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Snom 4S Media Server Administrator's Manual

  • Hello! I've reviewed the Administrator's Manual for the snom 4S Version 2.20 Media Server. This document provides detailed instructions on installation, configuration, and usage of the media server. I am ready to assist you with questions you may have about the device, its settings, and capabilities detailed in this manual, like the management of audio streams for VoIP, and the configuration of mailboxes, music on hold, and conference servers.
  • What is a SIP Media Server?
    What are the main differences between signaling and media in telephony?
    Why is the response time important for a media server?
    What kind of keys are used for licensing?
    What is the purpose of the HTTP port setting?
Administrator‘s
Manual
snom 4S
SIP Media Server
Version 2.20
snom technology AG • 3
snom 4S Media Server Version 2.20 Administrator Manual
1. Edition 2003
© 2003 snom technology Aktiengesellschaft. All Rights Reserved.
This document is supplied by snom technology AG for information purposes only to licensed
users of the snom 4S media server and is supplied on an “AS IS” basis, that is, without any
warranties whatsoever, express or implied.
Information in this document is subject to change without notice and does not represent any
commitment on the part of snom technology AG. The software described in this document
is furnished under a license agreement and may be used only in accordance with the terms
of that license agreement. It is against the law to copy or use this software except as
specically allowed in the license. No part of this document may be reproduced, republished
or retransmitted in any form or by any means whatsoever, whether electronically or
mechanically, including, but not limited to, by way of photocopying, recording, information
recording or through retrieval systems, without the express written permission of snom
technology AG.
snom technology AG • 3
“Welcome to the
Media Server!”
When you make phone calls, you often hear sounds like the
ring back tone or announcements like “The number you have dialed
is temporarily not available”. When you reach the auto attendant of a
company, you will hear something like “Welcome to snom technology!”
Audio messages are an important building block of modern telephony.
While modern VoIP phones generate a large set of tones directly
on the device, there is still the need to generate messages from the
network. By having a media server in the network, a VoIP telephony
system will have at least the same features as your “good old” PBX.
Technically, the media server is much more than a SIP media
server. It includes the logic to handle complex applications. Together with
an SIP proxy, the media server provides the functionality that fulls the
needs of your telephone users and might also offer some additional and
helpful features not known from traditional PBX.
An SIP network consists of several components. Some vendors
group an SIP proxy, registrar, location server and media server to soft
switch or iPBX. We have chosen the term media server to indicate that
this component takes care of just about everything that is related to audio
streams. This makes sense because handling audio is a real-time task
and places different requirements on the underlying hardware than the
not-so-critical requirements of the call control. SIP allows and encourages
this distinction and thus makes scalable systems easier to implement.
However, practically all components of a small to medium-sized installation
will run on the same machine.
Interoperability is the glue that binds the growing VoIP industry
together. We have tried to stick to the SIP standard as far as possible, and
carried out tests together with the equipment of other vendors wherever
we were able. We hope that this will help to build up a ourishing VoIP
telephone industry in which the products of the different vendors work
4 • Welcome to the Media Server
[ S N O M 4S ME D I A S ERVER M ANUAL ]
snom technology AG • 5
together like the products in the computer industry do today. We believe
that having a choice is benecial to you and therefore benecial to us.
This manual is the best way to get started with the snom 4S
media server. However, because it’s hard to keep a manual up-to-date
with all the new the issues that constantly come up, we provide a list of
frequently asked questions (FAQ) on our web site http://snom.com.
We hope that you enjoy using the media server and that it helps
you to set up a great communication environment!
Sincerely,
Dr. Christian Stredicke Nicolas Peter-Pohland
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snom technology AG • 5
Table of Contents
“Welcome to the Media Server!”................................3
Introduction ...............................................................9
Signaling and Media .................................................................... 9
Response Times ....................................................................... 10
Multitasking ................................................................................................................................................................................................ 10
Hard Disks .................................................................................................................................................................................................... 11
Privacy .................................................................................... 11
Installation ..............................................................13
Windows ................................................................................. 13
Installation................................................................................................................................................................................................... 13
Uninstalling in Windows............................................................................................................................................................ 18
Linux ...................................................................................... 19
Manual Starting..................................................................................................................................................................................... 19
Automatic Starting ........................................................................................................................................................................... 19
Command Line Options.............................................................. 21
Setting Up ................................................................23
Licensing ................................................................................. 23
Hostnames................................................................................................................................................................................................... 23
License Key................................................................................................................................................................................................. 24
Fundamental Settings................................................................ 25
IP Address..................................................................................................................................................................................................... 26
4.2.1 ..................................................................................................
