Cloud-- scrapers - zafaco

connect Professional 

Cloud-- 

scrapers 

Telephone systems can 

also be booked as a cloud 

service. When tested, 

several offers from the 

cloud took a few scrapes. 

Virtual phone systems, also known as 

“Centrex” in the technical jargon, promise many advantages: 

instead of hiring expensive and rapidly obsolete 

hardware, the customer subscribes to the IP 

switching technology as a cloud service. If he needs 

more extensions, he can book them quickly - or cancel 

them again if his company gets smaller. All the company 

needs is a fast Internet connection, which, alongside 

web and e-mail, then also provides the telephony. 

And each workplace has to be supplied with an Ethernet 

cable, which apart from the PC, also enables an IP 

phone to be connected. Or the employees telephone 

straight off by client software or mobile phone. 

Stress test for virtual telecommunication systems 

But do cloud telephone systems really keep what their 

providers promise in terms of voice quality and compatibility 

To get to the bottom of these questions, 

along with its trusted network test partner zafaco, 

connect put the Centrex services under the microscope 

in a four-week stress test. Hannes Rügheimer 

Fotos: © Peshkova – shutterstock.de 

114 6/2013 115


TeamFON 

The clear winner is “TeamSIP Centrex” from TeamFON. 

This is all the more remarkable because this provider 

does not supply any broadband access of its own. 

QSC 

A good second place was achieved by IPfonie 

Centraflex from QSC: the Cologners deliver a solid 

package of ADSL access and Centrex system. 

The range of TeamFON from Munich concentrates 

entirely on IP switching technology 

and, alongside hardware-based IP solutions, 

it also offers its own Centrex solution 

TeamSIP Centrex for this. This does not mean, 

however, that TeamFON makes any 

broad band access of its own available; for 

our test, the necessary connections were realised 

via a DSL 16 000 line from Deutsche 

Telekom. 

Just as TeamFON does not operate its own 

DSL network, this provider also has no mobile 

network of its own in its portfolio. However, 

the Munich specialists have nevertheless 

given a lot of thought to the integration 

of smartphones into their Centrex package. 

Thus TeamFON offers its own specially developed 

iPhone app “TeamSIP 2phone” 

which incorporates the Apple mobile in the 

Centrex functionalities as a VoIP client. 

TeamFON also has clients available for Android 

smartphones and BlackBerry devices 

with BlackBerry 7. And for all other smartphone 

systems the Munich team offers at 

least a browser application under the name 

“TeamSIP webphone”. In addition, with the 

Softphone “TeamSIP 2go” designed for 

Windows computers and with the combination 

of a web portal and any (also mobile) 

additional phones, further alternatives for 

the integration of mobile extensions are 

available to choose from. 

Abundant SIP hardware and software 

When booking up to ten extensions, each 

TeamSIP connection costs 6.90 Euros/ 

month net. From the eleventh extension the 

price level falls. If you book more than 51 

extensions, you only pay 5.90 Euros/month 

net for each. The Windows SIP client 

TeamSIP 2 go is available for an additional 

charge of 2 Euros/month net. TeamFON 

recommends Apple Mac users the IP soft 

phone “Bria” from the U.S. provider CounterPath 

(49.95 U.S. dollars). 

Telephone calls to the German fixed network 

are charged by TeamFON at 1.4 cents 

per minute net. Alternatively, a flat rate can 

be booked, which costs 4.90 Euros per 

month and per extension. Calls to German 

mobile networks cost 11.9 cents net per minute, 

and for international calls there is a 

price list that can be viewed at the address 

www.teamfon.de/tf/de/TeamSIP_Centrex/ 

preise. 

If you also want to buy suitable IP phones 

at TeamFON, you have the choice between 

several models from the manufacturers 

Siemens, Snom, Tiptel, Aastra and 

Grandstream - this range is also available 

on the website www.team-fon.de. Fundamentally, 

however, the service can also be 

used with all other SIP-compliant clients 

and phones. 

When it comes to the switching functions, 

TeamSIP shows no weaknesses at all. 

