dns load balancing failover

GTM Load Balancer

GTM Load Balancer

In today's fast-paced digital world, websites and applications face the constant challenge of handling high traffic loads while maintaining optimal performance. This is where Global Traffic Manager (GTM) load balancer comes into play. In this blog post, we will explore the key benefits and functionalities of GTM load balancer, and how it can significantly enhance the performance and reliability of your online presence.

GTM Load Balancer, or Global Traffic Manager, is a sophisticated, global server load balancing solution designed to distribute incoming network traffic across multiple servers or data centers. It operates at the DNS level, intelligently directing users to the most appropriate server based on factors such as geographic location, server health, and network conditions. By effectively distributing traffic, GTM load balancer ensures that no single server becomes overwhelmed, leading to improved response times, reduced latency, and enhanced user experience.

GTM load balancer offers a range of powerful features that enable efficient load balancing and traffic management. These include:

1. Geographic Load Balancing: By leveraging geolocation data, GTM load balancer directs users to the nearest or most optimal server based on their physical location, reducing latency and optimizing network performance.

2. Health Monitoring and Failover: GTM continuously monitors the health of servers and automatically redirects traffic away from servers experiencing issues or downtime. This ensures high availability and minimizes service disruptions.

3. Intelligent DNS Resolutions: GTM load balancer dynamically resolves DNS queries based on real-time performance and network conditions, ensuring that users are directed to the best available server at any given moment.

Scalability and Flexibility: One of the key advantages of GTM load balancer is its ability to scale and adapt to changing traffic patterns and business needs. Whether you are experiencing sudden spikes in traffic or expanding your global reach, GTM load balancer can seamlessly distribute the load across multiple servers or data centers. This scalability ensures that your website or application remains responsive and performs optimally, even during peak usage periods.

Integration with Existing Infrastructure: GTM load balancer is designed to integrate seamlessly with your existing infrastructure and networking environment. It can be easily deployed alongside other load balancing solutions, firewall systems, or content delivery networks (CDNs). This flexibility allows businesses to leverage their existing investments while harnessing the power and benefits of GTM load balancer.

In conclusion, GTM load balancer offers a robust and intelligent solution for achieving optimal performance and scalability in today's digital landscape. By effectively distributing traffic, monitoring server health, and adapting to changing conditions, GTM load balancer ensures that your website or application can handle high traffic loads without compromising on performance or user experience. Implementing GTM load balancer can be a game-changer for businesses seeking to enhance their online presence and stay ahead of the competition.

Highlights: GTM Load Balancer

The Role of Load Balancing

Load balancing involves spreading an application’s processing load over several different systems to improve overall performance in processing incoming requests. It splits the load that arrives into one server among several other devices, which can decrease the amount of processing done by the primary receiving server.

While splitting up different applications used to process a request among separate servers is usually the first step, there are several additional ways to increase your ability to split up and process loads—all for greater efficiency and performance. DNS load balancing failover, which we will discuss next, is the most straightforward way to load balance.

load balancing

DNS Load Balancing

DNS load balancing is the simplest form of load balancing. However, it is also one of the most powerful tools available. Directing incoming traffic to a set of servers quickly solves many performance problems. In spite of its ease and quickness, DNS load balancing cannot handle all situations.

A DNS server is a cluster of servers that answer queries together but cannot handle every DNS query on the planet. The solution lies in caching. Your system looks up servers from its storage by keeping a list of known servers in a cache. As a result, you can reduce the time it takes to walk a previously visited server’s DNS tree. Furthermore, it reduces the number of queries sent to the primary nodes.

nslookup command

The Role of a GTM Load Balancer

A GTM Load Balancer is a solution that efficiently distributes traffic across multiple web applications and services. In addition, it distributes traffic across various nodes, allowing for high availability and scalability. As a result, these load balancers enable organizations to improve website performance, reduce costs associated with hardware, and allow seamless scaling as application demand increases. It acts as a virtual traffic cop, ensuring incoming requests are routed to the most appropriate server or data center based on predefined rules and algorithms.

The Role of an LTM Load Balancer

The LTM Load Balancer, short for Local Traffic Manager Load Balancer, is a software-based solution that distributes incoming requests across multiple servers. This ensures efficient resource utilization and prevents any single server from being overwhelmed. By intelligently distributing traffic, the LTM Load Balancer ensures high availability, scalability, and improved performance for applications and services.

Continuously Monitors

GTM Load Balancers continuously monitor server health, network conditions, and application performance. They use this information to distribute incoming traffic intelligently, ensuring that each server or data center operates optimally. By spreading the load across multiple servers, GTM Load Balancers prevent any single server from becoming overwhelmed, thus minimizing the risk of downtime or performance degradation.

Traffic Patterns

GTM Load Balancers are designed to handle a variety of traffic patterns, such as round robin, least connections, and weighted least connections. It can also be configured to use dynamic server selection, allowing for high flexibility and scalability. GTM Load Balancers work with HTTP, HTTPS, TCP, and UDP protocols, which are well-suited to handle various applications and services.

GTM Load Balancers can be deployed in public, private, and hybrid cloud environments, making them a flexible and cost-effective solution for businesses of all sizes. GTM Load Balancers have advanced features such as automatic failover, health checks, and SSL acceleration.

Related: Both of you proceed. You may find the following helpful information:

  1. DNS Security Solutions
  2. OpenShift SDN
  3. ASA Failover
  4. Load Balancing and Scalability
  5. Data Center Failover
  6. Application Delivery Architecture
  7. Port 179
  8. Full Proxy
  9. Load Balancing



GTM Load Balancing.

Key GTM Load Balancer Discussion Points:


  • Introduction to load balancing with the GTM.

  • Discussion on DNS and how it works.

