| Asterisk telephone systems (PBXs) use voice over IP | | | | services, so that SIP Trunk services have built in |
| (voip) and ISDN for making telephone calls. The most | | | | redundancy even in the event of a major BT |
| common method is using Session Initiation Protocol | | | | backbone problem. |
| (SIP) which is the international standard for inter-vendor | | | | One of the other major benefits of using SIP trunks for |
| phone system communication. Asterisk voip telephone | | | | asterisk voip is portability. Once a phone number has |
| calls are typically transported over the internet to | | | | been assigned to the trunk, you are then able to then |
| reduce cost using a SIP trunk. SIP trunks offer | | | | "port" or move the phone number to another service |
| significant cost-savings for businesses, eliminating the | | | | provider. Furthermore moving the SIP trunk itself is |
| need for local PSTN gateways, costly ISDN BRIs | | | | simply a case of moving the broadband connection to |
| (Basic Rate Interfaces) or PRIs (Primary Rate | | | | another location which is relatively straightforward |
| Interfaces). The SIP trunk has multiple voice channels | | | | compared with an ISDN relocation where the chance |
| within it rather like a traditional ISDN service although | | | | of a prolonged outage is higher. Using SIP trunking, if |
| the number of channels within a trunk can be much | | | | you decide to move offices, you can take your BT |
| higher than an ISDN service and much cheaper. SIP | | | | telephone number with you using a porting service. For |
| trunks use voip to carry the voice streams over the | | | | example, if you are located in London with a 0208 or |
| internet, bypassing the local public switched telephone | | | | 0207 number, and move to Birmingham, you can take |
| network and hence reducing the cost of the call. | | | | your BT telephone number/s with you. |
| Typically a SIP trunk is set up using a broadband | | | | SIP trunks can also be used to connect asterisk voip |
| internet connection and the number of lines is limited by | | | | phone systems together and take advantage of free |
| the bandwidth available and the type of compression | | | | calls between them. This configuration is often used to |
| used. A configuration is put into the PBX to tell it where | | | | connect offices together within a business so that it |
| the host is, the type of compression to use, security | | | | can offer free inter-office calling and internal calling. |
| authentication method and various other settings. The | | | | The business can also take advantage of other |
| quality of the asterisk voip phone call is maintained in | | | | features like conferencing, virtual hunt groups and |
| various ways depending on the PBX owner's budget | | | | inbound call handling. |
| however for business asterisk voip, uncompressed | | | | With good providers of SIP trunks for your asterisk |
| voip (G.711 codec) is a good recommendation for most. | | | | voip phone system you should be able to handle the |
| This ensures that the call quality is always excellent | | | | whole process from provisioning to billing online with |
| using low latency, low hop count networks, but do | | | | activation possible instantly 24 X 7 X 365 through an |
| ensure your provider is partnered with the best Tier1 | | | | online self-provisioning portal. |
| carriers. When assessing your Asterisk voip SIP trunk | | | | Look out for providers offering a trial service so that |
| provider, a good service should look something like this: | | | | you can test the voice quality by making some calls. |
| 1. Data centre located in Telecity in London which is | | | | Setting up a SIP trunk is very easy compared with a |
| part of the London Internet Exchange (LINX). | | | | traditional, proprietary telephone system, and a good |
| 2. Staff that can assist customers in designing their | | | | provider will provide you with technical support and |
| network to optimise voice quality by separating voice | | | | may sometimes provide you with a working |
| and data traffic, using uncompressed voice and | | | | configuration for your telephone system if it has tested |
| choosing quality networking equipment (e.g. Cisco). | | | | its Asterisk voip service previously. Some common |
| 3. A provider whose network has no single point of | | | | systems that this is likely to apply to are Asterisk, |
| failure and who partners with more than one Tier1 | | | | Trixbox, Elastix, FreePBX, Vicidial and Atcom. |
| service provides for call termination and internet | | | | |