Fax support, a company-wide address 

book and extensive computer telephony 

functions can also be found in the equipment 

list. 

Top values even without their own DSL 

Typically, VoIP providers fare less well if 

they do not operate their own access network, 

because they have no influence on 

the quality-of-service parameters (QoS) 

of the broadband line. It is therefore all 

the more remarkable that TeamFON was 

able to work itself up to top position 

among all the candidates in this year’s 

test. The error rates of the test connections 

via the TeamFON service were the lowest 

in the entire test, and voice quality and call 

setup times were at a very good level. 

Though in at least 12 percent of the connections, 

the voice quality sank below the 

critical value of 4.0 PESQ (Perceptual Evaluation 

of Speech Quality, see also page 

122), even that was not enough to challenge 

TeamFO’s test victory 

connect verdict 

good (410 points) 

Quickly connected: alongside QSC (orange coloured) TeamFON 

(petrol) achieved the fastest call setup times in the test field. 

Tidy: the web interface 

for administration 

is clear and convenient 

at TeamSIP. 

Efficient: the most 

important settings 

per participant can 

be managed with 

a few clicks. 

The Cologne-based company QSC is a pioneer 

in SDSL connections, but has now also 

been providing the more popular ADSL 

technology for quite a while. The virtual 

phone system tested here, IPfonie Centraflex, 

is also based on the 16 000 ADSL connection 

“Q-DSL office”. This solution is 

offered by QSC from 4.50 Euros per month 

and per extension, however with a minimum 

purchase of ten extensions. If you 

wish, you can rent appropriate IP phones 

from a very wide product range from 

7 Euros per month. Analogue phones and 

fax adapters can also be found in the QSC 

range. 

Connections within the QSC network are 

free of charge – thus also calls between various 

branches, provided they all work with 

IPfonie Centraflex. Calls to the German 

fixed network cost net 1.17 cents per minute, 

calls to Telekom and Vodafone mobile 

networks cost a full 10.1 cents net per minute, 

connections to E-Plus or O2 are somewhat 

more expensive at 11.6 cents net 

per minute. Unlike at Telekom or Vodafone, 

mobile phone contracts are not offered 

as part of IPfonie. However, calls to mobile 

phones can be mediated, a parallel call to a 

mobile is configurable, and also the return 

of mobile calls to the Centrex system is 

supported. To this end, QSC offers its own 

Centraflex app for iOS and Android smartphones. 

It’s almost impossible to believe 

that an IP telephony provider 

without its own network can 

deliver such convincing quality 

values - but the Munich provider 

TeamFON shows that it is possible. 

TeamSIP convinces with its 

functions, particularly in the integration 

of mobile subscribers, 

and with its administration. 

Extensive options 

The Centrex package from QSC is fundamentally 

modular in design. In addition to 

the standard switching functions, the basic 

package tested by us also includes convenient 

features such as an individual voice box 

per participant and extensive fax capabilities 

CONCLUSION (fax to email and email to fax). In addi- 

CONCLUSION 

tion, using the “Assistant Enterprise” provided 

by QSC, phone numbers can be dialled 

directly from Outlook - the necessary tools 

are available for download on the QSC web 

page. Anyone wanting more specialised 

functions such as voice-controlled menu 

navigation (IVR – “Interactive Voice Response”), 

call centre support (ACD – “Automatic 

Call Distribution”) or their own client 

software for a telephone exchange 

(“Receptionist”) can book these as well. 

The same goes for the unified communications 

software “Estos ProCall”, and multimedia 

conferencing, consisting of telephone 

and web conferencing, can also 

be booked separately as a stand-alone 

module. 

Good test results, also when faxing 

As is usual with Centrex solutions, the 

connections booked can be configured via 

a web interface. The QSC version poses no 

riddles, but still has potential for improvement 

when it comes to the details of its 

user interface, especially with regard to 

the rapid availability of individual, important 

settings and information. 

