Load Balancer Concepts and Functions
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What is the primary purpose of employing load balancing strategies?

  • To improve the physical location of workers.
  • To ensure efficient distribution of tasks among workers. (correct)
  • To create more complicated communication protocols.
  • To increase the number of workers available.

    • Which load balancing strategy assigns requests to workers in a rotating order?

  • Sticky Session
  • Round Robin (correct)
  • Least Busy
  • Random

    • In the Least Busy strategy, how is the worker selected?

  • The worker with the fewest tasks is selected. (correct)
  • The worker that is physically closest to the client is selected.
  • A worker is chosen at random from all available workers.
  • The worker with the most experience is chosen.

    • How does the Sticky Session strategy determine which worker to route a client's request?

    <p>Based on session information or cookies.</p> Signup and view all the answers

    What defines the Random load balancing strategy?

    <p>It chooses a worker at random without specific criteria.</p> Signup and view all the answers

    Request Parameters in load balancing are used for what purpose?

    <p>To determine the worker based on specific request details.</p> Signup and view all the answers

    Which strategy is least likely to lead to uneven load distribution among workers?

    <p>Round Robin</p> Signup and view all the answers

    Which strategy could potentially result in prolonged wait times if one worker becomes overloaded?

    <p>Sticky Session</p> Signup and view all the answers

    What primary role does the load balancer's dispatcher play in a system?

    <p>It distributes requests across workers.</p> Signup and view all the answers

    Which benefit is directly associated with the use of a load balancer?

    <p>Improved efficiency and scalability.</p> Signup and view all the answers

    What happens if a single worker becomes overloaded in a load-balanced setup?

    <p>The dispatcher reroutes requests to other workers.</p> Signup and view all the answers

    What does a load balancer distribute?

    <p>Client requests.</p> Signup and view all the answers

    How does a load balancer improve scalability?

    <p>By balancing workload among multiple workers.</p> Signup and view all the answers

    What is one of the strategies mentioned for balancing the load?

    <p>Based on specific algorithms or policies.</p> Signup and view all the answers

    Which of the following best describes the collective management of workers by the load balancer?

    <p>Workers are grouped for more efficient management.</p> Signup and view all the answers

    What might happen if there is no load balancer in place for request management?

    <p>Increased response time due to request queuing.</p> Signup and view all the answers

    What is the primary role of the application layer in network communication?

    <p>To manage applications and user interfaces</p> Signup and view all the answers

    Which of the following services is NOT provided by the application layer?

    <p>Data encryption</p> Signup and view all the answers

    How does an HTTP request function in the OSI model?

    <p>It is initiated by the application layer to request resources.</p> Signup and view all the answers

    Which analogy best describes the application layer?

    <p>The apps you use on your phone or computer</p> Signup and view all the answers

    Which of the following protocols is part of the application layer?

    <p>HTTP</p> Signup and view all the answers

    What is the relationship between the application layer and the user?

    <p>It directly interfaces with users through applications.</p> Signup and view all the answers

    Which of the following is an example of a service provided by the application layer?

    <p>File Transfer Protocol (FTP)</p> Signup and view all the answers

    When a user loads a website, which layer first sends an HTTP request?

    <p>Application layer</p> Signup and view all the answers

    What is the primary purpose of load balancing?

    <p>To distribute network traffic efficiently across multiple servers.</p> Signup and view all the answers

    At which layer of the OSI model does Layer 4 load balancing operate?

    <p>Transport Layer</p> Signup and view all the answers

    Which of the following describes Layer 7 load balancing?

    <p>Directs traffic based on content and application data.</p> Signup and view all the answers

    In which scenario is Layer 4 load balancing particularly useful?

    <p>When overseeing millions of user connections with minimal delay.</p> Signup and view all the answers

    What is a real-world analogy used to describe Layer 4 load balancing?

    <p>Directing guests to sections of a venue based on entry point.</p> Signup and view all the answers

    Which of the following technologies is NOT commonly associated with Layer 4 load balancing?

    <p>Apache HTTP Server</p> Signup and view all the answers

    What does Layer 4 load balancing primarily utilize for traffic distribution?

    <p>IP addresses and port numbers.</p> Signup and view all the answers

    What aspect of performance does load balancing primarily enhance?

    <p>Overall application performance and reliability.</p> Signup and view all the answers

    What is one of the main benefits of using Layer 4 Load Balancers in combination with Layer 7 Load Balancers?

    <p>They ensure no single Layer 7 balancer becomes overwhelmed.</p> Signup and view all the answers

    Which feature of Layer 7 Load Balancers allows for advanced deployment strategies?

    <p>Intelligent routing based on application data.</p> Signup and view all the answers

    What is a potential downside of implementing both Layer 4 and Layer 7 Load Balancers?

    <p>Increased architectural complexity.</p> Signup and view all the answers

    What is a prime reason that most contemporary systems prefer software-based load balancers?

    <p>They offer greater flexibility and scalability.</p> Signup and view all the answers

    How do Layer 4 Load Balancers contribute to fault tolerance?

