Similar to AToM, L2TPv3 can carry ATM, Frame Relay, HDLC, PPP, Ethernet, ATM, and others.įor more on L2TPv3 see the post of L2TPv3īoth the AToM and L2TPv3 solutions use the same architecture, but the network that is carrying the service is different. The Layer 2 frames are encapsulated with an L2TPv3 header and are transported across the IP network. L2TPv3 is the Layer 2 transport service over an IP network. Carry the traffic across an IP backbone, which is the Layer 2 Tunneling Protocol version 3 (L2TPv3) solution.Carry the traffic across an MPLS backbone, which is the AToMsolution.Two solutions are available for transporting Layer 2 frames across a packet-switched network (PSN): ġ.3 AToM is completely transparent to the customer. Routers which area Connecting to SP n/w can use same encapsulation as before.ġ.2 No need to run an IP routing protocol to the provider edge routers as in the MPLS VPN solution. This eliminates the need for the legacy network from the service provider carrying these kinds of traffic and integrates this service into the MPLS network that already transports the MPLS VPN traffic.ĪToM is an open standards-based architecture that uses the label switching architecture of MPLS and can be integrated into any network that is running MPLS.ġ.1 Customer do not need to change anything. The customer routers interconnect with the service provider routers at Layer 2 (Ethernet, HDLC, PPP, ATM, or Frame Relay). PE(config-fr-pw-switching)# xconnect 10.0.0.203 70 encapsulation mpls Port-to-port modeĪToM is the Cisco name for the Layer 2 transport service over an MPLS backbone. PE(config)# connect frompls serial7/0 100 l2transport FRAME RELAYĭLCI-to-DLCI: One VC is carried over one pseudowire Port-to-Port: all VC are carried over one pseudowire DLCI-to-DLCI. The egress PE router adds the flags, address, control field, and FCS field before sending the frame to the CE. The AToM payload is the PPP frame, minus flags, address, control field, and FCS field. These fields are not transported in PPPoMPLS packets (that information can be implicitly gleaned because the VC type is PPP) and re-created at the disposition PE before transmitting to the remote CE The 0x7E flag and FCS fields being removed at imposition, the Address (0xFF) and Control (0x03) fields are stripped at the imposition router.
PPPoMPLS requires some interpretation of the PPP header. The egress PE router adds the FCS field and flags before sending the frame to the CE.
The AToM payload is the HDLC frame, minus the flags and the frame check sequence (FCS) field. Fields with yellow color are striped at AToM imposition, Frame flags and FCS are removed at ingress and re-created at egress
0 kommentar(er)