  • Discussion on the DNS TTL and how this may effect load balancing.

  • Highlighting DNS pinning and cache poisoning.

  • Load balancing methods.

  • A final note on Anycast.

Back to Basics: GTM load balancer

What is a Load Balancer?

A load balancer is a specialized device or software that distributes incoming network traffic across multiple servers or resources. Its primary objective is evenly distributing the workload, optimizing resource utilization, and minimizing response time. By intelligently routing traffic, load balancers prevent any single server from being overwhelmed, ensuring high availability and fault tolerance.

Load Balancer Functions and Features

Load balancers offer many functions and features that enhance network performance and scalability. Some essential functions include:

1. Traffic Distribution: Load balancers efficiently distribute incoming network traffic across multiple servers, ensuring no single server is overwhelmed.

2. Health Monitoring: Load balancers continuously monitor the health and availability of servers, automatically detecting and avoiding faulty or unresponsive ones.

3. Session Persistence: Load balancers can maintain session persistence, ensuring that requests from the same client are consistently routed to the same server, which is essential for specific applications.

4. SSL Offloading: Load balancers can offload the SSL/TLS encryption and decryption process, relieving the backend servers from this computationally intensive task.

5. Scalability: Load balancers allow for easy resource scaling by adding or removing servers dynamically, ensuring optimal performance as demand fluctuates.

Types of Load Balancers

Load balancers come in different types, each catering to specific network architectures and requirements. The most common types include:

1. Hardware Load Balancers: These devices are designed for load balancing. They offer high performance and scalability and often have advanced features.

2. Software Load Balancers: These are software-based load balancers that run on standard server hardware or virtual machines. They provide flexibility and cost-effectiveness while still delivering robust load-balancing capabilities.

3. Cloud Load Balancers: Cloud service providers offer load-balancing solutions as part of their infrastructure services. These load balancers are highly scalable, automatically adapting to changing traffic patterns, and can be easily integrated into cloud environments.

GTM and LTM Load Balancing Options

The Local Traffic Managers (LTM) and Enterprise Load Balancers (ELB) provide load-balancing services between two or more servers/applications in case of a local system failure. Global Traffic Managers (GTM) provide load-balancing services between two or more sites or geographic locations.

Local Traffic Managers, or Load Balancers, are devices or software applications that distribute incoming network traffic across multiple servers, applications, or network resources. They act as intermediaries between users and the servers or resources they are trying to access. By intelligently distributing traffic, LTMs help prevent server overload, minimize downtime, and improve system performance.

GTM Load Balancer

Main GTM Load Balaner Components

GTM Load Balancer

  • The GTM provides load-balancing services between two or more sites or geographic locations

  • GTM Load Balancers work with HTTP, HTTPS, TCP, and UDP protocols.

  • The GTM load balancer offers intelligent Domain Name System (DNS) resolution capability.

  • For security, it can enable DNS security designs and act as the authoritative DNS server or secondary authoritative DNS server web.

GTM and LTM Components

Before diving into the communication between GTM and LTM, let’s understand what each component does.

GTM, or Global Traffic Manager, is a robust DNS-based load-balancing solution that distributes incoming network traffic across multiple servers in different geographical regions. Its primary objective is to ensure high availability, scalability, and optimal performance by directing users to the most suitable server based on various factors such as geographic location, server health, and network conditions.

On the other hand, LTM, or Local Traffic Manager, is responsible for managing network traffic at the application layer. It works within a local data center or a specific geographic region, balancing the load across servers, optimizing performance, and ensuring secure connections.

As mentioned earlier, the most significant difference between the GTM and LTM is traffic doesn’t flow through the GTM to your servers.

  • GTM (Global Traffic Manager )

The GTM load balancer balances traffic between application servers across Data Centers. Using F5’s iQuery protocol for communication with other BIGIP F5 devices, GTM acts as an “Intelligent DNS” server, handling DNS resolutions based on intelligent monitors. The service determines where to resolve traffic requests among multiple data center infrastructures.

  • LTM (Local Traffic Manager)

LTM balances servers and caches, compresses, persists, etc. The LTM network acts as a full reverse proxy, handling client connections. The F5 LTM uses Virtual Services (VSs) and Virtual IPs (VIPs) to configure a load-balancing setup for a service.

LTMs offer two load balancing methods: nPath configuration and Secure Network Address Translation (SNAT). In addition to load balancing, LTM performs caching, compression, persistence, and other functions.

Load Balancing

Global Traffic Manager

Load Balancing Functions

  • The GTM is an intelligent name resolver, intelligently resolving names to IP addresses. The GTM works across data center.

  • Once the GTM provides you with an IP to route to you’re done with the GTM until you ask it to resolve another name for you.

  • Similar to a usual DNS server, the GTM does not provide any port information in its resolution.

Load Balancing

Local Traffic Manager 

Load Balancing Functions

  • The LTM doesn’t do any name resolution and assumes a DNS decision has already been made.

  • When traffic is directed to the LTM traffic flows directly through its’ full proxy architecture to the servers it’s load balancing.

  • Since the LTM is a full proxy it’s easy for it to listen on one port but direct traffic to multiple hosts listening on any port specified.

Communication between GTM and LTM:

BIG-IP Global Traffic Manager (GTM) uses the iQuery protocol to communicate with the local big3d agent and other BIG-IP big3d agents. GTM monitors BIG-IP systems’ availability, the network paths between them, and the local DNS servers attempting to connect to them.

The communication between GTM and LTM occurs in three key stages:

1. Configuration Synchronization:

GTM and LTM communicate to synchronize their configuration settings. This includes exchanging information about the availability of different LTM instances, their capacities, and other relevant parameters. By keeping the configuration settings current, GTM can efficiently make informed decisions on distributing traffic.

