QUESTION SEVEN
Explain the circumstances that might lead a router running the Routing Information Protocol to delete routes from its routing table? [2 marks]
The Routing Information Protocol version 2 introduces certain improvements to the Routing Information Protocol version 1. One of these improvements is the next hop address field. How would you interpret the value 0.0.0.0 in the next hop field? [2 marks]
Consider the following protocols: Ethernet, IP, ARP, RARP, BOOTP, DHCP, TCP, UDP, IPX, FTP, TFTP, DNS, NFS, ICMP, IGMP, RIP, OSPF, SMTP, SNMP, POP.
Draw a well-labelled protocol graph showing all of the above mentioned protocols. Your graph should clearly show the “who encapsulates who” kind of relationship. [7 marks]
Explain how the Priority and flow label fields are used in IPv6. [4 marks]
Discuss how the bits in the flag bits field of IPv4 are used. (3 marks)
Explain how you would use the Internet Control Message Protocol for path MTU discovery. [2 marks]
ANSWER
If the gateway to a destination says that the cost of the route is greater than 15, then the route is deleted.
RIP assumes that a gateway that does not send updates is dead. All routes through a gateway are deleted if no updates are received from that gateway for a specified time period
The next hop address is the IP address of the gateway that handles the route. If the address is 0.0.0.0, the source of the update packet is the gateway for the route. The next hop route permits a RIP-2 supplier to provide routing information about gateways that do not speak the RIP-2.
The FLOW LABEL and the PRIORITY fields in the IPv6 header may be used together by a host to identify those packets for which it requests special handling by IPv6 routers, such as non-default quality of service or "real-time" service. This capability is important in order to support applications, which require some degree of consistent throughput, delay, and/or jitter. Such applications are commonly described as "multi- media" or "real-time" applications.
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