An IP machine Q has a path to another IP machine H via three IP routers R1, R2, and R3.

Q—R1—R2—R3—H

H acts as an HTTP server, and Q connects to H via HTTP and downloads a file. Session layer encryption is used, with DES as the shared key encryption protocol. Consider the following four pieces of information:

$$[I1]$$ The URL of the file downloaded by Q
$$[I2]$$ The TCP port numbers at Q and H
$$[I3]$$ The IP addresses of Q and H
$$[I4]$$ The link layer addresses of Q and H

Which of $$[I1]$$, $$[I2]$$, $$[I3]$$, and $$[I4]$$ can an intruder learn through sniffing at R2 alone?

An IP router implementing Classless Inter-domain Routing (CIDR) receives a packet with address 131.23.151.76. The router’s routing table has the following entries:

The identifier of the output interface on which this packet will be forwarded is ______.

An IP router with a Maximum Transmission Unit (MTU) of 1500 bytes has received an IP packet of size 4404 bytes with an IP header of length 20 bytes. The values of the relevant fields in the header of the third IP fragment generated by the router for this packet are

Every host in an IPv4 network has a 1-second resolution real-time clock with battery backup. Each host needs to generate up to 1000 unique identifiers per second. Assume that each host has a globally unique IPv4 address. Design a 50-bit globally unique ID for this purpose. After what period (in seconds) will the identifiers generated by a host wrap around?