network, I often think of it as a spoiled child of an application. If it doesn’t get what it wants when it wants it, it will let you know straight away with a poor call quality tantrum. This can cause missed words, distortion, delay, frequency compression and in the worst case, dropped calls.  All this can be extremely frustrating and presents your company pretty badly. If you can’t be reached reliably by phone, then it will annoy your clients and damage your reputation.

At Cerberus, when we discuss IP telephony with our customers, we start with the benefits of the system, of course. But in the next breath, we start a conversation about network performance. The key considerations here are bandwidth and quality of service.

First, bandwidth: is there enough reliable bandwidth from the handset to the phone system, and then from the phone system to the telephony provider to deliver the call? On a typical local area network, the handset will be connected via 100Mbps or 1Gbps Ethernet, and a typical VoIP call requires about 100Kbps at the most, so a lack of bandwidth is rarely the issue. That said, it can often be worth putting the phones on their own dedicated switches to completely separate the voice traffic from the data network – especially when you want to provide power to the handsets without having separate power supplies all over the place.

streaming and torrent traffic is causing havoc with phone calls.

By far the most common place for bandwidth to be a problem is on the upstream connection to the telephony provider. This is because most business customers are using broadband Internet connections, and these will have lower upstream bandwidth than downstream bandwidth. This can cause congestion, something which IP telephony traffic hates. That is not to say the downstream bandwidth is not sometimes a problem as well. I’ve seen cases where customers are unwittingly saturating their downstream bandwidth with streaming and torrent traffic and this is causing havoc with their phone calls.

So in the real world what can we do to protect voice traffic on the Internet connection? Well this is where quality of service comes into play. You may well be familiar with Quality of Service (QoS) on routers and switches. This is the obvious place to start. Quality of Service policies on the router and firewall connecting to the Internet prioritise voice traffic over everything else. Once only seen in high-end routers and switches, QoS is now on most half-decent network equipment. The customer’s router and firewall decides what traffic to send up and pass down from the connection, prioritising voice traffic from the Internet received at the firewall to be sent to the LAN. Likewise the firewall can decide which traffic received from the LAN to send upstream on the Internet connection. Given that upstream bandwidth is usually where congestion first appears, that is a vital tool for properly supporting voice on the network.

downstream quality of service (QoS) on the customer’s router or firewall is largely irrelevant

But this misses one critical fact. When traffic is coming downstream from the Internet Service Provider (ISP) it is not the customer’s firewall or router that decides what traffic needs to be prioritised. It is the ISP’s equipment that makes those decisions. So any downstream quality of service on the customer’s router or firewall is largely irrelevant. Ouch. So what do we do about this if we want to make sure that we can trust the connection to support VoIP?

Broadly there are two options. The first one is the simplest but also the most expensive and in my opinion the less elegant. To be sure that no other traffic can interfere with your VoIP traffic, we can just dedicate the connection to VoIP and not allow any other traffic to use that connection. It’s obvious how this works but it also incurs extra costs by doubling up on connectivity.

Does your ISP do quality of service?

Option two is to put QoS on the Internet connection itself. Now this is easy to say but less easy in practice. It relies on the Internet Service Provider themselves to do that quality of service for you on their equipment. So the question is, does your ISP do quality of service?

At Cerberus, this is something we have been aware of for a long time and the answer is a big yes. We have had Quality of Service available on our Ethernet and broadband services for as long as we have been providing IP telephony. This is the only way that we can look our customers in the eye and say that we guarantee call quality when using VoIP. In fact it’s a key part of our MyCloud strategy of integrating connectivity and hosted services to ensure that they work together as part of a single solution.

So, is call quality up to scratch when using IP telephony? Well it certainly is if you use the right tools to ensure that you are giving the traffic the bandwidth and priority that it needs, end to end.

If you want to find out more about Cerberus’ range of IP telephony services or our VoIP-ready Internet connectivity services please contact our sales team