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How GSLB works?
Lets say, I have a GSLB for www.test.com and my Load Balancers are running on different Data Centers. So, the requests are routed to the corresponding Load Balancers based on the proximity.

Does GSLB has IP as such?

In general, when we hit an address in the browser, it goes to DNS to get IP address and establish connection.

  1. Check browser cache
  2. Check System cache
  3. Router cache
  4. ISP cache
  5. Root Domain Name Server
  6. Sub Domain Name Server
  7. 2nd Level domain Name Server
  8. Get IP - It returns list of IPs if there is more than one for a domain
  9. Browser connect with one of the IP from the list( Mostly with the 1st IP from the list )

But, with GSLB, How the flow works? If it caches, what if the cached Load Balancer becomes slow and How does it route to other Load Balancer?

Where does the GSLB sit in the flow?

user1578872
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1 Answers1

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TL;DR; Client request is routed through the GSLB appliances. The GLSB appliances use the DNS infrastructure to connect the client to the data center that best meets the criteria set. This is enabled by MEP (Metric Exchange Protocol) that allows the load balancers to exchange data.

From the Citrix Netscaler documentation:

When you configure GSLB on NetScaler appliances and enable Metric Exchange Protocol (MEP), the appliances use the DNS infrastructure to connect the client to the data center that best meets the criteria that you set. The criteria can designate the least loaded data center, the closest data center, the data center that responds most quickly to requests from the client’s location, a combination of those metrics, and SNMP metrics. An appliance keeps track of the location, performance, load, and availability of each data center and uses these factors to select the data center to which to send a client request.

From Cloudflare - GSLB Explained:

How does GSLB reduce latency? Even before an origin server overloads and stops fulfilling requests, high amounts of traffic to that server can still cause significant latency issues. A GSLB system can distribute that traffic among several different locations, ensuring that no single location is handling so many requests that it causes delay.

Additionally GSLB can greatly reduce the travel time of requests and responses between users and servers.

References:

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