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Mobile Backhaul by Esa Metsala, Juha Salmelin

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4.5 Ethernet and Carrier Ethernet

Ethernet's success in the enterprise and LAN area has enabled low port costs and also low cost for basic Ethernet hardware for Ethernet bridging. Ethernet also has the general benefit in the enterprise LANs that due to the flat MAC address space, hosts can be moved within the LAN without a need to reconfigure IP addresses.

Also, Ethernet is known for its autoconfiguration capabilities within the LAN. Due to MAC address learning, there is no need to install routes to destinations or run a routing protocol to learn those routes. Instead, bridges forward unknown frames to all stations in the LAN and gradually automatically learn of the port behind which the MAC address resides.

Originally Ethernet is a LAN technology, approved as IEEE 802.3 in 1983, supporting 10 Mbit/s, and in general standardized in IEEE 802 standards. What is a bit confusing, is that Ethernet is at the same time a L1 (Physical layer) and a L2 (Link layer) technology.

Since the inception, Ethernet (especially at L1) has evolved and the current Ethernet is quite different from the initial Ethernet LAN standards. Today, Ethernet is typically not a shared media on the physical layer, but a point-to-point link built with a pair of copper or fibre cables. At the center site, a switch connects all stations together.

Basic MAC bridging and frame forwarding concepts are, however, mostly kept intact. Ethernet also is known for its backwards-compatibility: New versions of standards allow ...

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