english version

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english version

ENGLISH VERSION
Reprint from MikroDatorn
nr 4 – 06
Published by IDG, the worlds largest publisher
of computer related trade press.
www.mikrodatorn.se
46
R E P R I NT MikroDatorn 4 | 2006
You’ll find more tests at: tester.mikrodatorn.se
Network and Security
Reprint from MikroDatorn
nr 4 – 06
Test: Six Gateways for IP telephony
Published by IDG, the worlds largest publisher
of computer related trade press.
Tested SIP Adapters
www.mikrodatorn.se
Draytek Vigortalk
Edge-core VG3306
tGrandstream Handytone 386
tIntertex Surfinbird IX67 FW Air GW2
Linksys PAP-2
Welltech Wellgate 1501-SIP
t=Best in Test
SIP Bridge Links
Ordinary Phones and IP
SIP is the protocol making it possible to integrate ordinary telephony with IP solutions, so businesses could
get a wide variety of features as well as lower costs.
The key to such a compound telephony solution are
the adapters we’re testing here.
text Peter Baeza
PHoto carl löfgren illustration kjell eriksson
I
f nothing else, Skype’s popularity shows
that it’s all the rage to make phone calls for
free over the Internet. So far, most users
are probably private persons, but today
companies needing more advanced features
could cut their costs with IP telephony as well.
That’s where the SIP standard comes in. It
makes it possible to connect products from
different suppliers to a telephony system that
works, both over the Internet and fixed telephony lines.
SIP, Session Initiation Protocol, is an open
and relatively simple standard which has
grown fast during the last couple of years.
Solutions based on this standard are the most
interesting alternatives for setting up IP telephony at small or medium-sized businesses.
Opportunity for Advanced Systems
The great advantage, compared to Skype, for
example, is that you get less dependent of the
computer. For the user, a SIP system could seem
to work just as an ordinary telephone, in spite
of using Internet as a carrier. You could build
fairly advanced systems with teleconferencing,
video, instant messaging, switchboard systems,
and much more.
To tie the old phone numbers to Internet you
have to have an Analog Telephony Adapter
(ATA) or a Voice Over IP Adapter (VOIP).
We’re testing five of those adapters and a firewall with a built-in SIP server and telephone
adapter.
Installation
Several adapters for connecting analog phones to IP are pre-configured and sold with accounts. With a bit of luck, such an installation
could be extremely simple, just to plug in the
cords and enter a code on the handset. But that
kind of installation could be problematic as
well, especially when there are firewalls or address translation (NAT) from the local network
to the Internet.
We are making our test a tad more difficult,
by starting with unconfigured adapters and
installing them to a separate account.
The installations of Draytek’s Vigortalk,
Grandstream’s Handytone, and Linksys’ PAP2, follow the same pattern. The gateway is connected to the local network, if there is a DCHP
server it will automatically be assigned an IP
address which you will get through a voice mail
menu on the phone. After that you just have to
go to the current address and make the necessary settings from the web browser. If DCHP
don’t work, a fixed IP address could be set via
the voice mail menu.
Intertex’s Surfinbird has a pre-configured
private IP address and is the DCHP server on
the local network, so you just have to connect
a computer with a dynamic IP address to one
of the network ports and enter the address to
Surfinbird through the web browser to get to
the settings.
Settings via Web Browser
Welltech’s Wellgate has a Windows-based
configuration program, where you can connect t
A lot of numbers
I read somewhere that you know that it’s 2006 if you have 15 different phone numbers for a
family of four. In theory, SIP could solve that problem, since a SIP address easily could be moved
when you log in at different locations. When I’m travelling and have the software phone installed on
the computer I’m reachable at my usual phone number as soon as the computer is connected to
the Internet.
In reality it feels, sadly enough, like it will be getting worse before it gets better. The traditional telephony will live on and SIP will only be more addresses to
keep in mind. With several accounts with different area codes it could even be
difficult to keep your own phone numbers in mind.
Peter Baeza is a freelance journalist and has worked with IT for 20 years, among other
things as a Technical Consultant for Nokia Data and Development Manager and CEO
for Alfaskop.
The best pure telephony adapter is Grandstream
Handytone 386, with a good combination of features and user-friendliness. It shares the victory with
Intertex Surfinbird IX 67 FW Air GW2, which isn’t just a
telephony adapter, but an excellent SIP-conscious firewall and a wireless access point as well.
