The concept of sites is central to NetScaler GSLB implementations. Unless otherwise specified, sites form a peering relationship among themselves. This peering relationship is used to exchange health information and then used to distribute load based on the selected algorithm.  There are many situations in which the peering relationship is not desirable among all GSLB sites primarily because of hierarchical nature of design. Reasons for not having all-peering implementation could be: 

  1. Need to clearly separate GSLB sites (sites that participate in resolving DNS queries) from Traffic Management sites (sites that only manage the application traffic)
  2. To reduce the volume of MEP traffic as the MEP traffic increases exponentially with increasing number of sites
  3. Hierarchical nature of network design
  4. To increase the number of sites that can be part of GSLB deployment

This can be achieved using the concept of parent and child sites in GSLB.  Using the parent-child relationship a 2 level hierarchical GSLB design can be built with the following characteristics: 

  1. At top level, there are parent sites that form peering relationship with other parents
  2. Each parent can have multiple children – each child can have only one parent
  3. Each parent site exchanges health information, including its children, with other parent sites
  4. A child only communicates with its parent – there is only one MEP connection

 This setup facilitates the formation of a hierarchical setup yet maintaining the effectiveness of underlying GSLB implementation. Sites are aware of complete topology and can take effective load distribution decisions based on the selected LB algorithm.  A design based on parent child hierarchy not only can lead to reduced MEP traffic but also a scalable design that is easy to manage.

A sample configuration:

# Parent Sites

  • add gslb site1 IP1
  • add gslb site2 IP2
  • add gslb site3 IP3

 # Child Sites

  • add gslb site-4 IP4 -parentSite Site-2
  • add gslb site-5 IP5 -parentSite Site-2
  • add gslb site-6 IP6 -parentSite Site-3