Chapter Questions
Create forwarding tables for all the routers in Figure 8.2. Which router or routers will benefit most from using a default route?
Examine the forwarding algorithm used on your local operating system. Are all forwarding cases mentioned in the chapter covered? Does the algorithm allow entries that are not described in the chapter?
When does a router modify the hop limit (or time-to-live) field in a datagram header?
Consider a machine with two physical network connections and two IP addresses $I_i$ and $I_2$. Is it possible for that machine to receive a datagram destined for $I_2$ over the network with address $I_i$ ? Explain.
In the above exercise, what is the appropriate response if such a situation arises?
Consider two hosts, $A$ and $B$, that both attach to a common physical network, $N$. What happens if another host on the network sends $A$ a datagram that has IP destination $B$ ?
Modify Algorithm 8.1 to accommodate the IPv4 source route options discussed in Chapter 7.
When it forwards a datagram, a router performs a computation that takes time proportional to the length of the datagram header. Explain the computation.
In the above question, can you find an optimization that performs the computation in a few machine instructions?
A network administrator wants to monitor traffic destined for host $H$, and has purchased a router $R$ with monitoring software. The manager only wants traffic destined for $H$ to pass through $R$. Explain how to arrange forwarding to satisfy the manager.
Does Algorithm 8.1 allow a manager to specify forwarding for a multicast address? Explain.
Does Algorithm 8.1 apply to fragments or only to complete datagrams? Explain.