Layer 7 load balancers can further distribute requests based on application specific data such as HTTP headers, cookies, or data within the application message itself, such as the value of a specific parameter.
Load balancers ensure reliability and availability by monitoring the "health" of applications and only sending requests to servers and applications that can respond in a timely manner. To learn more on load balancing, visit DevCentral. Skip to main content Skip to footer Skip to search. Another would be to load balance on the server side, where traffic passes through a load balancing device that distributes load over a pool of servers.
Both ways are valid, but DNS and client side load balancing is limited, and should be used with caution because DNS records are cached according to their time-to-live TTL attribute, and that will lead your client to non-operating nodes and produce a delay after changes. Server-side load balancing is powerful, it can provide fine-grain control, and enable immediate change to the interaction between client and application.
This book will mainly cover server-side load balancing. Server-side load balancers have evolved from simply routing packets, to being fully application aware. These are the two types of load balancers known as network load balancers and application load balancers. Both named with respect to the layer of the OSI model to which they operate. The application load balancers are where there are interesting advancements. Because the load balancer is able to understand the packet at the application level, it has more context to the way it balances and routes traffic.
Load balancers have also advanced in the variety of features that they provide. Being in line with the presentation of the application, an application load balancer is a great place to add another layer of security, or cache requests to lower response times. Network load balancers are great for simply and quickly distributing load. Application load balancers are important for routing specifics, such as session persistence and presentation.
Later in this book, you will learn how all of these types of load balancing techniques work together to serve your goal of a highly performant, secure, and reliable application. Skip to main content. Start your free trial. An Introduction to Load Balancing. About Load Balancers. History of Load Balancing.
Load Balancing and Security Load Balancing plays an important security role as computing moves evermore to the cloud. Load Balancing Algorithms There is a variety of load balancing methods , which use different algorithms best suited for a particular situation.
Least Connection Method — directs traffic to the server with the fewest active connections. Most useful when there are a large number of persistent connections in the traffic unevenly distributed between the servers. Least Response Time Method — directs traffic to the server with the fewest active connections and the lowest average response time. Round Robin Method — rotates servers by directing traffic to the first available server and then moves that server to the bottom of the queue.
Most useful when servers are of equal specification and there are not many persistent connections. IP Hash — the IP address of the client determines which server receives the request. Load Balancing Benefits. Load balancers have different capabilities, which include: L4 — directs traffic based on data from network and transport layer protocols, such as IP address and TCP port.
L7 — adds content switching to load balancing. Load Balancing with App Insights. Using a Software Load Balancer for Application Monitoring, Security, and End User Intelligence Administrators can have actionable application insights at their fingertips Reduce troubleshooting time from days to mere minutes Avoid finger-pointing and empowers collaborative issue resolution. Download Now.
Software Load Balancers vs. Hardware Load Balancers. Software Pros Flexibility to adjust for changing needs. Ability to scale beyond initial capacity by adding more software instances. Lower cost than purchasing and maintaining physical machines. Software can run on any standard device, which tends to be cheaper. Allows for load balancing in the cloud, which provides a managed, off-site solution that can draw resources from an elastic network of servers.
Cloud computing also allows for the flexibility of hybrid hosted and in-house solutions. The main load balancer could be in-house while the backup is a cloud load balancer.
Software Cons When scaling beyond initial capacity, there can be some delay while configuring load balancer software. Ongoing costs for upgrades. Hardware Pros Fast throughput due to software running on specialized processors. Increased security since only the organization can access the servers physically.
Fixed cost once purchased. Hardware Cons Require more staff and expertise to configure and program the physical machines. Inability to scale when the set limit on number of connections has been made. Connections are refused or service degraded until additional machines are purchased and installed. Higher cost for purchase and maintenance of physical network load balancer. Owning a hardware load balancer may also require paying for consultants to manage it.
This allows the control of multiple load balancing. It also helps the network to function like the virtualized versions of compute and storage. With the centralized control, networking policies and parameters can be programmed directly for more responsive and efficient application services.
This is how networks can become more agile. UDP load balancing is often used for live broadcasts and online games when speed is important and there is little need for error correction. UDP has low latency because it does not provide time-consuming health checks. TCP load balancing provides a reliable and error-checked stream of packets to IP addresses, which can otherwise easily be lost or corrupted. It prioritizes responses to the specific requests from clients over the network.
Server load balancing distributes client traffic to servers to ensure consistent, high-performance application delivery. Virtual — Virtual load balancing aims to mimic software-driven infrastructure through virtualization.
It runs the software of a physical load balancing appliance on a virtual machine. Virtual load balancers , however, do not avoid the architectural challenges of traditional hardware appliances which include limited scalability and automation, and lack of central management. Elastic — Elastic Load Balancing scales traffic to an application as demand changes over time. It uses system health checks to learn the status of application pool members application servers and routes traffic appropriately to available servers, manages fail-over to high availability targets, or automatically spins-up additional capacity.
Geographic — Geographic load balancing redistributes application traffic across data centers in different locations for maximum efficiency and security. While local load balancing happens within a single data center, geographic load balancing uses multiple data centers in many locations.
Multi-site — Multi-site load balancing, also known as global server load balancing GSLB , distributes traffic across servers located in multiple sites or locations around the world. The servers can be on-premises or hosted in a public or private cloud. Multi-site load balancing is important for quick disaster recovery and business continuity after a disaster in one location renders a server inoperable.
Load Balancer as a Service LBaaS — Load Balancer as a Service LBaaS uses advances in load balancing technology to meet the agility and application traffic demands of organizations implementing private cloud infrastructure. Using an as-a-service model, LBaaS creates a simple model for application teams to spin up load balancers.
Per App Load Balancing A per-app approach to load balancing equips an application with a dedicated set of application services to scale, accelerate, and secure the application. What is Weighted Load Balancing?
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