Ask the expert – Everything you wanted to know about Voice over IP (VoIP).

Ask the expert – Everything you wanted to know about Voice over IP (VoIP).

VoIP is often pronounced (voyp), but is also referred to as Voice over IP is a collection of technologies for the delivery of multimedia such as Voice, Video, Fax and SMS using Internet Protocol (IP) networks such as the Internet.

Traditionally, telephony is carried across the public switched telephone network (PSTN) whereas VoIP is transmitted over the public Internet. There are similarities such as signalling, setting up the channel to carry the audio converted from analogue to digital, then encoding into small chunks suitable for transmission called packets.

Unlike analogue telephony sent over the PSTN network, where the speech is transmitted and received in the order it was intended, whereas a packet-based network routes these packets across different paths across the internet, meaning they can be jumbled up and received out of sequence.

Using a little artistic licence, we can explain this s follows. Let us assume someone said “1,2,3,4,5” and each word was packaged into a single packet. So packet one contains the speech “1”, packet two contains the speech “2” and so on.

When these packets are sent in order “1”, “2”, “3”, “4” and “5” then they may be received as “2”, “1”, “5”, “3” and “4”, which would make no sense in a conversation, so they are collected and sorted into what is called a buffer and ordered into the correct sequence.

Because these packets need to be packed up, sent, received and unpacked at the other end and sorted quickly, then some of the methods used to ensure reliable transportation are relaxed, meaning a lost packet won’t be resent as there is simply no time to request the lost information.

In techie speak, this is known as using UDP as a protocol which is more leaner than TCP which doesn’t have the ability to request lost packets.

The method of packets being lost and arriving jumbled up out of sequence can cause a delay and something called jitter, which to the human ear sounds like unintelligible broken speech.

Using the chain analogy, a weak link in a chain could cause the whole chain to break. Likewise, there are links in a VoIP chain that can be problematic which we will explain.

Quality of service

A poorly designed and implementation of a VoIP system can provide call quality problems in contrast to the more traditional PSTN.

This is because a PSTN system would refuse new connections if there were insufficient capability while carrying the remainder of calls without any impairment. Compare this to an IP system that would try on a “best effort” basis to transmit all of the packets held in its buffer, leading to packet loss, delay, and low call quality.

Press Telecoms engineers address this problem by performing stringent tests at the customer’s premises, to ensure there is an acceptable quality of service under load conditions, providing there are available channels with low latency which is matched equally on a 1:1 basis at our network exchange.

In small businesses implementations, a single high-speed broadband connection can be used if there is some prioritisation on the service. This can be done at the router using QoS, which regulates what is happening inside your network, but what happens when the connection is outside of your control, i.e. when the data is being sent across the backhaul links to the core IP network?

Press Telecom have access to premium grade broadband accounts that do not traverse the usual links often used at the street cabinet level. We have access to the Ethernet circuits in the FTTC cabinets, meaning we can bypass the congestion caused by all other users, meaning your traffic is now using the fast lane.

One of the advantages to small business using a well designed and implemented IP telephone system, when compared to a PSTN system is economies of scale.

Traditional solutions using PSTN (Analogue / ISDN) need to be sized accordingly to predicted demand. Each channel on a PSTN solution typically costs more than a VoIP channel, so there is usually some fiscal discipline when ordering PSTN lines and can take weeks to organise upgrades.

An IP based system can dynamically allocate the available bandwidth on demand, meaning a business using IP can when implemented properly, increase its call capacity without suffering audio problems. For a small business, this could mean having the ability to receive an urgent business call.

Having this dynamic ability means there is no need to pay for underutilised PSTN lines
can be allocated to match the Voice call requirements on demand, giving small business the ability to cope with any sudden rise in calls without incurring planning delays and wasted costs.

Low bandwidth solutions

VoIP may not be suitable for businesses that have low bandwidth connections due to the upload speed. For a successful call without suffering call quality, typically there must be a minimum of 100kb of bandwidth both up and down.

There are ways to manage low bandwidth connections by choosing an alternative method of encoding, known as a codec (Coder/Decoder). Some popular codecs can compress the speech to just 8 kbit/s each way called G.729, which is akin to the compression of a picture using JPEG.

You can also consider dedicating the internet connection to voice only, therefore ensuring just voice traffic is utilising the bandwidth.

You can also consider products that re-balance the upload and download speeds, such as Annex M, which reduces the download speed, but increases the upload, therefore providing the necessary bandwidth for quality calls.

This article would not be called “Ask the expert – everything you wanted to know about Voice over IP (VoIP)” unless we dived deeply. We will discuss some of the VoIP protocols.


Session Initiation Protocol (SIP) is a connection management protocol developed by The Internet Engineering Task Force (IETF). Its purpose is to act as a negotiator between systems. So for example, you may have a low bandwidth connection and need to use g.729 8 kb/sec, but the other party need to use g.711. The protocol will negotiate the common standard and ensure both ends agree before joining the calls.