M i k ro Dat o r n 4 | 2 0 0 6 R E P R I N T
47
Draytek Vigortalk
Draytek Vigortalk is easy to manage, mainly since only the most
important features are included.
Vigortalk is the size of a pack of cigarettes,
which makes it easy to bring along on travels.
Since you can save five different network
profiles, it’s simple to do the settings for different places beforehand.
“Vigortalk is the sole adapter which can keep
track of five different network profiles”
t to the adapter through the Mac address and
make the basic network settings.
After that, you’ll do the settings from the web
browser. If you don’t have a Windows computer to run the configuration program from, you
could log in with terminal emulation via a serial
port.
In Edge-core’s VG3306 the basic settings
must be done through a terminal, connected to
the serial port. It’s quite tricky and feels antiquated.
The necessary settings are just about the
same for all the adapters. Except the network
configuration, it’s account and server information, plus a STUN server setting. (See page 51,
“Telephony + Firewalls = Problems”.) Welltech
Wellgate doesn’t support STUN. You have to
redirect a number of ports in the firewall and
inform the adapter of the firewall’s external IP
address. It’s rather complicated, but you can
get around it if you place Wellgate outside the
firewall. In that case, you shouldn’t connect any
Edge-core VG3306
An extra network connection makes it possible to connect
VG3306 when all the network connections are used. It gives
back the connection it uses.
Edge-Core VG3306 has four configurable telephone ports
and is different from the others. The port configuration is
done through Channel and the SIP entity option.
48
Grandstream Handytone 386
Handytone 386’s interface is
easy to comprehend with its
five folders; two identical for the
telephone ports.
When the red light on Handytone 386 blinks, the server
registration has failed. On the back you’ll find the telephone connections, and on the side the fixed telephony
connection, which can be used for emergency calls
and during power failures. To use a separate telephone
connection is smart, since it diminishes the chance of
making the wrong connection.
workstations to the network ports. Since Wellgate is a hub as well, it would be a security risk.
means that calls can be made between all the
units.
Touch-tones require Swedish Standard
Good Sound Quality
To get the telephone ports to work properly
with caller display and touch-tones, they have
to be set up according to the Swedish standard.
That’s most difficult with Linksys’ PAP-2
since ring tones, port impedance, touch-tone
signalling, etc. are set manually. With no mention in any part of the documentation of which
settings are valid in which country. It takes a lot
of know-how to succeed. Linksys has more than
400 configurable parameters, and that might be
overwhelming, but on the other hand it’s an
advantage for those who want to control every
setting in detail.
The choice of sound codec affects both quality
and bandwidth requirements. With the standard settings the sound quality usually is very
good in all the tested combinations. The sound
quality just went below the quality in analog
telephones during a few calls.
Features
Since SIP is a standard, telephones should
be able to communicate through the adapters
without problems. Theoretically. It works fairly
smooth in reality as well. Different phones can
be connected to the same external account.
Then they will all ring at the same time. Since
they are connected through the Internet, it’s
easy to connect several phones, in completely
different locations all over the world, to the
same account.
The sound conversion between two telephones has to be digitalised and compressed in a
sound codec. Before the call is connected, the
different equipments negotiate and try to find
a common codec. If no common codec could
be found, there won’t be any communication
at all. The number of supported sound codecs
is different in different adapters. Linksys PAP-2
supports eight, while Draytek Vigortalk only
supports three. The common denominator is
G.729a, which everyone supports, and this
All calls with bad sound quality were connected through Draytek Vigortalk, which in
some cases had problems calling up as well. The
phone kept on ringing after the called had hung
up. The same thing occurred a couple of times
with Edge-core VG3306.
Apart from that, Vigortalk is the sole adapter
which can keep track of five different network
profiles. It simplifies things if you have to move
the adapter between different locations. Inter- t
Introduction to SIP
Session Initiation Protocol (SIP) is a protocol defined by Engineering Task Force, intended for
teleconferencing, telephony, and instant messaging over the Internet. SIP can create and manage
sessions, but not the actual data transfer; in telephony, that’s usually managed by Real-Time
Transport Protocol. (RTP)
There are several rivalling protocols for IP telephony, for example H.323 and MGCP. SIP is different from the others since it’s got a simple and decentralised design, mainly because it began in
the Internet world, not in the Telecom world.
