Chap 4 network

Question 1

Key Aspects of Network Layer

Answer 1

1. Routing: to determine the best path for data packets.
2. IP Addressing: to uniquely identify devices on a network.
3. Fragmentation and Reassembly: fragment large packets into smaller ones at the source and reassembled at the destination.
4. Error Handling: to detect and handle errors that may occur during data transmission.
5. Logical Addressing: for communication between devices.
   1.** Packet Forwarding:** to select the next-hop router or outgoing interface.
6. Internet Protocol (IP): responsible for addressing, routing, and fragmenting/reassembling packets.
7. Virtual Private Networks (VPNs): to encrypt and encapsulate data packets for secure transmission.
   1.** Quality of Service (QoS):** to ensure critical applications get sufficient network resources and bandwidth for optimal performance.
   1.** Tunneling:** to encapsulate one protocol’s packets within another protocol’s packets for transmission across an intermediary network

Question 2

network layer and role

Answer 2

The Network Layer is the third layer of the OSI model.
*
It plays a crucial role in computer networks by facilitating communication and routing data between different networks.
*
It enables the Internet and other interconnected networks to function effectively.

Question 3

Routing Algorithm

Answer 3

Algorithms used by routers to determine the best path for data packets to travel.
*
Consider factors like:

1. ◦Network topology (layout)
2. ◦Traffic congestion
3. ◦Delay (latency)
4. ◦Cost (bandwidth)

Goal: Efficiently route data to its destination.
*
Categories include Static Routing and Dynamic Routing

Question 4

Static Routing

Answer 4

Manually configured paths for data packets.
*
Simple but inflexible, requires manual updates for network changes.
*
Each entry specifies:

1. ◦Destination network: The network to which the route applies.
2. ◦Next hop: The next router along the path.
3. ◦(Optional) Administrative distance: A metric influencing route selection

Question 5

Advantages of Static Routing

Answer 5

Simple and easy to implement: suitable for small networks or those with clearly defined routing requirements.
*
Predictable and reliable:
*
Enhanced security: tighter control over network access, restricting unauthorized traffic from entering specific areas

Question 6

Limitations of Static Routing

Answer 6

Scalability limitations: As a network changes, manually configuring static routes on every device becomes increasingly complex and time-consuming.
*
Lack of adaptability:
Increased maintenance overhead: .

Question 7

When to Use Static Routing

Answer 7

Small, stable networks: patterns are well-defined and unlikely to change frequently.
*
Specific control needed: want to manually define allowed routes.
*
Limited resources:

Question 8

Dynamic Routing

Answer 8

Adapts to network changes automatically.

More complex but offers greater flexibility and efficiency.

• Employ algorithms to discover and update network paths.
• Rely on information exchange between routers.

Main types:

• Distance Vector Routing (e.g., RIP)
• Link State Routing (e.g., OSPF)
• Hybrid Routing (combines elements of both)

Question 9

Distance Vector Routing

Answer 9

Routers exchange information about the “distance” (number of hops) to reach specific destinations with neighboring routers.
*
Simple and efficient, but may not always find the optimal path.
*
Example: RIP (Routing Information Protocol)

Question 10

Link State Routing

Answer 10

Routers share information about the entire network topology with all other routers.
*
Can discover the optimal path, but requires more processing power and bandwidth.
*
Example: OSPF (Open Shortest Path First)

Question 11

Benefits of Dynamic Routing

Answer 11

1. scalability:
2. Improved Efficiency:
3. Reduced Administrative Overhead:
4. Increased Reliability:

Question 12

Limitations of Dynamic Routing

Answer 12

1. Increased network overhead.
2. Complexity of configuration and management.
3. Convergence time.
4. Security concerns.
5. Propagation of routing information.
6. Impact of route flapping.
7. Vendor interoperability issues

Question 13

Routing Information Protocol (RIP)

Answer 13

A distance vector routing protocol.

