October 16, 2022 7:00 PM PDT
This document summarizes the key points discussed in a meeting focused on load balancers, their types, functionalities, and underlying network principles.
Presenter: Brother M
Load Balancer
- Definition: A load balancer distributes network or application traffic across multiple servers to ensure reliability and performance.
- Types:
- Software Load Balancers
- Hardware Load Balancers
Client-Based Classification
- URI: Used for server selection in applications such as gaming.
- Ribbon: A library for load balancing.
Load Balancer Levels
- Layer 4 (L4): Operates at the transport layer (TCP/UDP).
- Layer 7 (L7): Operates at the application layer (HTTP/HTTPS).
Importance of Load Balancers
- High Concurrency: Manages multiple simultaneous connections.
- High Data Volume: Handles large amounts of data efficiently.
OSI Model Overview
- Application Layer
- Presentation Layer
- Session Layer
- Transport Layer
- Network Layer
- Data Link Layer
- Physical Layer
- Requests start at the application layer and move down to the physical layer for transmission.
Load Balancing Algorithms
- Round Robin: Distributes requests evenly across servers.
- Weighted Round Robin: Assigns weights to servers based on their capacity.
- IP Hash: Directs requests based on the client's IP address.
- Least Hops: Chooses the server with the fewest hops.
Layer 7 Load Balancers
- Examples: Nginx, OpenResty, HAProxy.
- Features:
- Can inspect URIs.
- Manages connections (rate limiting, request throttling).
- Caches static resources.
- Supports protocol upgrades (e.g., WebSocket).
- Implements sticky sessions and Quality of Service (QoS).
Load Balancing Strategies
- Client to DNS: Resolves to Layer 7 load balancer, which forwards to the real server.
- Traffic Flow:
- L7: Returning traffic always goes through the load balancer.
- L4: Returning traffic may bypass the load balancer.
Basics of Local Network
- Addresses:
- MAC Address: Identifies the next hop for data packets.
- IP Address: Identifies devices on the network.
- ARP Protocol: Translates IP addresses to MAC addresses.
Packet Transmission
- Message Structure:
- Source IP
- Destination IP
- Source MAC
- Destination MAC
- Broadcasts occur if the destination MAC is set to a specific value.
Routing and NAT
- Routing Table: Determines the path for packet forwarding.
- NAT (Network Address Translation):
- Maps public IP:port to multiple internal IP:port pairs.
- D-NAT: Disadvantage includes visibility of incoming traffic's IP address.
Direct Routing (DR) Model
- Listens to a Virtual IP (VIP).
- Changes the MAC address to the real server's MAC for packet delivery.
- Introduces challenges with multiple machines sharing the same IP address.
Key Challenges
- Single Point of Failure: A critical issue in load balancing setups.
- Linux Configurations: Adjustments needed for handling VIP addresses effectively.