Snom 4S Media Server Administrator's Manual

Brand: Snom

Model: 4S Media Server

Type: Administrator's Manual

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

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

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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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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

8 • Table of Contents

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8 • Table of Contents

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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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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.

12 • Introduction

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12 • Introduction

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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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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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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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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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[ 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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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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./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.

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Snom 4S Media Server Administrator's Manual

Snom 4S Media Server Administrator's Manual

Snom 4S Media Server Administrator's Manual

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