Routers exchange information about the “distance” (number of hops) to reach specific destinations.

• Simple and efficient, suitable for small to medium-sized networks.
• Two versions: RIPv1 and RIPv2

Question 14

Two Main Versions of Routing Info Protocol

Answer 14

RIPv1:
* This is the original version of RIP.
* It utilizes classful routing, which can lead to inefficiencies in networks with varying subnet sizes.
* Lacks certain security features.

RIPv2:
* This version offers several improvements over RIPv1.
* Includes support for classless routing, which enables efficient routing across diverse network configurations.
* Introduces route tagging for better handling of different types of traffic.
* Provides authentication mechanisms to enhance security

Question 15

RIP Working (Advertisement, Routing Updates, Routing Table Updates, Convergence)

Answer 15

Advertisement: Each router periodically broadcasts its routing table information to neighboring routers through RIP updates.

Routing Updates: These updates include details like:
1. Destination network address
1. Next hop router towards that network
1. Distance (number of hops) required to reach the destination

Routing Table Updates: Upon receiving RIP updates from neighboring routers, each router incorporates the information into its own routing table. The router selects the path with the lowest hop count for each destination network.
*
Convergence: Through this process of information exchange and table updates, the network eventually converges to a loop-free routing path, ensuring efficient and reliable data flow

Question 16

RIP Advantages

Answer 16

1. Simple and easy to configure:
2. Efficient for small to medium-sized networks:
3. Low resource consumption
4. Improved security (RIPv2):

Question 17

Bellman-Ford Algorithm

Answer 17

Finds the shortest paths from a single source vertex to all other reachable vertices in a graph.

1. Handles graphs with negative edge weights
2. Iterative approach involving repeated relaxation steps to gradually refine the path estimations and eventually reach the optimal solution

Question 18

Bellman-Ford Working Initialization

Answer 18

The algorithm begins by assigning an initial distance of positive infinity to all vertices in the graph except the source vertex.
*
The source vertex is typically assigned a distance of 0, signifying its starting point.

Question 19

Bellman-Ford Working Relaxation

Answer 19

The core operation of the algorithm lies in the relaxation step.
*
This step iterates through each edge in the graph, examining the potential for a shorter path.
*
For each edge connecting vertex u to vertex v, the algorithm checks whether the total distance from the source vertex to v through vertex u (distance(source) + weight(u, v)) is shorter than the currently known distance of v.
*
If this condition is true, the distance of v is updated to reflect the shorter path, and the predecessor of v is also updated to point to vertex u (as u becomes the preceding vertex in the newly discovered shorter path)

Question 20

Bellman-Ford Working Iterations

Answer 20

The relaxation step is repeated V-1 times, where V represents the total number of vertices in the graph.
*
This repetitive process ensures that the algorithm has sufficient opportunities to discover and update paths throughout the graph, eventually converging to the optimal solution

Question 21

Bellman-Ford Applications

Answer 21

1. Network routing: Finding the shortest paths for data packets to travel across network connections.
2. Logistics: Determining the most efficient routes for transportation and delivery services.
3. Financial modeling: Calculating the minimum cost paths in financial networks with weighted edges representing risks or benefits.
4. Geographic information systems (GIS): Identifying the shortest routes for navigation within a map network

Question 22

Key Aspects of Network Layer (Quality of Service (QoS): )

Answer 22

to ensure applications get sufficient network resources and bandwidth for optimal performance.

Question 23

Key Aspects of Network Layer (tunneling)

Answer 23

: to encapsulate one protocol’s packets within another protocol’s packets for transmission across an intermediary network

Question 24

Key Aspects of Network Layer (VPN)

Answer 24

to encrypt and encapsulate data packets for secure transmission.

Question 25

IP Addressing

Answer 25

system used to uniquely identify devices (such as computers, servers, routers, etc.) on a network. It serves** two primary purposes**: Host/Network Identification and Location Addressing.

