Network Layer: Priority Scheduling

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Questions and Answers

What is the main difference between Priority Scheduling and Round Robin Scheduling?

Priority Scheduling serves packets from the highest priority queue, while Round Robin serves packets in a cyclic order. (correct)
Priority Scheduling serves packets in a cyclic order, while Round Robin serves packets from the highest priority queue.
Priority Scheduling and Round Robin Scheduling are the same scheduling policies.
Priority Scheduling does not classify incoming traffic, while Round Robin does.

What is the primary function of a router in the network layer?

To manage buffer allocation for packet arrivals
To provide network layer functions to applications
To forward packets based on destination IP addresses (correct)
To provide a user interface for network configuration

What is the purpose of subnetting in IPv4?

To improve network performance by reducing congestion
To reduce the size of IP address allocation
To increase the number of available IP addresses
To simplify IP address allocation and routing (correct)

What is the primary goal of weighted fair queueing (WFQ) in network scheduling?

To ensure fairness in bandwidth allocation among classes (A) Signup and view all the answers

What is the primary function of the Network Layer in the OSI model?

To provide routing and forwarding functions (B) Signup and view all the answers

What is the purpose of route aggregation in network routing?

To reduce the size of routing tables (A) Signup and view all the answers

What is the primary purpose of subnetting in IPv4?

To allocate a portion of a network ID to a specific subnet (D) Signup and view all the answers

What is the result of subnet mask in IPv4?

It defines the boundaries of a subnet (C) Signup and view all the answers

What is the purpose of Network Address Translation (NAT) in IPv4?

To improve network security by hiding internal IP addresses (A) Signup and view all the answers

What is the primary function of the routing processor in a router's control plane?

To operate in the millisecond time frame and make routing decisions (C) Signup and view all the answers

What is the purpose of IPv4 fragmentation and reassembly?

To break down large packets into smaller ones and reassemble them at the destination (C) Signup and view all the answers

What is the primary advantage of using IPv6 over IPv4?

Larger address space to accommodate more devices (D) Signup and view all the answers

What is the purpose of a subnet mask in IP address allocation?

To identify the network part of an IP address (B) Signup and view all the answers

What is the main advantage of Classless Inter-Domain Routing (CIDR)?

Efficient IP address allocation (B) Signup and view all the answers

A university has a class B network 130.50.0.0 and needs to allocate IP addresses to 35 departments. How would you subnet the network?

Use 6 bits for subnetting and 10 bits for hosts (B) Signup and view all the answers

What is the purpose of route aggregation?

To reduce routing table sizes (C) Signup and view all the answers

How do you determine the supernet address in route aggregation?

By converting the network IP address to binary and finding the common bit pattern (B) Signup and view all the answers

What is the result of performing a Boolean AND operation on a destination IP address and a subnet mask?

The network part of the IP address (B) Signup and view all the answers

What is the purpose of subnetting a network?

To organize a network into smaller subnetworks (B) Signup and view all the answers

How many bits are required to subnet a network into 64 subnets?

6 bits (A) Signup and view all the answers

What is the benefit of using a subnet mask?

It allows for efficient IP address allocation (D) Signup and view all the answers

What is the prefix length of the subnet mask 255.255.252.0?

/22 (D) Signup and view all the answers

Study Notes

Network Layer

Divided into two parts: data plane and control plane
Data plane is responsible for the forwarding of packets, while control plane is responsible for the routing and management of packets

Packet Scheduling

Deciding which packet to send next on a link
Types of packet scheduling:
- First Come First Served (FCFS)
- Priority Scheduling
- Round Robin (RR)
- Weighted Fair Queueing (WFQ)

Priority Scheduling

Arriving traffic is classified and queued by class
Any header fields can be used for classification
Send packet from highest priority queue that has buffered packets
FCFS within priority class

Round Robin (RR) Scheduling

Arriving traffic is classified and queued by class
Any header fields can be used for classification
Server cyclically, repeatedly scans class queues, sending one complete packet from each class (if available) in turn

Weighted Fair Queueing (WFQ)

Generalized Round Robin
Each class, i, has weight, wi, and gets a weighted amount of service in each cycle: wi / Σwj

Router Architecture

High-level view of generic router architecture:
- Routing: routing processor
- Management: control plane (software)
- High-speed switching fabric: data plane (hardware)
- Input ports: router input ports
- Output ports: router output ports

IPv4

Datagram format
Fragmentation and reassembly
Addressing: subnetting and subnet mask
Examples: IPv4 network analysis and design
Network Address Translation (NAT)

Subnetting

Identifies the network part of the IP address
Written as (for 24 bits mask) e.g. 255.255.255.0 or /24
When packet arrives, AND dest addr with mask of each subnet to check if result is the corresponding prefix

Classless Inter-Domain Routing (CIDR)

Allocates IP address blocks of variable size without regard to classes
Example: site needs 2000 addresses → assign a block of 2048 addresses

Subnet Mask

Example: 11111111.11111111.111111|00.00000000 255.255.252.0 /22
Calculates the subnet network address, first usable IP, last usable IP, and broadcast IP for each subnet

Route Aggregation

Same outgoing line for multiple contiguous entries can be aggregated
Single supernet entry
Example: 194.24.0.0/19
Helps reducing routing table sizes

Getting an IP Address

IP addresses can be obtained from Internet Service Providers (ISPs) or other organizations

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Description

This quiz covers the concept of priority scheduling in the Network Layer, including packet classification, queuing, and departures. It also explores the use of header fields for classification and the role of high and low priority queues.