SIP is basically peer-to-peer, which means that two intelligent end points are communicating
with each other through a network. It’s different from the traditional telephony systems, which are
hierarchical with “stupid” phones and the intelligence in the switchboard. The traditional telephony systems are quite like mainframe computers with terminals while IP telephony is like a pc
network.
SIP is in many ways similar to HTTP, since it’s designed around messages in plain language in a
request-order sequence. It’s also relatively simple for a network administrator to find eventual problems. SIP is an open standard, which means that there are is a wide and rapidly growing range of
hardware and software and that you won’t get as dependent on certain suppliers.
Compared to Skype, SIP has more to offer companies wanting to manage their telephony with
voice mail, call diversion, interactive answering services, and three-way conferencing, but it could
be attractive for private persons as well, mainly because the range of products which don’t require
an online computer to work are much bigger than Skype.
Even if it’s possible to connect two telephones directly, it requires that both know and can reach
the other’s IP address. Since that’s quite rare, it’s more common that the connection is made
through a proxy server intermediating the SIP messages between the parties. That kind of server
could also have a registry function which keeps tabs on the users which are available and also
offers other services like call diversion, number plan, etc. Note that when the negotiation over the
connection of a call I finished, the most common is that the voice traffic is direct between the two
phones.
If you want to delve further into SIP and how the technology works, go to SIP Center, (www.sipcenter.com) SIP forum, (www.sipforum.org), and VOIP Info. (www.vio.info.org).
49
Intertex Surfinbird IX67 FW Air GW2
The firewall’s
network settings
are shown in
Surfinbird’s interface. Note that
the access point
is set to letting the
wireless users access the Internet
only, not the local
network.
Surfinbird’s backside is full of connections. The
screen informs us about the current security setting.
The buttons can be used to make temporary changes
of the configuration or to reset the unit to factory
settings.
”It is certainly possible to connect several
phones to one port with dual connectors, but then both will be busy at the
same time”
ttex Surfinbird and Grandstream Handytone
has, except telephone ports, also a connection
to the fixed telephony net, which means that
you could make calls with the connected phones through a local telephone jack. It could be
handy for calling the emergency number, for
instance. In those cases it’s important for the
emergency service centre to see where the call
comes from.
Handytone redirects at power failures
With Surfinbird every user on the net could be
connected to the outgoing line, but when you
use Handytone it only works with phones, connected directly to the adapter. Handytone alone
has a feature that redirects the telephone ports
to the general phone jack at power failures.
50
Edge-core VG3306 has an extra network port
which means it can be connected when there’s
just one network connection, already in use.
Just plug in the adapter and connect the available equipment to the additional network port.
Welltech Wellgate is equipped with a four-port
hub.
Wrong Caller Display
The caller display works well, except with
Edge-Core VG3306 and Draytek Vigortalk. In
the first case the numbers are wrong, possibly
due to a lack of adaptation to the Swedish standard for touch-tones, and in the latter it doesn’t
work at all.
Grandstream Handytone, Intertex Surfinbird, and Linksys PAP-2 have built-in features
for transfer of calls and three-part conference
Surfinbird has a log-in feature
for users, where those who use
the telephone ports could enter
non-numeric addresses, among
other things.
calls. You could have a three-part conference
without a dedicated conference server.
Incoming calls
Edge-core, Surfinbird, and Linksys can notify
the user of incoming calls. This means that the
caller won’t get a busy signal. Instead, you get
a signal indicating another call on the line and
you can switch over to that call if you want to.
Handytone is supposed to have that feature as
well, but we never got any signal, but it worked
otherwise, so it might indicate some kind of
problem with the tested adapter.
With Edge-core, Handytone, and Linksys,
you can divert incoming calls to another phone,
even when the line is busy or no one answers.
Surfinbird can be diverted as well, but requires
an extra program called Sipswitch. Sipswitch
can be used to divert every phone in the local
network, whether their adapters support the
feature or not.
The address to a SIP user isn’t always numerical; sometimes it looks like an ordinary e-mail
address. You can’t dial it from an ordinary
phone, but Surfinbird’s elegant solution is to let
the user enter the address from a web page.
Linksys PAP-2
Linksys PAP-2 is elegantly designed, but the shiny
surface, which looks like metal is made of plastic.