On the whole, the measurements carried 

out by zafaco on behalf of connect 

give a pretty good picture of QSC. The 

voice transmission parameters measured 

in the test connections such as call setup 

time, error rates, and the average speech 

quality (PESQ) determined are all at a 

high level, although still somewhat behind 

the results of the test winner TeamFON. 

The PESQ value established is only below 

the critical level of 4.0 in about 6 percent 

of the test connections. The transmission 

of faxes via QSC’s IP network is above 

average: here the calculated error rate of 

1.83 percent is the best value in the entire 

test field. 



Reliable quality: parameters such as here the setup time of fax 

transfers (QSC: orange) remained largely stable in the test. 

Clear, but too many 

levels: the control 

concept of the web 

interface still needs 

improvement. 

Individually customisable: 

a separate 

profile can be administered 

for each 

participant. 

The runner-up QSC has no striking 

weaknesses in any area, but 

is clearly behind the winner 

TeamFON in the overall standings. 

However, in terms of 

points, it has a comparatively 

low lead on the next contender 

Telekom. The modular extensibility 

of the product is also good 

and leaves nothing to be desired. 

116 6/2013 117


Telekom 

The extensive DeutschlandLAN delivers good performance, 

except for only one connection type. 

With its DeutschlandLAN, Telekom focuses 

on business customers with five to 49 

employees. The smallest configuration for 

five participants took part in the test. The 

scope of delivery includes a lot of hardware: 

along with the DSL router, VoIP 

hardware router and firewall, there are five 

IP phones of the type Snom 870. This is 

combined with an SDSL line, which transports 

10 Mbit/s in both directions, and with 

flat rates to all German fixed and mobile 

networks. Calls from the mobiles included 

to the virtual telephone system at the 

company’s headquarters are also free. 

However, not only the offer, but also the 

monthly price of 495 Euros is imposing. 

If five employees really need the hard - 

ware and the inclusive tariffs, the offer is 

attractive though. 

Only minor defects in practice 

In practical application, only minor flaws 

are apparent. For example, if a mobile user 

calls a customer back, his mobile number is 

always transmitted – the transfer of the 

landline extension number, which is practical 

in many cases, is not possible so far. Also, 

calls cannot be patched back from the 

mobile phone to the company headquarters. 

And the web-based administration interface 

could be more convenient: although it 

positively glows with clarity, some important 

information can only be found in 

deeper menu levels. 

Good measurements with restrictions 

The measurement data obtained from zafaco 

is, on the whole, good: an average call 

setup time of 1.44 seconds, and a PESQ 

value of 4.15 are not to be sneezed at. 

However, the voice quality in the scenario 

“main office calls home office” sinks to 

only 3.8 (PESQ) - this was something that 

affected more than 23 percent of the test 

connections. Also, the error rate when it 

came to the fax connections via the IP line 

examined is pretty high, at 7.7 percent. 



CONCLUSION 

Top: the user administration is clear, 

however, important information is only 

available in deeper menu-levels. 

Bottom: when connecting the main office 

to the home office under a data load, the 

PESQ value drops significantly. 

Overall, the performance of the Deutschland- 

LAN is impressive. However, the voice 

quality on some of the test connections 

dropped to such an extent, that higher 

ranking is not possible. 

Vodafone 

Officenet offers good intelligibility and rapid call setup, 

but suffered a failure during the test period. 

The Düsseldorf-based communications 

group entered the running with its Centrex 

solution “Officenet” which is based on a 

DSL line with 16218/800 kbit/s and is characterised 

by extensive mobile integration. 

Thus, mobile phones can be fully fledged 

extensions in the virtual telephone system 

and “combined participants” telephone either 

via a landline or a mobile phone and 

can be reached by parallel call. The Vodafone 

network here caters for the integration 

of IP telephony and mobile telephony. 

Within the participants’ company, all calls 

are fundamentally covered by the flat rate. 

For an extra charge, further flat rates can be 

added - up to the “international” version, 

which is valid for many countries. 

Many functions, operation acceptable 

When it comes to switching and convenience 

functions, Vodafone supports everything 

that is standard and established. 

