(41) is a protocol that a host uses to inform a router when it joins or leaves an Internet multicast group. (42) is an error detection code that most data communication networks use. (43) is an interior gateway protocol that uses a distance vector algorithm to propagate routing information. (44) is a transfer mode in which all types of information are organized into fixed form cells on an asynchronous or non-periodic basis over a range of media. (45) is an identifier of a web page.