PDF user manual for CopperEdge 150

&URVV&RQQHFW1HWPRGHOThe Cross-Connect netmodel allows conversion of disparateframe formats between DSL and WAN interfaces. Under thisnetmodel, different forwarding modes support multiple encapsulationtypes as well as translation between different encapsulationtypes. For example, under the VC-VC Payload forwardingmode, a frame encapsulation on the DSL interface can be convertedinto an ATM encapsulation on the WAN interface.There are two types of Cross-Connect forwarding modes, determinedby the DSL port encapsulation: per-VC forwarding modesand per-port forwarding modes. Per-VC forwarding modes resultfrom a DSL encapsulation that allows multiple VCs per DSLport. Per-port forwarding modes result from a DSL encapsulationthat does not support VCs.Per-VC Forwarding ModesAll Cross-Connect per-VC encapsulations support up to 64PVCs on the DSL port multiplexed to a single WAN VC. EachDSL VC inherits its encapsulation from the DSL port. DLCInumbers identifying DSL VCs obey the same rules as they doon WAN VCs: numbers must be between 17 and 991, and theydo not have to be sequential. However, the numbers 16, 528,and 529 cannot be used.In general, the DSL VC’s forwarding mode is determined by theWAN VC. If the WAN encapsulation is not specified (None),packet forwarding is performed in VC-VC Payload forwardingmode. If the DSL and WAN encapsulations are the same, packetforwarding is performed in a transparent mode. If the DSL andWAN encapsulations differ, packet forwarding is performed in atranslation mode.Since the cmSubIface table has no FwdMode object, the Cross-Connect forwarding mode is found in the cmIfaceTable entry forthe WAN VC. The forwarding mode for the DSL port is per-VC,since each DSL VC has its own FwdMode.LMI is available on DSL links with per-VC forwarding modes.When LMI is in force, the CE150 acts as a DCE, and the CPEacts as a DTE. For more information, see the discussion on thecmIface and cmSubIface object groups in the CopperEdge 150CopperCraft Reference and MIB Definitions manual. Also seethe discussion of encapsulation in Appendix A.&RSSHU(GJH,QVWDOODWLRQDQG2SHUDWLQJ*XLGH