JUNOSe software supports the AAL5 relay method of encapsulation that is specified in the Martini draft. This method is also referred to as AAL5 service data unit (SDU) encapsulation.
ATM Martini encapsulation emulates ATM switch behavior by creating a pseudowire between pairs of ATM virtual circuits. When the router receives AAL5 packets on one of those circuits, it reassembles them, encapsulates them using Martini encapsulation, and forwards them to an MPLS tunnel. At the end of the tunnel, the packet is de-encapsulated, segmented back, and sent to a selected ATM VC.
In Figure 117, an MPLS tunnel connects two E-series routers, and ATM cross-connects provide a pseudowire between the ATM VCs on the two routers. All AAL5 packets on the pseudowire are encapsulated. The egress VC does not need the same ATM address as the ingress circuit.
Figure 117: AAL5 Pseudowire and MPLS Tunnel
To use AAL5 SDU encapsulation, you must use the aal5all encapsulation keyword when you configure ATM subinterfaces.
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