Very good notes david55!
[quote=“david55”]Please note that I deal with development model systems, not production ones, so cannot do the actual sizing, but these are some of the factors that might affect the sizing
Channel technologies used?
Is there any transcoding (particular expensive codecs like G.729 or GSM)?
Is any form of native bridging possible, in particular SIP direct media, and what is the peak erlang loading of traffic for which full direct media and native bridging are not possible? (Direct media removes the highest volume of traffic and the highest load on most systems, but is only possible if codecs match, the parties agree, and Asterisk not recording and has no interest in any DTMF.)
Do you use early media, or do you answer incoming calls before the outgoing leg answers (implies, at a minimum, that Asterisk will have to generate in band tones)?
Are you recording calls, and the codec used?
Use of conferences?
Use of queues?
Use of voice announcements?
What level of diagnostic logging, and how long do you intend to keep it?
What if any call accounting records, and how long do you want to keep them on the server?
Do you intend to use Asterisk Realtime Architecture and if so, what database?
Do you intend to use database features of the dialplan?
Do you intend to use AGI scripts or other external scripts?