NettyJaxrsServer.java is instantiating a HttpRequestDecoder using the default settings.
These are as follows:

• maxInitialLineLength=4096
• maxHeaderSize=8192
• maxChunkSize=8192

There is no way for a RestEasy user to specify different values. In my case I am interested in raising the maxHeaderSize since I am dealing with large cookies.
As per http://stackoverflow.com/questions/686217/maximum-on-http-header-values each server has different limits but 8K is in the lower end.