Question 26

2 Versions of IP Addresses

Answer 26

The two main versions of IP addresses are IPv4 (Internet Protocol version 4) and IPv6 (Internet Protocol version 6).

Question 27

2 Purposes of IP Address

Answer 27

Host or Network Identification: IP addresses are used to identify either a network interface (host) or an entire network. A host IP uniquely identifies a specific device within a network. A network IP identifies a group of devices connected to the same network segment. ◦ Location Addressing: IP addresses help in routing data packets across networks. They indicate the source and destination of data packets, facilitating proper transmission

Question 28

Breakdown of IPv4 Addresses

Answer 28

Format: Typically represented as X.X.X.X, where each X is an octet (8 bits) ranging from 0 to 255. This is known as dotted-decimal notation. Uniqueness: Each IPv4 address must be unique within a network or subnetwork. Classes (Historical): Historically divided into Class A, B, and C based on network size, with Class D for multicasting and Class E reserved. Classful addressing is no longer widely used due to CIDR (Classless Inter-Domain Routing). Subnet Mask: Used with the IP address to define the network portion and the host portion of the address. Private vs. Public: Private addresses are for use within private networks and are not routable on the public Internet. Public addresses are globally unique and routable on the Internet. DHCP (Dynamic Host Configuration Protocol): Commonly used to dynamically assign IPv4 addresses to devices. NAT (Network Address Translation): A technique used to conserve IPv4 address space by allowing multiple private devices to share a single public IP

Question 29

3 Key Parts of IPv4 Address

Answer 29

Network address: Identifies the specific network to which a device belongs. ◦ Subnet mask: Acts like a divider, separating the network and host portions of the address. ◦ Host address: Uniquely identifies a specific device within a network

Question 30

IPv4 Advantages

Answer 30

1. Familiarity:dominant for a long time, 1. Ease of Implementation 1. Compatibility: with older networking protocols. 1. Large Address Space (for its time): . 1. Efficiency in Certain Use Cases: efficient for small-scale

Question 31

IPv4 Limitations

Answer 31

1. Address Exhaustion: 32-bit address space insufficient for the growing # of devices. 1. No Built-in Security: 1. Fragmentation: Packets may need to be fragmented across networks . 1. Limited Support for QoS: challenging to prioritize certain types of traffic. 1. Hierarchical Addressing: inefficient allocation. 1. Inflexibility: Fixed 32-bit length

Question 32

Classes in IPv4

Answer 32

Class A: 126 Networks, 1,67,77,214 Hosts per Network. For large numbers of total hosts. Class B: 16,382 Networks, 65,534 Hosts per Network. For medium to large sized networks. Class C: 20,97,150 Networks, 254 Hosts per Network. Used in small local area networks (LANs). Class D: Not allocated to hosts, used for multicasting. Class E: Not allocated to hosts, reserved for research purposes

Question 32

IPv6 Breakdown of Addresses

Answer 32

Format: Represented as eight groups of four hexadecimal digits separated by colons Shorthand Notation: Leading zeros in each group can be omitted, and consecutive groups of zeros can be replaced with a double colon (::) once per address Hierarchical Structure: The first 64 bits typically represent the network prefix (for routing and subnetting), and the remaining 64 bits represent the interface identifier (uniquely identifies a network interface on a segment)

Question 32

IPv6 Different Address Types

Answer 32

Unicast Addresses: Identify a single interface. Types include global unicast, link-local (communication within the same network segment), and unique local. Multicast Addresses: Identify a group of interfaces; packets are sent to multiple recipients simultaneously. Anycast Addresses: Identify multiple interfaces, but packets are routed to the nearest interface sharing the same address

