CITS3002 Computer Networks

(for the week commencing 22nd April 2024)

Two questions from past exam papers:

Each IPv4 address is 32 bits wide, suggesting that there are 2³² possible addresses.

With reference to RFC 997, what is the maximum number of different hosts which may be addressed using the Internet Protocol addressing scheme (assume that just addresses of classes A, B and C are in use)?

What special cases do we have to consider?
Consider the case of two Ethernet LAN segments, connected by a single gateway device.
```
In the font they use in RFCs!
    ---------        --------------        ---------
    | HOST1 |        |   GATEWAY  |        | HOST2 |
    |  IP1  |        |  IP3  IP4  |        |  IP2  |
    |  mac1 |        | mac3  mac4 |        | mac2  |
    ---------        --------------        ---------
        |              |        |              |
   -----------------------    ---------------------
              LAN1                   LAN2
```
A host on one of the LAN segments wishes to send a UDP/IP datagram to a host on the other LAN segment. Both hosts know the IP address they should use to contact the gateway device.

Assuming that none of the three devices knows the Ethernet addresses used by the other two devices, describe the sequence of Ethernet frames necessary to deliver the datagram.

Chris McDonald
April 2024.