2. Health Checks and Monitoring:

GTM continuously monitors the health and availability of the LTM instances by regularly sending health check requests. These health checks ensure that only healthy LTM instances are included in the load-balancing decisions. If an LTM instance becomes unresponsive or experiences issues, GTM automatically removes it from the distribution pool, optimizing the traffic flow.

3. Dynamic Traffic Distribution:

GTM distributes incoming traffic to the most suitable LTM instances based on the configuration settings and real-time health monitoring. This ensures load balancing across multiple servers, prevents overloading, and improves the overall user experience. Additionally, GTM can reroute traffic to alternative LTM instances in case of failures or high traffic volumes, enhancing resilience and minimizing downtime.

  • A key point: TCP Port 4353

LTMs and GTMs can work together or separately. Most organizations that own both modules use them together, and that’s where the real power lies.
They use a proprietary protocol called iQuery to accomplish this.

Through TCP port 4353, iQuery reports VIP availability/performance to GTMs. A GTM can then dynamically resolve VIPs that reside on an LTM. With LTMs as servers in GTM configuration, there is no need to monitor VIPs directly with application monitors since the LTM is doing that, and iQuery reports it back to the GTM.

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  •  iQuery protocol to communicate with the local big3d agent and other BIG-IP big3d agents

  • communication between GTM and LTM occurs in three key stages:

  •  Local Traffic Manager, is responsible for managing network traffic at the application layer

  • Through TCP port 4353, iQuery reports VIP availability/performance to GTMs

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The Role of DNS With Load Balancing

The GTM load balancer offers intelligent Domain Name System (DNS) resolution capability to resolve queries from different sources to different data center locations. It loads and balances DNS queries to existing recursive DNS servers and caches the response or processes the resolution. This does two main things. First, for security, it can enable DNS security designs and act as the authoritative DNS server or secondary authoritative DNS server web. It implements several security services with DNSSEC, allowing it to protect against DNS-based DDoS attacks.

DNS relies on UDP for transport, so you are also subject to UDP control plane attacks and performance issues. DNS load balancing failover can improve performance for load balancing traffic to your data centers. DNS is much more graceful than Anycast and is a lightweight protocol.

gtm load balancer
Diagram: GTM and LTM load balancer. Source: Network Interview

DNS load balancing provides several significant advantages.

Adding a duplicate system may be a simple way to increase your load when you need to process more traffic. If you route multiple low-bandwidth Internet addresses to one server, the server will have a more significant amount of total bandwidth.

DNS load balancing is easy to configure. Adding the additional addresses to your DNS database is as easy as 1-2-3! It doesn’t get any easier than this!

Simple to debug: You can work with DNS using tools such as dig, ping, and nslookup. In addition, BIND includes tools for validating your configuration, and all testing can be conducted via the local loopback adapter.

You will need a DNS server to have a domain name since you have a web-based system. At some point, you will undoubtedly need a DNS server. Your existing platform can be quickly extended with DNS-based load balancing!

Issues with DNS Load Balancing

In addition to its limitations, DNS load balancing also has some advantages.

Dynamic applications suffer from sticky behavior, but static sites rarely experience it. HTTP (and, therefore, the Web) is a stateless protocol. Chronic amnesia prevents it from remembering one request from another. To overcome this, a unique identifier accompanies each request. Identifiers are stored in cookies, but there are other sneaky ways to do this.

Through this unique identifier, your web browser can collect information about your current interaction with the website. Since this data isn’t shared between servers, if a new DNS request is made to determine the IP, there is no guarantee you will return to the server with all of the previously established information.

As mentioned previously, one in two requests may be high-intensity, and one in two may be easy. In the worst-case scenario, all high-intensity requests would go to only one server while all low-intensity requests would go to the other. This is not a very balanced situation, and you should avoid it at all costs lest you ruin the website for half of the visitors.

A fault-tolerant system. DNS load balancers cannot detect when one web server goes down, so they still send traffic to the space left by the downed server. As a result, half of all request

Benefits of GTM Load Balancer:

1. Enhanced Website Performance: By efficiently distributing traffic, GTM Load Balancer helps balance the server load, preventing any single server from being overwhelmed. This leads to improved website performance, faster response times, and reduced latency, resulting in a seamless user experience.

2. Increased Scalability: As online businesses grow, the demand for server resources increases. GTM Load Balancer allows enterprises to scale their infrastructure by adding more servers or data centers. This ensures that the website can handle increasing traffic without compromising performance.

3. Improved Availability and Redundancy: GTM Load Balancer offers high availability by continuously monitoring server health and automatically redirecting traffic away from any server experiencing issues. It can detect server failures and quickly reroute traffic to healthy servers, minimizing downtime and ensuring uninterrupted service.

4. Geolocation-based Routing: Businesses often cater to a diverse audience across different regions in a globalized world. GTM Load Balancer can intelligently route traffic based on the user’s geolocation, directing them to the nearest server or data center. This reduces latency and improves the overall user experience.

5. Traffic Steering: GTM Load Balancer allows businesses to prioritize traffic based on specific criteria. For example, it can direct high-priority traffic to servers with more resources or specific geographic locations. This ensures that critical requests are processed efficiently, meeting the needs of different user segments.

Key Features of GTM Load Balancer:

1. Geographic Load Balancing: GTM Load Balancer uses geolocation-based routing to direct users to the nearest server location. This reduces latency and ensures that users are connected to the server with the lowest network hops, resulting in faster response times.

2. Health Monitoring: The load balancer continuously monitors the health and availability of servers. If a server becomes unresponsive or experiences a high load, GTM Load Balancer automatically redirects traffic to healthy servers, minimizing service disruptions and maintaining high availability.

