Optimize RFsimulator to improve E2E performance

This improves the RFsimulator code to reach a ~40% E2E throughput
improvement (depending on the machines).

Changes:
- reduce ring buffer size
- code cleanup for readability
- set TCP kernel parameters

radio/rfsimulator/stored_node.c

@@ -186,14 +186,10 @@ int main(int argc, char *argv[]) {
     serviceSock=client_start(argv[2],atoi(argv[3]));
   }
 
-  uint64_t typeStamp=ENB_MAGICDL;
   bool raw = false;
 
   if ( argc == 5 ) {
     raw=true;
-
-    if (strcmp(argv[4],"UL") == 0 )
-      typeStamp=UE_MAGICDL;
   }
 
   samplesBlockHeader_t header;
@@ -213,7 +209,6 @@ int main(int argc, char *argv[]) {
     setblocking(serviceSock, blocking);
 
     if ( raw ) {
-      header.magic=typeStamp;
       header.size=blockSize;
       header.nbAnt=1;
       header.timestamp=timestamp;