Despite these shortcomings, non PBT/PBB enabled Ethernet-based MANs are used for two primary purposes: For small scale deployments (under a few hundred customers), a pure Ethernet MAN can be highly cost-effective. It also has the advantage of not requiring advanced knowledge of IP and related protocols, such as BGP and MPLS, which are necessary for an MPLS-based deployment.
Even for larger scale deployments for thousands and thousands of customers can be achieved if careful network design rules are followed. In order to do this effectively skilled networking professionals need to be utilized.
In large scale Metro Ethernets, it is common for the access part of the network to use a pure layer 2 design. At this level, the pure layer 2 design is deemed to be cheaper while still operating under its design limitations. From the distribution layer and above, traffic is aggregated and routed using an MPLS-based Metro Ethernet design. In very large networks MPLS may be unavoidable, but with careful network design, the use of both PBT and MPLS and their associated cost and complexity can be postponed if not eliminated entirely by careful network planning and design.
December 16, 2011