The only thing that Officenet users have to 

do without is unified fax messaging. The 

administration interface could be a little 

clearer when it comes to viewing the status 

of the individual participants. The main 

functions are, however, accessible with a 

few mouse clicks. 

System error during the test period 

The measurements collected by zafaco 

give a mixed picture: Vodafone excels 

with very good speech intelligibility 

(average PESQ value: 4.36 – it was only 

below the critical level of 4.0 in about 

4 percent of cases) and brisk call setup. 

However, during the test period, the 

Düsseldorf-based provider experienced 

problems in a central network component 

for about a day, with the effect that during 

this period not many test calls came about. 

Since this disorder affected all Officenet 

customers, we decided not to exclude it 

from the assessment. This led to a relatively 

high error rate of 1.4 percent and 

cost points. 


satisfactory (358 points) 

CONCLUSION 

Top: the web-based interface could be a 

little clearer. Bottom: the call setup 

time shown under load (Vodafone: red 

curve) rises sharply at the time of the 

system error. 

A system error over about 20 hours cost 

Vodafone valuable points. Without it, the 

result for Vodafone would certainly have 

been better, especially as the performance 

of Officenet as a whole was convincing. 

118 6/2013


nfon 

The range of functions puts the other candidates in the 

shade. However, the measurements provide for losses. 

Sipgate 

The range of functions and mobile integration is 

appealing, but the measurements reveal problems. 

The Munich-based provider nfon 

delivered its Centrex solution “TK- 

Anlage” for our test with an SDSL line, 

which, at 2.3 Mbit/s in both directions, is 

not outstandingly fast. However, for a 

handful of IP telephone connections, the 

capacity is more than sufficient, and if 

that’s not enough, nfon also offers faster 

types of line. The telephone system’s 

range of functions is extremely extensive. 

nfon provides around 150 telephone 

system functions in its network, including 

specialties such as the so-called IVR 

system (Interactive Voice Response). 

Furthermore, the provider supplies an 

interface to Microsoft’s unified messaging 

solution Lync and the integration 

of mobile extensions in cooperation 

with O2. 

Widest range of functions in the test field 

Extensive call centre functions such as 

monitoring and voice recording, project 

codes and cost centres, customised hold 

music and much more are also part of 

the package. If the hardware supports it, 

IP calls can also be encrypted. And with 

the so-called hot desking, employees 

can use their extension number to log 

on and off the IP phones at various 

workstations. Moreover, extensive 

unified messaging solutions are part 

of the package. 

Losses on DTMF and fax 

The assessment in this network test is, 

however, based solely on the measured 

values established by zafaco – unfortunately 

there are no points for the range 

of functions. Therefore, the total score 

allocated for nfon is not quite sufficient 

for a top spot: though voice quality and 

call setup times are, on the whole, okay, 

problems for example with the DTMF 

and fax transmissions also tested cost a 

lot of points. 



CONCLUSION 

Top: the good impression made by the 

huge range of functions is confirmed by 

the convenient interface. 

Bottom: there are high error rates with 

fax transmissions (nfon: light blue) 

Although it’s not quite enough for a top 

position, the Centrex solution from nfon 

delivers very reasonable network quality 

and thus can easily hold its own against 

the competition. 

The provider Sipgate, which is also wellknown 

among private VoIP customers, provides 

a Centrex system for business customers 

under the name “Sipgate team”. The 

variant “team 3” which took part in the test 

is designed for three participants, however, 

the Düsseldorf provider also has packages 

for up to 250 participants in its range. 

However, Sipgate does not provide its own 

broadband lines, so in the test, the offer 

was examined via a DSL 16 000 Telekom 

line. Instead of the connection prices 

shown in the table below, flat rates can also 

be booked. For a voice flat rate to the fixed 

network, Sipgate customers simply pay 

double the monthly price, in the present 

case, this would, for example, be a further 

14.95 Euros. 

Mobile integration as MVNO 

Comprehensive mobile integration is new 

to Sipgate. Here, the provider acts as the 

“MVNO” (Mobile Virtual Network Operator): 

it provides its customers with 

Sipgate’s own SIM cards, however the mobile 

phone calls are then transported via the 

E-Plus network. Mobile phones which are 

thus integrated into the “Sipgate team” are 

fully-fledged extensions of the virtual telephone 

system, and the control of the switching 

functions is carried out via key 

codes. Each participant booked can either 

be effected as a fixed or mobile extension. 

