rtical platforms. The second issue was upgradeability. Often times when a new standard was created it was impossible to implement this new capability on exist- ing already-deployed hardware and the new standard required hardware forklifts. The third issue was ambiguity. Despite best efforts by the standards committees, full interoperability has always been a difficult goal that is only achieved after multiple rounds of pairwise testing and bug fixes. This pairwise integration resulted in significant testing cost and lost time to network operators. While the core network supports multiple services with a common pool of packet capacity, edge routers and switches generally supported one or two services per platform driven in large part by fundamental limits of vertically integrated packet edge platforms. In practice, network edge platforms are limited or constrained in four dimensions: port-constrained is the number of physical ports facing access and the customer on the limited real estate of a chassis line card system; logical-constrained pertains to the size of tables that are constrained by memory size; CPU-constrained for processing signaling messages and basic router functions, and network pipeline; and throughput-constrained maximum Gigabits per second. For edge routers port, logical, and CPU constraints typically surface long in advance of pipeline throughput constraints. As a result, strategies such as using Ethernet multiplexing with low-cost Ethernet switches in front of the network edge plat- form to overcome port constraints and aggregation routers to combine traffic from multiple network edge routers to increase utilization prior to long-distance transport become necessary (Figure 12.2). In addition, strategies of periodic fork-lifting CPU router cards and entire routers when memory limits are hit were a necessary evil that network operators had to manage. Frequently, routers had lowest common denominator issues where a new card may have new silicon, software, and features but if there was an older gen