code: public boolean authenticate(AuthToken token, Message msg) {
          if ((token != null) && (token instanceof FixedMembershipToken) && (this.memberList != null)) {
              PhysicalAddress src = (PhysicalAddress) auth.down(new Event(Event.GET_PHYSICAL_ADDRESS, msg.getSrc()));
              if (src == null) {
                  log.error(Util.getMessage("DidnTFindPhysicalAddressFor") + msg.getSrc());
                  return false;
              }
              return isInMembersList((IpAddress)src);
          }
  
          if (log.isWarnEnabled())
              log.warn("Invalid AuthToken instance - wrong type or null");
          return false;
      }
docs: /*public void start() throws Exception {
  super.start();
  IpAddress self=(IpAddress)auth.getPhysicalAddress();
  if(!isInMembersList(self))
  throw new IllegalStateException("own physical address " + self + " is not in members (" + memberList + ")");
  }