Module 1 Flashcards
Learning Unit 1 (39 cards)
Physical vs Logical Topologies
- how roads are laid out vs route taken regardless of actual road layout
- Physical Topology: the hardware layout of devices, cables, or radio signals in a network.
- Logical Topology: how software manages access to resources and controls how data is transmitted across the network.
Peer-To-Peer (P2P) Network Model: Key features and disadvantages
- neighbours delivering directly to each other without post office
- Each device manages its own resources without centralised control.
- Features:
- simple to set up
- low costs
- ideal for small networks (<15 devices)
*Disadvantages:
- not scalable
- weak security
- hard to manage many users/resources
Client-Server Network Model
- everyone sends and receives mail through a central post office that manages all deliveries
- Model uses a central server with a Network OS to manage access via a directory like Active Directory
*Benefits:
- centralised account and resource control
- scalable
- easier management and troubleshooting
- requires more memory, processing, and storage (often use RAID) to handle multiple client requests.
Roles of a Network Operating System (NOS) in a client-server network
- postmaster running the central post office: manages routes, deliveries, and access
- Manage data/resources for clients
- Authorize and restrict user access
- Enforce file access rules
- Control login timing and location
- Set communication rules
- Provide apps and files to clients
Client-Server Application
- system where the sender asks the post office to deliver a letter, and the post office handles the entire process from end to end
- A client requests data or a service from a server over a network.
- Involves at least two endpoint devices (e.g. PC, smartphone).
- Can operate across different networks (e.g. Internet).
- These applications are examples of network services.
Role of Protocols in Client-Server Communication
- agreed-upon mailing formats and delivery rules between the sender, the post office, and the receiver
- Devices use protocols to communicate.
- Protocols define how data is requested, transmitted, and received.
- Client and server must agree on a protocol.
- Two key protocols: TCP (Transmission Control Protocol) and IP (Internet Protocol).
- Protocols are part of the TCP/IP suite.
Web Services & HTTP/HTTPS
- Sending/receiving digital postcards or packages through express (HTTP) or secured (HTTPS) services
- Web servers deliver web pages to clients (browsers) using HTTP.
- HTTPS = HTTP + SSL/TLS for encryption.
- Popular web server software: Apache, Nginx (Linux-based, open source), IIS (Windows Server).
Email Services & Protocols
- Standard mailboxes and mail trucks designed for email
- Sending: SMTP (Simple Mail Transfer Protocol).
- Receiving:
- POP3: Downloads and removes email from server.
- IMAP4: Manages email on the server.
- Secure versions use SSL/TLS.
- Examples: Microsoft Exchange Server (server), Outlook (client).
DNS (Domain Name System) Service
- phonebook that tells the post office where a person lives when you give their name instead of an address
- DNS translates domain names into IP addresses.
- Used to find web servers on the Internet or internal networks.
- Provided by ISPs, companies, or public servers (e.g. Google DNS).
FTP (File Transfer Protocol) Service
- courier service for sending large packages between businesses
- Used to transfer files between client and server.
- Not encrypted = insecure.
- Browsers can act as clients, but apps like FileZilla or CuteFTP offer more features.
Database Services & SQL
- mailroom with filing cabinets; you send in a form (SQL query) asking for specific documents, and it finds and returns them
- Databases store large amounts of organized data.
- Accessed via a DBMS (Database Management System).
- Uses SQL (Structured Query Language) to manage data.
- Examples: Microsoft SQL Server, Oracle, MySQL.
Remote Access Services (Telnet, SSH, RDP)
- authorized individuals controlling the mailroom remotely to read or manage letters without being there in person
- Allow users/admins to control remote computers.
- Telnet: Unencrypted, outdated.
- SSH: Encrypted, used in Linux.
- RDP: Encrypted, used in Windows.
- Used for remote support, troubleshooting, or software maintenance.
LAN and Switch Basics
- local neighborhood post office and a sorting center that sends mail only to the intended local house
- A LAN (Local Area Network) connects devices in a small area (e.g., office).
- Devices connect to a switch via wired connections.
