Any Transport over MPLS (AToM) transports data link layer (Layer 2) packets over a Multiprotocol Label Switching (MPLS) backbone. AToM encapsulates Layer 2 frames at the ingress PE and sends them to a corresponding PE at the other end of a pseudowire, which is a connection between the two PE routers. The egress PE removes the encapsulation and sends out the Layer 2 frame.
AToM supports the following like-to-like transport types:
• ATM Adaptation Layer Type-5 (AAL5) over MPLS
• ATM Cell Relay over MPLS
• Ethernet over MPLS (VLAN and port modes)
• Frame Relay over MPLS
• PPP over MPLS
• High-Level Data Link Control (HDLC) over MPLS
BENEFITS of AToM
The AToM product set accommodates many types of Layer 2 packets, including Ethernet and Frame
Relay, across multiple Cisco router platforms, such as the Cisco 7200 and 7500 series routers. This
enables the service provider to transport all types of traffic over the backbone and accommodate all
types of customers.
Upgrading to AToM is transparent to the customer. Because the service provider network is separate from the customer network, the service provider can upgrade to AToM without disruption of service to the customer. The customers assume that they are using a traditional Layer 2 backbone.
PART 1 (Ethernet over MPLS VLAN Based Configuration)
PART 2 (EoMPLS Preferred Path using IP routing)
PART 3 (EoMPLS Preferred Path using MPLS TE and path protection using FRR)
AToM can use MPLS traffic engineering (TE) tunnels with fast reroute (FRR) support. AToM VCs can
be rerouted around a failed link or node at the same time as MPLS and IP prefixes.
http://fengnet.com/book/layer%202%20vpn%20architectures/ch09.html
http://www.cisco.com/en/US/docs/ios/mpls/configuration/guide/12_4t/mp_12_4t_book.html
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