Monday, January 29, 2007

The Evaporating LAN WAN Difference

There has always been something of a technical "digital divide" between Local Area Networks or LANs, and Wide Area Networks or WANs. The difference in standards reflects the difference in heritage. LANs came from the computer industry and WANs came from the telephone industry. But today those standards are beginning to merge.

Local Area Networks were developed to link computers within a building or corporate campus. Hence the name local. Various protocols have been used over the last sixty or so years, but the overwhelming favorite has become Ethernet. Ethernet is a packet based protocol that runs on both copper and fiber optic cable. Unshielded twisted pair copper is the cabling of choice. Nearly every piece of computing gear from PCs through routers support Ethernet connections. Basic Ethernet speed is 10 Mbps, but Fast Ethernet at 100 Mbps is more common, with Gigabit Ethernet or GigE as the emerging standard. Ten GigE or 10 Gbps Ethernet is being deployed in larger organizations to keep up with the demand for user bandwidth.

On the other side of the fence, Wide Area Networking has typically been the purview of the telephone companies. WANs extend your network across town or interstate to international distances. The Bell System had a virtual lock on all landlines until deregulation. They developed the standards for voice and data lines. Voice grade lines will support low bandwidth modems, but digital carriers are needed for higher speeds. The low end is dominated by T1 lines running at 1.5 Mbps with an upgrade path to T3 lines at 45 Mbps. The T-carriers, as they are called, use TDM or time division multiplexing technology developed to carry phone calls rather than the information packets used by Ethernet. Protocol conversion is needed to go from one standard to another.

At the high end, telco based WANs are based on SONET or Synchronous Optical NETwork standards. The basic service is OC3 running at 155 Mbps, with OC12 at 622 Mbps and OC48 at 2.5 Gbps reasonably available. Network backbones might use OC192 at 10 Gbps for metro and long haul traffic. SONET is also TDM based and originally designed for voice trunking. But the bandwidths of the available SONET circuits are suitable for carrying equivalent Ethernet data. For instance, OC3 will support Fast Ethernet, OC48 will carry GigE and OC192 can handle 10GigE.

Various forces are at work to promote Ethernet and its WAN equivalent IP Networking as a universal standard. Most visible is the Internet, which is based on TCP/IP standards. Heavy business need for point to point and mesh networking between physically diverse locations is a driving factor for efficient WAN networking. The ongoing corporate switch from TDM based telephone systems to VoIP telephony is also driving this desire for a single protocol end to end.

In response, IP WANs and Carrier Ethernet are emerging as alternatives to the traditional telecommunication links. The MEF or Metro Ethernet Forum is the standards body defining Carrier Ethernet services. E-Line is a point to point Ethernet service. It is available in two flavors, EPL or Ethernet Private Line and EVPL or Ethernet Virtual Private Line. The virtual service allows more than one Ethernet service at the same User Network Interface. ELAN is multipoint to multipoint virtual Ethernet service.

As IP packet networks proliferate, the line between LAN and WAN will blur and then disappear. Your far-flung business locations across the country or even around the world will be interconnected on business networks that appear to be one large company LAN.

Can your business benefit from Carrier Ethernet or better pricing on traditional T1 and DS3 services for voice and data? The sure way to find out is to talk it over with one of our expert Shop For T1 consultants. Let us know what you are interested in at T1 Rex now.

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