ackCseq.setValue(requestCseq.toString().replace(RFC3261.METHOD_INVITE, RFC3261.METHOD_ACK));
//add Via with only the branchid parameter
SipHeaderFieldValue via = new SipHeaderFieldValue("");
SipHeaderParamName branchIdName = new SipHeaderParamName(RFC3261.PARAM_BRANCH);
via.addParam(branchIdName, Utils.generateBranchId());
ackHeaders.add(new SipHeaderFieldName(RFC3261.HDR_VIA), via, 0);
//TODO authentication headers