Internet infrastructure
Extranet vs Intranet
- Extranet: A network that is connected to the internet.
- Intranet: A network that is not connected to the internet.
Architecture
The global internet is connected by fiber optic cables, with Internet Service Providers (ISP) connecting devices to the internet. The optic cables are prone to natural hazards as well as human activities like ship anchoring.
The ISPs connect to the internet through Network Access Points (NAP). They are high speed routers that connect to the internet.
Speed
Network protocols
A format for transmitting packets (data) that has been agreed by a standard organization or industry. IP: Internet Protocol TCP: Transmission Control Protocol
- The data is divided into packets.
- Each packet is transmitted to the destination through the network by different paths.
- The destination is responsible for reassembling the packets into the original data.
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TCP: Ordering packets\ Forming packets (adding headers and control information), dividing and reassembling, collision control (error checking)
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IP: Routing packets\ Send to proper destination, addresses
IP Addresses
A unique identifier for a device on the internet. Generic form called IPv4. x.x.x.x where x is a number between 0 and 255.
When device connected to internet, it is assigned a temporary IP address. When the connection is lost, the IP address is released and assigned to another device.
A distributed database that translates domain names to IP addresses. It is stored by your ISPs.
Open source software
Software that is free to use, modify, and distribute.
- Free: Free of charge
- Source code: Available for public inspection
- Licensed: Original author retains copyright and terms of use.
- Repository: Code is usually shared on GitHub, users can freely download, use, modify, and distribute.
There are a few problems that comes with open source software:
- Support: There is no guarantee of support from the original author.
- Administration: Malware and viruses can be introduced unintentionally.
- Quality assurance: Quality of contribution is not guaranteed.
- Legal issues: Legal disputes may arise from patent infringement.
- Security: Security vulnerabilities may exist in the software.
The total cost of owning a software system beyond the purchase price. This includes costs like maintenance, upgrades, service, and support. For OSS, the TCO is usually lower than that of proprietary software, as the cost of support is distributed among the users.
The usage of 4 OSS to build a web service, powering services such as Youtube.
- Linux: Operating system
- Apache: Web server
- MySQL: Database
- PHP: Programming language
Cloud computing
Data sent to shared computing resources over the internet, and sent back when completed.
- Infrastructure as a Service (IaaS): Provides virtualized computing resources over the internet.
- Platform as a Service (PaaS): Provides a platform for developing and deploying applications.
- Software as a Service (SaaS): Provides software applications that are accessed over the internet.
Potential problems of cloud computing:
- Data privacy: Data may be leaked to other users.
- Service availability: Service may be unavailable.
- Vendor lock-in: Switching to another vendor is difficult as the data is usually held by the vendor.
Internet of things (IoT)
A network of physical devices that can connect and exchange data over a network without requiring human-to-computer interaction. It consists of 3 layers:
- Perception layer: Interact with the physical environment, like Sensors & actuators
- Network layer: Discovers, connects & translates the perception layer to the application layer
- Application layer: Store & process data