| White Paper On Sip Trunking - Definition And Benefits | | | | internal software if the system is quite new. The |
| In direct response to frequent questioning on the topic | | | | system effectively 'sees' the trunks as normal ISDN |
| from clients, we have prepared this 'low tech' white | | | | lines, so nothing is changed from the user perspective. |
| paper to help you to understand what is happening in | | | | 3. What are the benefits? |
| this part of the converging worlds of IT and Telecoms. | | | | Typical uses of SIP trunks are: |
| We hope that it is of interest. | | | | - Disaster recovery/Business Continuity |
| 1. What is SIP Trunking? | | | | The ability to re-present individual DDI numbers to any |
| SIP (Session Initiation Protocol) trunking is the | | | | location is one of the key benefits of SIP trunking. |
| technology that is expected to replace ISDN ultimately | | | | Traditional DDI can only be routed to a single number in |
| as the transport mechanism for voice traffic from the | | | | an emergency; in most cases, this would mean |
| PSTN (Public Switched Telephone Network) to | | | | hundreds of numbers reverting to a single operator, |
| corporate telephony systems or PABXs. It provides | | | | which would be hard to manage. |
| access to the PSTN using Voice over IP (VoIP) and | | | | With SIP trunking, key DDIs can be set up to route to |
| there are numerous benefits to the end user from | | | | the user's mobile phone or dedicated landlines in a |
| cost saving to flexibility and disaster recovery. BT's | | | | different location; alternatively, hosted IP PBX |
| 21st Century Network (21CN) is based around the | | | | extensions could be used as a back up and logged |
| conversion of traditional exchanges to delivering VoIP | | | | into from any Internet connection. The key point is that |
| to all end users and the use of SIP will feature more | | | | inbound numbers are not confined to a single location |
| and more in the years to come. | | | | any more and a variety of plans can be made around |
| 2. How does it work? | | | | this simple change. |
| The service provider or carrier will port a subscriber's | | | | - Geographic number portability |
| number(s) into its own exchange network or hosting | | | | Numbers are also no longer confined to the local |
| platform, which will be located in a secure data centre. | | | | exchange. If an office relocates to what would |
| These numbers are then re-presented across a | | | | normally be a different exchange area, it makes no |
| private IP network (MPLS, VPLS) or Internet | | | | difference with SIP trunks as they are just |
| connection back to the subscriber's premises. Quality | | | | re-presented across the new network/Internet |
| of Service (QoS) is essential in a corporate VoIP | | | | connection. |
| environment and this can only be offered over leased | | | | - Cost Reduction |
| line, MPLS or VPLS networks. Thus a leased line is | | | | The cost of SIP trunks is approximately £5 per |
| provided to connect into the MPLS 'cloud', which in turn | | | | line per month, against £17 per line per month for |
| is linked to the carrier, who will have their links into the | | | | ISDN 30. The leased line connection to the MPLS |
| PSTN. In addition Virtual Route Forwarding can be set | | | | network must also be taken into account; however, |
| up to provide Internet access from the same leased | | | | this can be off-set if combined with VRF or an Internet |
| line connection to reduce costs (See Fig 1, high level | | | | gateway service, i.e. two costs are rolled into one, |
| schematic). | | | | ISDN and Internet. |
| ADSL Broadband can be used in certain | | | | There is also a potential saving of thousands when |
| circumstances where user numbers are low, but it | | | | compared to traditional DR services involving the |
| does not carry any QoS and should be used in | | | | delivery of a lorry with a temporary phone system or |
| isolation to data services. It is ideal for homeworkers | | | | an off site disaster recovery location, held at great |
| and small branch offices. | | | | cost and potentially never used. |
| The service provider will usually supply both the | | | | 4. How will it benefit my business? |
| exchange and MPLS connection as a single product, | | | | There are literally dozens of scenarios where |
| although in many cases this will be through | | | | organisations can save money and improve their |
| interconnect agreements and links between different | | | | business continuity plans. Voice is nearly always the |
| providers (as also happens with traditional telephone | | | | forgotten relation when preparing for the worst and |
| lines). The end user will be unaware of who is providing | | | | yet is usually the operational jugular. Cut your |
| the various sections of their service. | | | | customers' and support staffs' ability to talk to you and |
| The SIP trunks are presented onto existing PBX | | | | at best you can expect to flail wildly before collapsing |
| equipment, either using an external media gateway or | | | | in an undignified heap! |