code: public final boolean isViaHeaderExternal(ViaHeader viaHeader) {
  		if (viaHeader != null) {
  			return isExternal(viaHeader.getHost(), viaHeader.getPort(), viaHeader.getTransport());
  		}
  		return true;
  	}
docs: Check if the via header is external
  @param viaHeader the via header to check
  @return true if the via header is external, false otherwise