Future Networks

SIP trunk makes life easier for ICT departments

With All-IP, companies can now have precisely as many voice channels as they need – and no longer just trunks with two or 30 channels.

All-IP is revolutionizing the way in which companies operate their telephony infrastructure. With SIP trunks, they can adjust their communication capacities as they wish for the first time.

Companies have never been spoilt for choice with ISDN. There were only two options  to choose from when implementing a new network line: a basic access with two user channels (B channels) per copper twin wire or a first data multiplexer with 30 user channels. The downside: If a company grew and required 18 more channels, it chose the multiplex interface, because this cost less than nine basic accesses – even though this solution was actually over-dimensioned. Plus, a technician was needed on-site for installation of cables and  the network termination equipment (NTPM).

Online scaling

All-IP makes it easier for ICT departments to provide voice channels. There are indeed SIP connections that only offer a few user channels much like a multi line. But IP PBXs – or "SIP trunks" – provide a variable number of voice channels, without the need to install a new network termination unit or new cables. Companies simply book new channels online, paying only for as many as they use. Thanks to vectoring technology, as many as 164 parallel calls can be transmitted in guaranteed quality via copper twin wire. The number of channels set up at a company site is only limited by the amount of bandwidth available there. This can differ from site to site.
Companies should check with their providers and clarify the call number types (multiple subscriber numbers or system numbers) they can transfer from ISDN lines to corresponding SIP lines. For instance, call numbers from multiterminal lines and PBX lines cannot be ported to a local SIP trunk at the same time. First data multiplexer that each work with their own call number blocks (instead of a shared one) cannot be transferred together with the numbers into a local SIP trunk. Companies must install different SIP trunks on-site for such configurations. Alternatively, they can use a central SIP trunk because all call numbers can be transferred to it (the following article contains more information on this).

IP-compatible special services

One of the most important steps in switching to a SIP trunk is to determine what kinds of telecommunications lines a company has and which applications it uses. This is because the lines are sometimes also used by devices and special services that are not IP-compatible without further technical adjustments. With alarm systems, for example, the interface between user and security service must be upgraded regularly so that an identification signal can be sent continuously. Or, if possible, the analog line can remain as it is, and the IP platform works in the background.

New design for local telephone networks

Many large companies have long been using Voice over IP (VoIP) via their existing LAN infrastructure in their local networks. Smaller and medium-sized companies still work to some degree with their own cabling for telephony. Old, non-IP-enabled infrastructures can also be used on an SIP trunk with an interconnected media gateway. However, with a switch to SIP lines, it makes sense to immediately acquire an IP PBX and IP-enabled phones, or perhaps to even use a cloud solution. The telephone system will then use the LAN, as will all other applications. As a result, the company will operate only one local network instead of two.
In addition, the ICT department can also configure all related devices and functions centrally and online via VoIP technology. If an employee changes desks, he or she will simply take along the phone and then plug it in. This is possible because the called party is automatically determined via the phone or a PIN, and he or she will receive calls in the switched LAN on any Ethernet plug. A technician used to be required for such relocations because every extension had a specific telephone line or subscriber line module (TAE) assigned to it.

Telephones are now simply software

Alternatively, companies can get rid of desktop phones completely and go for telephony apps, which are also referred to as "softphones". By doing so, they do not have to buy new IP phones. In addition, they no longer have to think about supplying power to the new phones. In the past, the devices drew power from the phone cable. Modern IP desktop phones require their own power cable or they get their power from the network cable (Power over Ethernet, PoE). However, this technology does require PoE-enabled switches in the LAN – an investment that is considered too expensive by some companies.
Softphones provide one of the most important benefits of All-IP: separation of services from the physical network. Like e-mails, video conferences and instant messaging, telephony now also runs as an application on a computer and uses the computer's existing network access. Employees then use headsets instead of bulky desktop phones.

The next step

Any company using VoIP in its LAN and the carrier's SIP trunks can plan and provide telephony services even easier than before, and not just at individual locations. Another groundbreaking innovation is opening up for companies with several sites: telephony centralization. Read more about this in the next article from our perspective series – Future Networks.

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