[Freeswitch-users] How to eliminate acoustic echo from server side(FreeSwitch)

In the multi-party conference, because some termianl phone does not process echo, which causes the call have echo, so SERVER side needs to do echo processing. How to eliminate echo in this scenario? Do I need to add hareware device? If I want to implement it using software competely, what kind of open source echo library can be used? Does SPEEX work in Server Side? So many VIOP termianl use SPEEX, how to use it in the server side? Processing echo in server side should be different from client side, there are some complicated secnarios shuch as network delay and package lost, how to deal with these? Any advice will be appriciated.