3. Flexible Load Balancing Algorithms: GTM Load Balancer offers a range of load balancing algorithms, including round-robin, weighted round-robin, and least connections. These algorithms enable businesses to customize the traffic distribution strategy based on their specific needs, ensuring optimal performance for different types of web applications.

Back to Basic: DNS Load Balancing Failover

DNS load balancing is the simplest form of load balancing. As for the actual load balancing, it is somewhat straightforward in how it works. It uses a direct method called round robin to distribute connections over the group of servers it knows for a specific domain. It does this sequentially. This means going first, second, third, etc.). To add DNS load balancing failover to your server, you must add multiple A records for a domain.

dns load balancing failover
Diagram: DNS load balancing. Source Imperva

GTM load balancer and LTM 

DNS load balancing failover

The GTM load balancer and the Local Traffic Manager (LTM) provide load-balancing services towards physically dispersed endpoints. Endpoints are in separate locations but logically grouped in the eyes of the GTM. For data center failover events, DNS is much more graceful than Anycast. With GTM DNS failover, end nodes are restarted (cold move) into secondary data centers with a different IP address.

As long as the DNS FQDN remains the same, new client connections are directed to the restarted hosts in the new data center. The failover is performed with a DNS change, making it a viable option for disaster recovery, disaster avoidance, and data center migration.

On the other hand, stretch clusters and active-active data centers pose a separate set of challenges. In this case, other mechanisms, such as FHRP localization and LISP, are combined with the GTM to influence ingress and egress traffic flows.

 

DNS Namespace Basics

Packets traverse the Internet using numeric IP addresses, not names, to identify communication devices. DNS was developed to map the IP address to a user-friendly name to make numeric IP addresses memorable and user-friendly. Employing memorable names instead of numerical IP addresses dates back to the early 1980s in ARPANET. Localhost files called HOSTS.txt mapped IP to names on all the ARPANET computers. The resolution was local, and any changes were implemented on all computers.

DNS basics
Diagram: DNS Basics. Source is Novell

Example: DNS Structure

This was sufficient for small networks, but with the rapid growth of networking, a hierarchical distributed model known as a DNS namespace was introduced. The database is distributed worldwide on what’s known as DNS nameservers that consist of a DNS structure. It resembles an inverted tree, with branches representing domains, zones, and subzones.

At the very top of the domain is the “root” domain, and then further down, we have Top-Level domains (TLD), such as .com or .net. and Second-Level domains (SLD), such as www.network-insight.net.

The IANA delegates management of the TLD to other organizations such as Verisign for.COM and. NET. Authoritative DNS nameservers exist for each zone. They hold information about the domain tree structure. Essentially, the name server stores the DNS records for that domain.

DNS Tree Structure

You interact with the DNS infrastructure with the process known as RESOLUTION. First, end stations request a DNS to their local DNS (LDNS). If the LDNS supports caching and has a cached response for the query, it will respond to the client’s requests.

DNS caching stores DNS queries for some time, which is specified in the DNS TTL. Caching improves DNS efficiency by reducing DNS traffic on the Internet. If the LDNS doesn’t have a cached response, it will trigger what is known as the recursive resolution process.

Next, the LDNS queries the authoritative DNS server in the “root” zones. These name servers will not have the mapping in their database but will refer the request to the appropriate TLD. The process continues, and the LDNS queries the authoritative DNS in the appropriate.COM .NET or. ORG zones. The method has many steps and is called “walking a tree.” However, it is based on a quick transport protocol (UDP) and takes only a few milliseconds.

 

DNS Load Balancing Failover Key Components

DNS TTL

Once the LDNS gets a positive result, it caches the response for some time, referenced by the DNS TTL. The DNS TTL setting is specified in the DNS response by the authoritative nameserver for that domain. Previously, an older and common TTL value for DNS was 86400 seconds (24 hours).

This meant that if there were a change of record on the DNS authoritative server, the DNS servers around the globe would not register that change for the TTL value of 86400 seconds.

This was later changed to 5 minutes for more accurate DNS results. Unfortunately, TTL in some end hosts’ browsers is 30 minutes, so if there is a failover data center event and traffic needs to move from DC1 to DC2, some ingress traffic will take time to switch to the other DC, causing long tails. 

DNS TTL
Diagram: DNS TTL. Source is Varonis

DNS pinning and DNS cache poisoning

Web browsers implement a security mechanism known as DNS pinning, where they refuse to take low TTL as there are many security concerns with low TTL settings, such as cache poisoning. Every time you read from the DNS namespace, there is potential DNS cache poisoning and a DNS reflection attack.

Because of this, all browser companies ignored low TTL and implemented their aging mechanism, which is about 10 minutes.

In addition, there are embedded applications that carry out a DNS lookup only once when you start the application, for example, a Facebook client on your phone. During data center failover events, this may cause a very long tail, and some sessions may time out.

DNS Packet Capture1

GTM Load Balancer and GTM Listeners

The first step is to configure GTM Listeners. A listener is a DNS object that processes DNS queries. It is configured with an IP address and listens to traffic destined to that address on port 53, the standard DNS port. It can respond to DNS queries with accelerated DNS resolution or GTM intelligent DNS resolution.

GTM intelligent Resolution is also known as Global Server Load Balancing (GSLB) and is just one of the ways you can get GTM to resolve DNS queries. It monitors a lot of conditions to determine the best response.

The GTM monitors LTM and other GTMs with a proprietary protocol called IQUERY. IQUERY is configured with the bigip_add utility. It’s a script that exchanges SSL certificates with remote BIG-IP systems. Both systems must be configured to allow port 22 on their respective self-IPs.

