Cellular Network Infrastructure » Core Network (CN) » OsmoSTP

There are some M3UA implementations out there who use a routing context during the ASPAC
procedure, but who then don't use it in subsequent DATA transmission.

This behavior seems to be at the edge of what's possible within the spec:

 Routing Context: 32 bits (unsigned integer)

      The Routing Context parameter contains the Routing Context value
      associated with the DATA message.  Where a Routing Key has not
      been coordinated between the SGP and ASP, sending of Routing
      Context is not required.  Where multiple Routing Keys and Routing
      Contexts are used across a common association, the Routing Context
      MUST be sent to identify the traffic flow, assisting in the
      internal distribution of Data messages.

So if you don't configure a routing context, it is not required to be sent. And if you have multiple routing contexts, it must be sent. But the situation where a routing context has been configured (but not multiple) is not really covered.