1.0 Explaining Network Topologies Flashcards
Full-duplex
Bidirectional, simultaneous transmission.
Duplex
Bidirectional data flow.
Half Duplex
Bidirectional, non-simultaneous transmission.
VPN (Virtual Private Network):
A VPN creates a secure, encrypted connection over a public network, allowing remote access to a private network.
VLAN (Virtual Local Area Network):
VLANs are like creating separate virtual networks on the same physical network.
Host
Any Device on a network that can send or receive data(e.g., computers, servers, routers).
Datagram
A datagram is a self-contained, independent packet of data sent over a network.
Client
A device or software that request services from a server(e.g., a web browser accessing a website).
OSI Model
A 7-layer framework for network communication:
1. Physical – Transmits raw data.
2. Data Link – MAC addresses, frames.
3. Network – IP addressing, routing.
4. Transport – Reliable delivery (TCP/UDP).
5. Session – Manages connections.
6. Presentation – Formats, encrypts data.
7. Application – User-facing protocols (HTTP, FTP).
Physical Layer (L1)
Transfers raw bits over a medium.
-Cables,fiber optics, radio waves.
- Devices: Hubs, repeaters, network adapters
Data Link Layer (L2)
Frames data, manages MAC addresses, and detects errors in Ethernet, Wi-Fi, VLANs, and ARP using switches, NICs, and bridges.
Network Layer (3)
Routes packets using IP addresses.
- IP, ICMP, subnets, routing tables
- Devices: Routers, layer 3 switches
Transport Layer (L4)
Reliable, ordered data delivery between applications using port numbers.
Session Layer(L5)
Manages the establishment, maintenance, and termination of communication between devices. (Function)
*Authentication, API sessions, handshakes.(Process/ Example)
* Devices : Proxies, session managers (Device/Software)
Function: What the Session Layer does.
• Processes/Examples: How it does it (specific mechanisms).
• Devices/Software: What performs these functions
Presentation Layer (6)
Formats, encrypts, and compresses data.
*SSL/TLS, ASCII, Unicode, MIME.
* Devices: Codecs, encryption appliances.
Encapsulation (Packing Data)
Encapsulation is the process of adding headers to data as it moves through network layers. Each layer wraps the data with extra information needed for delivery.
Application Layer(L7)
Interfaces with user applications and services.
- HTTP, FTP, SMTP, IMAP
- Devices: Web servers, email clients, browsers.
Protocol Data Unit (PDU)
A chunk of data that is formatted and processed at each layer of the OSI model as it moves through the network.
Decapsulation (Unpacking Data)
Decapsulation is like unwrapping layers of packaging to get to the actual message (the data).
Adjacent Layer Interaction
Adjacent layer interaction is when each network layer passes information directly up or down to the layer next to it.
Cabled
: Physical connections between nodes, like copper or fiber optic cables. Also called bounded media.
Wireless
Communication without wires, using radio waves in the air.” (Specifically mentions radio waves and air as the medium)
Node:
A device (e.g., computer, router) connected to a network.
Physical Topology
The layout of network connections, often divided into segments for better performance and security.
Physical Interface:
The design of network connections, like cables, connectors, and antennas.
Signaling
The method of sending data via electrical, light, or radio signals.
Tranceiver
Sends and receives signals over the network.
Repeater
Boosts a signal to extend its range.
Hub
A device that connects multiple nodes, working like a central hub.
Repeater
Boosts a signal to extend its range.
Data Link
The layer responsible for transferring data between nodes over a physical connection. It handles error checking and data formatting.
Media Converter:
Changes one type of network signal to another.
Network Adapter (NIC): A device that connects a computer to the network so it can send and receive data.
Bridge
A device that connects two parts of a network to reduce traffic and improve performance.
Frame
A piece of data that is sent between devices over a network. This is at the data link level.
Switch
A device with many ports that connects multiple devices on a network more efficiently.
Wireless Access Point (AP)
A device that allows wireless devices to connect to a wired network.
Name 4 devices that operate at the data link level.
1)Network adapter
2) Bridge
3) Switch
4) Wireless Access Point(AP)
Heterogeneous
Heterogeneneous means the networks are made up of a mix of different technologies, not all the same.
What is the main device or appliance working at level 3?
A router is the main appliance working at level 3 which is a networking device.
Firewall (Layer 3):
A device that acts like a security gate, blocking or allowing data to pass between networks based on rules.
Access Control List (ACL)
A list of rules that tells the firewall which types of data (based on address or type) are allowed or blocked.
Internet work
A group of connected networks that allows communication between them.
What are some devices at the transport level(L4).
Devices at the Transport layer include multilayer switches that help balance traffic across servers and security devices like advanced firewalls and intrusion detection systems (IDS) that protect against attacks.
Think of Level 4 as the TRAFFIC CONTROLLER!
LAN
A network in a single location is often described as a local area network (LAN). LAM+
A Small Office/Home Office (SOHO) network
A LAN for a small number of users, typically using a single wireless router for routing, switching, Wi-Fi, and firewall functions, providing both local and Internet connectivity.”
ARP Table
A temporary list stored in memory that maps IP addresses to MAC addresses, helping ARP find devices on a network. Entries are removed after a while to stay accurate.
Proxy
A proxy is a network node acting as an intermediary.
Intermediary Node
Forwards data between nodes, not the source/destination. Receives, processes, retransmits.
Examples:
Router (Internet)
Satellite (Space Comm.)
Mesh Node (Bluetooth)
Trouble Shooting Methodology
Structured approach to problem-solving using identification, theory of cause, testing, planning, implementation, verification, and documentation steps.
What is the Question the Obvious Trouble Shooting Approach?
A quick method that steps through what should happen, identifying failures or errors (e.g., checking if a network cable is plugged in). Best for spotting simple oversights early in troubleshooting.
What is the “Methodically Prove Functionality” approach?
A thorough method that tests each component in sequence to confirm functionality. Best for complex problems requiring detailed validation, though it is more time-consuming.
What is the “Top-to-Bottom/Bottom-to-Top OSI Model” approach?
A methodical process testing each OSI layer (e.g., starting at Physical Layer 1 or Application Layer 7) in sequence, moving only after ruling out a layer. Best for structured troubleshooting of network issues, like diagnosing a workstation from hardware to software.
What is the Divide and Conquer approach
A strategy starting at the most likely Problematic layer, then moving up or down based on results. Best for efficient trouble shooting when the issue’s source is uncertain, adapting to findings.
Define escalation
Escalation is when you pass a problem to someone who has more expertise, authority, or resources to solve it, because you can’t fix it yourself within the required time.
Framework for defining words
- Comprehensive Definition: Start with a complete and accurate definition, including key elements and nuances.
- Elaboration/Explanation: Provide detailed explanations of the components of the definition, clarifying any ambiguous terms or concepts.
- Contextualization: Discuss the term’s significance and usage in various relevant contexts (e.g., support procedures, incident response, software development, etc.).
- Examples: Offer real-world examples to illustrate the term’s application.
- Differentiation (If Applicable): Distinguish the term from similar or related concepts, highlighting the key differences.
- Simplified Definition: Provide a concise, easy-to-understand definition that captures the core essence of the term.
Failover services
Failover services are a strategy to minimize the impact of network downtime by having a backup system that automatically takes over if the primary system fails.
ARP
ARP (Address Resolution Protocol) acts like a translator on local networks, converting logical IPs to physical MACs so devices can connect.
