Study Info

Packet Switching

Messages are divided into small packets and sent independently.

Advantage of Packet Switching

Line efficiency (multiple users can share the same line) and 'Store and Forward' capability (packets are stored until the next link is clear).

Security Risk of Packet Switching

Packets can be intercepted or misrouted.

TCP/IP vs. OSI

The Internet (Network) Layer is responsible for addressing via IP.

QUIC (Quick UDP)

A protocol designed to reduce latency while maintaining security; vital for e-commerce performance.

DNS (Domain Name System)

Created because the old host.txt files were not scalable.

Vulnerability in DNS

DNS Spoofing/Cache Poisoning allows attackers to redirect your traffic to a malicious server.

N-Tier Architecture

The 'Gold Standard' for secure e-commerce providing Firewall separation, Tier isolation, and Minimized direct access to the data layer.

Disadvantage of N-Tier Architecture

Can lead to slower performance due to increased network overhead between tiers.

Vertical Scaling

Adding more RAM/CPU to a single server.

Horizontal Scaling

Adding more server units to a pool.

Web Proxy

Acts as a gateway/firewall to control traffic and improve security.

Caching

Improves performance by reducing latency and bandwidth usage.

Conditional GET

A request that asks the server to send the page only if it has changed, saving bandwidth.

HTML

An open standard by the W3C used for structuring content on the web.

Tag

Represents an ordered list in HTML.

Tag

Represents an unordered list in HTML.

Tag

Defines a list item in HTML.

Tag

Line break in HTML, considered a void element with no closing tag.

Tag

Defines a hyperlink in HTML, requiring an href attribute.

PHP Basics

PHP is server-side; executed on the server and not in the browser.

Semicolon in PHP

Every statement must end with a semicolon (;).

unlink() in PHP

Function used to delete a file.

echo or print() in PHP

Functions to output text.

PHP Data Types

Character is NOT a valid data type; use String instead.

Security of POST vs. GET

POST is more secure than GET for transmitting sensitive data.

Relational Model

Data organized into tables called relations.

Attribute in SQL

A column in a table.

Tuple in SQL

A row in a table.

SQL Query Example

SELECT * FROM Products WHERE Price > 50;.

XML Syntax

Uses tags similar to HTML but all tags must close and be nested properly.

SAX Parser

An event-based parser for XML.

DOM Parser

A tree-based parser for XML that is memory-intensive.

Client in E-Commerce Architecture

Browser that sends HTTP GET/POST requests and uses cookies for state management.

Web Server/Proxy Role

Caches content to reduce latency and acts as a firewall.

Business Logic Tier

Application server where logic processes occur, isolated from the data layer by a firewall.

Data Tier in E-Commerce

Uses SQL for queries and stores products, users, and orders in a relational model.

HTTP Status Code 200

Indicates that the request was successful.

HTTP Status Code 307

Indicates a temporary redirect of the resource.

HTTP Status Code 400

Indicates a bad request due to malformed syntax.

HTTP Status Code 404

Indicates that the requested page was not found.

HTTP Status Code 5xx

Indicates server errors due to internal issues.