The GTM allows you to group virtual servers, one from each data center, into a pool. These pools are then grouped into a larger object known as a Wide IP, which maps the FQDN to a set of virtual servers. The Wide IP may contain Wild cards.

F5 GTM

Load Balancing Methods

When the GTM receives a DNS query that matches the Wide IP, it selects the virtual server and sends back the response. Several load balancing methods (Static and Dynamic) are used to select the pool; the default is round-robin. Static load balancing includes round-robin, ratio, global availability, static persists, drop packets, topology, fallback IP, and return to DNS.

Dynamic load balancing includes round trip time, completion time, hops, least connections, packet rate, QoS, and kilobytes per second. Both methods involve predefined configurations, but dynamic considers real-time events.

For example, topology load balancing allows you to select a DNS query response based on geolocation information. Queries are resolved based on the resource’s physical proximity, such as LDNS country, continent, or user-defined fields. It uses an IP geolocation database to help make the decisions. It helps service users with correct weather and news based on location. All this configuration is carried out with Topology Records (TR).

 Anycast and GTM DNS for DC failover

Anycast means you advertise the same address from multiple locations. It is a viable option when data centers are geographically far apart. Anycast solves the DNS problem, but we also have a routing plane to consider. Getting people to another DC with Anycast can take time and effort.

It’s hard to get someone to go to data center A when the routing table says go to data center B. The best approach is to change the actual routing. As a failover mechanism, Anycast is not as graceful as DNS migration with F5 GTM.

Generally, if session disruption is a viable option, go for Anycast. Web applications would be OK with some session disruption. HTTP is stateless, and it will just resend. However, other types of applications might not be so tolerant. If session disruption is not an option and graceful shutdown is needed, you must use DNS-based load balancing. Remember that you will always have long tails due to DNS pinning in browsers, and eventually, some sessions will be disrupted.

 Scale-Out Applications

The best approach is to do a fantastic scale-out application architecture. Begin with parallel application stacks in both data centers and implement global load balancing based on DNS. Start migrating users to the other data center, and when you move all the other users, you can shut down the instance in the first data center. It is much cleaner and safer to do COLD migrations. Live migrations and HOT moves (keep sessions intact) are challenging over Layer 2 links.

You need a different IP address. You don’t want to have stretched VLANs across data centers. It’s much easier to make a COLD move, change the IP, and then use DNS. The load balancer config can be synchronized to vCenter, so the load balancer definitions are updated based on vCenter VM groups.

Another reason for failures in data centers during scale-outs could be the lack of airtight sealing, otherwise known as hermetic sealing. Not having an efficient seal brings semiconductors in contact with water vapor and other harmful gases in the atmosphere. As a result, ignitors, sensors, circuits, transistors, microchips, and much more don’t get the protection they require to function correctly.

Data and Database Challenges.

The main challenge with active-active data centers and failover events is with your actual DATA and Databases. If data center A fails, how accurate will your data be? You cannot afford to lose any data if you are running a transaction database.

Resilience is achieved by storage or database-level replication that employs log shipping or distribution between two data centers with a two-phase commit. Log shipping has an RPO of non-zero, as transactions could happen a minute before. A two-phase commit synchronizes multiple copies of the database but can slow down due to latency.

GTM Load Balancer is a robust solution for optimizing website performance and ensuring high availability. With its advanced features and intelligent traffic routing capabilities, businesses can enhance their online presence, improve user experience, and handle growing traffic demands. By leveraging the power of GTM Load Balancer, online companies can stay competitive in today’s fast-paced digital landscape.

Efficient communication between GTM and LTM is essential for businesses to optimize network traffic management. By collaborating seamlessly, GTM and LTM provide enhanced performance, scalability, and high availability, ensuring a seamless experience for end-users. Leveraging this powerful duo, businesses can deliver their services reliably and efficiently, meeting the demands of today’s digital landscape.

Summary: GTM Load Balancer

GTM Load Balancer is a sophisticated traffic management solution that distributes incoming user requests across multiple servers or data centers. Its primary purpose is to optimize resource utilization and enhance the user experience by intelligently directing traffic to the most suitable backend server based on predefined criteria.

Key Features and Functionality

GTM Load Balancer offers a wide range of features that make it a powerful tool for traffic management. Some of its notable functionalities include:

1. Health Monitoring: GTM Load Balancer continuously monitors the health and availability of backend servers, ensuring that only healthy servers receive traffic.

2. Load Distribution Algorithms: It employs various load distribution algorithms, such as Round Robin, Least Connections, and IP Hashing, to intelligently distribute traffic based on different factors like server capacity, response time, or geographical location.

3. Geographical Load Balancing: With geolocation-based load balancing, GTM can direct users to the nearest server based on location, reducing latency and improving performance.

4. Failover and Redundancy: In case of server failure, GTM Load Balancer automatically redirects traffic to other healthy servers, ensuring high availability and minimizing downtime.

Implementation Best Practices

Implementing a GTM Load Balancer requires careful planning and configuration. Here are some best practices to consider:

1. Define Traffic Distribution Criteria: Clearly define the criteria to distribute traffic, such as server capacity, geographical location, or any specific business requirements.

2. Set Up Health Monitors: Configure health monitors to regularly check the status and availability of backend servers. This helps in avoiding directing traffic to unhealthy or overloaded servers.

3. Fine-tune Load Balancing Algorithms: Based on your specific requirements, fine-tune the load balancing algorithms to achieve optimal traffic distribution and server utilization.

4. Regularly Monitor and Evaluate: Continuously monitor the performance and effectiveness of the GTM Load Balancer, making necessary adjustments as your traffic patterns and server infrastructure evolve.

