Hypertext Transfer Protocol (HTTP/1.1) Activity Identifiers
It is very common that implementers of HTTP severs require the ability to associate an identifier to an HTTP request and or response, this can be for a number of reasons which could include checking for duplicate requests, allowing the caller of an API to maintain a record of their interaction with the server or to track client/server requests through a disparate system of services. In any case, the implementer will quite often use a custom HTTP header and either assign a value itself or require the caller to supply the value. This document outlines a consistent storage mechanism for this identifier by way of a standard HTTP header and a new status code for when a mandated identifier is omitted. The purpose is to create better consistency for clients of third party HTTP servers and HTTP based APIs by introducing this standard request and response header.