Networking notes

Types of networks

• LAN — local area network, single farm connected through wires. (Not a server farm)
• MAN — Metropolitan area network. When a city or area is connected through internet connection.
• WAN- Wide Area Network is when a country or the whole world is connected together.

Topology of a network

• Mesh: two way connections in between nodes. It is complex
• bus: Single wire shared by multiple computers. If there is a disturbance the whole network gets disturbed.
• star: If one device crashes it doesn’t crash the whole system.
• ring: Connected in a circular fashion. Passes tokens between devices. If any devices crash then the whole network gets destroyed.

Networking Devices

• Routers: They help in routing, create a path. It is an IP resolver.
• hub: provides half duplex communications.
• Switch: provides full duplex communication. It is intelligent because it allows two way communication.
• Bridges: Helps my computer and the network connect to each other. It creates a path.
• Firewalls: Lets some information in and keeps other information out. Accept information (allowing traffic), reject information (blocking trafic and reporting) or drop information (blocking traffic without giving a message).
• Gateways: Helps block unnecessary data that will come and hamper your system.

Servers

• OSI: Open system interconnection. First ever structur for web communication between any two devices. There are 7 layers.

7 server layers.

A network engineer will work on the layers 2–7.

1. Application layer: produces data.
2. Presentation Layer: Translation layer. Encrypts and decrypts.
3. Session Layer: Software layers ^Is responsible for establishment of connection, authentication and security between the devices.
4. Transport Layer: Heart of OSN model. End to end delivery of the complete message.
5. Network Layer: Transmission of data from one host to the other if both of the devices are located at different networks.
6. Data Link Layer: With the data link layer is responsible for node to node delivery of messages in physical layer.
7. Physical Layer Hardware layers ^: responsible for actual physical connection between devices. It carries information in bit format. It has certain functions. It has certain functions such as bit synchronization, bit rate control.

Firewall functions

• accept information: Allows traffic.
• reject information: rejects traffic with a report.
• gateways: rejects traffic without giving a message.

IP (Internet protocol)

• Public IP: Dynamic. Changes every time you connect to the internet.
• Private IP: Static.
• ipv4: Previously established internet protocol. First version of ip. It uses 32 bit address scheme which means it has 4 billion addresses. Only has numbers.
• ipv6: latest version of ip which is more secure because it uses 128 bit address Scheme. Has Hexadecimal values.
• DNS: domain name.

TCP/IP architectures

TCP

• Stands for: Transmission Control Protocol
• Synchronization: follows it and therefore is good for chatting.
• Used at server and client end.
• Layer 1: Application and presentation are merged together
• Layer 2: Session Layer:
• Layer 3: Transport layer network layer and data link layer are merged together
• Layer 4: physical layer.

UDP

• Synchronization: Never follows it, and is therefore good for live broadcasting.

Terms

• half duplex: two way, but one at a time. Think walkie talkie.
• Full duplex: both can send messages and receive messages at the same time.
• bit synchronization: it is like having a clock between the sender and receiver to control the flow of bits.
• bit rate control: bits sent per second, a measuring unit. ie: 30 bits per second.
• Scatter format: breaking up messages into smaller packets which travel at different rates.

Hyper visor

• Virtualization layer: Duplicate servers running as backups. .imaginary layer, like virtual layer. Lets say we launch in 3 servers. If one crashes it will slide to the next server. aka VM, Hypervisor.

Cloud computing

• Provides the look and feel of a desktop over a different server. Device which has a browser and an internet connection. You can use this OS on any device.
• Internet based service
• On-demand delivery of computer power, database and other it resources
• pay per use basis.
• Broad network access, you can access different options: tablet iphone notebook different devices.
• Rapid elasticity: compute power grows and shrinks with needs.
• Pay for what you use, not what you don’t use.
• On demand self service. Whenever you need it, it is available to you.
• resource pooling: Large scale it resources to serve multiple clients.

Cloud deployment models: or types of cloud

1. Public cloud: Made accessible to the general public such as a public github.
2. private cloud: Cloud services are fully dedicated towards a specific organization. If any employee does any work, it will be viewable to anyone in the organization.
3. hybrid cloud: combination of both public and private cloud.
4. community cloud: share between organizations that have similar requirements such as college campuses. Lets say there is the engineering branch, the medical branch. they do have similar requirements of a network and so they share similar infrastructure.

Service Models

1. SAS: Software as a service, such as gmail. Data is on the cloud, not the memory of the client device. Google Drive is software as a service.
2. Paas: Platform as a service, gives a software environment. Select one programming language and start coding such as LeetCode. You do not need to install python on your machine and Google App Engine, you can choose a language and start coding.
3. Computation: (Iaas) Infrastructure as a service. It helps you in providing new compute capacity, it will give you different flavors of OS, different architecture, network capacity. A new desktop, Amazon EC2, Microsoft Azure.
4. Storage: (Daas) Data-storage as a service. Examples are Amazon S3 and Google Drive. Google Drive can be used as both Saas and Daas.
5. Network as a Service (Naas): Examples: AWS Internet Gateway.
6. Hardware as a Service (Haas): Allows you to operate manage and upgrade the hardwares.

Amazon Web Services (AWS)

• Aws has everything we needed. AWS is more reliable than other competitors and it is scalable as well. It is affordable as well. They have multiple services within each category.

EC2

• Elastic compute cloud, it is a web service that grows and shrinks compute capacity. Launch as many or as few virtual instances. If you have a user signed in, you have one EC2. If you have a million users and 100,000 active users, you have 100,000 EC2 instances. Creates a new virtual desktop for you.
• Features: Instances, AMI (Amazon Machine Instances) keeps your operating system type (Linux, Windows, MacOS could be available but isn’t), Key Pairs: Keeps security login information. When I create an instance I need to log in to that particular instance. Security Groups: Firewall to specify protocols, port and source IP, Instance Store volumes: default provides 30GB, EBS Volume: if 30GB is insufficient your storage can grow with Elastic Block Storage, so it grows in increments of Gigabytes. Regions and availability zones: You can keep it on different availability zones. Elastic IP Address: Creates static public ip address. Metadata: tags for amazon resources.