Linksys has more than 400 settings, which means a high level of detailed management for the skilled technician. Unfortunately it has no simple guide, so
every setting is done separately.
Handytone and Linksys can call another IP
address directly, but it’s not very practical and
must be seen as an ad hoc solution. Draytek Vigortalk, Edge-core, Linksys, and Welltech Wellgate can call alphanumeric addresses through
speed dialling, if the addresses are entered in the
telephone book.
Speed Dialling in Several Places
Features can often be accessed in several places with a SIP-based telephony solution. Speed
dialling is an example, since they can be stored
in the phone, in the adapter, or at some server.
Same thing goes for a couple of other features.
Draytek Vigortalk is the most easy to use of
the tested adapters, but in a solution where a lot
of features are server based, it won’t necessarily
be a disadvantage. Linksys and Grandstream
Handytone have the most pre-installed features,
which makes them suitable if you don’t want to
be dependent on server programs.
Edge-core’s Four Ports
The number of telephony ports varies. Draytek Vigortalk and Welltech Wellgate have one
each; Edge-core has four, and the rest two. In
Edge-core the ports could be grouped as well,
to ring at the same time or in a certain order if
the line is busy.
It is certainly possible to connect several
phones to one port with dual connectors, but
then both will be busy at the same time. With
an adapter with several ports, the same account
could be used, but you could still use the different phones at the same time, for different
calls. The ports could also be used for separate
accounts with different phone numbers.
User-friendly
An advantage with using an adapter to connect analog phones to the Internet is of course
that the caller doesn’t have to learn anything
new. It’s just calling as usual. Or nearly the same
as usual. There are some differences.
Calling services like three-way calls or switching between different calls is done through
the R-button, just like in Telia’s Plus services.
But call diversion, on the other hand, won’t
work with *21*. You have to use the web interface. The web interface is good, but we miss the
possibility to do it from the handset.
t
Telephony + Firewalls = Problems
Most small companies with broadband access use some kind of broadband router with a built-in
firewall. Commonly they are protecting the internal nets, as well as managing the address translation (NAT) since the internal net usually doesn’t have any official IP addresses.
One of the purposes with NAT is that all communication must be initiated from the local network. No computer from the Internet is allowed to start communicating in the local network.
Usually, that’s good, but when an IP telephone inside the firewall is going to accept calls, it’s a
complication.
A solution is to open a number of ports on the firewall and redirect them to the IP telephone, but
that’s tricky since SIP use several ports for different calls. To open up for SIP like that isn’t just difficult, it’s a security risk.
Instead there is the standardised protocol STUN (Simple Traversal of UDP through NATS) which
makes it possible to communicate through a firewall with NAT. The principle is that the telephone
should be able to detect which kind of NAT the firewall uses and which official IP address is used
to communicate with a STUN server on the internet. By adapting the communication to the real IP
address and send dummy traffic through the firewall to keep the communication open, the IP telephone could work, in spite of NAT.
A disadvantage to STUN is that it doesn’t work with all kinds of NAT, but it works with most of
the common broadband routers. If you wonder if it will work in your net, test with the Win Stun
program. (mikrodatorn.se/a/355) Other problems with STUN are the security risks and that telephones and adapters must support the standard.
Microsoft uses SIP in Windows Messenger, which consequently has problems with NAT. That’s
why the company has suggested an expansion of the Universal Plug and Play standard (UPNP)
to make Windows computers with Messenger able to change the setting in the firewall to let SIP
traffic through. Even if it could work in smaller nets, to let Windows computers open holes in the
firewall is not a very appetizing solution, from a security viewpoint.
The best solution for small businesses is definitely a firewall which recognises SIP from start,
but in very small nets or as ad hoc solutions, STUN might be an alternative.
For larger businesses there are other solutions; a SIP server could, for example, be placed in an
isolated zone.
51
Welltech Wellgate 1501-SIP
Under Voice Setting in Welltech Wellgate’s
configuration menu it’s easy to set the
priority for each of the sound codecs.
Through the serial port on the front of Wellgate you can access the configuration with an asynchronous terminal. It’s not for the home user, but a
good alternative for the professional installer.
In the Voice Settings option in Welltech Wellgate’s configuration menu
it’s easy to set the priority for the different sound codecs.
