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In the context of networking when we say "switch" we always think of Ethernet switch.

But do we have X.25 switch, Frame Relay switch, ATM switch, and MPLS switch?

If yes, how are they different from Ethernet switch? How do they look like? Do they have different ports? What brands/models can I google to see how they look?

If no, then what kind of hardware do they use?

Note: I already googled these terms but I always only see diagrams and no actual pictures.

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    Dec 17, 2020 at 21:21

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There were, in fact, dedicated X.25 hardware switches produced by the likes of BBN (and others) in the late 70's and into the 80's. Pictures of this sort of thing would be the domain of various museums out there, as dedicated X.25 switches were retired by the early 90's (nb - obviously some amount of this stuff probably persisted in some dusty corner, likely to this day).

In practice X.25 and Frame Relay services grew and were extended in the 90's via the early generations of carrier-oriented ATM switches (Stratacom, Cascade, Fore, etc), which actually provided these protocols as part of their offerings. In later generations ATM switches were also the platform upon which the first MPLS switching was developed, originally as a way for packet switched networks to natively utilize ATM services.

Concurrent with the later generations of these ATM switches, routers (..particularly by the late 90's into 2000) began to get much faster and denser and supported switching of these technologies both natively and via various encapsulations/overlays. It's probably safe to say the routers (or, more properly, packet switching) won and now both IP and MPLS are handled on common hardware platforms (i.e. routers).

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  • I've never heard of any ATM hardware doing MPLS. (FRF5/FRF8 for transport and termination of FR isn't MPLS, but does mean one didn't need dedicated FR switches) MPOA was a thing for a few years, but never really gained much traction as IP and Ethernet were supplanting everything else.
    – Ricky
    Sep 7, 2020 at 21:42
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    As an example of ATM switches doing MPLS see the BPX 8680 - which literally used a router as a tag switch controller to program the actual ATM switch. The original MPLS drafts were actually in the context of standardizing Cisco's tag switching and IBM's ARIS - both of which were trying to make the ATM fabric move IP at speed. As for FR in the 90's? Most of it was actually ATM switches providing Frame Relay - again see the Cisco Stratacom, Nortel, Fore, etc WAN switches (although a few like Sprint used routers).
    – rnxrx
    Sep 8, 2020 at 0:41
  • So basically, they didn't do MPLS. They had what some would today call "SDN"... something outside the ATM switch handling MPLS, and programming the ATM switch(es) to do what they do: VCs and routing/switching of ATM cells.
    – Ricky
    Sep 8, 2020 at 3:38
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    Nope - it's literally where the term MPLS originated - to include LDP et al. The original implementations mapped the label space (..and thus signaled LSP's) to VPI/VCI values. Later flavors of MPLS mapped to other transports/namepaces - like G-MPLS to WDM lambdas, etc. Take a look at the original tag switching draft authored by Cisco - tools.ietf.org/id/draft-doolan-tdp-spec-00.txt from '96 which, among other things, introduced the forerunner of LDP (TDP), etc.
    – rnxrx
    Sep 9, 2020 at 1:30
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Historically, Frame and ATM used purpose built devices. X.25 is a bit before my time, so I don't know if anyone had hardware switches for it. Today, almost everything is done with "soft switch" gear -- i.e. software. A Cisco IOS router can be configured to perform frame-relay, atm, and x.25 switching.

MPLS is functionally just a fancy [simpler, faster] way of routing, and that's how manufacturers have dealt with it. While larger iron may have hardware support for MPLS (like they do for IPv4, IPv6, ethernet switching, routing, etc.), it's not an independent layer-2 protocol.

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  • So basically, MPLS does not have its own hardware switch -- it uses IP routers, right?
    – Noob_Guy
    Sep 7, 2020 at 4:41
  • In the sense that MPLS isn't a layer-2 protocol, no. But MPLS protocol support is definitely baked into various bits of hardware.
    – Ricky
    Sep 8, 2020 at 3:40
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    How do you define the difference between switching and routing? Surely MPLS is more like switching than like routing, except for the first router which sets the MPLS header
    – user253751
    Feb 15, 2021 at 15:23
  • switching is a layer-2 term, routing is layer-3. MPLS is technically a layer-2, but it's on the fence. Once labeled, it's "switching", but the addition/removal of a label is "routing". However, (as stated) MPLS is never put "on the wire" as-is, there's always some other layer-2 first.
    – Ricky
    Feb 16, 2021 at 1:35

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