Following the link Istio/Distributed tracing, I can get the tracing working with zipkin.
Currently in order for the client/caller to know about the x-request-id (in case no id is sent, zipkin creates one), he needs to send it as a part of the request.
This gives him the ability of trace the request. All works well.
However, I am thinking maybe it is not a good idea for the client to send the x-request-id to avoid issues of constraints/duplication.
It would be good if it is possible that at the istio level, one should be able to modify the response headers and send the x-request-id back.
I am not finding such capabilities for istio at present. If there is a way to achieve this, please let me know.