ms/http_lookup is a SAP Parameter attribute which is used to control Lookup for SAP specific URL attributes information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
This parameter specifies which methods are used to search for
SAP-specific parameters in the HTTP request.
Following values are possible:
Only the URL is searched.
First the URL is searched, then the form specification.
The URL is searched, then the form specification, and then the cookie.
The search is done according to SAP specifications.
sap-trace : Activates the trace for this request; the trace results are
written to the trace file on the message server (dev_ms).
sap-group : Load balancing using the SAP logon groups.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.