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Frame Relay is a technology that exists from 1988 (more or less). Ethernet is older (mid 70's).

Why we classify as a WAN technology Frame Relay if Ethernet can do the same (and even better!)?

As far as I understand, with ATM it's almost the same...

I really don't understand the use of Frame Relay or ATM to interconnect two networks in the WAN world because we can do it with Ethernet connections (i.e. a L2 Ethernet switch).

It is because the need of being able to transmit both voice and data and the time-frame of this technologies?

If I need to connect two IP LANs I would do it using a router or a switch so... why these technologies? What is changing if I need to connect two networks in the "WAN world"?

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You're missing a historical perspective. WAN technologies such as frame relay and ATM were created to use existing telecommunications circuitry at a time when everything was based on, and needed to be compatible with, telephony technology. While these technologies are significantly slower than Ethernet, they provided data prioritization at a time when QoS was immature. Also, at the time, Ethernet was usually limited to 10 Mb

As speeds and technologies increased, long range Ethernet became possible and gradually replaced other WAN technologies.

ATM and frame relay are essentially obsolete technologies, although they are still used in some parts of the world that have been slower to upgrade to the latest speeds.

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  • When you say "telephony technology" you mean analog telephony technology? I see then ATM/FR are alive because they are legacy technologies, right?
    – T.G.
    Commented Jan 20, 2018 at 19:26
  • Yes. Analog and digital. By digital I don’t mean VoIP.
    – Ron Trunk
    Commented Jan 21, 2018 at 1:35
  • Almost exclusively digital. ATM (Asynchronous Transfer Mode) was actually developed around the same time as the SONET/STM (Synchronous Transfer Mode) standards, which were the mechanisms to finally move from the T-, E- and J- series digital systems in NA, Europe and Japan respectively to the OC/STS system that's now more familiar. While running ATM over nxT1's with IMA became a bit more common later in the game the first common ATM interfaces were OC3 (and T3/E3, of course). Indeed, a lot of early adoption of ATM by carriers was because it was the only OC3 interface to be had in a router.
    – rnxrx
    Commented Jan 21, 2018 at 3:53

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