[sip-overload] draft-ietf-soc-overload-control-07 section 6.3 algorithm

[Eric McMurry <[e-mail]>]

I'm a bit confused on the default loss-based algorithm in section 6.3 of draft-ietf-soc-overload-control-07.  Based on the text, I believe that this algorithm is intended to apply to outbound messages from a client and to use previously stored information about the overload condition of the downstream server the message is targeted to.

When I read through the algorithm part though, I'm not sure of the intent.  I've made some changes in the algorithm to try to communicate what I think it was saying.  Does this match the intent?

    cat1 := 40.0          // Category 1 --- subject to reduction
   cat2 := 100.0 - cat1  // Category 2 --- Not subject to
                         // reduction.  40/60 mix.
   in_oc := false        // Not operating under overload

   while (true)  {
     sip_msg := get_outgoing_sip_msg()
     if (is_response(sip_msg))  {
         process_msg(sip_msg)
     }
     else if (is_request(sip_msg))  {

       // Determine if target server wants to enter overload or is
       // in overload
       target_server := extract_target(sip_msg)
       in_oc := lookup_in_oc(target_server)

       // Get validity value
       oc_validity := lookup_oc_validity(target_server)

       // Get oc parameter value
       oc_value := lookup_oc_value(target_server)

       pct_to_reduce := oc_value / cat1 * 100
       // Example: if oc=10,
       // server uses 10 / 40 * 100 = 25 or 25% of messages in
       // Category 1 can be reduced.

       if (in_oc == false)  {
         process_msg(sip_msg)
       }
       else  {

         // Either Category 1 or Category 2
         assign_msg_to_category(sip_msg)

         if (oc_validity is in effect)  {
           process_msg(get_msg_from_cat2())
           sip_msg := get_msg_from_cat1()

           // Draw a random number between 1 and 100
           r := random()

           if (r <= pct_to_reduce)  {
               // Do not send to server, handle locally by
               // generating a final response
           }
           else  {
             process_msg(sip_msg)
           }
         }
       }
     }
   }