Network Layer 4.3

WHAT IS A SUBNET? What is meant by an IP subnet?

1. A set of device interfaces that can physically reach each other without passing through an intervening router. 2. A set of devices that have a common set of leading high order bits in their IP address.

WHAT IS THE INTERNET PROTOCOL? What are the principal components of the IPv4 protocol (check all that apply)?

1. IPv4 datagram format 2. IPv4 addressing conventions 3. Packet handling conventions at routers (e.g. segmentation/reassembly)

SUBNETTING Consider the three subnets in the diagram What is the maximum # of interfaces in the 223.1.2/24 network?

256

SUBNETTING Consider the three subnets in the diagram What is the maximum # of interfaces in the 223.1.3/29 network?

8

DHCP REQUEST MESSAGE Which of the following statements about a DHCP request message are true? Hint: Figure 4.24 in the 7th and 8th edition of textbook

The transaction ID in a DHCP request message will be used to associate this message with future DHCP messages sent from, or to, this client. A DHCP request message may contain the IP address that the client will use. A DHCP request message is sent broadcast, using the 255.255.255.255 IP destination address.

PURPOSE OF DHCP What is the purpose of the Dynamic Host Configuration Protocol?

To obtain an IP address for a host attaching to an IP network.

WHAT IS AN IP ADDRESS ACTUALLY ASSOCIATED WITH? Which of the following statements is true regarding an IP address?

1. If a host has more than one interface, then it has more that one IP address at which it can be reached. 2. An IP address is associated with an interface. 3. If a router has more than one interface, then it has more that one IP address at which it can be reached.

IPV4 VERSUS IPV6 Which of the following fields occur ONLY in the IPv6 datagram header (i.e., appear in the IPv6 header but not in the IPv4 header)?

128-bit source and destination IP addresses the flow label field

SUBNETTING Consider the three subnets in the diagram Which of the following addresses can not be used by an interface in the 223.1.3/29 network?

223.1.2.6 223.1.3.28 223.1.3.16

PLUG-AND-PLAY What is meant by saying that DHCP is a "plug and play" protocol?

No manual configuration is needed for the host to join the network.

THE IPV4 HEADER

Version field = contains the IP protocol version number Type-of-service field = contains Explicit Congestion Notification (ECN) and differentiated service bits Fragmentation offset field = used for datagram fragmentation/reassembly Time-to-live field = value in this field is decremented at each router; when it reaches zero, the packet must be dropped (this prevents datagrams from looping forever in the network) Header checksum field = contains the Internet checksum of this datagram's header fields Upper layer field = contains the "protocol number" for the transport-layer protocol to which the datagram's payload will be multiplexed - UDP or TCP, for example Payload/data field = contains a UDP or TCP segment Datagram length field = indicates the total number of bytes in datagram