addRequestProxyHeaders(clientStream, headers);
customizeRequestHeaders(clientStream, headers);
convert(clientSession.getVersion(), serverVersion, headers);
SynInfo serverSynInfo = new SynInfo(headers, clientSynInfo.isClose());
StreamFrameListener listener = new ProxyStreamFrameListener(clientStream);
StreamPromise promise = new StreamPromise(clientStream, serverSynInfo);
clientStream.setAttribute(STREAM_PROMISE_ATTRIBUTE, promise);
serverSession.syn(serverSynInfo, listener, promise);
return this;
}