Ethernet isn't just ubiquitous in the LAN. It's now become commonplace in carrier networks too. Find out why Ethernet successfully made the leap from the LAN to the WAN.

An MPLS Leased line is a leased line that uses a technology called Multi-Protocol Label Switching.

MPLS enables traffic to be split into multiple classes of service, which can then be treated differently as they travel across the WAN, so that time-sensitive traffic, such as VoIP phone calls, can be prioritised over less time-sensitive traffic such as general web traffic.

An SDSL Leased line can provide you with a 2Mb dedicated circuit. But what if SDSL isn't available at your local exchange? And what if you want more than 2Mbit/s of connectivity?

T1 leased lines offer speeds of 1.544 Mbit/s upstream and downstream. T1′s are used in America, Japan and South Korea.

Why 1.544Mbit/s? Well AT&T Long Lines was conducting tests in Chicago. They chose the bit-rate based on the speed that could be achieved over 2km long copper cables (once a safety margin was added). Why 2km? It's because the loading coils and cable vault manholes were 2km apart.

In Europe, E1's are used instead of T1's. E1's offer 2.048Mbit/s downstream and upstream.