Course13:IT Advanced 2 - 04 Conferencing and DECT

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This book describes how to run a 3rd party DECT conference and a conference object at the same time



In this book, we will take a look at conferences and discuss how a three-way DECT conference works in conjunction with a conference object.

Although the IP411 is able to host a conference with 5 soft conference channels, we will need the IP811 for this lesson, consequently we will need a free POE port on our switch. Fortunately Richard Roe is a DECT user now and does not need his IP222 anymore. So please remove your IP222 from your switch and plug your IP811 into this switch port instead. Your network should screenshot.png look like this afterwards.

Since we are using a new device, we need to load a new startconfig to your devices by pressing this button.

Please check that your IP811 is connected to your devices app. If not, you need to provision the gateway as explained fish-help.png here. Please usethis link to start the Install at your IP811 and add device to the installtion.

(Further Hints) Please make sure that you activated the Test mode at your IP411LEFT and your IP811

Create conference rooms

In the IT Connect training we learned how to set up a conference object with multiple rooms through the Conference PBX manager plugin. We will need this knowledge for this chapter again. If you have trouble remembering you can consult the link_intern.png Conference book in the wiki.


At first we screenshot.png create a conference object in the PBX through our Conference PBX manager plugin.
  • Please use the Name Conference
  • Please use the SIP ID conference
  • Please set the number of the conference object to 60


To hear announcements when calling the conference room, we need to upload announcement files to our files app. You can either use English announcement files or you can download announcement files from fish-help.png our wiki in different languages.

Conference Interface

By clicking at the search button you will find 3 possible conference interfaces. screenshot.png We will select the software conference interface of the IP811. Furthermore screenshot.png please activate the PBX Channels licenses and set used channel to 10.


Please screenshot.png create 3 conference rooms without any PIN.
  • Please create a room called conf-hq with 8 reserved channels and the number should be 10
  • Please create a room called conf-jane with 7 reserved channels and the number should be 20
  • Please create a room called conf-john with 3 reserved channels and and the number should be 30
(Further Hints) Do not configure a conference room with more reserved channels than the number of channels available for this interface. This means if you decrease the number of used channels in the interface configuration you have less channels available for the size of a conference room.

Try it

Please connect your analogue phone to the TEL-1 port of your IP411LEFT and call 6010. You will be connected to the conference room conf-hq.

Soft conference interface

We already mentioned the software conferencing interface but let's discuss it a little bit further.

screenshot.png The SCNF (soft conferencing) can be used for audio, video and application-sharing conferences, but is not tied to DSP resources like the CONF interface. Nevertheless, SCNF also has its limitations as well. You cannot have conference rooms with an unlimited number of participants. The capacity of each single device is listed fish-help.png in this wiki article. It is a software-only solution that only supports the G.711 A-Law and the G.711 u-Law codec. Other codecs are not supported. You can use the CONF and SCNF interfaces simultaneously on the same device, but you cannot merge the channel of these conference interfaces to gain one huge conference room. The SCNF and CONF interfaces work independently of each other.

(Further Hints) The SCNF feature cannot be used for audio fax.

Channel allocation

Now that we have created 3 different conference rooms with a total of more reserved than available channels, we will discuss how they work when used simultaneously.

Let's do a simple test.
  • Please call 6010 from Edward Hyde (IP232). He will be the first to enter the conference room conf-hq.
  • Please call 6030 from John Doe (IP111) to enter the the conference room conf-john.
You will see the call from John Doe is released with the error code channel not free. Once we called the conference room conf-hq with Edward Hyde, the conference interface reserved 8 channels from the available 10 channels. When we tried to enter the second conference room with John Doe, the required 3 conference channels could not be allocated. video2.png As a result the call was released. This means that once the reserved channels are allocated by a conference room, no other conference room can use these channels although they are currently not in use by a call.

