22 Questions
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.
What is the primary function of a router in the network layer?
To forward packets based on destination IP addresses
What is the purpose of subnetting in IPv4?
To simplify IP address allocation and routing
What is the primary goal of weighted fair queueing (WFQ) in network scheduling?
To ensure fairness in bandwidth allocation among classes
What is the primary function of the Network Layer in the OSI model?
To provide routing and forwarding functions
What is the purpose of route aggregation in network routing?
To reduce the size of routing tables
What is the primary purpose of subnetting in IPv4?
To allocate a portion of a network ID to a specific subnet
What is the result of subnet mask in IPv4?
It defines the boundaries of a subnet
What is the purpose of Network Address Translation (NAT) in IPv4?
To improve network security by hiding internal IP addresses
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
What is the purpose of IPv4 fragmentation and reassembly?
To break down large packets into smaller ones and reassemble them at the destination
What is the primary advantage of using IPv6 over IPv4?
Larger address space to accommodate more devices
What is the purpose of a subnet mask in IP address allocation?
To identify the network part of an IP address
What is the main advantage of Classless Inter-Domain Routing (CIDR)?
Efficient IP address allocation
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
What is the purpose of route aggregation?
To reduce routing table sizes
How do you determine the supernet address in route aggregation?
By converting the network IP address to binary and finding the common bit pattern
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
What is the purpose of subnetting a network?
To organize a network into smaller subnetworks
How many bits are required to subnet a network into 64 subnets?
6 bits
What is the benefit of using a subnet mask?
It allows for efficient IP address allocation
What is the prefix length of the subnet mask 255.255.252.0?
/22
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
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.
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