Question 33

IPv6 Advantages

Answer 33

1. Larger Address Space: 1. Address Autoconfiguration (SLAAC): Devices can automatically configure addresses without manual setup 1. Efficient Routing and Packet Processing: 1. Improved Quality of Service (QoS): 1. Enhanced Security Features: 1. Simplified Header Structure: 1. Support for Mobile Devices and IoT: 1. Future-Proofing

Question 34

IPv6 Limitations

Answer 34

1. Compatibility Issues: dual stack (running both IPv4 and IPv6) can be resource-intensive. 1. Security Concerns: 1. Deployment Challenges: 1. Limited Support in Certain Regions:

Question 35

IPv4 Header

Answer 35

1. Version (4 bits): Specifies IP version 1. Header Length (4 bits): 32-bit words. 1. Type of Service (8 bits): QoS parameters. 1. Total Length (16 bits): Total packet length (header + payload). 1. Identification (16 bits): For fragmentation/reassembly. 1. Flags (3 bits): Control flags for fragmentation. 1. Fragment Offset (13 bits): Fragment's position in the original datagram. 1. Time to Live (TTL) (8 bits): Max hops before discarding. 1. Protocol (8 bits): Protocol in the payload 1. Header Checksum (16 bits): Error detection in the header. 1. Source IP Address (32 bits 1. Destination IP Address (32 bits) 1. Options (Variable): Optional fields. 1. Payload (Data): Actual data being transmitted

Question 36

Ipv4

Answer 36

IPv4 is the older and more widely used version, employing 32-bit numerical values.

Question 37

Ipv6

Answer 37

IPv6 was developed to address the limitations of IPv4 address exhaustion and uses 128-bit hexadecimal values

Question 38

OSPF (Open Shortest Path First)

Answer 38

* routing protocol in IP networks, used to find the best path for forwarding data packets across the network. * link-state routing protocol: routers exchange information about the state of their links with other routers in the network. * info is used to build a complete topological map of the network. * uses the Dijkstra algorithm

Question 39

How does OSPF calculate the shortest path?

Answer 39

Dijkstra algorithm * calculate the shortest path tree from each router to every other router in the network. * Each router maintains a database of link state advertisements (LSAs) received from neighboring routers, which is used to calculate the shortest path tree

Question 40

What are OSPF areas and why are they used?

Answer 40

OSPF networks are typically divided into areas * to improve scalability * reduce the amount of routing info that needs to be exchanged. * Routers within the same area have detailed knowledge of the network topology within that area * routers in different areas only have summary information about other areas

Question 41

What is OSPF hierarchical design?

Answer 41

routers organized into a hierarchy of areas. * reduce the amount of routing information that needs to be exchanged between routers * improves network scalability

Question 42

What are OSPF LSAs and what information do they contain?

Answer 42

Each router in an OSPF network generates Link-State Advertisements (LSAs). LSAs contain crucial information about: *Directly connected networks *Cost of reaching those networks (e.g., bandwidth, delay) *Router ID and area ID (if OSPF areas are used) LSAs are flooded throughout the OSPF area, ensuring every router possesses a complete understanding of the network layout.

Question 43

What are the benefits of OSPF?

Answer 43

OSPF benefits include: 1. Efficient Routing: 1. Scalability 1. Fast Convergence: network changes, OSPF rapidly adapts: minimizing disruption. 1. Loop Prevention

Question 44

What is Dijkstra's link-state routing algorithm?

Answer 44

* ensures data packets traverse the network along the most efficient paths. * employed in protocols like OSPF and IS-IS (Intermediate System to Intermediate System)

Question 45

How does Dijkstra's algorithm work?

Answer 45

1. start w set of tentative distances for each node, 1. initially setting the distance of the source node to 0 all other nodes to infinity. 1. It iteratively selects the node with the smallest tentative distance, known as the "current node," and updates the tentative distances of its neighboring nodes based on their current distances the weights of the edges connecting them. 1. The algorithm continues this process until all nodes have been visited until the destination node is reached.

Question 46

What are the steps in the working of link-state routing with Dijkstra's algorithm?