All the settings, such as the outgoing caller 

ID, can be determined via the convenient 

web interface. 

Mixed measurement results 

In the current test, which is limited to 

fixed-line extensions, Sipgate loses a lot of 

points though. The speech delay of 231 

milliseconds is, for example, conspicuously 

high. Almost 27 percent of the connections 

remain below the critical PESQ value 

of 4.0. And more than half of the attempted 

fax connections failed 


sufficient (282 points) 

Successful: the convenient 

configuration 

of Sipgate serves 

as a shining example 

for all the other 

candidates. 

CONCLUSION 

The new mobile extensions offered by Sipgate 

played no role in this test, and in the 

fixed network measurements, the very convenient 

service unfortunately came bottom 

of the table. 

vio:networks 

Berlin-based provider delivers a decent Centrex 

product with generally acceptable results. 

With vio:pbx, the Berlin-based company 

vio:networks offers an extensive Centrex 

solution. According to the provider, the 

virtual phone system can be scaled for 

between three and 1,000 people. The 

prices are graded: starting at 6.50 Euros 

net per person, per month, and from ten 

participants discounts apply. The scope 

of services not only includes the standard 

switching functions, but also unified 

communications functions such as CTI 

(Computer Telephony Integration), instant 

messaging, PC fax functions or mobile 

phone integration. Like TeamFON and 

Sipgate, however, vio:networks also has 

no broadband connection of its own, 

which is why we tested their offer via 

a DSL 16 000 Telekom line. 

Up to three devices per extension 

Per extension, up to three end devices 

can be used, for example an IP phone, a 

PC telephony client and a mobile phone. 

For all three, the extension number of the 

virtual system can be transferred for 

outgoing calls. Also telephone conferences, 

the implementation of interactive voice 

response systems, waiting loops, and 

many other features are included in the 

scope of services. The configuration is 

web based, but could be clearer and 

more convenient for most of the solutions 

tested. 

Decent overall measurement results 

In the network test conducted by zafaco, 

on the whole, vio:pbx achieved decent 

results. Call setup times and voice quality 

gave no cause for complaint; only connections 

from the home office to the 

simulated headquarters saw a significant 

rise in the error rate on several days of 

testing. In the DTMF and fax test, the 

solution from vio:pbx put up a good fight. 

All in all, transmission times and error 

rates were all within an acceptable 

range here. 



CONCLUSION 

Top: the admin interface could give more 

detailed information. Bottom: on several 

days of testing, the error rates increased 

for connections from the home office to the 

main office (vio:networks: purple) 

Apart from a few exceptions in the connections 

between the simulated home office and 

the simulated company headquarters, the 

virtual phone system from vio:networks 

earned respectable test results. 

VIRTUAL TELEPHONE SYSTEMS: FEATURES AND PRICES 

PROVIDER Teamfon QSC Telekom Vodafone nfon vio:networks sipgate 

Product 

TeamSIP 

Centrex 

IPfonie 

centraflex 

DeutschlandLAN 

Classic 

OfficeNet 

nfon TK-Anlage 

+ nconnect 2500 

vio:pbx sipgate team 3 

Price 

5.90-6.90 Euros/month From 4.50 Euros/month and ext.; From 495 Euros/month for From 7.95 Euros/month and 6.80 Euros/month and ext.; 

14.95 Euros/month for 3 

and extension 

6.50 Euros/month and ext. 

Q-DSL office 34 Euros/month 5 participants 

extension nconnect 2500: 79 Euro/m. 

participants 

Internet connection (up/down) 16000/1024 kbit/s 1 16100/1024 kbit/s 10000/10000 kbit/s 16128/800 kbit/s 2300/2300 kbit/s 16000/1024 kbit/s 1 16000/1024 kbit/s 1 

