Intro to IP

Which layer addresses, routes, encapsulates, and decapsulates packets between hosts?

The Network Layer.

What delivery model does IPv4 use?

Connectionless, Best-effort (unreliable) delivery.

Why does IPv4 not handle packet recovery?

Reliability is handled by protocols at other layers, allowing IP to stay efficient.

Is IPv4 dependent on the physical transmission medium?

No, it is media independent.

What are three things the sender does not know in a connectionless IP delivery?

• If the receiver is present
• If the packet arrived
• If the receiver can read the packet

What does the receiver not know in a connectionless IP delivery?

When the packet is coming.

What does “best effort” delivery mean in IPv4?

IPv4 forwards packets as quickly as possible but does not guarantee delivery.

Why is IPv4 considered unreliable?

It cannot manage or recover lost or corrupted packets.

Who is responsible for reliability if IP does not provide it?

Upper-layer protocols (e.g., TCP).

How does the lack of reliability features benefit IPv4?

It allows high efficiency at the Network Layer.

What network layer concern exists despite media independence?

The Maximum Transmission Unit (MTU).

What happens when a packet exceeds the MTU of the outgoing medium?

Fragmentation.

What is the MTU for copper Ethernet?

1518 bytes.

Which technology has the smallest MTU listed: Copper Serial Frame Relay, Optical ATM, or Wireless 802.11?

Copper Serial Frame Relay (512 bytes).

What is the MTU size for optical fiber using ATM?

17,966 bytes.

What is the MTU size for wireless 802.11?

2,272 bytes.

What IPv4 header field limits how many router hops a packet can take?

Time To Live (TTL).

What IPv4 header field indicates the upper-layer protocol (such as TCP or UDP)?

The Protocol field.

What IPv4 header field contains the 32-bit address of the sender?

Source Address.

What IPv4 header field contains the 32-bit address of the destination?

Destination Address.

What field is used to help reassemble packet fragments?

Fragment Offset (and Flags).

What IPv4 header field stores Quality of Service (QoS) information such as DSCP?

Type of Service (now DSCP/ToS).

Why separate hosts into Networks?

Performance, Security, Address Management.

IP Addresses are divided into what?

Network and Host.

What does a subnet mask bit of 1 indicate?

The bit belongs to the network portion.

What does a subnet mask bit of 0 indicate?

The bit belongs to the host portion.

CIDR notation uses a slash followed by what number?

The number of network bits in the address.

What is the difference between a MAC address and a Network (IP) address?

MAC is physical Layer 2; IP is logical Layer 3.

What is the default gateway for a host?

The router interface address used to exit the local network.

What condition must be true for a default gateway to work?

Its network portion must match the host’s network.

Can a router forward packets without a route?

No.

What does the routing table store?

Information about directly connected and remote networks.

How are remote networks learned by a router?

Manually configured or learned dynamically.

What does ARP do?

Maps an IPv4 address to a MAC address.

What is ARP’s request format?

“Who has this IP address?”

What was one major limitation of IPv4 leading to IPv6 development?

Insufficient address space.

Which organizations and trends helped drive IPv6 adoption?

Government policy, 3GPP, IEEE, and growth of mobile hardware.

How are IPv6 addresses written?

In colon-hexadecimal format.

What are two rules for shortening IPv6 addresses?

Remove leading zeros in each group, and compress one sequence of all-zero groups.

Name three IPv6 address assignment methods.

Manual, DHCPv6, and Stateless Auto-Configuration (SLAAC/EUI-64).