Answer 46

1.Topology Discovery: Each router maintains information about its directly connected neighbors and the state of the links to those neighbors. 2.Link-State Advertisement (LSAs): 3.Building Network Topology: use of LSA 4.Shortest Path Calculation 5.Routing Table Construction: based on 4 6.Updating and Maintenance: periodically exchange updated LSAs to reflect network changes. routers recalculate shortest paths

Question 47

MTU (Maximum Transmission Unit)

Answer 47

max size of packets network can handle, Significance: largest possible link-level frame. Different link types have different MTUs

Question 48

Fragmentation

Answer 48

process of breaking down a large IP packet into smaller fragments when it exceeds the (MTU) of a network link. * Necessity: When a router or device encounters an IP packet larger than the outgoing network interface's MTU, it needs to fragment the packet

Question 49

Reassembly

Answer 49

fragments of an IP packet are collected and put back together into the original packet by reciever Mechanism: Fragment Offset and Flags fields in each fragment header determine the correct order and whether all fragments have been received. Fragments with the same Identification value are reassembled based on their Fragment Offset.

Question 50

Fragment Header

Answer 50

Each fragment of an IP packet includes a fragment header that contains additional fields to assist in reassembling the fragments at the destination. Fragment Offset: Indicates the position of the fragment in the original packet's data stream. Flags: Include control bits to indicate whether more fragments are expected or if this is the last fragment. Identification: Contains a unique identifier for the original packet, allowing the fragments to be associated with each other during reassembly.

Question 51

Fragmentation and Reassembly Transmission

Answer 51

Process: Each fragment is transmitted individually across the network to the destination. Path Variability: Fragments may take different paths through the network and may arrive out of order/ with varying delays. Reassembly Location: occurs only at destination

Question 52

Routing Table

Answer 52

data structure used by routers to store information about available network paths. Contents: It contains entries that specify destination networks, next-hop routers or interfaces, and routing metrics. Updates: dynamically updated by routing protocols or manually configured in static routing.

Question 53

Routing Protocols

Answer 53

protocols used by routers to exchange routing information and update routing tables dynamically. Purpose: automate the process of route discovery and maintenance. Types: Interior Gateway Protocols (IGPs) and Exterior Gateway Protocols (EGPs)

Question 54

IGP (Interior Gateway Protocols)

Answer 54

routing protocols that operate within an autonomous system (AS). * Examples: Routing Information Protocol (RIP), Open Shortest Path First (OSPF), and Intermediate System to Intermediate System (IS-IS)

Question 55

EGP (Exterior Gateway Protocols)

Answer 55

routing protocols that are used between different autonomous systems. Example: Border Gateway Protocol (BGP)

Question 56

Routing Metrics

Answer 56

values used to determine the best path for packet delivery. Factors: hop count, bandwidth, delay, reliability, and cost. Different routing protocols may prioritize metrics differently

Question 57

IP Routing Working

Answer 57

Step 1: Packet Forwarding: A device creates a packet with the destination IP address. Step 2: Destination Address Lookup: checks its routing table to determine the next hop. Step 3: Routing Decision: determines the next hop, often using the longest matching prefix. Step 4: Packet Forwarding: The device forwards the packet to the appropriate interface connected to that next hop. Step 5: Repeat Steps: repeats at each router until the packet reaches its destination network

Question 58

Packet Switching vs Circuit Switching

Answer 58

Packet Switching: * Efficient use of bandwidth: Bandwidth is shared. * Flexible and Scalable. * Lower cost. * Higher latency. * Limited QoS guarantees. * Potential for packet loss. Circuit Switching: * Guaranteed bandwidth. * Low latency. * Predictable performance. * Inefficient use of bandwidth. * Limited scalability. * High cost.

