Wide area network
Like a MAN, a wide area network (WAN) is typically deployed using a carrier service. Unlike a MAN, however, a WAN can be either intraLATA (for large LATA) or interLATA. It is commonly the latter. In fact, the line between a MAN and a WAN is somewhat arbitrary. If a customer were to build a frame relay backbone within a single metro area, we could appropriately refer to it as a MAN. Some would call it a WAN simply because it uses a technology more commonly associated with large-scale backbones. Now build a similar backbone that happens to span two adjacent metro areas within the same LATA. Is it a MAN or a WAN? Again, either term could be used appropriately. Once we go to an interLATA solution, however, it would be unusual to hear such a service referred to as a MAN.
Historically, customers have purchased Layer 1 (e.g., private line, SONET) or Layer 2 (frame relay, ATM) services for use in the wide area. By 2005, two new services were rapidly emerging. Many carriers were introducing a new Layer 1 or Layer 2 option—Ethernet. Ethernet private line services gave customers the bandwidth stability of a private line with a native Ethernet port as the handoff. Layer 2 Ethernet services gave customers a new switched option along with frame relay and ATM.
There was also a strong movement in the industry for carriers to provide a Layer 3 WAN option in the form of a private IP backbone. The carrier technology underlying this new WAN service was, and is, most commonly something called Multiprotocol Label Switching (MPLS). MPLS is a packet technology that provides for Layer 2 switching with Layer 3 signaling and routing intelligence.
A customer can connect multiple LANs in multiple locations to their WAN; it can also use its MAN to access a larger WAN service. In the former case, the customer usually provides the interconnection between the LAN and the MAN, and this is usually a switch or a router. In the latter case, the interconnection is most commonly found inside the carrier’s network, and again takes the form of a router, a switch, or both.