Solutions to Homework #3

Homework #3 Grade Distribution:

Points	Frequency
10	1
12	2
13	1
15	4
16	1
18	1
24	3
27	1
30	5
33	4
34	1
36	5
39	3
42	3

1. (max 30 points)

6 points for default router and why
6 points for subnet mask and why
6 points for DNS server and why
6 points for registering or identifying name and why
3 points each for other possibilities and why
3 points for saying ARP can be used to find default router address
(It was not necessary to cover each category completely to get full credit.)

• The host needs to know the IP address of routers on the local network and at the very least, the address of the default router, since the routers forward packets outside the local network.
• The host needs to know the subnet mask to determine if a packet is to be delivered locally or should be forwarded outside the network.
• The host needs to know the address of a DNS server so it can convert human friendly addresses to IP addresses.
• If the host is a server, it needs to register its name with a local DNS server, or somehow identify itself to client hosts.
• A host may also need the following: Network IP broadcast address, servers for alternate naming schemes such as WINS for Windows machines, its own domain name for protocols that require translation between domain names and IP addresses, etc.

2. ( 12 points)

6 points for embedding address
6 points for implications

• One possibility is to embed the 48 bit link layer or MAC address into the IPv6 address.
• With this scheme, there is no need to use ARP for resolving the link layer address, since this can be determined by looking at the part of the IPv6 address that contains the MAC address.