”If they are going to be sold to private
customers and smaller businesses,
better documentation is needed”
t With Grandstream Handytone and Linksys
PAP-2 you can access all the calling services
from the handset, but instead of the R-button,
you have to hang up, and quickly get a dial tone
again, followed by entering the correct code.
The codes for call diversion are predefined, by
American standard, but with Linksys you can
set them to the Swedish Plus codes instead. With
Edge-core VG3306 it’s quite tricky to use call
diversion from the handset, since you have to
do it through a voice menu.
Grandstream has a centrally placed light,
which blinks in red when something is wrong,
for example server registration. On Surfinbird
there are some LED’s serving the same purpose.
To get the same information from the others,
you have to log in to the administrative interface.
Folders with settings
All of the tested adapters have web based administrative interfaces, which mainly consists
of folders with the configurable parameters.
Surfinbird is the only one with a comprehensive help system, and in spite of being the most
advanced product, it’s the easiest to work with.
Linksys has a huge number of settings, and is
a bit complicated to use. Some form of guides
would have been helpful.
Documentation
It’s clear that these products are mainly sold
to operators and system integrators who know
the technology. If they are going to be sold to
private customers and smaller businesses, better documentation is needed.
The only really good documentation is Intertex Surfinbird’s. A comprehensive guide for
What Does a Call Cost?
It’s free to make calls between two IP telephones, no matter where they are located. At least as
long as they don’t have Internet access with traffic fees, but that’s unusual outside the mobile connections.
The cost for outgoing calls to the regular telephone net varies, depending on the operator, but it’s
usually cheaper than corresponding calls with a regular phone.
The big gain is the costs for international calls. It’s possible to use different operators and making
all the calls local. For companies with clients all over the world, it would be a great service, since the
clients always could call a local phone number. Companies with several offices could also gain a lot,
since the different locations could be connected over the Internet, with both data communication
and telephony.
52
quick-starting the system is included, the rest of
the documentation can be found online.
The documentation for Draytek and Grandstream is adequate, but the other products’
documentation is not up to par.
No Linksys handbook
Linksys PAP-2 is delivered with a quick-start
guide, assuming that the net and adapter are
pre-configured. A complete administrative
handbook wasn’t included and could not be
found at Linksys’ web site.
After a lot of searching we found the documentation on one of the reseller’s web site. To
our surprise, it was well-written and detailed. It
should have been included from the beginning,
along with a better quick-start guide.
Edge-core’s and Welltech’s handbooks are
insufficient, both in design and content-wise.
The Welltech handbook was at least included
on a CD, but Edge-cores had to be downloaded
from the company web site.
Firewall with everything
Intertex Surfinbird is different from the rest of
the test, since it’s not just a telephone adapter;
it’s a firewall, a wireless access point, a hub, and
a SIP server as well. The firewall is unique, since
it recognises SIP traffic automatically, without
having to open ports or use complicated solutions like STUN.
The other adapters in the local network just
has to be configured with account and server
information, which makes the installation so
much easier, and cheaper, compared to manage
a separate SIP server.
Another advantage with Surfinbird is that
it can control Quality of Service, QoS; it’s an
assurance that the IP telephony gets enough
bandwidth, even if someone else in the network
is playing online games or downloading large
files.
Build Your Own Company Switchboard
All you need to get started and evaluate SIP at your company can be found in free test versions or
free programs. For servers/switchboards there is Asterisk, (asterisk.org) SER (www.iptel.org/ser)
for Linux, and Ondo (brekeke.com) for Windows.
Useful software phones are, for example, SJ Phone, (sjlabs.com) SIP Xphone, (www.sipfoundry.
org/sipXphone) and Eyebeam Softphone. (www.xten.com)
To connect to the regular telephone net you can get an account from Woize (www.woize.se) were
you only pay for outgoing calls. There are several international operators as well, for example Free
Word Dialup (www.freeworddialup.com) in the US, and Gossiptel (www.gossiptel.com) in Great
Britain.
Buying extra licences
The SIP server in Surfinbird includes licenses
for five users, but you can buy extra licences if
you need. Then there is the additional program
Sipswitch, which is an extended switchboard
version with call diversion, speed dialling, number plan for using different operators depending
on destination, and other finesses.
Sipswitch has five user licenses as well, and
you could buy more if needed.
MikroDatorn’s Conclusions
The different adapters seem very alike at first
sight, but the differences where in fact quite big.