Conclusion: In a world where online presence is critical for businesses, ensuring seamless traffic distribution and optimal performance is a top priority. GTM Load Balancer is a powerful solution that offers advanced functionalities, intelligent load distribution, and enhanced availability. By effectively implementing GTM Load Balancer and following best practices, businesses can achieve a robust and scalable infrastructure that delivers an exceptional user experience, ultimately driving success in today’s digital landscape.

rsz_load_balancing_

Full Proxy

Full Proxy

In the vast realm of computer networks, the concept of full proxy stands tall as a powerful tool that enhances security and optimizes performance. Understanding its intricacies and potential benefits can empower network administrators and users alike. In this blog post, we will delve into the world of full proxy, exploring its key features, advantages, and real-world applications.

Full proxy is a network architecture approach that involves intercepting and processing all network traffic between clients and servers. Unlike other methods that only handle specific protocols or applications, full proxy examines and analyzes every packet passing through, regardless of the protocol or application used. This comprehensive inspection allows for enhanced security measures and advanced traffic management capabilities.

a) Enhanced Security: By inspecting each packet, full proxy enables deep content inspection, allowing for the detection and prevention of various threats, such as malware, viruses, and intrusion attempts. It acts as a robust barrier safeguarding the network from potential vulnerabilities.

b) Advanced Traffic Management: Full proxy provides granular control over network traffic, allowing administrators to prioritize, shape, and optimize data flows. This capability enhances network performance by ensuring critical applications receive the necessary bandwidth while mitigating bottlenecks and congestion.

c) Application Layer Filtering: Full proxy possesses the ability to filter traffic at the application layer, enabling fine-grained control over the types of content that can pass through the network. This feature is particularly useful in environments where specific protocols or applications need to be regulated or restricted.

a) Enterprise Networks: Full proxy finds extensive use in large-scale enterprise networks, where security and performance are paramount. It enables organizations to establish robust defenses against cyber threats while optimizing the flow of data across their infrastructures.

b) Web Filtering and Content Control: Educational institutions and public networks often leverage full proxy solutions to implement web filtering and content control measures. By examining the content of web pages and applications, full proxy allows administrators to enforce policies and ensure compliance with acceptable usage guidelines.

In conclusion, full proxy represents a powerful network architecture approach that offers enhanced security measures, advanced traffic management capabilities, and application layer filtering. Its real-world applications span across enterprise networks, educational institutions, and public environments. Embracing full proxy can empower organizations and individuals to establish resilient network infrastructures while fostering a safer and more efficient digital environment.

Highlights: Full Proxy

Full Proxy Mode

A full proxy mode is a proxy server that acts as an intermediary between a user and a destination server. The proxy server acts as a gateway between the user and the destination server, handling all requests and responses on behalf of the user. A full proxy mode aims to provide users with added security, privacy, and performance by relaying traffic between two or more locations.

In full proxy mode, the proxy server takes on the client role, initiating requests and receiving responses from the destination server. All requests are made on behalf of the user, and the proxy server handles the entire process and provides the user with the response. This provides the user with an added layer of security, as the proxy server can authenticate the user before allowing them access to the destination server.

Increase in Privacy

The full proxy mode also increases privacy, as the proxy server is the only point of contact between the user and the destination server. All requests sent from the user are relayed through the proxy server, ensuring that the user’s identity remains hidden. Additionally, the full proxy mode can improve performance by caching commonly requested content, reducing lag times, and improving the user experience.

Related: Before you proceed, you may find the following helpful information

  1. Load Balancer Scaling
  2. TCP IP Optimizer
  3. Kubernetes Networking 101
  4. Nested Hypervisors
  5. Routing Control
  6. CASB Tools



LTM Load Balancer.

Key Full Proxy Discussion Points:


  • Introduction to load balancing with the LTM load balancer.

  • Discussion on full proxy vs half proxy.

  • Discussion on the full proxy architecture and the components involved.

  • BIG-IP traffic processing.

  • Source Address Translation (SNAT).

  • A final note load balancing and health monitoring.

 

Back to Basics: What is a proxy server

The term ‘Proxy’ is a contraction from the middle English word procuracy, a legal term meaning to act on behalf of another. For example, you may have heard of a proxy vote. You submit your choice, and someone else votes the ballot on your behalf. In networking and web traffic, a proxy is a device or server that acts on behalf of other devices. It sits between two entities and performs a service. Proxies are hardware or software solutions that sit between the client and the server and do something to request and sometimes respond.

A proxy server sits between the client requesting a web document and the target server. A proxy server facilitates communication between the sending client and the receiving target server in its most straightforward form without modifying requests or replies.

When a client initiates a request for a resource from the target server, a webpage, or a document, the proxy server hijacks our connection. It represents itself as a client to the target server, requesting the resource on our behalf. If a reply is received, the proxy server returns it to us, giving a feeling that we have communicated with the target server.

Example product: Local Traffic Manager

Local Traffic Manager (LTM) is part of a suite of BIG-IP products that adds intelligence to connections by intercepting, analyzing, and redirecting traffic. Its architecture is based on full proxy mode, meaning the LTM load balancer completely understands the connection, enabling it to be an endpoint and originator of client and server-side connections.

All kinds of full or standard proxies act as a gateway from one network to another. They sit between two entities and mediate connections. The difference in F5 full proxy architecture becomes apparent with their distinctions in flow handling. So the main difference in the full proxy vs. half proxy debate is how connections are handled.

  • Enhancing Web Performance:

One of the critical advantages of Full Proxy is its ability to enhance web performance. By employing techniques like caching and compression, Full Proxy servers can significantly reduce the load on origin servers and improve the overall response time for clients. Caching frequently accessed content at the proxy level reduces latency and bandwidth consumption, resulting in a faster and more efficient web experience.

