TCP/IP for z/OS HA. Sysplex Distributor vs External Balancer

Load balancing based on TCP connections distribution is one of the best solutions that we can find for improving response time and application availability. A set of application instances, running on different operating systems, can respond to client requests previously redirected by a load balancer element in accordance with a  specific criteria.
Application instances can run on operating systems without any relation between them, or can run in a specific environment where the relative performance of theoperating system, with regard to other operating systems, is known, or even in a  specific environment where the performance of the instances with regard to the restof the instances is also known.

Working with Sysplex, internal and external balancers can be used. Sysplex Distributor is the internal balancer included in IBM Communications Server for z/OS, it isimplemented in z/OS TCP/IP stack and it distributes connections to whatever target  node of the Sysplex. Sysplex outdoors, several load balancing solutions can be found, some of them work with Sysplex in a coordinated way, receiving updated information about the workload state of the application instances, so load balancing decision will be taken under the most accurate criteria: the performance state of the instance with  regard to the rest of the same application instances.