- A switch forwards data only to the intended device(s), reducing traffic.
- The physical layout with devices connecting to one central switch is called a star topology.
Hubs
- loud postman who shouts out every letter to every house, regardless of who it’s for
- A hub is an outdated device that broadcasts data to all connected devices.
- Hubs were once central points in star topologies but are inefficient.
- Switches replaced hubs because they reduce unnecessary network traffic.
Network Ports and NICs
- mail slots and personal mailboxes at each house (device) and the mail carrier tags that identify who they belong to
- Network ports connect devices via network cables.
- Ports can be built into the motherboard or added via NICs (Network Interface Cards).
- NICs allow devices to communicate on a network and are sometimes called network adapters.
Multiple Switches and Network Backbone
- several post offices connected by a superhighway for efficient mail delivery across towns
- Networks can have multiple switches connected in series (daisy-chained).
- The high-capacity connection between switches is called a backbone.
- Backbones often use faster media and cabling to handle heavy traffic and longer distances.
Types of Topologies
- bus: a single long street.
- star: all houses connect to one central post office.
- ring: houses arranged in a circle; each house passes the mail to the next.
- mesh: every house has a direct line to every other house
- Star: Devices connect to central switch; easy to manage.
- Bus: Devices connected in a line with backbone; vulnerable to backbone failure.
- Ring: Devices form a circle; token controls who transmits; rare now.
- Mesh: Devices connect to multiple others; very reliable but complex.
- Hybrid: Mix of topologies (e.g., star + bus); flexible and scalable.
Routers and Their Role
- smart post offices that decide the best route to send a letter across cities
- Routers connect multiple networks and route traffic between them.
- In small offices, consumer-grade routers connect LANs to the Internet.
- Enterprise routers connect multiple LANs and have different network addresses for each network.
- Routers act as gateways; switches only operate within one LAN.
Nodes vs. Hosts
- nodes: any location involved in the mail process (sorters, trucks)
- hosts: the homes sending/receiving letters
- A node is any network device that can be addressed (e.g., router, switch, computer). * A host is a node that provides or accesses network resources (e.g., server, computer, printer). * Networking devices (routers, switches) are nodes but not hosts; hosts are called end devices or endpoints.
Types of Networks by Size
- LAN: Neighborhood mail delivery.
- MAN: City-wide delivery.
- WAN: Country-to-country delivery.
- PAN: Person-to-person delivery.
- LAN: Local Area Network (small geographic area).
- MAN: Metropolitan Area Network (LANs connected within a city or campus).
- WAN: Wide Area Network (LANs connected over large geographic areas).
- PAN: Personal Area Network (personal devices like smartphone and computer syncing).
Other Network Types
- BAN: sending messages between gadgets on your own body
- SAN: private mail system just for moving big files between storage rooms (not for people)
- WLAN: sending neighborhood mail using drones (Wi-Fi) instead of mail trucks (cables)
- BAN (Body Area Network): Wearable personal devices (smartwatch, fitness tracker).
- SAN (Storage Area Network): High-capacity storage devices connected in a dedicated network.
- WLAN (Wireless LAN): Two or more devices connected wirelessly.
OSI Layer 7 – Application Layer
- you write the letter and decide what you want to say. (User interface)
- Defines the interface between applications on different hosts
- Uses protocols like HTTP, SMTP, FTP, DNS, Telnet, SSH, SNMP, RDP
- Supports user-facing services (e.g., web browsing) and system utilities (e.g., SNMP monitoring)
- Data exchanged is called the payload
- Devices at each end are called hosts
OSI Layer 6 – Presentation Layer
- you translate your message into a language the receiver understands. (Encoding/encryption)
- Handles data formatting, compression, and encryption
- Ensures the receiving application can properly interpret the data
- Example: Email encryption handled by the email client or OS
OSI Layer 5 – Session Layer
- you start the conversation by opening a channel with the receiver. (Start/end connection)
- Manages and maintains communication sessions between applications
- Ensures synchronization and recovery if messages are lost or corrupted
- Example: Zoom uses the session layer to keep a video call active and stable