SMTP Setup................................................................................................................................................................................................. 26
Log Level ........................................................................................................................................................................................................ 27
Default SIP Domain......................................................................................................................................................................... 28
Start RTP Port and End RTP Port ................................................................................................................................. 28
Max. Number of Connections............................................................................................................................................ 28
HTTP port....................................................................................................................................................................................................... 28
HTTP User and Password......................................................................................................................................................... 28
Outbound Proxy and Initial Route.............................................................................................................................. 29
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SIP Port............................................................................................................................................................................................................. 29
Follow RTP address.......................................................................................................................................................................... 30
Session Timer.......................................................................................................................................................................................... 30
Retry Timeout.......................................................................................................................................................................................... 30
Max-Forwards.......................................................................................................................................................................................... 30
Codecs .................................................................................... 31
Representing User Input.......................................................................................................................................................... 33
Accounts ..................................................................35
Registering Accounts ................................................................. 35
Passwords ............................................................................... 36
Music On Hold .......................................................................... 37
How to use MOH.................................................................................................................................................................................. 37
Conguration of the MOH account............................................................................................................................. 37
Mailbox ................................................................................... 38
Using the Mailbox Account.................................................................................................................................................... 38
Conguring a Mailbox Account........................................................................................................................................ 39
Answer Delay ......................................................................................................................................................................................... 39
Email..................................................................................................................................................................................................................... 39
Identity.............................................................................................................................................................................................................. 39
MWI Destination................................................................................................................................................................................... 39
Record Length......................................................................................................................................................................................... 40
Register and Pass............................................................................................................................................................................... 40
Conference Server .................................................................... 40
Calling a Conference...................................................................................................................................................................... 40
Remote Initiation of Conferences................................................................................................................................ 41
Auto Attendant......................................................................... 41
Error-Information ..................................................................... 42
Playing Messages using SIP................................................................................................................................................ 42
Playing Messages using HTTP........................................................................................................................................... 43
Instant Mailbox ........................................................45
Media Bridge ............................................................47
Calling Cards ...........................................................49
Creating a calling card account ................................................... 49
Setting up calling cards ............................................................. 51
Maintenance.............................................................53
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Trace ...................................................................................... 53
Logle..................................................................................... 54
Stored Messages ...................................................................... 54
Open Calls ............................................................................... 54
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snom technology AG • 9
1
8 • Table of Contents
snom technology AG • 9
Introduction
This chapter explains how a media server works in principle and
gives you a feeling of what is important. You will learn the difference
between signaling and media and the fundamentals of operating a media
server.
This is not intended to serve as an introduction to VoIP and SIP
in general. You will nd great introductions and numerous links on the
Internet and in the literature.
If you are already familiar with the underlying problems of a
media server, you can go straight to the next chapter.
Signaling and Media
To put it briey, there are two fundamental problems with
telephony: nding the user you want to talk to and talking.
Finding the user is done with signaling. SIP is one way to nd the
party you want to talk to. This job is characterized by a certain amount of
complexity; for example when a user has redirected his phone or can be
reached at several locations. Whether the nding process takes a second
more or less is not so critical.
When the user has been found, the problem shifts to transporting
the speech as quickly as possible between the participants. One second
taken to transport the voice from one user to another is a great burden
for the communication and establishing a conversation like this takes a
lot of discipline. When users are talking, typically every 20 ms a piece of
the conversation is transported over the network. If this stream of packet
stalls, the other side will experience a poor audio quality.
While operating systems are very good at scheduling tasks
(so nothing gets forgotten), reacting very quickly sometimes provides
problems. If you need to send a packet every 20 ms, you do not usually
have the time to get audio data from a network server, and even accessing
the local hard disk can degrade the quality.
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Response Times
A modern PC is an unbelievable workhorse. An off-the-shelf PC
can process more than a billion operations per second and store easily a
month of a conversation. The bandwidth of a standard Ethernet card is
enough to handle more than a thousand uncompressed media streams.
Set up correctly, it can handle tens or even hundreds of parallel calls
without a problem. You would have to spend ten or a hundred times the
amount of money to have such an effective workhorse as traditional PBX
hardware.
