Lec 7: Networking

Question 1

What is a network?

Answer 1

-A network can be defined as a group of devices connected for data exchange.
-Each of the devices on the network is a node and each node has at least one unique address.

Question 2

What is an IP Address?

Answer 2

-IP: Internet Protocol
-It is an Internet Protocol address, which is a numerical label assigned to each device connected to a network that uses the Internet Protocol for communication.
-IP address is decided by its network portion and host portion.

Question 3

IPv4: How many bytes?

Answer 3

An IPv4 (Internet Protocol version 4) address has 4 bytes (32 bits) separated by periods.
e.g., 192.168.1.10

Question 4

IPv4 address parts

Answer 4

Network portion: first R bits
Host portion: remaining H bits (32 - R)
Subnet mask: determines the values for R and H

Question 5

What are the network portion and host portion for this IP address?

IPv4 address “192.168.1.10” with a subnet mask of “255.255.255.0”.

Answer 5

A notation: 192.168.1.10/24
CIDR (Classless Inter-Domain Routing) notation

Question 6

How many possible IP addresses does this subnet have?
e.g., 130.95.141.192 with a subnet mask of 255.255.255.192

Answer 6

CIDR notation: 130.95.141.192/26
IP address number: 64

Question 7

how many possible hosts does this subnet have?
130.95.141.192 with a subnet mask of 255.255.255.192

Answer 7

-CIDR notation: 130.95.141.192/26
-Host number: 62 (Network address and broadcast address cannot be assigned to hosts).
-Network address: 130.95.141.192
-Broadcast address: 130.95.141.255

Question 8

What is a subnet mask?

Answer 8

Subnet mask is used for IP address management.

Question 9

What is CIDR?

Answer 9

CIDR (Classless Inter-Domain Routing)
-CIDR is a notation to represent IP addresses and their associated subnet masks.
-In CIDR notation, an IP address (e.g., 130.95.141.192/26) is followed by a slash (“/”) and a number. This number represents the bit length of the network portion.

Question 10

Is B in the same subnet with A? Justify your answer.
A: 172.16.17.30/20
B: 172.16.28.15/20

Answer 10

For A:
IP address: 172.16.17.30: 10101100.00010000.00010001.00011110

Subnet mask: 255.255.240.0: 11111111.11111111.11110000.00000000

Network portion for this subnet can be done via a bitwise AND on the IP address and subnet mask
172.16.17.30: 10101100.00010000.00010001.00011110
255.255.240.0: 11111111.11111111.11110000.00000000
=
172.16.16.0: 10101100.00010000.00010000.00000000

For B:
IP address: 172.16.28.15: 10101100.00010000.00011100.00001111

Subnet mask: 255.255.240.0: 11111111.11111111.11110000.00000000

Network portion for this subnet can be done via a bitwise AND on the IP address and subnet mask
172.16.28.15: 10101100.00010000.00011100.00001111
255.255.240.0: 11111111.11111111.11110000.00000000
=
172.16.16.0: 10101100.00010000.00010000.00000000

Question 11

Suppose the public IPv4 address has a CIDR notation of 212.114.20.0/24, this specifies the subnet where the IPv4 address resides. How many IPv4 addresses does this subnet have?

Answer 11

“/24” indicates the network portion of 24 bits, leaving 8 (32-24) bits for the host portion of the IP address. Therefore, the total number of IPv4 addresses is: 2^8 = 256 addresses.

Question 12

If the Internet service provider divides the original /24 subnet using /27, how many small subnets will be created?

Answer 12

When dividing a /24 subnet into multiple /27 subnets, the ISP uses additional (27-24) bits to create small subnets. The number of small subnets created: 2^(27 - 24) = 8.

Question 13

For each created subnet, how many IPv4 addresses does it have? Justify your answers.

Answer 13

Within each of the small /27 subnets, (32 - 27) bits are available for the host portion. The total number of IPv4 Addresses is: 2^5 = 32.

Question 14

What is a domain name?

Answer 14

It uses alphanumeric characters and symbols separated by periods to create a hierarchical naming structure. This structure is organized from right to left.

Question 15

What are the parts of a domain name?

Answer 15

For www.javasoft.com
“com” is the top-level domain (TLD).
“ javasoft” is the second-level domain (SLD).
“www” is a subdomain of “ javasoft.”

Question 16

What is DNS?

Answer 16

-Domain Name System
-Domain names are also known as mnemonic textual Internet addresses.
-DNS servers are responsible for translating mnemonic textual Internet addresses into the numeric addresses.

Question 17

What is the difference between a domain name and a URL?

