MPLS – AToM (Any Transport of MPLS) and EoM (Ethernet over MPLS) overview, very high level review of technology, some configuration examples as well!

MPLS_Top1

So this is getting pretty out of bounds of what I know / have worked with at all, however I  wanted to make a quick note on these technologies so I have reference to them, those two being AToM (Anything over MPLS) and EoM (Ethernet over MPLS).

From my understanding AToM is for more dated Layer 2 technologies like Frame-Relay or ATM (Serial Connections) to an MPLS Provider Edge, whereas EoM is still Layer 2 but Ethernet to the Provider Edge, meaning of course the MPLS Provider Edge is the Transport for this Layer 2 traffic over a Layer 3 (technically) Label Switched Network.

Unlike L2TP these are both MPLS Based Layer 2 Transport technologies, these are both considered “Point to Point” Protocols, and are essentially like plugging into a Provider “Cloud” as though it were a giant switch / Ethernet segment.

Given my new understanding of EoM, I will lab it in another section (or attempt to).

AToM Terminology explained

  • AC = Attachment Circuit = Connection from CE to PE that may be a Layer 2 tech like Frame-Relay or ATM traffic
  • PSN = Packet Switched Network = “Pseudowire” = CE to CE communication over an MPLS meaning a Pseudo-Layer 2 connection via MPLS
  • Target LDP Session = Two labels are specifically created for communication for AToM communication
  • VC Label = BoS Label used in AToM Session, identifies Egress PE device to use (where the CE is that needs this packet)
  • Tunnel Label = Regular MPLS Label to allow traffic to be normally Packet Switched
  • P.I.D / PW ID = Psuedowire ID = Created to identify traffic in cloud belonging to a specific Target LDP Session

AToM Configuration explained – Not able to configure on current lab

I might come back to lab this some day as my current routers only support FastEthernet and Ethernet cards in the slots, and I won’t be building a new MPLS network for demonstration, but the configuration is extremely simple:

PE Router

psuedowire-class (name)
encapsulation mpls

CE Router

int s0/0
encapsulation hdlc
xconnect 172.12.100.1 100 pw-class (name)

The # 100 is a “psuedowire ID #” that would match on both the CE and PE devices.

Ethernet over MPLS overview

This was not included in instructor led material so I am digging into Cisco documentation for this info, EoM is a variation of AToM, and actually since it seems possible to lab I am going to attempt to lab it on my existing MPLS Lab in a new post!

That wraps up my level of knowledge of AToM for MPLS!

The devices in my MPLS Lab in EVE do not support Serial Interfaces, I am not going to go out of my way to build a new MPLS cloud for Frame-Relay / ATM concepts, so I will leave it at just knowing the configuration and what AToM does!

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