Let's do another simple test.
  • Please call 6030 from John Doe (IP111), Richard Roe (IP64), Edward Hyde (IP232) and Henry Jekyll (analog phone) so that all users are connected to conf-john.
You may wonder why the last participant is able to join the conference even though this conference has only 3 reserved channels. As long as free non-reserved channels are available, the conference room can allocate additional conference channels.
  • Please call 6020 from Jane Doe (IP112) to enter the conference room conf-jane.
Again the call will be released with the error code channel not free. The problem in this case is, that we overbooked the conference room conf-john. The conf-john conference room is using 4 channels consequently the conference interface is not able to allocate the required 7 channels for the conference room conf-jane video2.png as shown in the video

3-way DECT conference

Neither the IP1202 nor the DECT handset itself is capable of mixing an ad-hoc 3-way conference, like an innovaphone phone is able to. Fortunately, an innovaphone Gateway with a CONF or SCNF (soft conferencing) interface can be used to provide conferencing functionality for the DECT phones.

Of course you could create another dedicate room in your conference plugin for the DECT conferences and enter the number of this room as conference unit at the IP-DECT master ( DECT / Config / Master). Although this is an easy solution we do not recommend it because this would allow only one DECT ad-hoc conference at the same time.

Luckily there is a better solution which we will discuss in the following chapters.

VoIP Interfaces

To realize our solution we have to talk about how to route traffic from the PBX to the gateway layer. In the end we want to use the SCNF of the IP811 as resource for our DECT conferences as well.

Gateway object

The Gateway object is similar to a trunk line object. While the trunk line object is specifically designed to connect the PBX to the PSTN via a SIP or ISDN trunk. The use of the Gateway object is more versatile. Any VoIP application can register to a Gateway object using either H.323 or SIP.
Enabling the Prefix option on a Gateway object will remove the object's own number from CGPN of outgoing calls and append it to the CDPN of incoming calls. By activating this function the Gateway object behaves like the trunk line object.

Create screenshot.png a Gateway Object in the PBX at PBX / Objects.
  • Please assign the Long name dect-conf to this object
  • Please give the object the Number 61.
  • Create screenshot.png a Hardware ID 009033410004-GW1 for this object.
  • Set the TLS Only checkmark for this Hardware ID.
  • Set the screenshot.png Prefix checkmark at the Gateway tab of the object.

GW Interface

A GW Interface is used to connect the gateway layer of a device to another VoIP device. In our case we want to connect the gateway layer of our IP811 to our Gateway object we just created.
Signaling protocol
  • H.323
  • H.323/TCP
  • H.323/TLS
  • Websocket
If you connect an interface to an Innovaphone device we always recommend to use H.323/TLS. H.323/TLS is TCP based and uses TLS to encrypt signaling traffic. H.323/TCP is the unencrypted TCP variant of H.323, while just H.323 uses UDP as transport layer and is not encrypted as well.

SIP, TSIP and SIPS are all flavours of the SIP protocol. SIP is UDP based while TSIP is the TCP based variant of the SIP protocol. SIPS is TCP based as well but uses TLS to encrypt the signaling traffic.

Websocket is mainly used for an internal purpose and not meant to be used in a productive environment. We do not recommend to use it.
Registration method
Your main selection screenshot.png in this drop-down menu is either Register as Gateway or Gateway without registration. All other methods are rather special and not part of this course. The difference between the previously mentioned methods is whether the GW interface should register at the far end or not. If you choose Register as Gateway, the interface registers at the destination and a client/server relationship is established. If you choose Gateway without Registration, a message is only sent to the destination if necessary. For incoming messages, it accepts calls from the far side at any time.

Now we are going to register the GW1 interface of our IP811 to the newly created Gateway object. To do this, we go to Gateway / GK and open the GW1 interface.
(Further Hints) As of 13r2, a new checkbox has been added called Obtain Channels lic on outgoing call. This checkbox allows us to use PBX channel licenses on a gateway object. In 13r1 PBX channel licenses can only be activated on the conference object (conference plugin), thus gateway channel licenses must be used for 3-way DECT conference in 13r1.

Routing Engine

Now we have to create a logic in our routing table so that calls coming from GW1 are routed to the SCNF interface. This configuration is done at Gateway / Routes. If you look at your routing table you will screenshot.png see 2 already existing routes.

