Frame relay and ATM are protocols that were designed for WAN links, where as Ethernet (now evolved to Gigabit Ethernet) was designed for LAN networks.
The selection between frame relay and ATM as a WAN protocol depends on your company's needs, budget and of course -- your provider's ability to provide you with such links. ATM provides robustness, high speeds and flexibility that frame relay can't match. However, for small speeds links, some companies prefer frame relay because it turns out cheaper and suites them better.
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It really comes down to what you need and how much you want to spend.
In closing, Ethernet comes in three different flavors: Ethernet (10Mbits), Fast Ethernet (100 Mbits) and Gigabit Ethernet (1000 Mbps). These three are the most common speeds, but you can also get 10 Gpbs using the latest high-end switches available on the market.
So, as you can see, for LAN environments, we have a number of Ethernet speeds available and generally LAN speeds are always much greater than WAN link speeds and the cost is much smaller.
This was first published in August 2007