netty: SSLHandler slows down large file transfer

I try to send a file larger then 5MB over the following pipeline:

1. SSLHandler
2. ByteToMessageCodec
3. IdleStateHandler
4. SimpleChannelInboundHandler

Sending a 10MB file takes arround 3Sekonds. When I remove the SSLHandler the file is transferred within 800ms. I found out that the SSLHandler Chunks the bytebuffer into very tiny pieces, that take forever to be sent.

I use the UnpooledByteBufAllocator.DEFAULT in my ChannelOptions. my encode method form the ByteToMessageCodec looks like this:

protected void encode(ChannelHandlerContext channelHandlerContext, IMessage iMessage, ByteBuf byteBuf) throws Exception {
    if(byteBuf.isWritable()){
        byteBuf.writeBytes((serializer.serialize(iMessage) + RECORD_SEPARATOR).getBytes());
    }
}

Is there a way to tweek the SSLHandler?

Maybe the SSLEngine is the troublemaker? I found the following line of code inside the SSLHandler, but this constructor is depricated:

wantsLargeOutboundNetworkBuffer = !opensslEngine;

Netty version

4.0.40

JVM version

java version “1.8.0_111” Java™ SE Runtime Environment (build 1.8.0_111-b14) Java HotSpot™ 64-Bit Server VM (build 25.111-b14, mixed mode)

OS version

Win10

StackOverflow

netty-sslhandler-slows-down-file-transfer-5mb