  • Load Balancing:

Full Proxy also provides load balancing capabilities, distributing incoming requests across multiple servers to ensure optimal resource utilization. By intelligently distributing the load, Full Proxy helps prevent server overload, improving scalability and reliability. This is especially crucial for high-traffic websites or applications with many concurrent users.

  • Security and Protection:

In the age of increasing cyber threats, Full Proxy plays a vital role in safeguarding sensitive data and protecting web applications. Acting as a gatekeeper, Full Proxy can inspect, filter, and block malicious traffic, protecting servers from distributed denial-of-service (DDoS) attacks, SQL injections, and other standard web vulnerabilities. Additionally, Full Proxy can enforce SSL encryption, ensuring secure data transmission between clients and servers.

  • Granular Control and Flexibility:

Full Proxy offers organizations granular control over web traffic, allowing them to define access policies and implement content filtering rules. This enables administrators to regulate access to specific websites, control bandwidth usage, and monitor user activity. By providing a centralized control point, Full Proxy empowers organizations to enforce security measures and maintain compliance with data protection regulations.

Full proxy vs half proxy

When considering full proxy vs half proxy. The half-proxy sets up a call, and the client and server do their thing. Half-proxies are known to be suitable for Direct Server Return (DSR). You’ll have the initial setup for streaming protocols, but instead of going through the proxy for the rest of the connections, the server will bypass the proxy and go straight to the client.

This is so you don’t waste resources on the proxy for something that can be done directly from server to client. A full proxy, on the other hand, handles all the traffic. A full proxy creates a client connection and a separate server connection with a little gap in the middle.

Full proxy vs half proxy
Diagram: Full proxy vs half proxy. The source is F5.

The full proxy intelligence is in that OSI Gap. With a half-proxy, it is primarily client-side traffic on the way in during a request and then does what it needs…with a full proxy, you can manipulate, inspect, drop, and do what you need to the traffic on both sides and in both directions. Whether a request or response, you can manipulate traffic on the client-side request, the server-side request, the server-side response or the client-side response. So you get a lot more power with a full proxy than you would with a half proxy.

Highlighting F5 full proxy architecture

Full proxy architecture offers much more granularity than a half proxy ( full proxy vs half proxy )  by implementing dual network stacks for client and server connections and creating two separate entities with two different session tables – one on the client side and another on the server side. The BIG-IP LTM load balancer manages the two sessions independently.

The connections between the client and the LTM are different and independent of the connections between the LTM and the backend server. You will notice this from the diagram below. Again, there is a client-side connection and a server-side connection.  The result is that each connection has its TCP behaviors and optimizations.

Different profiles for different types of clients

Generally, client connections have longer paths to take and are exposed to higher latency levels than server-side connections. It’s more than likely that the majority of client connections will experience higher latency. A full proxy addresses these challenges by implementing different profiles and properties to server and client connections and allowing more advanced traffic management. Traffic flow through a standard proxy is end-to-end; usually, the proxy cannot simultaneously optimize for both connections.

full proxy vs half proxy
Diagram: Full proxy architecture with different load-balancing profiles.

F5 full proxy architecture: Default BIP-IP traffic processing

Clients send a request to the Virtual IP address that represents backend pool members. Once a load-balancing decision is made, a second connection is opened to the pool member. We now have two connections, one for the client and the server. The source IP address is still that of the original sending client, but the destination IP address changes to the pool member, which is known as destination-based NAT. The response is the reverse.

The source address is the pool member and the original client’s destination. This process requires that all traffic passes through the LTM, enabling these requests to be undone. The source address is translated from the pool member to the Virtual Server IP address.

Response traffic must flow back through the LTM load balancer to ensure the translation can be undone. For this to happen, servers (pool members) use LTM as their Default Gateway. Any off-net traffic flows through the LTM. What happens if requests come through the BIG-IP, but the response goes through a different default gateway?

  • A key point: Source address translation (SNAT)

The source address will be the responding pool member, but the sending client does not have a connection with the pool member; it has a connection to the VIP located on the LTM. In addition to doing destination address translation, the LTM can do Source address translation (SNAT). This forces the response back to the LTM, and the transitions are undone. It is expected to use the Auto Map Source Address Selection feature- the BIG-IP selects one of its “IP” addresses as the IP for the SNAT.

 

F5 full proxy architecture and virtual server types

Virtual servers have independent packet handling techniques that vary by virtual server type. The following are examples of some of the available virtual servers. Standard virtual server with Layer 7 functionality, Performance Layer 4 Virtual Server, Performance HTTP virtual server, Forwarding Layer 2 virtual server, Forwarding IP virtual server, Reject virtual server, Stateless, DHCP Relay, Message Routing. The example below displays the TCP connection setup for a Virtual server with Layer 7 functionality.

full proxy vs half proxy
Diagram: Load balancing operations.

Stage

Details of Stage

Load Balancing Step 1

The client sends an SYN request to LTM Virtual Server

Load Balancing Step 2

LTM sends back an SYN-ACK TCP segment

Load Balancing Step 3

The client responds with an ACK to acknowledge receiving the SYN-ACK

Load Balancing Step 4

The client sends an HTTP GET request to the LTM

Load Balancing Step 5

The LTM sends ACK to acknowledge receiving the GET request

Load Balancing Step 6

The LTM sends an SYN request to the pool member

Load Balancing Step 7

The pool member sends an SYN-ACK to the LTM

Load Balancing Step 8

LTM sends an ACK packet to acknowledge receiving the SYN-ACK
 

LMT forwards the HTTP GET requests to the Pool member

When the client-to-LTM handshake is complete, it waits for the initial HTTP request (HTTP_GET) before making a load-balancing decision. Then, it does a full TCP session with the pool member, but this time, the LTM is the client in the TCP session. For the client connection, the LTM was the server. The BIG-IP waits for the initial traffic flow to set up the load balancing to mitigate against DoS attacks and preserve resources.

