Week 3 Flashcards
(37 cards)
Deploying networking devices
Modern networks rely on intermediate systems to simplify design, reduce costs, and enhance functionality. They play a crucial role in keeping networks efficient, flexible, and scalable.
Repeaters: They “boost” the signal. ensuring it remains strong and clear over longer distances. Physical layer(Layer 1)
Hubs: A is like a megaphone that broadcasts data to everyone connected to it, regardless of whether they’re intended recipient or not. Physical layer. Only 1 device can communicate with the hub at a time, increasing the chances of data collisions.
Bridges: Data Link(Layer 2). They connect two network segments and make intelligent decisions on where to forward traffic based on MAC addresses. Help reduce traffic and improve network performance.
Switches: Switches, like advanced bridges, are the backbone of modern networks. Layer 2, they read MAC addresses and only forward data to intended recipient. Unlike hubs, they are full-duplex communication which means they can send and receive data simultaneously.
Routers: Network Layer(Layer 3): When data needs to leave the local network. Routers direct data between different networks using IP addresses. They are essential for connecting LAN’s to larger networks like WAN;s by determining the best path for data travel.
Media Converters: Different types of cables coexist, converters ensure that everything speaks the same language. Operate in Layer 1. Like copper to fibre optic cabling. Good for expanding networks.
Physical Layer Devices: Understanding the Physical layer
The physical layer (layer 1) of the OSI model is where raw data bits are transmitted over a network. Physical aspects that include the electrical signals, optical signals , and wireless signals. Does not concern itself with understanding or interpreting data, only send and receive data.
Physical Layer Devices: Transmission Media
Copper Cabling: Twisted pair cables and coaxial.
Fibre Optic Cabling: Single-mode fibre and Multimode fibre.
Wireless Transmission: Radio waves, microwaves, infrared. To transfer over air.
Physical Layer Devices: Key Devices at the Physical Layer
Repeater: Boosts signal for extended range.
Hub: Multiport repeater. Takes incoming signals and sends it across all ports.
Media Converter: Enables seamless communication between different types of physical media.
Transceivers: Transmits and receives signals. For example, the SFP(Small Form-Factor Pluggable) which is used to link switches and routers to fibre optic cables.
Physical Layer Devices: Signal Transmission Methods
Electrical Signals: Sent over copper cabling, susceptible to interference(Electromagnetic interference, EMI)
Optical Signals: Transmitted over fibre optic cables, less prone to interference and attenuation.
Wireless Signals: Transmit data using electromagnetic waves.
Physical Layer Devices: Physical Layer Functions
Bit Synchronizations: Timing is critical. Devices are Synchronized so that data can be sent and received at the correct time.
Data Encoding and Signalling: Before transmission, bits are converted into the appropriate form for the transmission medium.
Transmission Mode: Physical Layer defines whether data is sent in half-duplex or full-duplex. Half is data being sent in one direction at a time, full is data being sent two-way.
Transmission Speed: The rate at which data is transmitted, in (Mbps) or (Gbps).
Data Link Layer Devices (Layer 2)
Responsible for node-to-node communication and ensures that data frames are transferred between devices on the same network segment. Crucial for error detection, frame synchronization, and access to the physical medium. Organises how data flows across the network, reducing collisions, improving efficiency.
Data Link Layer Devices: Bride: Separating Physical Network Segments
A bridge works in the Data Link Layer to divide a network into separate segments while maintaining a single logical network. Isolates traffic within each segment, Uses MAC addresses to forward or filter frames between these segments.
How a Bridge works: When a frame arrives at a bridge, it reads the source and destination MAC addresses to decide whether the frame should be forwarded to another segment or kept within the current one. They maintain a MAC address table that stores the addresses of all the devices within each segment.
Advantages of using bridges: Reducing the size of collision domains, improve performance and make troubleshooting easier, also connect different types of media (Ethernet and Wi-Fi) and manage traffic between them.
Data Link Layer Devices: Ethernet Layer 2 Switch: The Modern Bridge
Switch performs the same functions as a bridge but on a much larger scale. More ports allowing them to connect to many devices simultaneously.
Each port on a switch creates a separate collision domain. 2 Devices connected to different ports on a switch won’t interfere with other devices on the network.
How a ethernet Switch Works: Reads the source and destination MA addresses of incoming frames and forwards them only to the port where the destination device is connected. Same as Bridges but much faster and efficient.
Benefits of Ethernet Layer 2 Switches:
Scalability: Handle more devices than bridges
Performance: Each port operates as a separate collision domain, and full-duplex communication allows devices to send and receive data simultaneously.
Efficiency: Use intelligent MAC address forwarding, reducing unnecessary traffic and improving network efficiency.
Network Interfaces: network Interfaces and Ethernet Frames
Network interface is crucial component that connects a device(Node) to the transmission media, allowing it to exchange data with other devices on the network. Enables communication by converting data into signals suitable for transmission.
Network Interfaces: Network Interface Cards (NIC)
NIC provides the physical interface between the transmission medium and the device. Most ethernet adapters are designed for use with copper cabling and support 10/100/1000 operation, meaning compatible with Gigabit Ethernet(1000 Mbps), Fast Ethernet(100Mbps), and 10BASE-T(10Mbps).
Each Ethernet Network Interface has unique hardware know as Media Access Control (MAC) address.
