ntral offices that are located close to customers. For remote countries in which carriers have a switch, large carriers including Verizon and AT&T have agreements with local providers. These agreements specify the type of circuit (local access line) from the customer to the local provider's network and at what price the local provider will lay cabling from the distant office to the MPLS carrier's switch. MPLS carriers place orders with local providers for access lines to the remote offices of MPLS customers. This creates international MPLS networks. An issue in designing MPLS networks for international organizations is that rural and sparsely populated areas often don't have MPLS available from the same carrier that installs the service for the rest of the enterprise. (Because of technical and network management incompatibilities, MPLS requires that the same carrier supply end-to-end service for each site on the network.) This is particularly problematic in underdeveloped areas such as parts of Africa and outside of most populated cities in Latin America. Prioritizing Traffic via Classes of Service When customers want to differentiate certain traffic for specific treatment, they select from their carrier's list of classes of service. These classes of service are used to define the priority given to traffic for each class. For example, there might be three classes for data, one for voice, and another (the most expensive) for video. Voice and video are generally assigned higher priorities than data. Routers at customer sites add bits to packet www.TechnicalPDF.com headers with Class of Service (CoS) designations. At the MPLS edge router, these designations are added to the MPLS labels, along with addressing data. Some organizations use the lowest-priced CoS for most data and higher-priced CoS for database lookups. This can vary by industry. Retail organizations that depend on point-of-sale credit card lookups for revenue might assign these applications the highest priority. Carriers apply CoS according to tags atta