Posted: August 18th, 2016

riefly describe how fragmentation works and, given that there is no change to higherlevel data, explain how this mechanism could contribute to congestion

IPv4 uses a checksum to determine if any errors have occurred in the transmission of a datagram, however this checksum only checks for errors in the IPv4 header. Discuss why only the header is checked by IPv4 for errors, and discuss whether it is necessary to check for errors at all given that Ethernet already checks the entire frame using CRC. b) Given a subnet mask of 255.255.192.0, demonstrate for an IP address of your choosing the calculation of the range of addresses that are valid from that network (host ID all 0s through to host ID of all 1s). Note: The IP address you choose must consist of four decimal numbers that are greater than or equal to 101, and must be odd numbers. c) The fragmentation mechanism provided by IPv4 can contribute to network congestion. Briefly describe how fragmentation works and, given that there is no change to higherlevel data, explain how this mechanism could contribute to congestion. d) Consider implementing a negative acknowledgement mechanism for IPv4 that would alert a source host to a datagram being discarded due to a corruption in the path between the communicating hosts at any router in the path or the destination host. i. Briefly describe how your protocol would work. ii. Illustrate the operation of your protocol using a time diagram/sequence diagram (see Session 5 Slide 39 for an example), including both successful and unsuccessful delivery of datagrams. iii. Discuss two advantages and two disadvantages of your protocol.