From reading product descriptions and brochures we would never have guessed that Draytek
Vigortalk and Linksys PAP-2 were fundamentally different. Vigortalk is super simple, both
when it comes to features and administration,
while PAP-2 is extremely adaptable with lots of
features.
That several products are completely different
but look very much alike on the surface makes it
hard for the customer. And there are of course
lots of other models on the market as well.
Maybe that’s why these products often are
sold pre-configured and with accounts.
To increase the direct sales to customers most
of the suppliers have to get their act together
when it comes to localisation and comprehensive instructions to get started. Surfinbird is a
great example of an advanced product, made in
a comprehensive manner.
Since the products are quite different it’s hard
to appoint a single winner. We can at least say
that Welltech Wellgate and Edge-core VG3306
might work better in larger installations, with
other products from the same suppliers. And
they should also be installed and configured by
specially trained people.
The price differences between Draytek Vigortalk, Grandstream Handytone, and Linksys
PAP-2 are quite negligible, but the latter two
have the double amount of telephone connections. Vigortalk is a good choice, but only if you
want the easiest administration possible.
When choosing between Handytone and
Linksys, we believe that the extra outgoing
connection and the easier administration make
Handytone the better choice. If a company
wants control over the small details, and still
want to do all the settings centrally, Linksys is
a better choice.
The most obvious conclusion of the test is
that an installation of Internet Surfinbird as a
firewall and SIP server is a great first step for
home users or a small businesses, wanting to
start with IP telephony, a step that will make the
later work so much easier. l
How the Test was Done
The adapters were tested with support for STUN (see page 51) and were
configured for passing through a regular gateway with NAT (address translation) and connecting to the public SIP server at Woize (www.woize.se). After
that we called back and forth, both between the phones on each adapter,
and between IP telephones and the regular phone net.
Then we replaced the firewall with Intertex Surfinbird and tested it both
Manufacturer
Product
Contact
Web address
Price, ex VAT
Connections
Phone/Net
LAN/WAN
RTH
WO RICE
P
ITS
TH
OR
E
TW
NO PRIC
ITS
Draytek
Vigortalk
Migrax
www.draytek.se
59 EUR
1/0
RTH
WO RICE
P
ITS
TH
OR
E
TW
NO PRIC
ITS
with direct connection from the adapters to Woize and with
Surfinbird as SIP server with call diversion to Telavox and
Woize.
We also went through the documentation for each adapter and tested the
most interesting features. The broadband connection we used was an 8
Mbit business connection from Telia.
Edge-core
VG3306
Direktronik
www.edge-core.com
391 EUR
BEST IN TEST
Grandstream
Handytone-386
Migrax
www.grandstream.com
RTH
79 EUR
WO ICE
BEST IN TEST
Intertex
Surfinbird IX67 FW Air GW2
Intertex
www.intertex.se
RTH
297 EUR
WO ICE
Linksys
PAP-2
Cisco
www.linksys.com
78 EUR
Welltech
Wellgate 1501-SIP
Direktronik
www.welltech.com
141 EUR
4/0
2/1
2/1
2/0
1/0
1/1
3/1
No
No
No
No
ITS
PR
TH
OR
E
TW
NO PRIC
ITS
0/1
1/1
0/1
No
No
No
No
No
No
Pros
Easy to get started
Four telephone ports, can be
grouped
Emergency connection to the
telephony net, easy to use
Cons
Only basic features
Swedish caller ID not working, Non-adaptable codes for
tricky installation, bad docu- service activation
mentation
Grade
Good
Sufficient
Very Good
Good
46%
Grade
Sufficient
Good
Sufficient
Inadequate
32%
WLAN
Firewall
Installation
Features
User-friendliness
Documentation
Total
Weight
1
3
2
1
Grade
Good
Excellent
Good
Good
71%
ITS
4/1
801.11b/g
Yes
PR
TH
OR
E
TW
NO PRIC
ITS
Switch, several users, VPN,
Extremely adaptable
Good help, online handbook,
lots of features
None
Complicated configuration,
bad quick start guide
Built-in hub
Grade
Very Good
Excellent
Excellent
Very Good
93%
Grade
Good
Good
Sufficient
Inadequate
36%
Grade
Sufficient
Excellent
Good
Sufficient
64%
Bad documentation, tricky
installation
53

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