CS2005 - Lecture 8 - Network Layer II Flashcards
(48 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 MTU; Each fragment has the same ID and includes offset info
How does a receiving host reassemble fragmented IP datagrams?
Uses identification 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
What layers are present in end systems but not routers?
Application, Transport layers are present in end hosts only; Routers only use Network, Data Link, Physical layers
Which layers are found in routers according to the diagram?
Network; Data link; Physical
What does the layering in the diagram imply about packet handling?
Each router examines only the network layer; Hosts encapsulate/decapsulate at all layers
In the diagram, what component is responsible for packet forwarding?
The network layer within each router
What is the purpose of showing multiple paths in the diagram?
Illustrates routing across different routers and networks
What layers are involved in wireless communication between host and router?
Physical, Data Link, and Network layers
What difference do you observe between wireless and wired segments in the diagram?
Wireless hosts connect to routers via wireless access points; Wired connections are shown using switches and cables
What does the ‘fragment offset’ field represent?
Position of the fragment within the original datagram; Helps in reassembly
What is stored in the ‘header checksum’ field?
A value to detect errors in the IP header; Recomputed at each router