Answer 17

-Domain name: a human-readable hierarchical structure, which consists of alphanumeric characters and symbols separated by periods.

-URL (Uniform Resource Locator): a complete address to locate a specific resource on a given website. It consists of:
–a network protocol,
–a domain name,
–an additional path and/or query parameters.
e.g., https://www.example.com/products/category?id=123&sort=asc
—the protocol is “https”, the domain name is “www.example.com”, the path is “/products/category”,
—the query parameters are “?id=123&sort=asc”

Question 18

What is a port?

Answer 18

-An IP address identifies a device on the Internet.
-An IP port identifies a specific application protocol running on an Internet device.
-A port is identified by a number, the port number.
-There are some port numbers which are allocated for specific application protocols.
HTTP: 80
HTTPS: 443
SSH: 22

Question 19

What is a protocol?

Answer 19

A set of rules that govern how data is transmitted over a network.

Examples:
-HTTP (Hypertext Transfer Protocol),
-TCP (Transmission Control Protocol),
-IP (Internet Protocol)

-Each protocol is designed based on a layered model.
–A real-world model : TCP/IP.
–A conceptual model : OSI (Open Systems Interconnection)

Question 20

OSI Model vs TCP/IP Original vs TCP/IP Updated

Answer 20

OSI Model:
App > Presentation> Session
Transport
Network
Data Link > Physical

TCP/IP Original
App
Transport
Internet
Link

TCP/IP Updated
App
Transport
Network
Data Link > Physical

Question 21

5-Layer TCP/IP Model: Application Layer

Answer 21

-Application Layer provides network services directly to applications. It hosts various application-specific protocols.

-Examples of protocols for different applications:
–HTTP and HTTPS for web browsing, and
–SSH (Secure Shell) for secure remote access.

Question 22

5-Layer TCP/IP Model: Transport Layer

Answer 22

-Transport Layer establishes and manages the end-to-end data transfer between applications running on different devices.

-Examples of protocols for network connection:
–TCP (Transmission Control Protocol) for reliable connections,
–UDP (User Datagram Protocol) for fast communication.

Question 23

5-Layer TCP/IP Model: Network Layer

Answer 23

-Network Layer routes packets of data to reach their destination.

-Examples of protocols for packet routing:
–IP (Internet Protocol),
–ICMP (Internet Control Message Protocol)

Question 24

5-Layer TCP/IP Model: Data Link Layer

Answer 24

-Data Link Layer provides node-to-node data transfer.

-Particularly, it uses MAC (Media Access Control) addresses to identify Network Interface Cards (NICs).

-Examples of protocols for node addressing:
–Ethernet,
–Wi-Fi

Question 25

5-Layer TCP/IP Model: Physical Layer

Answer 25

-Physical Layer deals with data transmission over a physical medium.

-Examples of medium:
–Optical fibers,
–Wireless radio waves

Question 26

Transmit Data with TCP/IP Model Diagram

Answer 26

5 App Layer Msg

4 Transport Layer TCP/UDP Segment/Datagram
-Source/Destination Port
-(Segment header)

3 Network Layer IP
-Source/Destination IP Address
-(Packet header)

2 Data Link Layer MAC
-Source/Dest MAC Address
-(Frame header)

1 Physical Layer

Question 27

What is data encapsulation?

Answer 27

From Sending computer > App > Transport > Network > Data Link > Physical

Question 28

What is de-encapsulation?

Answer 28

Opposite; from Physical to Receiving Computer

Question 29

What is ELB?

Answer 29

-Elastic Load Balancing

-ELB serves as the single point of contact for clients, distributing incoming requests across multiple target groups of multiple targets (e.g., EC2 instances and containers).

-Listenerchecks for incoming network requests from clients using pre-configured protocol and port.

Question 30

Path-based routing: Rule 1

Answer 30

If the URL is https://example.com/public/home, the listener routes the request to the PublicWebServer target group.

[ {
“Field”: “path-pattern”,
“PathPatternConfig”: {
“Values”: [“/public/*”]
}
} ]

Question 31

Path-based routing: Rule 2

Answer 31

If the URL is https://example.com/admin/settings, the listener routes the request to the AdminConsole target group.

[ {
“Field”: “path-pattern”,
“PathPatternConfig”: {
“Values”: [“/admin/*”]
}
} ]

Question 32

What are the benefits of ELB?

Answer 32

-Increases the availability and fault tolerance of web applications.
-More compute resources can be added (horizontal scaling)
-Enables health check of compute resources.
–Healthy: a compute resource is responsive and functioning as expected.