Question 59

VPNs (Virtual Private Networks)

Answer 59

provide secure communication over a public network by encrypting data traffic and creating a private tunnel between the communicating parties. Common Uses: Remote access to corporate networks, secure data transmission over the internet, and secure connections between branch offices. Network Layer Focus: operating at the Network layer focus on securing the entire data packet.

Question 60

IPsec (Internet Protocol Security)

Answer 60

suite of protocols developed by the IETF to secure communication at the IP layer. Offers data integrity, prevents tampering, and provides confidentiality by encrypting the data payload.

Question 61

Two Modes of IPsec

Answer 61

Transport Mode: Encrypts the payload (data) of the IP packet, leaving the header information unencrypted. Useful for selective encryption of specific applications. Tunnel Mode: Encrypts the entire IP packet, including both header and payload. Provides end-to-end security for the entire data transmission

Question 62

IPsec Two Protocols

Answer 62

AH (Authentication Header): Ensures data integrity and prevents tampering during transmission. ESP (Encapsulating Security Payload): Provides confidentiality by encrypting the data payload.

Question 63

SSL/TLS (Secure Sockets Layer/Transport Layer Security)

Answer 63

secure communication protocol often used for applications like HTTPS but can also be used for VPN connections. Operates at the Transport Layer Establishes a secure connection through a handshake process involving digital certificates and encryption algorithms

Question 64

ARP (Address Resolution Protocol)

Answer 64

networking protocol used for mapping a network layer address to a hardware layer address Primarily used in Ethernet networks for communication between devices within the same local network segment

Question 65

Logical Address

Answer 65

virtual address assigned to a device, process, or resource in a computer network or system. Examples: IP address, Port number, URL

Question 66

Physical Address

Answer 66

aka hardware address, unique identifier assigned to a specific hardware component within a computer or network device. Example: MAC address

Question 67

ARP Working

Answer 67

Step 1: Mapping IP to MAC Addresses: Step 2: sending device broadcasts an ARP request packet containing the target IP address. Step 3: device with the target IP address responds with an ARP reply packet containing its MAC address. Step 4: Devices cache the IP-to-MAC address mappings in an ARP table or ARP cache for future communication

Question 68

Static NAT

Answer 68

maps a private IP address to a single, fixed public IP address on a one-to-one basis.

Question 69

Dynamic NAT

Answer 69

assigns a public IP address from a pool of available addresses to a private IP address on a temporary basis, allowing many-to-one mapping

Question 70

PAT (Port Address Translation)

Answer 70

type of dynamic NAT that allows multiple private IP addresses to be mapped to a single public IP address using port numbers to differentiate between devices, enabling many-to-one mapping with port differentiation

Question 71

NAT Working

Answer 71

Step 1: device on the private network sends a request. Step 2: NAT device replaces the private source IP address with its own public IP address. Step 3: translated packet is forwarded to the internet. Step 4: response arrives at the NAT device's public IP address. Step 5: NAT device uses the destination port number to translate the public IP address back to the original private IP address. Step 6: NAT device delivers the packet to the correct device on the private network

Question 72

Benefits of NAT

Answer 72

* Conserves Public IP Addresses: * Enhances Network Security: * Simplifies Network Management:

Question 73

Importance of QoS

Answer 73

* Ensures reliable transmission * optimal performance * consistent user experience * supporting real-time applications. Without QoS, real-time applications can experience delays, jitter, and buffering during network congestion. more predictable and reliable network experience for applications requiring low latency and minimal jitter

Question 74

Components of QoS

Answer 74

1. Bandwidth Management: 1. Traffic Prioritization: 1. Congestion Control: 1. Packet Classification and Marking: 1. Traffic Shaping and Policing:

Question 75

Benefits of QoS

Answer 75

* Improved application performance: Minimal delays and jitter for real-time applications. * Enhanced user experience: More predictable and reliable network experience. * Efficient network resource allocation: Critical applications get the bandwidth they need. * Reduced congestion: Helps alleviate network congestion by prioritizing traffic