asterisk users - Jan 2008 - asterisk chan_sip tuning

hi,

can i ask what settings do you recommend for a lot(1000-10000) of 
different sip phones which are behind NAT(many different routers)?

i have
qualify=5000
nat=yes

cli>sip show settings
Reg. min duration       60 secs
Reg. max duration:      3600 secs
Reg. default duration:  120 secs
Outbound reg. timeout:  20 secs
Outbound reg. attempts: 0

asterisk 1.4

thanks

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Marek Cervenka
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