Conditions 

Number of extensions from … to 1 – 1000 10 – 500, more possible 5 – 50 5 – 48 2 – 20 000 3 – 1000 3 – 250 

Hardware in scope of delivery 

Í (Telephones are offered 

for sale) 

Í (Optional e.g. from 

Aastra or Panasonic) 

Å (5 IP Phones Snom 870, 

hardware firewall) 

Í (6 types of devices on 

offer-purchase or rental) 

Í 

Í 

Í (large range of devices 

for sale) 

Cost of calls to German fixed 

1.9 cents/min, alternatively 1.1 cents/min to the 

0.84 cents/min; 

1,4 cents/min 1,17 cents/min Flat rate 

1 cent/min 

network 

flat rate 2 Euros/ext. nearest second 

optional flat rate 

… to German mobile networks 11,9 cents/min 

D networks: 10,1 cents/min, 

E networks: 11,6 cents/min 

Flat rate 

13.5 cents/min, alternatively 9.9 cents/min to the 

flat rate of 3 Euros/ext. nearest second 

9 cents/min 

10.84 cents/min; 

optional flat rate 

Internal call/between branches free/free beides kostenlos im QSC-Netz free/free free/free free/free free/free free/free 

Minimum term/sales none/none 12 months / 100 Euros/month 24 months/none 24 months/none none/none none/none none/none 

Integration of mobile phones 

Parallel call/transfer mobile-landline Å/Å Å/Í Å/Í Å/Å Å /Å Å/Å Å/Å 

Call forwarding/toggling/call 

back to mobile phone 

Å/Å/Å Å/Å/Í Å/Å/Å Å/Å/Å Å/Å/Å Å/Å/Å Å/Å/Å 

VoIP client for smartphones 

Å (iOS, Android, 

Blackberry 7) 

Å (iOS, Android) Í Í 

Å/Å (iOS, Android, 

Blackberry, Symbian) 

Å/Å (iOS, Android) 

Í (mobiles integrated via 

Sipgate SIM card) 

Switching/luxury functions 

Softphone Windows/Mac Å/Å Å/Å Å/Í Å/Í Å/Å Å/Å Å/Å 

Presence-/CTI functions 

Å/Å Å/Å Å/Å ( CTI via third-party provider) Å/Å Å/Å Å/Å Å (online)/Å 

(computer telephony) 

Call forwarding/answer phone per ext. Å/Å Å/Å Å/Å (Voicemail T-Mobile) Å/Å Å/Å Å/Å Å/Å 

Queue, boss/secretary Å/Å Å/Å Í/Å Å/Å Å/Å Å/Å Í/Í 

Company-wide address book Å Å Å Å Å Å Å 

Fax to PC, PC to fax Å / Å Å / Å optional/optional Í / Í Å/Å Å/Å Å/Å 

Conferencing 

Tel./web/video conferences Å/Í/Í optional/optional/Í Å/Å/Å Å/Å/Å Å /Í/Í Å/Í/Í Í/Í/Í 

Desktop sharing/file sharing Í/Í Í/Í Å/Å Å/Å Í/Í Í/Í Í/Í 

Special features 

Own softphone client with 

instant messaging and 

Outlook integration, call 

centre functions (ACD) 

Assistant Enterprise (dial 

from Outlook) TAPI 2.1, 

Receptionist (switching 

platform); Unified Communications 

(ESTOS Call Pro 

Enterprise) 

Valid April 2013; all prices are net (plus 19% VAT) 1 No own access offer, tested with Telekom DSL 16 000 

Subsidised phones as 

part of the package for a 

surcharge 

Indiv. flat rates up to international 

flat available per ext.; 

mobile phone integration without 

additional software, fixed 

network prices at com-pany 

locations; attendant console 

Automatic tel. config.; over 

150 system functions; 

(Pickup, IVR ...), voice 

encryption; integration 

MS Lync; integr. with O2 

(“Office Voice Cloud”) 

Discount system from ten 

extensions; IVR, conference 

rooms, waiting loops, etc. 

included free-of-charge 

Fixed line ext. no. recognition 

on outgoing mobile 

phone calls; transcripts of 

voice mails; SMS rec. also 

via web or landline; complete 

online management 

120 6/2013 121


HOW CONNECT AND ZAFACO TEST 

Connect is again cooperating with 

the renowned fixed-network test 

Institute zafaco. 

