Fine-Tuning Your SIP Infrastructure

November, 2013

Sytel has considerable experience in configuring SIP services for a range of markets. Based on this, here are 3 potential issues that can seriously degrade the quality of your service.
Over the next three months we will be looking at SIP infrastructure and configuration – one of the major causes of headache for IT managers working with new IP contact center installations.

Sytel has considerable experience in setting up and configuring SIP services for a range of markets, from global market research to cloud contact center service providers. Here, we look at three major challenges faced in maintaining high voice quality, and offer solutions based on this experience.

1 –  The challenge of voice break-up

Back in the days of analog phones with T1/E1 lines to the network, there was no complication; no configuration was needed and the network manager could sleep at night.

With SIP, every service you are trying to use – voice, ad hoc video, data up/download, etc – is contending for bandwidth. This can lead to poor voice quality and unacceptable breakup, as voice fights for enough resource.


The only way to achieve consistently high quality voice is to prioritise voice over other traffic. For that you must use managed switching throughout the network, and also make sure your network backbone has enough capacity to deal with total load.

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2 –  The challenge of voice delay

In the world of SIP, as we know, voice sessions are split up into many packets. When these are sent over the wire, two things happen:

  1. At each leg of the journey, packets are held in a queue until they can be ordered properly. But a journey can contain many legs, and at each one, delay (or latency) is increased.
  2. In the interests of efficiency, each leg of the journey may use one of several compression protocols. But each time any translation is required from one to another, a delay is introduced. Again, over the course of a journey, these add up.


To minimize latency, firstly minimize the number of legs in a journey by certifying your SIP telephony stack directly with your carrier. Secondly, use  session border policies to minimize the compression/ decompression events within a journey.

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3 –  The challenge of virtualization management

Virtual Machines (VMs) are great – great for saving money on hardware, great for compartmentalizing processes. Trouble is that, unlike dedicated hardware, VMs will be contending for memory & CPU resources. As SIP and RTP processing is resource-intensive, a strict policy to dedicate resources is essential. The temptation is that when times get tough, and other VMs require extra resources, these are taken from the contact center allocation.


Don’t do it! Do not change or reallocate under any circumstances. Things can get messed up very quickly. The easiest way to manage this is to ensure the contact center infrastructure has its own set of dedicated VM hosts.

Read more

In our next blogs, we will expand on these topics, focusing on what you can do to meet these challenges and ensure you have a great SIP service.

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