However, in order to operate this workhorse you need to follow
a few rules.
Multitasking
All modern operating systems like Windows 32 and Linux support
multiprocessing or multitasking. Several processes share the same CPU in
that the CPU works for a short time on the rst process and then continues
with the next process. The switching is done around a hundred times per
second and typically the user does not recognize this.
However, in a VoIP environment we are talking about sending
packets at a rate of fty packets per second per call and this might result
in a high frequency of process switches.
The operating system knows that the media server has higher
requirements on time-critical task switching (this is signaled during the
starting of the media server). However, when there are other tasks being
carried out on this computer, the operating system might not be able to
give all of them the CPU attention that they need. So in short, if you are
running the media server and some video games on the same machine
don’t be surprised if your users complain about your stuttering voice.
The best approach to solve this problem is to run the media
server on a dedicated host. Because the proxy does not usually request
time-critical priority from the operating system, it is usually not a problem
to run the proxy on that machine as well. However, it is not a good idea
to run the media server on a le server.
We would like to point out that from a media server perspective,
both Windows and Linux are great operating systems to run the media
server process.
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snom technology AG • 11
Hard Disks
Hard disks are another miracle of the computer industry. A
modern, off-the-shelf hard disk can store several high-quality lms,
meaning that it should denitely be good enough to store some mailbox
messages.
The price to pay for this is access time. When information on the
hard disk is scattered, the time to gather information can become too long
to answer requests within twenty milliseconds.
Missing the twenty-millisecond answer time does not mean the
end of the call. Phones usually tolerate late packets to a certain degree
and if the packet is missing it will ll the gap with other information. Only
when too many packets get lost will the call stop.
The general strategy for avoiding situations like these is called
caching. Operating systems usually keep les that have already been
opened in the main memory until they are no longer used and are
replaced with information that is needed more urgently. As long as a le
stays cached there will be no problem.
Needless to say, accessing les (which are also stored on hard
disks) via the network is not an option if a continuous media stream is
desired.
Privacy
There is another reason to use a dedicated server for the media
server: privacy. Remember that voicemails are normally strictly private,
and therefore it makes sense to separate them from normal le access.
There is nothing better than a physically separated server for this.
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snom technology AG • 13
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Installation
Windows
Installation
Tip: If you are doing an update, you need to stop and uninstall
the old media server rst (see below).
After double clicking on the setup executable, the installations
program starts up. Press Next to begin the installation.
At the beginning of the installation the setup program asks you
to accept the license conditions. Please read them carefully, and then
select the “accept” button and press “next” to accept the conditions. If
you decline, the installation will be aborted.
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snom technology AG • 15
[ S N O M 4S ME D I A S ERVER M ANUAL ]
After accepting the license agreement, the next screen asks you to enter your
personal information. Enter your name and the name of your organization. This
information is not linked to the licensing, which is done after the installation
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[ S N O M 4S ME D I A S ERVER M ANUAL ]
You can then select the location where the media server’s les
will be put. The installation program proposes a reasonable location but
you can change this if you wish. After this, the installation asks you for
the location where the media information will be put. This directory needs
write access and will contain the information for registered users. The
installation program proposes a location relative to the media server
installation directory, but it might be useful to specify a different location
for this, e.g. a temporary directory. It is important that the directory
already exists; the media server will not create this directory.
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[ S N O M 4S ME D I A S ERVER M ANUAL ]
Remember that for a good performance of the media server, the
media directory should be on the local hard disk.
In the next step you can select the installation type. We
recommend using the Typical installation. If you select Minimal, the
documentation will not be installed.
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Before the installation nishes, you need to dene on which ports
the media server will operate. This is important as otherwise it will be
hard for you to nd the right port.
The http port denes where the web server of the media server
can be accessed. The default port for web servers is 80, and if you are
not running any other web services on the computer, port 80 is a good
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snom technology AG • 19
[ S N O M 4S ME D I A S ERVER M ANUAL ]
choice. Otherwise, choose a free port and write the port number down
somewhere so you don’t have to search for it. If you don’t ll in any data
or cancel the dialog, port 80 will be used.
From a service perspective, it is ok to choose a different port
than port 80. Users normally don’t access the media server via the web
browser, so there is no reason to choose the “prominent” port 80.