Question 33

What are horizonal scaling and vertical scaling?

Answer 33

Horizontal:
Vertical: add more resources

Question 34

Set up an ALB

Answer 34

1. Navigate to EC2 Dashboard, click Load balancers
2. Configure: scheme (internal facing, internal), IP address type (IPv4, Dualstack)

Question 35

Internet facing vs internal scheme

Answer 35

-Internet-facing indicates the ALB has a public IP address.
Internal means the ALB has a private IP address.

-Both schemes route the client’s requests to targets’ private IP addresses.

-Targets do NOT need public IP addresses to receive requests from the ALB.

Question 36

IPv4 vs Dualstack

Answer 36

IPv4 (Internet Protocol version 4)
Dualstack includes IPv4 and IPv6 (Internet Protocol version 6)

IPv4: it is widely used in real-world.

Question 37

What is the main reason why IPv6 is needed?

Answer 37

IPv4 uses an address format with 4 bytes (32 bits)
IPv4 allows for about 4.3 billion addresses: 2^32= 2^32
The number of internet-connected devices has been increasing all the time.

IPv6 uses an address format with 16 bytes (128 bits)
IPv4 allows for a much larger of number of addresses: 2^128

Question 38

How to address the IPv4 exhaustion problem?

Answer 38

Fundamental solution: IPv6.
Mitigation: network address translation (NAT) and private IPv4 address ranges

Question 39

What is NAT?

Answer 39

NAT: it is a way to map multiple private IPv4 addresses inside an internal network to a public IPv4 address before transmitting data to the internet.

All the devices in an internal network use a single public IPv4 address.

Question 40

What is a private IPv4 address range?

Answer 40

private IPv4 address range: it is a reserved IP address block that is not routable on the internet.

It is used for internal communication among devices within the same internal/private network.

Three address ranges:
Range | CIDR | Total Addresses
10.0.0.0 to 10.255.255.255 | 10.0.0.0/8 | 2^24 (24 = 32-8)
172.16.0.0 to 172.31.255.255 | 172.16.0.0/12 | 2^20 (20 = 32-12)
192.168.0.0 to 192.168.255.255 | 192.168.0.0/16 | 2^16 (16 = 32-16)

Question 41

How NAT works

Answer 41

LAN local area network with 4 hosts with local IP address selected from a specific IP add range (single public IPv4 add)
-All hosts have a translation table, all mapped to the same single public IP address but with different source ports
-Host C sends a packet to the internet
-Packet goes through router
-Router will maintain the translation table, it will translate the source IP address and the source port based on the source IP add and source port number
-When Host C receives a package from the internet, it will use the same translation table

Question 42

Set up an ALB

Answer 42

Basic Configuration
Load Balancer Name
Scheme: Internal
IP Address Type: IPv4

Network Configuration
Network Mapping
VPC: VPC ID
Mappings: at least two availability zones

Security Group
-select up to 5
-inbound rules
-outbound rules

Listeners and Routing
-Protocol and Port (HTTP, 80)
-Default action: Forward to <target>
-Listener tag</target>

Question 43

Virtual Private Cloud VPC

Answer 43

VPC(virtual private cloud): it is a virtual network dedicated to an AWS account.

It is logically isolated from other virtual networks in the AWS Cloud.

Question 44

VPC Internet Gateway

Answer 44

-Provides VPC with internet access
-Manage outbound traffic to the internet and inbound traffic to the AWS resources.

Question 45

VPC Subnet

Answer 45

Subnet: it is a range of IP addresses in a VPC.
-It is used to divide a VPC into multiple logical sub-networks.
-It can be either public or private sub-network.
-It must reside entirely within one Availability Zone.

Question 46

What is a listener?

Answer 46

Listener: it is a process that checks for network requests using the protocol and port we configure.

A Listener in ALB supports protocols and ports:
Protocols: HTTP, HTTPS with Ports: 1-65535

Question 47

Create target group

Answer 47

Basic Configuration
-Choose a target type:
–Instances: specify targets via EC2 instance IDs
–IP add: specify targets via IP addresses or IP address ranges

Question 48

Discuss 3 reasons why you would use Application Load Balancing to load balance a Python Django application.

Answer 48

High fault-tolerance: the ALB can distribute traffic to multiple targets in multiple groups, making the Django application healthy and improving its fault-tolerance.

High scalability: As the ALB can distribute traffic evenly, the Django application can be scaled horizontally. For example, when traffic increases, more targets can be added, and the ALB can distribute traffic to them.

Good match: Django is a web framework accepting http and https requests. The main responsibility of ALB is to optimize http and https traffic.