Chapter Questions
What is the single greatest advantage of having a checksum cover only the datagram header and not the payload? What is the disadvantage?
Is it necessary to use an IP checksum when sending packets over an Ethernet? Why or why not?
What is the MTU of an 802.11 network? Fibre Channel? 802.15.4?
Do you expect a high-speed local area network to have larger or smaller MTU than a wide area network? Why?
Argue that a fragment should not resemble a datagram.
Ethernet assigns a new type value for IPv6, which means the frame type can be used to distinguish between arriving IPv6 and IPv4 datagrams. Why is it necessary to have a version number in the first four bits of each datagram?
In the previous exercise, estimate how many total bits are transmitted around the world each year just to carry the 4-bit version number.
What is the advantage of using a one's complement checksum for IP instead of a Cyclic Redundancy Check?
Suppose the Internet design was changed to allow routers along a path to reassemble datagrams. How would the change affect security?
What is the minimum network MTU required to send an IPv4 datagram that contains at least one octet of data? An IPv6 datagram?
Suppose you are hired to implement IP datagram processing in hardware. Is there any rearrangement of fields in the header that would make your hardware more efficient? Easier to build?
When a minimum-size IP datagram travels across an Ethemet, how large is the frame? Explain.
The differentiated services interpretation of the SERVICE TYPE field allows up to 64 separate service levels. Argue that fewer levels are needed (i.e., make a list of all possible services that a user might access).