Global Site Load Balancing Services: To accelerate the disaster recovery service and the dynamic distribution of the workload between the primary and secondary data centers, Cisco provides different network services to optimize the access and the distribution of the user traffic to the remote sites using a Global Site Load Balancing (GSLB) solution. This global GSLB solution for traditional Layer 3 interconnection between sites relies on three major technologies:
Intelligent Domain Name System: An intelligent Domain Name System (DNS) known as the Global Site Selector (GSS) redirects the requests from end-users to the physical location where the application is active and fewer network resources are consumed. In addition, the GSS can be used to distribute traffic across multiple active sites, either in collaboration with the local services of a server load balancing (SLB) application. For example, a Cisco Application Control Engine (ACE) is deployed on each data center to inform the GSS of the health of the service it offers, or based on the load of the network, or in collaboration with the existing WAN edge routers in the data center (e.g. redirection based on physical distances between the user and the application3), just to name the most common functions. Hence the user traffic is distributed accordingly across the routed WAN.
HTTP Traffic Redirection Between Sites: In case of insufficient resources, the local SLB device will return an HTTP redirection message type (HTTP status code 3xx) to the end-user so that the web browser of the client can be automatically and transparently redirected to the elected backup data center where resources and information are available.
Route Health Injection: Route Health Injection (RHI) provides a real-time, very granular distribution of user traffic across multiple sites based on application availability. This method is initiated by an SLB device that will inform the upward router about the presence or absence of selected applications based on extremely accurate information. This information is usually related to the status of the services that it supports. Therefore, the redirection of the user request to a remote site occurs in real time.