Antonio's link gives lots of in-depth information. You probably need to start by mapping out the priority for all regions, with APAC and Aus being special cases, and then work from there.
If readers would like a simpler document to start lerning about GLB, then this doc may be helpful:
http://www.brocade.com/en/backend-content/pdf-page.html?/content/dam/common/documents/content-types/whitepaper/brocade-virtual-traffic-manager-global-load-balancing-wp.pdf
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