Internal registration

If you register an interface (except a GW interface) internally to an Innovaphone PBX, 2 routes are created between the interface and the VoIP interface.

The implicit VoIP interfaces are named R plus a short-hand notation for the interface. For example the routes SCNF->RSCF and RSCF->SCNF were created when you selected the Software Conferencing interface of the IP811 in your conference plugin. You automatically created an internal registration from the SCNF to the Conference object in the PBX.


Before we proceed we have to discuss the term route in more detail. A route always consists of screenshot.png a FROM and a TO part. In other words, a route is a path between at least one source interface and at least one destination interface.You can have more than one route from the same source interface. In this case the routing table is searched for a matching route from top to bottom. The first matching route is used. If no route applies or no route is defined, the call will be disconnected.

Keep in mind that a route defines only one direction. If you need traffic in both directions, screenshot.png you need to create a separate route. For this reason, two routes are created when you register an interface internally. One for each direction.

To add a new route we need screenshot.png to click the icon on the far left. screenshot.png A new window will appear that allows you to select multiple source interface. screenshot.png The drop down menu, on the right side, allows you to select the destination interface of that route. The new route will be inserted below the already existing one.

To edit a route, you can screenshot.png click on the arrow in the middle of the route. The same window appears as if you create a new route.

Please video2.png add a new route so that calls from GW1 are routed to the SCNF interface. The SCNF will never make an outbound call, so a route from the SCNF to GW1 is not necessary.

Route vs Map

A common misunderstanding is screenshot.png the difference between a map and a route. As we talked before a route consists of at least one source interface and at least one destination interface. Each route has one ore more maps which define to which destination interface a call is routed. The decision is either based on the CDPN or the CGPN. Additionally you can apply number manipulations to a map to change the CDPN and the CGPN.

DECT conference

To complete our configuration we have to tell the IP-DECT master how to access the conference resource.

To do this, we go to DECT / Config / Master and add the number of the gateway object we just created followed by *1#, which is a fish-help.png call-setup commando to open a room at the conference interface, as Conferencing unit number. In other words screenshot.png please configure 61*1# as Conferencing unit number.

(Further Hints) This configuration option is not replicated between your two IP-DECT master in mirror mode. As a consequence you have to configure the same option at your IP1202B as well.

Let's try it

After configuring the IP-DECT master, we want to try out if the configuration is working as expected.
  • Please call 14 from Jane Doe's phone (IP112) and answer the call on your IP65
  • Press the R key (top right) followed by 15 (Henry Jekyll) at your IP65
  • Pick up the call at your analog phone
  • Press the R key at your IP65 again and then 3
  • Afterwards the word Conference appears on the display of your IP65 and you will be connected to all participants.
But what happens if you call 6010 from Edward Hyde now?

Again not enough channels can be allocated therefore video2.png the call will be released. You will experience the problem the other way around as well. If you call the conf-hq conference first and then try to initiate a 3rd party conference at your DECT handset, it will fail because video2.png not enough channels are available.

Of course this is very frustrating for the user. Consequently you have to create a solution to minimize the problem. So let us revisit the configuration optionscreenshot.png used channels inside your conferences PBX manager plugin. If you set it to 7, you will be able to create at least one 3rd party DECT conference at any time. But don't forget to decrease the number of reserved channels for the conference room conf-hq as well, otherwise you can never use it because you cannot allocate enough channels for this room.

Call counter

There is also a possibility to limit the number of simultaneous DECT conferences in case a conference room should always be accessible. That's why we want to take a closer look at the feature call counter inside a route.

Call counter

A Call counter specifies the maximum number of allowed calls for a number of maps within the routing table. You can use the same name of a Call counter for several different maps. Each active call through a map with the same call counter name counts for the amount of this call counter. If the max value of this Call counter is reached no further call through this map is allowed and the call will be passed on to the next map.

Please screenshot.png add the Call counter named dect with the max value 3 to the route GW1->SCNF.

This way you can have just one ad-hoc 3rd party DECT conference at the same time and the conference room conf-jane is always accessible.

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