I am unable to get our SRX220 to fully support Skype 4 Business desktop sharing in a branch office. Skype4B calls, internet access etc. works without any problems, only desktop sharing fails 9 of 10 times.
For testing purposes the SRX has a minimum config with NAT between an external zone and internal zone generated by the install wizard.
Under flow I have no-syn-check and no-sequence-check. The SIP ALG is disabled. All other settings are default to keep things simple. No licenses for UTM or IDS are enabled.
I have tried the releases 12.1X45-D50, 12.1X46D45 and even 12.3X48D25 to test the new SIP ALG TCP support.
Replacing the SRX with a cheap consumer router/firewall that does simple NAT and a default config works without problems.
Any suggestions to get the SRX to support Skype4B\Lync working are highly appreciated.