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Global load balancer concepts

Global load balancer concepts

This document contains some concepts and definitions related to the global load balancer and how it affects your IBM Cloud® Internet Services deployment.

Global load balancer

A global load balancer manages traffic across server resources located in multiple regions. The origin server can serve up all of the content for a website, provided that the web traffic does not extend beyond the server's processing capabilities and latency is not a primary concern. A global load balancer manages a pool implementation that allows for the traffic to be distributed to multiple origins. This pool capability provides many benefits including:

  • Minimizes response time
  • Creates higher availability through redundancy
  • Maximizes traffic throughput

A global load balancer routes traffic to the pool with the highest priority, distributing the load among its origin servers. See the following Pool section for how traffic is distributed within a pool. If the primary pool becomes unavailable, traffic is routed automatically to the next pool in the list based on priority.

If pools are set up for specific regions, traffic from those regions is sent to the pools for the specified region first. Traffic falls back to the default pools only when all pools for a given region are down. In this case the fallback pool is the pool with the lowest priority.

How it works

When a global load balancer is created, a DNS record is automatically added for it with the name of the load balancer. The load balancer then returns one of the origin IP addresses to a client making a DNS request.

For example, an origin pool is created with two origins identifying IP addresses and If a global load balancer is created with the name using the origin pool, then a client on the internet can execute the command:

$ ping
PING ( 56 data bytes

In this example, CIS:

  • Created a DNS record named
  • Used the global load balancer to resolve the DNS name to one of the IP addresses identified in the origin pool.

Notice that the global load balancer does not terminate the TCP connection.

Setting a DNS element or global load balancer to proxy changes the behavior. If, for example, you turn on proxy and Security > TLS > Mode to something besides Off, the CIS now terminates the TCP connection and establishes a second connection between CIS and the originator.

In this example, CIS:

  • Created a DNS record named:
  • Used the global load balancer to resolve the DNS name to a CIS provided IP address.

Now, connections to are terminated by CIS, and HTTPS certificates are hosted by CIS (which is required for TCP termination).

After the client connects to the application the picture looks like this:

[client]<--tls-->[cis]<-->[origin server]