Pick SIP… for Quality Sake

Everyone should be well-aware of SIP trunking and how it is used to replace legacy TDM physical trunks. SIP trunking has become a mature technology over the years. However, its adoption is driven predominately by cost. In fact, during panel discussions at the last UC Summit, it appeared that the only reason for choosing SIP was cost savings. SIP trunking can save money in a number of ways: by reducing the number of ports, consolidating the communications infrastructure into centralized sites, or can even arbitrage between multiple providers. And yet, the move to SIP has not moved as quickly as one would expect. While this is due to a wide range of reasons, often price reductions for existing ISDN trunks eliminates the financial incentives to move to SIP. For the service provider, encouraging the continued use of an ISDN trunk is a good financial plan, as it continues the use of a depreciated asset, as well as avoiding the competitive potential of a SIP services procurement. Beyond the price considerations, concerns about the reliability of a SIP trunking service or the associated IP access or MPLS service required is also always listed as a factor holding back businesses from adopting SIP.    

The result is that SIP trunk adoption, while growing steadily, has not been an overwhelmingly rapid transition. In a recent regional user group of a major UC vendor, more than 80% of the users represented said their companies/organizations still used ISDN lines. When asked why they were still using TDM, some commented that they had not transitioned to VoIP at all, but most respondents said they had transitioned only partially to VoIP and were still using the ISDN trunks for the reasons noted above.

The problem here is that voice quality is at risk when an organization deploys SIP trunking in such hybrid environments. Earlier this year, in a No Jitter post, Phil Edholm raised the issue of VoIPmaggedon. The essential concept of VoIPmaggedon is that combining SIP trunking services with ISDN lines has been shown to introduce significantly increased latency resulting from multiple VoIP packet processes, multiple transcoding, and echo issues, all of which dramatically degrade voice quality. As business VoIP endpoint adoption in North America is reaching 50%, these issues are now impacting a significant number of calls. For a more detailed analysis of the issues, read a white paper here.

Making the switch to a 100% SIP trunking based telecommunications service can dramatically enhance quality of the voice call. As the call stays as a VoIP call end-to-end, there is only one packet process. This can reduce latency by up to 67% versus a call with ISDN trunks on both ends and the carrier also using VoIP/SIP. The result is that the latency of the SIP call is typically less than 200msecs, while the ISDN call can be over a half a second or more, which is really push to talk. As such, one key way of improving overall voice quality is to move to SIP. 

However, to realize this premise, your SIP trunking vendor needs to be carefully selected, based on how their VoIP and IP network is set up. How your SIP vendor peers with other service providers both at SIP as well as at IP level can have a dramatic impact on the voice quality. For example, some services have minimal peering, so a voice call to someone down the street may be peering between your carrier and theirs on the other side of the country. Similarly, IP peering is often done haphazardly, as paths and latency are much less important for email and streaming than for real time services. These issues can be further exacerbated by SIP transcoding. When selecting a SIP provider, it is critical to discuss how the network of your service provider is set up.

For any organization moving to SIP trunking to replace ISDN lines is not just a cost question, it is a quality requirement. Any company with ISDN trunks will experience increasingly more quality issues today, growing rapidly as the number of VoIP endpoints increase. So moving to SIP is not an option – it is a requirement! Choosing the right SIP vendor is a critical part of that decision. Going with the wrong SIP/IP vendor could be a lot like jumping from the frying pan into the fire…choose wisely!

By Dries Plasman, VP Marketing and Product Management, Voxbone