ology. They make this decision because of cost. MPLS has been aggressively sold by the major carriers in the past few years, making it more attractive than its rival technologies. While MPLS used to be a specialty service reserved for those willing to pay for it, the major providers have made it mainstream through competitive pricing. I did a 300-node MPLS migration for a company that had reached the end of its Frame Relay contract. The price quoted for full T1 service to each location with dual OC3s at the head end was significantly less than the fractional T1 Frame Relay network with DS3s at the head end. The company got faster connections at every site for a significant reduction in cost-who wouldn't take that deal? The challenge was getting the new WAN integrated with the existing network. MPLS uses a significantly different method of logical connectivity than Frame Relay, and mi- grating can be a challenge. Frame Relay works on the fundamental principal of virtual circuits. With 300 locations connecting to one of two headquarters buildings, we had 300 virtual circuits to manage and maintain between two routers. Figure 24-1 shows the design as it was when it incorporated Frame Relay. This design worked fine, but there were some pretty significant limitations. For exam- ple, should HQ-1 fail, the branches connected to it would be offline, since there was no dynamic failover to HQ-2. While each branch could have been connected to both HQ offices, this would require another Frame Relay PVC to be built at significant ad- ditional cost. Instead, loss of potentially one-half of the branches was considered to be an acceptable risk given the cost of full redundancy. ISDN lines were used as emergency backup links, which introduced more problems since ISDN usage was (and is) ex- tremely expensive. This solution was designed before broadband was widely available, though, SO we had to work with the cards we were dealt. MPLS would allow us some significant improvements, not the least of which was an increase in speed. Per