Before SIP, there was another protocol known as H.323, which is considered one of the first VoIP call signalling and control protocols. While SIP continues to gain popularity, H323 can be found in many products such as CCTV, door entry and video phones, although deployments are now being limited due to the population of emerging technologies.

Media Gateway Control Protocol (MGCP) is a connection management solution for media gateways also known as H.248. Media Gateways are used to interface between traditional PSTN and modern packet-based systems.

VoIP Devices

As you can imagine, a regular telephone is unsuitable for IP telephony; however, there are devices that can be used to convert the old into new technology. These are known as Analogue Telephone Adaptors or ATAs.

While on paper they sound ideal, they can be problematic with echo.

While some devices offer echo cancellation to correct the problem, on PSTN lines that have underlying faults that vary the impedance, or characteristics of the line, then the auto-correction of the echo cancellation can be as annoying as the echo trying to be corrected.

Some but not all ATAs have a failsafe solution which ensures the Telephone remains connected to the PSTN line in the event of power failure, something that may be important, especially if you wish to make a call.

Softphones clients are available that allow you to make and receive calls using your computer. The cost of these softphone applications varies from free for personal use, to around £100.

We tend to steer away from the softphone client solution namely because computers can go on the go-slow, which impacts the ability to maintain a phone call, which is far from ideal.

Hard Phones

The most satisfying development of IP telephony for myself is the future proofing when it comes to hardware.

In the past with traditional PSTN systems, the phones on the desk were manufactured for the particular phone system and could not be used on different manufactures systems.

With IP systems that use SIP, you can mix and match different manufacturers on the same system. So this means you can choose a phone that matches your needs in terms of function and budget, plus you can add new devices that haven’t even been dreamt up, as long as they use the SIP standard.

Hosted VoIP

Hosted VoIP has been implemented in many ways ranging from the equipment you own being placed (hosted) into a data centre, to a phone system you don’t own being hosted from a data centre(s). Other terms such as Cloud Telephony are often used, which mean the same thing.

We will cover the topic of which system is best for my business in more depth in another article, but the main points we find with Hosted / Cloud telephony is that there are weaknesses that are seldom mentioned.

Hosted Telephony usually come with great promises of reliability, but the reality is, things do go wrong and often on a colossus scale creating widespread outages that can impact your business.

Here at Press Telecom, we provide Hybrid Phone System solutions that take all of the best bits from today’s technology such as IP Telephony SIP trunking, with on-premise equipment, with robust failover so that all of the eggs for businesses customers are not being carried in the preverbal Cloud Telephony basket.

Hosted systems are designed by the suppliers to be scalable so that they can sell the product easily. To achieve this they often use auto-provisioning services, which allows a company to send an unconfigured handset directly to the end user. When powered up, the handset communicates with the manufacturers provisioning server to obtain the next set of instructions which ultimately end up with a config file being downloaded by the handset and the phone is provisioned.

With the ease of selling a hosted solution, it opens the market to anyone who wants to sell these services, which can include new entrants into the world of telephony such as IT companies who may not have the traditional telephony experience.

So its no wonder that there is so much emphasis on Cloud Telephony and you could be forgiven to think that this is the only solutions due to the heavy and highly competitive marketing.

The Hosted VoIP market tends to be a one size fits all solution, which when you begin reviewing the checklist of features, everything seemingly appears to fulfil your needs, especially if you are upgrading from an old outdated system.

The Achilles heel of hosted is, there needs to be some restraint on usage. For example, call recording is limited to months, not years and so workarounds are offered to resolve this such as you can download your calls – who has the time to do this?

Call recording is one of the most useful tools a business can possess. We have seen many cases where employees have gone bad and evidence to confirm this was found with call recording.

Our Hybrid solutions are specified around your businesses needs, so if you need to have a recording facility that retains data for six years, you’ve got it.

There are other serious drawbacks with Hosted Cloud Telephony and that Internet outages mean there are no communications, but again there is another workaround offered, which is to divert your calls to mobile phones.

While that sounds okay, the reality of this can be far from ideal. To begin with, if you need help with this, try contacting the supplier for help when they are facing a complete meltdown due to all of their customers facing the same problem. They are in effect paralysed unable to help, which at this point you realise despite all of the assurances, that Hosted Cloud Telephony may not have been the best choice retrospectively.

With our hybrid solutions, we offer physical connections to real telephone lines, so that in the event of an Internet outage, it can be business as usual.

I will go a little off-piste at this point and discuss choosing a system and provider carefully, and we will write a separate article focusing on ARCs.

As a service provider ourselves, we receive calls from people who have found that they are locked into a contract with their provider, that automatically renews, with specific and narrow opportunity to serve notice to escape meaning they are tied to a bad marriage.

Usually, the reason why people wish to leave is due to poor service, so to compliment this poor service, there are poor agreements that favour the poor performing provider, which to my amazement, people don’t fully read.

While the exact reasons people don’t read the terms and conditions of contract will vary, its hardly surprising to hear when questioned was, they found them lengthy, difficult to understand and quite frankly they did not have the time to spend reading the agreement and thought it would be as friendly as the friendly salesperson selling the contract – wrong.

