What are SIP Trunks?

SIP Trunks are the way that phone lines will be supplied in near future and will eventually replace analogue, ISDN and broadband circuits!  As this article is penned (April 2011) it is not the moment that we’d recommend our clients to take the plunge into the realm the 21^st Century Network being rolled out by British Telecom (or by other providers’ versions of it).  SIP Trunks are akin to the cables that link your computer into the office LAN.  However, in this case the network is not purely local, but national, and anyone that links into it will require a fixed IP address.

For Voice-Over-IP comms system there is a requirement that “Voice-data-packets” have a higher priority than “Data-data-packets”. If they don’t - the quality of the conversation will be rather poor – can you imagine waiting for a word the amount of time you sometimes have to wait for a new screen on a website?  The Quality-Of-Service feature in switches and routers that overcomes this problem has the acronym - QOS.  At the date of writing, not all carriers’ offerings of SIP Trunks deliver Q O S and hence any voice traffic being delivered to you over SIP Trunks might not be quite up to the standard you want.  For other Internet communications it’ll be fine.

When suppliers can guarantee Q-O-S on their SIP Trunks it will be then worth considering - if the pricing will give you the returns over the years to come.  As with the introduction of ISDN2 and ISDN30 we found out that not everyone’s interpretation of the standards was the same. As a result some manufacturers argued with BT & OFTEL that their product conformed but the ISDN-2, didn’t.  Some were in fact right and the PTT’s had to make software design changes.  SIP Trunks will be the same – so delay until the dust has settled and the networks are resilient and performing consistently 24 hours a day and 7 days a week.  It’s the same with any emerging technology – the technicians operating it have to be trained up to support it correctly when problems develop.