What’s the Correct use of the term Pseudo-wire when referring to AToM/L2TPv3 vs VPLS?


I need someone to clarify the use of the term pseudo-wire. Is it true that when some one is using the term pseudo-wire they are referring to either an AToM or L2TPv3 instance for the VPWS family? and if some one use the pseudo-wire terminology to refer to a VPLS implementation is that correct and is it ever correct to refer to a VPLS instance as pseudo-wire? I need understanding as I work through the INE CCIE-SP Advanced Technologies mini labs. Any help would be appreciated.


  • Atom means "any transport over MPLS". A pseudo-wire, or a "cross-connect" is an emmulated wire over a transport network. In the case of AToM, this "wire" is using MPLS for transport. In the case of L2TPv3, it is using IP for transport. The end result is that 2 disjoint L2 domains are connected via the pseudo-wire, regardless of the underlaying transport. 

    VPLS is a collection of pseudo-wires. It allows for a collection of disjoint (not just 2) L2 networks to be connected over an MPLS network. In its most basic form, VPLS uses a mesh of statically configured pseudo-wires between the PE routers at the edge of each L2 domain. However, VPLS can also be signaled using only BGP - the PEs can discover themselves automatically, as well as signal the labels for the data-plane to work.

  • Thank you. I finally understand.

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