If you require help on this topic, the contact us for free on 0800 6800 139 and we shall try to help you.

Returning back to VoIP and particular hosted.

With all of the hosted systems we have seen, the emphasis is for you, the business owner to become the Telephone Engineer and program how you want the system to work, which is fine if that’s what you want to do however in practice you may only make adjustments once in a while and you may have forgotten on how-to do something, which is usually when you can least afford the time to resolve.

When you choose a system from Press Telecom, we are there by your side to make these changes so you don’t have to.

The costs of Hybrid from ourselves are on-par and in some cases less than many of the Hosted only providers, so given the choice of PSTN, Hosted or Hybrid – we recommend hybrid as you are getting more benefits for your business and less of the headaches.

Emergency calls

A telephone connected to a landline has a direct relationship between the telephone number and its installation address, meaning that when an emergency call is received, the location is automatically determined.

On a hosted cloud-based system, things can be very different.

With hosted cloud-based systems you are not tied to a physical location, just like a mobile phone, therefore when you make a call to the emergency services, you need to be able to give your location.

With a mobile phone, your location can be known, whereas a call placed on an IP network would need additional and timely steps to learn your location.

You can try this for yourselves by searching online for “what is my IP address” and you may be surprised to see that your location is being shown as the other end of the country.

To know where the call was originating from, the emergency service operator would need to liaise with the Internet service provider to provide the customer information for that particular IP Address being used at that moment in time.

As you can see this is unlikely to happen as time is of the essence when it comes to emergency calls.

With hosted cloud-based telephony, if there are problems such as internet connectivity, then you may not be able to place any calls let alone emergency ones, which is why many providers state that calls to emergency services are not supported.

With a hybrid solution, you could choose to connect to the PSTN line for those particular calls.

Fax support

While faxes are in decline, some sectors still use the fax machine.

For many businesses, they no longer send faxes but still have the occasional need to receive them, so we offer a FAX to Email service, which has the benefit of reduced costs in terms of line rental, fax ink/toner and paper.

When it comes to sending faxes or Fax over IP (FoIP), the transmission of fax documents used to be a problem due to the codec being used that were designed for voice calls.

A reliable fax-over-IP standard was developed called the T.38 protocol that allows transmissions over IP, which has been incorporated into some newer fax machines.

Power requirements

The telephone you have in your home is likely to be an analogue phone that is plugged directly into the phone socket, which derives its power from the local exchange.

When you shift away from basic telephony, you tend to require external power to use the devices. This is true for traditional PBX as it is for IP based telephony, with the only differences being the amount of power required.

With IP devices consuming up to 15 watts of power, you would need some substantial uninterruptable power supplies to operate a modern IP system, which if this is important to your business, then this needs to be factored into the overall solution.

Security and GDPR

Security has always been our focal point, which is why we have an exemplary record in protecting our customers.

There are many vectors of attack to consider and the most basic and natural thing to do is reduce those areas so that an attacker would find it more difficult to strike.

Like most creatures, that curl up into a ball to protect themselves, making their footprint smaller. Security is most effective when this principle is adopted.

If your a large single entity, such as a cloud-based solution provider then in an attackers eyes, you are a large worthwhile target compared to the small business on the high street.

If you look at all of the breaches of security, they are all big name companies who you would have thought would have had the resources to prevent this.

As I write this, there are fresh headlines when you search online for “security breach”, exposing users personal details, meaning there is a breach of GDPR and if you’re caught up in this, will this have an impact on your business?

With private hybrid solutions, you are able to achieve your own businesses security goals better because you are able to adjust risk particular to your business.

For example, the most secure systems are those disconnected from the world, which may at first seem obvious, but when it comes to telephony unless your only making calls internally, you will want to communicate with the world.

With a hosted cloud-based solution, your security is influenced by the provider, which may not match your needs. Using our hybrid system, a business can choose at a granular level what they need to make accessible.

We don’t see all businesses the same, which is why we provide Hybrid to ensure we carefully set the security to each businesses requirements.

With GDPR now in force, the financial and public reputation of getting things wrong are more severe than ever before and so we predict that there will be a return to the on-premise solutions for all things IT and Telephony as the real impact of cloud-based service provider security failures become more publically known.

Caller ID

With old-school technology, your phone number was tied to a particular telephone exchange. If you wanted to relocate businesses premises, then you may have to give up your phone number as it could mean a change in a telephone exchange.

In a real case example, one of our clients had retained its phone number for over 75 years. They had decided to move into larger premises just 3/4 mile away, which was unfortunately served by a different telephone exchange.

Despite being in eyeshot of each location, the number could not be retained using traditional methods. So in steps the term “Number Porting”.

By porting their number over to Press Telecom, we were able to retain the number and deliver it to their new location over IP, meaning the company can continue to receive calls on a number that has so much recognition amongst their customers.

Book your free communications audit today.

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