How To Upgrade To SIP – 7 Mistakes You Don’t Know You Are Making

Upgrading to SIP – what mistakes are you in danger of making?

Some time ago BT announced that by 2025 their entire network will be IP. For business systems this will invariably mean a migration to a SIP trunk (Session Initiation Protocol – the Internet telephony equivalent of an ISDN trunk). At some time before this cut off date, all ISDN services will reach end of life. Although it may be tempting to sit back and wait until nearer the time there are many said business reasons to make the change sooner rather than later.

Some business leaders may be sitting back and waiting because they have heard of so many SIP migration disasters and they would rather not join the club.
So, what mistakes are you in danger of making that may cause your SIP migration fail?

Mistake 1

Not allowing sufficient time for planning.

Investing sufficient time in planning for migration from your current legacy telephony provision to a SIP provision is a recipe for failure. Any migration of telecommunications or IT services needs to be given full attention to ensure all aspects of the change are considered in the migration plan. This is particularly important if you are porting existing phone numbers over to the new SIP service.

Mistake 2

Failing to enable the LAN for SIP and IP voice services in general.

Although there is typically adequate bandwidth on a LAN to support hundreds or even thousands of voice channels with ease, this should be left to chance. LANs can suffer with congestion which could have a significant impact on voice quality. Leaving this to chance may work out and may not present any problems. However, in the event of a problem the more elements of the network that can be ruled out as a cause of the problem the sooner service will be restored. The LAN house must be in sufficient order that in the event of a problem (which are often intermittent on voice circuits) you will be confident the LAN is not the cause because it has been provisioned with voice traffic in mind.

Mistake 3

Failing to consider the potential interoperability challenges.

Standards are a good thing but it is important to note that a manufacturer or SIP Service Provider may use a particular variant, or subset of the SIP standard. These cause variations may render a telephone system to SIP Service Provider’s interface incompatible. Some telephone system vendors insist on using certain ‘approved’ SIP service provider for their particular system. Others may insist that you interface between the telephone system and the SIP service provider is via a Session Border Controller (SBC). An SBC can be used to resolve interfacing issues as well as to improve SIP security.

Mistake 4

Underestimating the amount of bandwidth required for SIP Trunk delivery

This is critical to the success of your SIP deployment. Always check with your system vendor but as a rule of thumb 100Kbps should be allocated per voice channel for toll quality voice. This allows for 64Kbps for the digitised voice channel plus a protocol overhead.

It is vitally important to bear this in mind for asymmetrical access circuits. For example, if you are considering an ADSL service for a small number of SIP channels the downlink speed is rarely an issue. The greatest challenge is the uplink speed as this may be 400Kbps or less. Even if the ADSL service is dedicated to the SIP service, the uplink speed offers little margin for error and may lack the reliability to support one channel.

Mistake 5

In the event of any technical uncertainties, failing to run a trial.

If there are any doubts as to whether SIP is going to work in your environment and meet with your expectations, it is advisable to run a meaningful and structured trial on your own network. This generally comes at a cost as this requires some engineering work by your provider and a time commitment for your own team. The trial must have clear goals with a detailed test plan so all parties understand what constitutes success and failure.

If the test is successful, the time and energy spent on the trial will reap benefits during the full implementation as the migration is much more likely to go smoothly. A trial will reduce the risk to the business by affording you the comfort to testing the new SIP provision while the existing legacy services remain operational.

Mistake 6

Failing to understand the implications regarding Emergency Services numbers.

Many take for granted that when we call 999, should anything happen to us before we complete the call the emergency service will be able to trace the call, locate our whereabouts and notify and deploy the Emergency Services. The ability to accurately locate the caller on 999 (and 112) calls save lives.

Legacy land line services were relatively easy to locate as every line and telephone number was associated with a physical address within a specific exchange area. Even users of mobile users can be located in many areas as their handsets associate with cell antennas.

The challenge with SIP and any other Voice over IP service is that the call invariably breaks out to the public network in a location totally remote from the user’s location. It could even be in another city. It may be possible to register your numbers with the Emergency Services Database so your 999 or 112 call can be routed to the relevant Emergency Services handling centre for your location. However, some SIP systems break out in other countries and in that case, they may stipulate that calls to the Emergency Services are not available from these handsets.

Always ask about calls to Emergency Services and ensure you have a thorough understanding of the implications (if any) so you can inform your staff, contractors, visitors and anyone else that may use your phone system.

Mistake 7

Failing to take adequate measures to secure your SIP service.

There is no doubt that SIP fraud is a big problem. This is nothing new to the data world as we have had to protect against hackers attempting to fraudulently access our systems since before the World Wide Web was conceived. Yet even with the benefit of over 25 years’ experience, many organisations have still failed to take appropriate action to secure their SIP service.

SIP fraud attacks vary and some attacks are easier to spot than others. A ‘ram raid’ style attack where attackers prepare their attack to coincide when there is the least possible chance of detection can run up bills of astronomic scale. For example, a system may be attacked on a Friday night and be used as a platform to handle hundreds of International calls. The first you may know of this is when you arrive on Monday morning to a bill running in tens of thousands of pounds. You may not even know by Monday and the attack may still be progressing. This will depend largely on your SIP provider and their tools for monitoring ‘out of character’ activity.

Ram raid attacks are usually short and very painful and once discovered it is usually possible to fill the security gap. There is another type of attack that is very low profile, using occasional illegal access over a long, time-period. This is far less obvious and may go on for years. This type of attack also pre-dates the Internet.

There are many things we can do to make our SIP services more secure, the exact choice of equipment and services may depend upon the inherent security facilities of your telephone system and your SIP provider. All of this requires careful consideration and configuration to maintain optimum security. Furthermore, any equipment and software used must be maintained with the relevant security patches as and when they become available.

For more information…

Many years ago a professional decorator was talking to me about his less professional fellow tradesman cutting corners. He summed it up by saying. “Anyone can paint over dirt”. This is something that has stuck with me for many years as it also applies to what we do in telecoms and IT. When we migrate any IT service we must never assume that everything is ready for the migration. Preparation is key to ensure your migration is as smooth as possible just as it is to ensure you get a professional smooth finish to your paintwork. Absolute attention to detail is essential to avoid making the above mistakes and enjoying a trouble-free SIP migration.

I hope you have found this article useful. If you would like more information on SIP migration, please check out our Migrating to SIP guide which you can access using the form below.

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