Sets up simulcast for 2 layers.

modules/xmpp/TraceablePeerConnection.js

     var Interop = require('sdp-interop').Interop;
     this.interop = new Interop();
     var Simulcast = require('sdp-simulcast');
-    this.simulcast = new Simulcast({numOfLayers: 3, explodeRemoteSimulcast: false});
+    this.simulcast = new Simulcast({numOfLayers: 2, explodeRemoteSimulcast: false});
 
     // override as desired
     this.trace = function (what, info) {
         function() {
             var desc = this.peerconnection.localDescription;
 
+            // TODO this should be after the Unified Plan -> Plan B
+            // transformation.
             desc = SSRCReplacement.mungeLocalVideoSSRC(desc);
 
             this.trace('getLocalDescription::preTransform', dumpSDP(desc));