From 18 March to 14 April 2013 (four 

weeks), zafaco set up around 50 000 

test connections with its equipment 

and put the network quality of our candidates 

under the microscope. 

In order to reproduce realistic 

conditions, the measurement setup 

used several sites, which simulated 

a headquarters in a city with 

several home offices distributed 

around Germany. 

To this end, zafaco used hardware installations 

in Düsseldorf, Kiel, Magdeburg, 

Munich and Nuremberg. Participants 

with their own network connections 

made this available in the test 

centre with the related hardware. For 

Sipgate, TeamFON and vio:networks, 

standard 16 000 DSL connections from 

the market leader Telecom were used. 

FritzBoxes of the type 7390 served for 

the network connection. In each of the 

cities Düsseldorf, Kiel, Magdeburg, Munich 

and Nuremberg an industrial PC 

set up the connections. By way of reference, 

zafaco also determined the qua- 

lity of connections via the conventional 

ISDN network. For this, several quad 

ISDN cards and the corresponding 

ISDN connections were used. 

The SIP connections were set up by 

PC softphones. 

Different connection types were 

taken into account for the measurements. 

Using the hardware constellation described, 

the experts set up several scenarios 

- calls from SIP to ISDN, from 

ISDN to SIP and from SIP-to-SIP - in 

practice therefore within the IP networks 

of the respective candidates. 

Here, how the IP connections behave 

under load played an important role. To 

simulate a realistic load on the internet 

lines, parallel to the telephone calls the 

test system carried out FTP uploads 

and HTTP downloads of large test files. 

The voice calls were carried out with 

the typical G.711 codec that does not 

use voice compression. 

The values measured are collected 

in the table below. 

The averages of the values collected 

per candidate in around 6000 individual 

connections were used as a basis for 

awarding points. However, the deviation 

from the average also flowed 

into the assessment. The idea behind 

this: big differences are more noticeable 

in everyday life than when dialling 

anyway takes a bit longer. If many 

connections took more than five 

seconds for a connection, this led to 

the deduction of points. This also applied 

to connections that broke off because 

of high error rates. To evaluate 

the speech intelligibility, zafaco determined 

the so-called PESQ value 

(Perceptual Evaluation of Speech Quality). 

This is an ITU-T standardised process 

for measuring the intelligibility of 

voice transmission. Values between 4.0 

and 4.5 stand for very good voice 

transmission, a value of 3.5 corresponds 

to a good mobile connection, 

and below 2.7 the intelligibility decreases. 

A further set of measurement values 

represents the language delay. If 

this exceeds 150 milliseconds, it starts 

to have a disturbing effect - as known 

from trans-Atlantic satellite links, especially 

as calls to the mobile network, to 

DECT phones or via Bluetooth headsets 

add further delays. 

Hardware in continuous operation: all 

systems tested were running day and 

night in Düsseldorf, Kiel, Magdeburg, 

Munich and Nuremberg and delivered 

approximately 50 000 test in four weeks. 

zafaco also took dual-tone multifrequencies 

(DTMF) and fax transmissions 

into account. 

DTMF tones are especially important 

for the operation of voice menus on 

hotlines and information services. And 

as Centrex lines are intended to replace 

the traditional telephone line, they 

should be able to cope with fax machines. 

For this we determined transmission 

times and error rates. If the fax 

was not transmitted after 180 seconds, 

the transmission was stopped. 

TELEFON- 

ANLAGE 

AUS DER 

CLOUD! 

