Do I need a telephone service for DSL

IP telephone connection - these are the advantages and disadvantages

Daniel Behrens, Peter Stelzel-Morawietz

Are you still making calls or are you already "VoIP"? Sooner or later your connection will also be switched to IP telephony, if it is not already. Read here what advantages and disadvantages this has for you.

EnlargeIP connection instead of analog landline

The landline is dead - long live the landline. Because the fixed network, as it once started, will soon no longer exist. The telephone line itself is by no means obsolete. But its former sole purpose, namely the transmission of voice, has long been a minor matter in the age of DSL from a technical point of view. Today it is already noisy for many customers - without them explicitly noticing anything - only as a narrow-band digital Voice-over-IP data stream ("VoIP") parallel to YouTube streams and Internet pages through the Internet connection. And in a few years it will be the case for almost every household in Germany.

IP connection: Conventional telephone connections are being phased out

The classic, circuit-switched telephone service with analog or ISDN technology occupies a comparatively broad frequency spectrum on the twin copper wires of the connections. If you switch it off and use the free capacity for DSL signals, either the range and / or the speed of the connection can be increased. Range is the maximum distance between the exchange and the user's home, at which DSL can be achieved up to a certain speed.

EnlargeModernized cable distributor: The technology integrated in it and its direct connection to the fiber optic network is the basis for a purely IP-based telephone network.

Another disadvantage of the conventional telephone service from the point of view of a telecommunications provider: To do this, he has to operate a decentralized network of telephone exchanges. With IP telephony, on the other hand, he can bundle the technology at a few central points. This results in enormous cost savings. If a network operator then also relocates the DSL remote stations (DSLAMs) from the exchanges to the distribution boxes on the roadside (outdoor DSLAMS), as is the case with VDSL, it can close and sell most of the exchange locations. The interest of network operators - above all Telekom - to convert as many customers as possible to IP telephony as quickly as possible is therefore correspondingly great. The plan: by the end of 2018, all telephone connections are to be converted to VoIP.

Forced changeover:Don't be afraid of VoIP

Telekom is converting pure analog and ISDN connections in such a way that customers do not notice anything. In these cases, the data is converted by Telekom in the exchanges or cable distributors. It is still uncertain whether this also applies to ISDN primary rate connections that are used in medium-sized and large companies.

In the case of landline connections via which DSL is also used, however, it is a matter of clearing the frequency ranges that were previously permanently occupied by the analog or ISDN connection in order to gain additional DSL bandwidth. Therefore, the conversion of the voice into IP packets takes place on the part of the user, usually through his router with an integrated VoIP-enabled telephone system.

Anyone who gets Internet and telephone from a Telekom competitor is usually already using IP telephony. Because competitors can rent the bare connection line to the customer (TAL) from Telekom. This already saves you having to set up and operate decentralized telephone exchanges. Providers of Internet connections that run via the TV cable connection have relied on VoIP-like technology from the start.

This is how the VoIP technology of IP connections works

With IP telephony, the telephone is not plugged into the TAE socket on the telephone socket on the wall, into an ISDN box or into a splitter, but into the VoIP-capable cable modem or DSL router. It digitizes the sound waves converted into electrical impulses by the analog telephone, compresses them if necessary, packs them into data packets and sends them to the provider's telephone server via the Internet protocol. This exchanges the data with the conversation partner. If the other party does not use IP telephony or is a customer of another provider, the data is fed into the conventional telephone network via a transfer point (gateway).

EnlargeGoodbye cable clutter: For connections with IP telephony, just connect the DSL cable to the telephone socket. Plug your telephone into the TAE socket on the router.

So that you can be reached for incoming calls at any time, it is necessary that the router remains permanently online. With some providers, it sets up a second connection ("PPPoE session") - invisible to the user. This is then only responsible for telephone traffic. Other providers, for example Telekom, also use the normal online connection for telephony. The router and the network components of the provider prioritize the VoIP data packets so that interference-free calls are possible even when there is a high load.

Reading tip:Tips & tricks for your IP telephone connection

As long as there are no calls being made, the VoIP bandwidth is usually also available for other Internet transmissions - a decisive advantage over conventional telephony. Whereby the bandwidth requirement with VoIP is very low anyway.

In contrast to classic Internet telephony such as Skype, the IP telephony data at Telekom, Vodafone, O2 & Co are not routed over the Internet, but only within their own network. In this way, the providers can direct them to the recipient via the shortest route and prioritize them along the entire route. Dropouts, delays or disconnections can thus be virtually ruled out. Of course, this only applies if the DSL access is stable.

The voice quality is basically comparable to conventional telephony. If both parties call in the same network and use telephones that support the G.722 voice codec, the voice quality is even significantly better. The procedure is also known as "HD telephony" or - in the case of cordless telephones - as "CAT-iq".

Use VoIP on your smartphone

In principle, Voice over IP is possible wherever you have an online connection, including on your smartphone. All you need is a suitable app, Android has already integrated a client for SIP / VoIP telephony. To do this, click in the normal telephone application on "Settings -> Call settings -> Settings for internet calls -> Accounts for internet calls (SIP)". However, individual device manufacturers have removed the option. The alternative apps Zoiper, CSipSimple and Acrobits are more powerful anyway.

If you use one of the preconfigured VoIP providers from the lists in the respective app, setting up the account is easy. Otherwise you have to fight your way through various settings, this also applies to Telekom customers. Because the company's "Help" page is more confusing than useful, we have summarized the relevant entries for the telephone apps and programs here.

Host / Server:

Username: Your landline phone number based on the international model including area code, i.e. + 49089fx (089 as an example for Munich).

Username / authentication: your T-Online e-mail address (possibly to be created in the web customer center first).

Password: Your e-mail password (not the one for the customer center), not the password for Internet access.

Outbound proxy / outgoing proxy address:

We have to leave the entry for the STUN server (specified by Telekom: "") blank, otherwise the line will not be established in our tests. The setting in Telekom's own Hometalk app (Android and iOS) is easier; all you have to do here is enter your phone number, email address and password.