generally inband means included in the voice/data channel....out of band means signalling travels on a different channel. An example of inband is a voicemail system such as Unity/Octel attached to a PBX with only analog ports. It sends identification, control and other info in-band using dtmf tones. An out-of-band example is an Unity/Octel attached to Call Manager with Skinny/SMDI. Unity uses Skinny call control messages send in separate packets to Call Manager and the Octel would use SMDI as its out-of-band mechanism. Hope it helps.