The SIP port denes where the SIP trafc is expected. The default
port is 5060, but if you are running a proxy on the same host you will
probably have to choose a different port. In this case, port 5062 is a good
choice. Again, as the users normally don’t directly call the media server
(they go though the proxy), it is recommended to choose a different port
than port 5060.
After nishing the setup wizard, check that the media server is
running. If you do not want to reboot your system (because it is running
other critical applications), you can also manually start the service in the
services section of the Windows control interface.
Check that the installation has been successful by checking the
Services eld of Windows. Open the services Window and look for “snom
4S SIP Media Server”. The status should be “Started”. If this is not the
case you should invoke the media server by selecting “start”. In this case,
we recommend rebooting the system to make sure that the media server
is running after the reboot.
After making sure the media server is running, you should connect
the media server to a web browser. In order to do this, you can connect
to the address of the local computer (http://127.0.0.1:8080 if you are
running the web browser on the same machine). If the http port is already
occupied by other programs, the media server will try to use ports 5068,
5069, 5070 and so on. It is important that you connect the media server
to a web browser, as that is the only way to control the media server.
Uninstalling in Windows
To uninstall the media server, rst stop it in the services window.
Then go to the Software Window and click on “remove” for snom 4S SIP
Media Server.
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[ S N O M 4S ME D I A S ERVER M ANUAL ]
Linux
Manual Starting
If you just want to try the media server, it should be sufcient to
start the media server manually. Load the tarball to a directory of your
choice and start the media server with the command “mediaserver”. You
can use the command line arguments shown in the next chapter. You
don‘t need to have root permissions to run the media server in this mode,
as normal user rights are enough (although in this case the media server
process might not get a high priority).
Automatic Starting
If you want the media server to be started automatically after
a reboot, you need to set up some les as a root. Make sure that you
are logged in as root and go to the directory where you want to put the
media server. This directory will have subdirectories for the different
media server versions and for registrations. It typically also contains the
conguration information.
cd /usr/local
mkdir mediaserver
cd /usr/local/mediaserver
Extract the les from the tarball:
su -
cd /usr/local
tar xvfz ~/snom_sip_mediaserver-i386-linux-2.20.tgz
If you are updating a version, you may stop the media server
with rcmediaserver stop and remove the symbolic link pointing to the old
installation. This will force a completely new installation. After this you
can continue the installation in the directory where you extracted the new
version.
cd snom_sip_mediaserver -i386-linux-2.20
The tarball includes a shell script with the name install.sh, which
sets up the necessary les and links for you.
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[ S N O M 4S ME D I A S ERVER M ANUAL ]
./install.sh
The le /etc/rc.cong (for SuSe Linux) and /etc/init.d/functions
(for RedHat) are appended with the variable „START_MEDIASERVER“ and
the MEDIASERVER_OPTS variable is set to a value depending on the html
port that you specify. You can edit the le and modify the value.
The installation script will install a command rcmediaserver.
rcmediaserver start will start the media server while rcmediaserver stop
will terminate the media server process.
After the installation, open a web browser to see if the media
server is up and running. Reboot the system and check whether the sip
media server was started automatically after the reboot. You can then
continue with the installation using the web browser. Stop and restart
the media server with the rcmediaserver command to check whether the
conguration has been saved.
After several installations, the directory could look like this:
lrwxrwxrwx 1 root root 30 Aug 24 11:42 mediaserver -> snom_
mediaserver-i386-linux-2.12
-rw------- 1 root root 1472 Aug 22 16:17 mediaserver.txt
drwx--x--x 3 root root 4096 Jul 19 15:04 snom_mediaserver -i386-
linux-2.14
-rw------- 1 root root 3900938 Jul 19 15:04 snom_mediaserver -i386-
linux-2.14.tgz
drwx--x--x 3 root root 4096 Aug 12 14:09 snom_mediaserver -i386-
linux-2.20
-rw------- 1 root root 3902694 Aug 12 14:09 snom_mediaserver -i386-
linux-2.20.tgz
To update a version, copy the latest tarball into the directory and
run the install script of the new version. It will automatically shut down
the old media server and run the new one.
Unfortunately, the media server keeps a lot of stateful
information, which makes it hard to do a smooth software update without
users experiencing any service interruptions. We therefore recommend
two approaches:
1. Do the software upgrade when service disruptions will not
disturb the users too much (e.g. at night, early morning). This is probably
the easiest approach and should be easy in small and medium-sized
enterprise environments.
2
/