As discussed, all virtual servers have different packet-handling techniques. For example, clients send initial SYN to the LTM with the performance virtual server. The LTM system makes the load-balancing decision and passes the SYN request to the pool member without completing the full TCP handshake.

 

Load balancing and health monitoring

The client requests the destination IP address in the IPv4 or IPv6 header. However, this destination IP address could get overwhelmed by large requests. Therefore, the LTM distributes client requests (based on a load balancing method) to multiple servers instead of to the single specified destination IP address. The load balancing method determines the pattern or metric used to distribute traffic.

These methods are categorized as either Static or Dynamic. Dynamic load balancing considers real-time events and includes least connections, fastest, observed, predictive, etc. Static load balancing includes both round-robin and ratio-based systems. Round-robin-based load balancing works well if servers are equal (homogeneous), but what if you have nonhomogeneous servers? 

Ratio load balancing 

In this case, Ratio load balancing can distribute traffic unevenly based on predefined ratios. For example, Ratio 3 is assigned to servers 1 and 2, and Ratio 1 is assigned to servers 3. This configuration results in that for every 1 packet assigned to server 3, both servers 1 and 2 will get 3. Initially, it starts with a round-robin, but subsequent flows are differentiated based on the ratios.

A feature known as priority-based member activation allows you to configure pool members into priority groups. High priority gets more traffic. For example, you group the two high-spec servers (server 1 and server 2) in a high-priority group and a low-spec server (server 3) in a low-priority group. The old server will not be used unless there is a failure in priority group 1.

F5 full proxy architecture: Health and performance monitors

Health and performance monitors are associated with a pool to determine if servers are operational and can receive traffic. The type of health monitor used depends on the type of traffic you want to monitor. There are several predefined monitors, and you can customize your own. For example, LTM attempts FTP to download a specified file to the /var/tmp directory, and the check is successful if the file is retrieved.

Some HTTP monitors permit the inclusion of a username and password to retrieve a page on the website. You also have LDAP, MYSQL, ICMP, HTTPS, NTP, Oracle, POP3, Radius, RPC, and many others. iRules allows you to manage traffic based on business logic. For example, you can direct customers to the correct server based on language preference in their browsers. An iRule can be the trigger to inspect this header (accept language) and select the right pool of application servers based on the value specified in the header.

 

Increase backend server performance.

It’sIt’says computationally more exhausting to set up a new connection rather than receive requests over an existing OPEN connection. That’s HTTP keepalives invented and made standard in HTTP v1. LTM has a feature known as “One connect” that leverages HTTP keepalives to reuse connections for multiple clients, not just a single client. It works with HTTP keepalives to make existing connections available for other clients, not just a single client. Fewer open connection means lower resource consumption per server.

When the LTM receives the HTTP request from the client, it makes the load-balancing decision before the “One connect” is considered. If there are no OPEN or IDLE server-side connections, the BIP-IP creates a new TCP connection to the server. When the server responds with the HTTP response, the connection is left open on the BIP-IP for reuse. The connection is held in a table buffer called the connection reuse pool.

New requests from other clients can reuse the OPEN IDLE connection, not needing to set up a new TCP connection. The source mask on the OC profile determines which clients can reuse open and idle server-side connections. Using SNAT, the source address is translated before applying the OC profile.

Summary: Full Proxy

In today’s digital age, connectivity is the lifeblood of our society. The Internet has become an indispensable tool for communication, information sharing, and business transactions. However, numerous barriers still hinder universal access to the vast realm of online resources. One promising solution that has emerged in recent years is the concept of fully proxy networks. In this blog post, we delved into the world of fully proxy networks, exploring their potential to revolutionize internet accessibility.

Section 1: Understanding Fully Proxy Networks

Fully proxy networks, also known as reverse proxy networks, are innovative systems designed to enhance internet accessibility for users. Unlike traditional networks that rely on direct connections between users and online resources, fully proxy networks act as intermediaries between the user and the internet. They intercept requests from users and fetch the requested content on their behalf, optimizing the delivery process and bypassing potential obstacles.

Section 2: Overcoming Geographical Restrictions

One of the primary benefits of fully proxy networks is their ability to overcome geographical restrictions imposed by content providers. With these networks, users can access websites and online services that are typically inaccessible due to regional limitations. By routing traffic through proxy servers located in different regions, fully proxy networks enable users to bypass geo-blocking and enjoy unrestricted access to online content.

Section 3: Enhanced Security and Privacy

Another significant advantage of fully proxy networks lies in their ability to enhance security and privacy. By acting as intermediaries, these networks add an extra layer of protection between users and online resources. The proxy servers can mask users’ IP addresses, making it more challenging for malicious actors to track their online activities. Additionally, fully proxy networks can encrypt data transmissions, safeguarding sensitive information from potential threats.

Section 4: Accelerating Internet Performance

In addition to improving accessibility and security, fully proxy networks can significantly enhance internet performance. By caching and optimizing content delivery, these networks can reduce latency and speed up web page loading times. Users can experience faster and more responsive browsing experiences, especially for frequently accessed websites. Moreover, fully proxy networks can alleviate bandwidth constraints during peak usage periods, ensuring a seamless online experience for users.

Conclusion:

Fully proxy networks offer a promising solution to the challenges of internet accessibility. By bypassing geographical restrictions, enhancing security and privacy, and accelerating internet performance, these networks can unlock a new era of online accessibility for users worldwide. As technology continues to evolve, fully proxy networks are poised to play a crucial role in bridging the digital divide and creating a more inclusive internet landscape.