Die Zukunft der Business-Kommunikation: 

endlos kostenlose Updates 

Über 5.000 zufriedene Unternehmen nutzen nfon, z.B.: 

MEASUREMENTS AND TEST RESULTS 

Provider teamFON QSC Telekom Vodafone nfon vio:networks sipgate 

ISDN 

reference 

MEASUREMENTS 

Number of test samples speech and DTMF 5066 5081 4575 5009 4946 5082 4786 4745 

Number of test samples fax 1173 1256 1208 1195 1256 1211 1234 1194 

CONNECT SETUP DURATION 

Connect Setup Duration 1,68 1,58 1,44 1,84 1,41 1,77 1,87 2,47 

Connect Setup Duration (standard deviation) s 1,61 1,72 0,99 1,57 1,32 1,58 1,48 0,69 

Connect Setup Duration > 5 sec % 1,13 1,51 0,18 3,95 1,14 1,15 1,54 0,34 

CALL FAILURE RATE 

Call Failure Ratio % 0,12 0,65 0,35 1,40 0,71 1,06 0,81 0 

VOICE QUALITY 

PESQ MOS 4,26 4,32 4,15 4,36 4,31 4,32 4,11 4,45 

PESQ MOS (standard deviation) 0,20 0,17 0,27 0,14 0,20 0,16 0,29 0,02 

PESQ MOS < 4 % 12,08 6,42 23,24 4,05 7,85 6,33 26,9 0 

SPEECH DELAY 

Speech delay ms 143,13 133,18 149,05 119,61 128,93 138,46 231,32 19,72 

Speech delay (standard deviation ms 33,33 22,43 41,40 18,60 23,04 18,96 62,41 2,34 

Speech delay > 150 ms % 39,11 25,56 36,37 12,98 25,69 36,39 89,22 0 

DTMF AND FAX 

DTMF Errors % 1,71 2,28 2,41 1,51 2,05 1,52 3,64 0 

Fax Setup Duration s 45,5 40,3 48,6 34,2 39,1 45,6 33,74 30,56 

Fax Transmission Duration s 94,3 86,0 79,0 80,0 94,0 94,3 94,0 81,8 

Fax Failure Ratio % 3,33 1,83 7,70 2,59 12,6 4,62 51,38 1,68 

TEST RESULTS 

Connect Setup Duration max. 40 30 26 40 14 34 30 28 36 

Call Failure Ratio max. 200 200 160 200 120 160 120 160 200 

Voice Quality max. 80 68 76 56 76 72 76 56 80 

Speech Delay max. 40 40 52 36 64 52 48 8 80 

DTMF transmission max. 40 32 24 24 32 24 32 16 40 

Fax transmission max. 60 40 52 30 52 12 32 14 60 

122 6/2013 

VERDICT(max. 500) 

410 

good 

390 

good 

386 

good 

358 

satisfactory 

354 

satisfactory 

338 

satisfactory 

282 

sufficient 

494 

very good 

CONCLUSION 

Hannes Rügheimer, 

connect specialist 

zafaco and connect last tested virtual 

phone systems in the issue 11/2011. 

Comparing the previous results with this 

year’s rankings reveals some surprises. 

The most impressive thing is the rise of 

the test winner TeamFON: from last place back then to first place now! And that’s 

although TeamFON still does not operate its own DSL network. With the combination of 

its own DSL network and its virtual telephone system, QSC achieved a good second 

place. The Cologne-based team was also well ahead in 2011. The offers from Telecom 

and Vodafone have slipped from pole position to midfield. 

With Telekom’s DeutschlandLAN it was above all deficiencies in voice quality in some 

of the connections that prevented a better result. The Vodafone product Officenet had 

a bit of bad luck: without the system error which occurred during the test period, the 

Düsseldorf-based company would probably have fared much better. nfon, vio:networks 

and, lagging slightly behind, Sipgate, also offer decent Centrex solutions, which, however, 

experienced difficulties in some situations. For these offers therefore is, techni cally 

speaking, still room for improvement. 

Erfolgreiches Geschäft beginnt mit nfon: 

ndless business communication 

08000-636624 

www.nfon.net/tk

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