    <p>By redirecting traffic to another Layer 7 balancer if one fails.</p> Signup and view all the answers

    What is a key characteristic of HAProxy in the context of load balancing?

    <p>It is an open-source tool known for reliability and performance.</p> Signup and view all the answers

    Which concept can result from the architectural complexity of using both Layer 4 and Layer 7 Load Balancers?

    <p>Increased latency in request processing.</p> Signup and view all the answers

    Which of the following does not represent a pro of combining Layer 4 and Layer 7 Load Balancers?

    <p>Increased redundancy in components.</p> Signup and view all the answers

    What is the primary role of a reverse proxy in a network setup?

    <p>To manage incoming requests and route them appropriately.</p> Signup and view all the answers

    How does caching in a reverse proxy improve system performance?

    <p>It stores frequently accessed data to reduce load on servers.</p> Signup and view all the answers

    What important security function does a reverse proxy provide?

    <p>It mitigates DDoS attacks and manages SSL termination.</p> Signup and view all the answers

    Which scenario would be best suited for a reverse proxy’s traffic routing feature?

    <p>Routing vote submissions to a specialized voting service.</p> Signup and view all the answers

    How does a reverse proxy handle incoming requests during a polling event?

    <p>It identifies the type of request and routes it to the right service.</p> Signup and view all the answers

    What is a benefit of using a reverse proxy in a social polling app?

    <p>Enhanced user experience through faster response times.</p> Signup and view all the answers

    Why is SSL termination an important feature of a reverse proxy?

    <p>It simplifies the management of SSL certificates.</p> Signup and view all the answers

    What happens to backend servers when a reverse proxy is implemented?

    <p>They are hidden and protected from direct exposure.</p> Signup and view all the answers

    Study Notes

    Load Balancer

    • Distributes incoming client requests across multiple servers
    • Ensures scalability and reliability
    • Prevents overloading of resources
    • Eliminates single point of failure
    • Enhances performance and availability

    Load Balancer Diagram Components

    • Client: Sends requests to the dispatcher
    • Dispatcher: Receives requests from the client and routes them to workers.
      • Implements load balancing strategies
        • Random selection of workers
        • Round-robin allocation of requests to workers
        • Selecting the worker with the least busy tasks
        • Using persistent sessions/cookies to route requests to a specific worker
        • Using request parameters
    • Workers: Multiple worker nodes handling requests independently. Associated with a storage unit (e.g., database).

    Additional Features

    • SSL termination (decrypts incoming requests and encrypts server responses)
    • Session persistence (using cookies to route clients to the same server)

    Load Balancing Metrics

    • Random
    • Least loaded
    • Session/Cookies
    • Round Robin/Weighted Round Robin
    • Layer 4
    • Layer 7

    Layer 4 Load Balancing

    • Definition: Operates at the Transport Layer
    • Distributes traffic based on IP addresses and ports

    Layer 7 Load Balancing

    • Definition: Operates at the Application Layer
    • Distributes traffic based on HTTP/HTTPS data
    • Key concepts: Content-Based Routing

    Reverse Proxy (Web Server)

    • Definition: Centralizes internal services, and forwards client requests to appropriate servers
    • Benefits: Increased security, scalability & flexibility, SSL termination, compression, caching, serving static content
    • Disadvantages: Increased complexity, single point of failure
    • Popular technologies: NGINX, Apache HTTP Server, HAProxy

    Horizontal Scaling

    • Definition: Scaling out by adding more commodity machines
    • Advantages: cost-efficient, higher availability, easier to hire talent
    • Disadvantages: increased complexity, requires server cloning, downstream servers must handle more connections
    • Best practices: stateless servers, store sessions in centralized data stores (e.g., SQL, NoSQL, Redis, Memcached)
    • Disadvantages (load balancer): performance bottleneck, complexity increase with multiple load balancer, single point of failure

    OSI Model

    • Layers: Physical, Data Link, Network, Transport, Session, Presentation, Application
    • Importance: Standardizes networking protocols, facilitates troubleshooting, enhances modularity

    Software Load Balancers

    • NGINX
    • HAProxy
    • AWS ELB & ALB

    Hardware Load Balancers

    • F5 BIG-IP
    • Citrix ADC

    Managed vs. In-House

    • Managed (Cloud-Based): Pros: Easy scalability, low maintenance. Cons: Vendor lock-in, less granular control.
    • In-House (Self-Managed): Pros: Full control, customization. Cons: Requires more expertise, ongoing maintenance.

    Best Practices (for Interview)

    • Outline the problem clearly
    • Introduce load balancing early
    • Detail the roles of each layer

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    Related Documents

    Load Balancer, Reverse Proxy (Web Server) PDF

    Description

    This quiz covers essential concepts related to load balancers, including their role in distributing client requests, enhancing performance, and ensuring reliability. Additionally, it explores different load balancing strategies and key components like dispatchers and workers. Test your knowledge on how load balancers prevent resource overloading and eliminate single points of failure.

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