3CX SBC Max Recommended

[mujin1]

Hi,

We have multiple branch offices is there a maximum amount of SBC you can deploy? Is more then one SBC supported? Currently all our SIP trunks terminate at our HQ and the branch offices are generally quite small so was thinking to do a hub and spoke deployment a SBC at each site on Debian.


Thanks,
Carl

 

[cobaltit]

There is no documented max and yes you can have more than one SBC either for multiple sites or even on the same site if you have more extensions at a site than can be supported on a single SBC or for redundancy. The other option would be to use VPN if you already have one in place.

 

[Andyshawn]

There is no documented max and yes you can have more than one SBC either for multiple sites or even on the same site if you have more extensions at a site than can be supported on a single SBC or for redundancy. The other option would be to use VPN if you already have one in place.

cobaltit, Can you use a VPN instead of the SBC to connect the remote phones to the main site?

 

[cobaltit]

Absolutely and some would say it's preferred. Using a VPN would let 3CX consider all the phones as 'Local' which will give you the widest base as far as supported phones as there are many legacy phones that are only officially supported that way. It's also one less link in the chain as far as potential failure. Using the SBC has the advantage of a little bit of bandwidth savings as well as PnP ability for supported phones.

 

[Andyshawn]

Absolutely and some would say it's preferred. Using a VPN would let 3CX consider all the phones as 'Local' which will give you the widest base as far as supported phones as there are many legacy phones that are only officially supported that way. It's also one less link in the chain as far as potential failure. Using the SBC has the advantage of a little bit of bandwidth savings as well as PnP ability for supported phones.

Very interesting. So your saying, it would be better to setup a site to site VPN instead of using the SBC to connect the remote phones to the main location where the PBX is?

 

[cobaltit]

Many partners prefer the VPN over SBC, especially because the SBC used to be pretty shaky. It's gotta a lot better now and they can be setup redundantly if you know how. But if you already have a VPN in place then it makes sense to use that and it's what we'd do typically.

 

[Andyshawn]

Hi,

We have multiple branch offices is there a maximum amount of SBC you can deploy? Is more then one SBC supported? Currently all our SIP trunks terminate at our HQ and the branch offices are generally quite small so was thinking to do a hub and spoke deployment a SBC at each site on Debian.
Thanks,
Carl

So basically Multiple SBC can be used and you have another option of just simply using a site to site VPN instead of the SBC for connecting the remote location IP Phones to the main office.

 

[DSXVOICE]

Please keep in mind that the SBC consolidates BLF and manages RTP connections. If you use a VPN, all of that traffic goes thru the VPN. In the case of RTP, it prevents audio from traversing the VPN unnecessarily - potentially improving call quality.

With most connections being > 50M these days, voip bandwidth itself is rarely a concern. But VPN routers themselves have licensed limits that are sometimes much lower. Make sure to validate this in the deployment planning phase.

 

[cobaltit]

@DSXDATA

It's not typically a licensing issue with the VPN speeds but a CPU limitation due to the encryption overhead. The licensing comes into play typically for the # of VPN connections. Also, since the OP already has the VPN in place I assume it's sized appropriately already.

 

[DSXVOICE]

Sorry - we use virtual CISCO ASA's - so you're right, it's not typical - just in my world

 

[cobaltit]

Ahh I see what you mean. It looks like they decided to standardize the CPU and then use the license to limit the throughput vs having different processors per model. I guess it's the trade-off on paying for more hardware up front then you might need vs haven't to replace the hardware if you outgrow it.

 

[cobaltit]

Doh, having re-read that. Is that basically just software on a VM or is that using the Cisco 'servers'?

 

[DSXVOICE]

Yep - any VM host will do. Our infrastructure is 100% virtual - routers & switches. Makes it easy to manage in multiple datacenters. Given the VM hosts are robust, the rest is need & deploy - same day.

 

[Andyshawn]

Please keep in mind that the SBC consolidates BLF and manages RTP connections. If you use a VPN, all of that traffic goes thru the VPN. In the case of RTP, it prevents audio from traversing the VPN unnecessarily - potentially improving call quality..

@DSADATA
With regards to the RTP traffic, this statement is only true if both the IP Phones are behind the same SBC. Because If an extension at the remote site calls an extension at another location, that RTP traffic will go through the SBC, however, if both IP phones are behind the same SBC, that RTP traffic stays local on that LAN only. Is that correct?


I am of the opinion then, that if you have the option of setting up a site to site VPN between remote and main office, this would be a better solution that adding an SBC into the design.

 

[DSXVOICE]

Depends on the SBC in use - we're usually talking about the 3CX SBC - and in that case, direct RTP only happens on ext-to-ext calls going thru the same SBC.

 

[mujin1]

Hi Everyone, thanks for all the input very good feed back for me to consider!