CS2005 - Lecture 8 - Network Layer II Flashcards
(26 cards)
What are the two main components of the network layer?
Data plane: router-level functions that forward datagrams
Control plane: network-wide logic for routing decisions
What does the network layer protocol enable?
Logical communication between hosts
Encapsulation and delivery of transport layer segments
What is the function of the IPv4 version number field?
Identifies the IP version (e.g., IPv4 or IPv6)
Guides routers on how to interpret the datagram
Why is the IPv4 header length field needed?
Indicates where the payload begins
Accounts for optional header fields
What is the purpose of the TTL (Time To Live) field in IPv4?
Prevents infinite looping of datagrams
Decrements at each router (if 0, the datagram is dropped)
What does the type of service (TOS) field indicate?
Differentiates between real-time and non-real-time traffic
Can prioritize traffic (e.g., low delay, high throughput)
How does IPv4 handle datagram fragmentation?
Splits large datagrams into fragments based on Maximum
Transmission Units (MTU)
Each fragment has the same ID and includes offset info
How does a receiving host reassemble fragmented IP datagrams?
Uses ID number and offset field, recognizes the final fragment using the flag bit = 0
What happens if fragments are lost during transmission?
IPv4 is unreliable—missing fragments prevent reassembly, Entire datagram is dropped if incomplete
What is an IP address technically associated with?
A network interface, not the host itself
How are IP addresses formatted?
32-bit binary values, written in dotted-decimal notation (e.g., 192.168.1.1)
What does the /24 in an IP address like 192.168.0.0/24 mean?
The first 24 bits represent the network portion, also called the subnet mask
What is Classless Interdomain Routing (CIDR)?
Strategy where IP addresses use the format a.b.c.d/x; x defines the prefix length (network portion)
Define a subnet in IPv4 addressing.
A logical grouping of connected devices that can communicate without a router (devices in the same subnet share a common IP prefix)
How are IPv6 addresses different from IPv4?
128 bits long
Includes new anycast address type
Fixed 40-byte header for faster routing
Why is the total length field important in an IPv4 header?
Indicates combined size of header and payload
How many bits are reserved for source and destination addresses in IPv4?
32 bits each
What protocol handles fragmentation and reassembly?
IPv4
What does the offset field value represent?
Position of the fragment’s data in 8-byte units
What does the /23 notation mean for 200.23.16.0/23?
First 23 bits are network/subnet bits, the rest are for hosts
What does the host part of an address represent?
The unique identifier of a device within a subnet
What connects the subnets together?
A router with interfaces in each subnet
What is the purpose of the subnet mask /24?
Defines that the first 24 bits are the network part
What do addresses like 223.1.9.2 represent?
IP addresses of router interfaces
