Paging about 35 desk phones connected via SBC

[Chris Wheeler]

I have a client who would like to implement 3CX hosted. Approximately 35 desk phones. They have a need to page all of the phones. Seeing that they would connect via the local SBC, are there any issues with this type of setup and this number of phones?
I was going to use an i3 Shuttle for the SBC with 16GB RAM if the SBC resources come into play.

 

[Evolute IT]

I have a client who would like to implement 3CX hosted. Approximately 35 desk phones. They have a need to page all of the phones. Seeing that they would connect via the local SBC, are there any issues with this type of setup and this number of phones?
I was going to use an i3 Shuttle for the SBC with 16GB RAM if the SBC resources come into play.

Not really but I am unsure what's the paging limit when not using multicast (since the SBC can't forward the multicast.)

 

[Chris Wheeler]

Not really but I am unsure what's the paging limit when not using multicast (since the SBC can't forward the multicast.)

I believe the published limit is 64 phones with alert paging. I just havent done so with a 3CX hosted setup and wasnt sure about resources used or delay with this setup.

 

[Evolute IT]

I believe the published limit is 64 phones with alert paging. I just havent done so with a 3CX hosted setup and wasnt sure about resources used or delay with this setup.

Can't speak to that, we never use paging on that many phones. Max we did was 15 and it worked fine on a good i5 Linux SBC.

 

[NickD_3CX]

@Chris Wheeler There is not "hard limit" to the amount of phones that can be used as part of an "Alert" Paging Group, but the limit is more a "soft limit".
The reason we recommend no more than 64 devices is because the PBX will initiate X amount of INVITE messages in the same split second. As the replies start arriving back, the PBX might need 3-4 seconds to process them all and establish an Audio communication with them.

While this is not a problem on a one-to-one call, the Initiator of the Paging Group will have to wait for those 3-4 seconds before hearing the tone signalling them to start talking which they will get after the last device has answered.
Factor into this a slight delay overhead due to all traffic going through the SBC, so I generally we don't recommend adding more that this number for this reason.

Also, regarding the SBC 35 Sim Calls at the exact same split second will momentarily send the Hardware Utilization through the roof, so make sure you don't get the absolute minimum specs for the SBC, especially if this will be a fairly frequently used PG.

 

[Chris Wheeler]

@Chris Wheeler There is not "hard limit" to the amount of phones that can be used as part of an "Alert" Paging Group, but the limit is more a "soft limit".
The reason we recommend no more than 64 devices is because the PBX will initiate X amount of INVITE messages in the same split second. As the replies start arriving back, the PBX might need 3-4 seconds to process them all and establish an Audio communication with them.

While this is not a problem on a one-to-one call, the Initiator of the Paging Group will have to wait for those 3-4 seconds before hearing the tone signalling them to start talking which they will get after the last device has answered.
Factor into this a slight delay overhead due to all traffic going through the SBC, so I generally we don't recommend adding more that this number for this reason.

Also, regarding the SBC 35 Sim Calls at the exact same split second will momentarily send the Hardware Utilization through the roof, so make sure you don't get the absolute minimum specs for the SBC, especially if this will be a fairly frequently used PG.

Nick, thank you. So doing mid 30s then shouldnt be an issue especially if I go with additional resources for the local SBC.

 

[NickD_3CX]

Nick, thank you. So doing mid 30s then shouldnt be an issue especially if I go with additional resources for the local SBC.

No, spec-wise I think you will be OK, the only thing you would want to test and check is how long the Caller that called the PG group needs to wait before starting to speak, so that his first words aren't cut off.

I am guessing around the 2.5s mark.

 

[cobaltit]

Hey Chris, I recommend upvoting this: https://www.3cx.com/community/threads/multicast-page-relay.64146/

What we typically do in these scenarios is use a Cyberdata paging adapter. It's SIP to the Cyberdata and then multicast from there.

 

[pmterp]

Depending on the phones you're using, multicast paging may be a better solution. It does require manual programming or a custom template so it isn't officially supported but works very well.

Edit: according to the below thread, I was wrong about the simultaneous call limitation so I've removed it from my reply. https://www.3cx.com/community/threads/license-limit-reached-with-paging-group.56968/post-237550

 

[ASC Admin]

I think a page only counts as one call (even without using multicast). We have 11 or so phones that receive our pages, and we only have a free 8SC license.

 

[NickD_3CX]

I think a page only counts as one call (even without using multicast). We have 11 or so phones that receive our pages, and we only have a free 8SC license.

You are right about this.

 

[Chris Wheeler]

Depending on the phones you're using, multicast paging may be a better solution. It does require manual programming or a custom template so it isn't officially supported but works very well.

Edit: according to the below thread, I was wrong about the simultaneous call limitation so I've removed it from my reply. https://www.3cx.com/community/threads/license-limit-reached-with-paging-group.56968/post-237550

Thanks.. Are custom templates supported with 3CX Hosted implementations? I hadnt thought so.

 

[NickD_3CX]

Thanks.. Are custom templates supported with 3CX Hosted implementations? I hadnt thought so.

No, on "Hosted by 3CX" you cannot create custom templates. Your only option, although not recommended for obvious reasons, is to configure the IP Phone, remove the provisioning link, then do whatever manual settings you want.

Note though that by doing this you will not get Firmware and Template Updates.

 

[Chris Wheeler]

Hey Chris, I recommend upvoting this: https://www.3cx.com/community/threads/multicast-page-relay.64146/

What we typically do in these scenarios is use a Cyberdata paging adapter. It's SIP to the Cyberdata and then multicast from there.

That Cyberdata device is also not supported behind an SBC correct? Is it working ok for you in a 3CX Hosted setup? Do you call the adapter extension which then hits the phones via the multicast address and page that way?