2013 Nov 29
For a long time, all but the most security-obsessive companies trusted their telecommunications carriers.
If you have two data centres, say, one in New York and another in California, you likely need significant reliable connectivity between the two to transfer data, administrative maintenance, backups and other purposes. While minor traffic can go over the Internet, protected by a Virtual Private Network (VPN), for reliable connections you use a dedicated backhaul link, perhaps an older carrier-provided T1 or MPLS.