[asterisk-users] Maximum number of users

Gareth Blades mailinglist+asterisk at dns99.co.uk
Thu Dec 19 03:27:14 CST 2013

Thats fine for calculating how many users a particular speed network 
connection can cope with. 640 concurrent calls on a 100Mbps connection 
is doable on a decent machine as long as you are not doing much codec 

Once you get to the point where you start having hundreds of users then 
you really need to think about redundancy. OpenSIPS is a good way 
forward as it is very light weight and can easily handle tens of 
thousands of registered phones. As calls come in then it can forward 
them directly or if additional services are required such as possibly 
voicemail it can pass them onto one or more asterisk servers in a load 
balancing arrangement. Using a couple of database servers replicating to 
each other and a virtual IP address (or DNS SRV if the clients properly 
support it) will give you redundancy and allow you to add more server to 
expand the capacity.

On 19/12/13 05:19, Brian LaVallee wrote:
> Hi Bilal,
> Assuming you have the latest hardware, sufficient memory, cpu, etc...
> The key to determine the maximum number of users comes down to the 
> office type, RTP path, network interface, and primary codec used.
> First we need to determine the over-subscription rate, how many people 
> will be using the phones at any given time.
> For a call center, the ratio is 1:1.
> For a normal office, the industry standard is 4:1.
> {This ratio is also used to determine the number of PSTN channels you 
> will need too}
> Will the PSTN connections be Digium card(s) in your server or external 
> gateway(s)?
> Assuming Diguim card(s), the RTP will be going through your server.
> Determine the network interface.  10/100/1000baseT
> Then we need to consider the largest codec used, and divide the 
> available bandwidth by the typical packet size.
> µ-law/A-law is roughly 80 kbps, so we can support 128/1280/13107 audio 
> streams.
> Divide that by 2 (just to be safe) and allow RTP in both directions. 
> 64/640/6553
> Now multiple the result by the over-subscription ratio.  4:1 = 
> 256/2560/26212
> So we see that the maximum number of users is 2560 for a normal office 
> when there is a 100baseT NIC in your Asterisk server.
> You would also need to have 640 channels (28 T1 PRI's) connecting to 
> the PSTN.
> /Using SIP trunks to connect to the PSTN through the same 100baseT NIC 
> will reduce the maximum number of users you can support./
> The real challenge is not supporting thousands of users (IP Phones), 
> it's connecting a sufficient number of PSTN connections to support 
> those users.
> Sincerely,
> Brian LaVallee
> On 12/18/13, 11:45 PM, bilal ghayyad wrote:
>> Hello;
>> Can someone advise me what is the maximum number of users (IP Phones) 
>> that can be supported by asterisk 1.8 or later?
>> Regards
>> Bilal
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