Today, by popular demand, we’re going to provide some useful technical content – something that you can actually implement today on your Metaswitch – and help people across the country to interrupt their colleagues with important announcements: by setting up a Paging Group using Yealink IP phones.
If you’re already a hosted PBX expert then you may already know how to do this, but if you’re just getting started this is the kind of feature that can take a little while to figure out – so hopefully you find this useful.
What is a Paging Group?
Paging is basically an announcement that is broadcast over some kind of speaker system. In our case it’s an announcement that suddenly blares out of your phone without the phone ringing and without you answering it.
If you configured a single-destination page this would be similar to an intercom system – where an executive might hit a button on the phone to speak to his/her assistant – except that a page is a one-way announcement (whereas an intercom call has two-way audio). However, a multi-destination page could be used to request help from everyone in a particular department, or even to announce a security alert to all employees.
Whereas most features of a hosted PBX deployment are implemented using the SIP protocol controlled by the cloud-based PBX platform, paging is actually handled entirely by the phones themselves using an IP technology named multicast.
Basically what happens is that you configure each phone within the paging group to “listen” to a certain multicast IP address (there are ranges of IPs that are set aside for multicast and can’t be assigned to devices). Then when a phone wants to broadcast audio to these phones it sends out an RTP stream to this same multicast IP and port, and the local network switches and routers forward these RTP packets on to the listening phones. The listening phones then play the RTP stream out of their speakers as soon as they receive the packets.
Obviously this needs to be supported by the local IP network, but multicast is a pretty standard technology that’s widely supported. I set this up in my home office lab and it worked right out of the box – I didn’t have to make any changes to my consumer grade router. Of course, if the phones are spread over multiple subnets then things may get a little more complex, but it can still work (see this article from Microsoft for more details).
How to configure Paging Groups using Yealink phones on a Metaswitch
In my simple lab set up I have two phones – a broadcaster and a listener – and I’m using a Yealink T42S and a T46S. Here’s the configuration (from the Metaswitch Phone Profile interface – linked under the Phones section of a line in Metaview Web) on the listening phone. I’m configuring this as the service provider, but I believe a BG admin could also make these changes.
In my case I just have one listening phone, but you’ll want to repeat this set up (with identical configuration) on all the other phones you want to receive pages.
There are a couple of ways to approach the configuration of the broadcast phone, but the simplest option looks like this.
In fact, here’s a little demo of the feature.
What if I need a more complex set up
What we’ve done so far is simple enough, if you have a single paging group, but what if you need something more complex, what if you have 10 different paging groups each with different combinations of phones?
Well, actually it’s not that hard to set up.
Firstly, on the listening side, you’ll have noticed that when we configured the phone as a listener there were actually 10 different sets of listening group configuration – so a single phone can be a member of up to 10 different paging groups. You just need a different IP address and port combination for each listening group.
If you choose, you could configure a different hard/soft key on the phone for every single paging group, and follow exactly the same model as we did before – but if you have more than a couple that could become hard to manage.
The other option is to configure each broadcast multicast address:port combo explicitly as a Paging Group on the phone, and then use the Paging Lists feature to show the user a list of the available options when they wish to make an announcement.
The Paging Groups configuration is found directly under the Listening Groups.
What happens if I’m on the phone when a page comes in?
Good question. The short answer is that by default the page will interrupt your call and place the other party on hold. It is possible to modify this configuration, but the settings are hard to find.
If you want a phone call to always have priority over the page, you need to add the following “free setting” to the bottom of your phone configuration page for each listening phone. The free setting section of the Metaswitch configuration basically allows you to assign values to other parameters that aren’t exposed through the standard interface. If you’re not using Metaswitch to handle phone configuration then you can find this on the web interface of the phones under Directory -> Multicast IP. A setting of 0 sets the phone call to the highest priority (above all pages).
Can I do this without Metaswitch Phone Provisioning Server?
Yes. As I mentioned earlier, there’s actually no configuration taking place on your phone switch at all – you can configure this all directly on the phones or through another phone provisioning mechanism.
Can I do this with other phone models?
Yes, although the precise mechanism used varies a little between different phones. The Metaswitch LearnHowTo manuals cover how to set this up for Polycom phones – and the process is very similar to what I’ve described here.
Can I mix and match phone models?
In theory, yes. Multi-cast is a standard protocol, so as long as the phones are configured with the same multi-cast IP and port they should hopefully be able to communicate with each other. However in practice I’ve heard there are some challenges as different phones use different multicast IPs and different channels within that – so I’d recommend testing your particular set up before assuming it will work.
Can the same phone both be a broadcaster and a receiver?
Yes – you simply have to configure both sets of function on the same phone.
That’s all for today folks. I hope you found this useful, and if you have ideas for future articles please don’t hesitate to contact me and we’ll add them to the list.