Network Interfaces: Ethernet Frame Format
Data is transmitted within a structure known as a frame. Frame contains various headers and fields that control how the data is handled. Frames include information such as source and destination MAC addresses, data payload, and error checking.
Basic Ethernet Frame Format:
Preamble, SFD, Destination MAC, Source MAC, Ether Type, Payload, FCS.
Ensuring data moves efficiently across a network. Frame is passed through different layers of the OSI model, carrying the payload from higher-layer protocols, such as TCP/IP, within the protocol data unit (PDU).
Network Interfaces: Protocol Analysers and Packet Sniffers
Protocol analysers and packet sniffers are invaluable tools for network troubleshooting and security monitoring. A protocol analyser inspects the traffic received by host or passing over a network link, providing deep insights into the protocols in use, the structure of the frames, and any potential issues.
A packet sniffer is a specific type of protocol analyser used to capture frames as they more across the network. Good for troubleshooting issues, detect unauthorized traffic, and analyse data performance.
Network Troubleshooting Methodology: The 7 Steps
- Identify the problem
- Establish a Theory of Probable Cause
- Test the Theory to Determine the Cause
- Establish a Plan of Action and Identify potential Effects
- Implement the Solution or Escalate
- Verify Full System Functionality
- Document Findings, Actions, and Outcomes
Network Troubleshooting Methodology: Troubleshooting Methodology Steps
- Identify the problem:
Gather information, Duplicate the problem if possible, Question users, Identify symptoms, Determine if anything has changed, Approach multiple problems individually. - Establish a theory of probable cause:
Question the obvious, Consider multiple approaches, Top-to-bottom/bottom-to-top OSI model analysis, Divide and conquer. - Test the theory to determine the cause:
Once the theory is confirmed, determine next steps to resolve the problem, if the theory is not confirmed, re-establish a new theory or escalate. - Establish a plan of action to resolve the problem and identify potential effects:
Develop a strategy to implement to solution while minimizing potential risks. - Implement the solution or escalate as necessary:
Take action to resolve the problem based on the plan or escalate the issue to appropriate level. - Verify full system functionality, and if applicable, implement preventive measures:
Ensure the system is functioning correctly after the fix, implement measures to prevent the issue from recurring in the future. - Document findings, actions, and outcomes:
Keep detailed records of the issue, steps taken, and final resolution for future reference.
Internet service provider
Internet service provider(ISP)
Troubleshooting common cable connectivity problems
Network issues, cable connectivity problems are a common culprit. Faulty cables or improper configurations can lead to intermitted connectivity, slow data transfers, or complete loss of network access. Applying layer-by-layer approach to network troubleshooting can greatly assist with isolating the symptoms and causes of these issues.
Troubleshooting common cable connectivity problems: Layer-by-Layer troubleshooting Approach
Using the OSI model as a guide, network troubleshooting starts from Physical Layer(Layer 1) then upwards. Helps pinpoint the source of the problem.
Troubleshooting common cable connectivity problems: Physical Layer(Layer 1): Checking Physical connections
Most cable connectivity issues occur at the Physical Layer.
1. Check Cables: Ensure cables are properly connected to their respective ports. Look for signs of physical damage.
2. Test Ports: Plug the cable into a different port on the switch, router or computer to rule out faulty hardware
3. Use Cable Testers: Tools like cable testers and continuity testers help verify the integrity of the cable.
4. Replace Suspect Cables: If you suspect a cable is at fault, swap it out for a know good one to see if the issue is resolved.
Troubleshooting common cable connectivity problems: Data Link Layer(Layer 2): Analysing Frame Transmission
Check how data is transferred across the network.
1. Check MAC address Tables: Verify that switches are properly associating MAC addresses with their corresponding ports.
2. Inspect Switches for Errors: Review switch logs for any errors related to specific ports.
3. Test with Protocol Analysers: Use protocol analyser to check whether Ethernet frames are being transmitted correctly over the cable.
Troubleshooting common cable connectivity problems: Network Layer(Layer 3): Verifying IP Address and Routing
- Verify IP Configuration: Ensure that the device connected to the cable has a valid IP address and that it matches the subnet of network.
- Check Routing Tables: Inspect the router’s routing table to verify that data is being forwarded correctly.
- Test Ping and Traceroute: Use ping and traceroute to test connectivity between devices and to detect where communication breaks down.
Troubleshooting common cable connectivity problems: Transport Layer(Layer 4): and Above: Verifying Data Flow
- TCP Handshakes: Verify that TCP connections are being properly established.
- Application-Level Checks: If everything is functional at the lower layers, verify that applications are able to communicate over the network without drops.
Troubleshooting common cable connectivity problems: Common Cable Connectivity Problems and Solutions
- Intermitted Connectivity: Often caused by loose or damaged cables.
- Signal Loss(Attenuation): Long cable runs can result in signal loss. If the cable exceeds the recommended distance, consider adding a repeater or switch to boost the signal.
- Cross-talk or interference: Electrical interference from other devices or cables can cause data corruption. Shielded cables (STP) or better cable management can reduce interference in high-noise environments.
- No Connectivity: Complete loss of connectivity could indicate a broken cable or damaged port. Swap cable and test different ports.
Troubleshooting common cable connectivity problems: Troubleshooting Links: Performance, Attenuation, and Interference
Essential to compare the expected performance with the actual performance to diagnose any issues.
