14.9.2. Restrictions 
- General restrictions
Refer not supported - Disable REFER on Skype for Business Mediation Server -
OS4K REFER is disabled in profile and no manual action needed SoftGate
doesn’t support comfort noise.
- Feature restrictions
- Dual forking - Simultaneously ring - Video call - Media bypass - E911 -
DNS load balancing is not supported by OpenScape 4000 - No tones on Skype
for Business client after OpenScape 4000 stn make transfer ringing -
Call not encrypted shown on display in case that security is enabled -
Call transfer initiated from OS4K to Skype for Business if caller is
Skype for Business if security enabled - Call forward via rerouting
not possible
- SIP trunk connected to Skype for Business can be configured only on vSTMI or on STMIX/STMIY.
See above restrictions on feature basis.
- Call Forward is available only on Skype for Business full Client comparison below
https://technet.microsoft.com/en-us/library/dn933896.aspx?f=255&MSPPError=-2147217396
Codecs:
- G.711a-Law, ptime=20msec preferred codec G.711 a -Law - G.729 is
not supported by Skype for Business - G.723 is not supported by the Softgate
or Skype for Business - silence suppression for g711 not possible while
different signalling - Skype for Business uses Comfort Noise PT (13);
not supported by Softgate - vHG/OS4K uses attribute: silenceSupp:on
;not not supported by Skype for Business -DTMF for RFC2833 is supported
for tones 0-15