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Understanding ATM DXI Concepts

117375-A Rev. A 2-5

Refer to “ATM DXI Modes of Operation” later in this chapter for details.

ATM DXI LMI Support

The router supports a proprietary version of the ATM DXI Local Management

Interface (LMI). This proprietary version of the LMI was a precursor to the

standardized ATM Forum version.

LMI uses an SNMP-like protocol to query network management statistics

maintained on the DSU/CSU MIB. The DSU/CSU may also send asynchronous

events in the form of trap messages to the router.

Simulated Multicast Packet Support

ATM DXI supports multicast packets, enabling the router to take advantage of

multicast functionality, if it is available from the ATM network. ATM multicasting

reserves select network-assigned VPIs/VCIs as multicast addresses. The ATM

network maps multiple recipients to a single VPI/VCI and delivers copies of all

ATM cells to each member of the address group. As a cell passes through the

ATM network, the network manipulates the cell to reveal the actual source to the

cell recipient.

If no multicast address is available for the protocol (because the network interface

has direct PVC access, you have not set up the service yet, or the VPI/VCI has not

been entered in the Adjacent Host Table), ATM DXI simulates a broadcast packet

by forwarding a copy of the message to each known PVC.

Simulated multicasting is generally used in certain address resolution techniques

and for applications that require the delivery of identical information to multiple

recipients.

Note: The ETag and BTag ﬁelds verify that the reassembled AAL3/4 common

part convergence sublayer (CPCS) frame is not just two frames concatenated

together. If these two ﬁelds do not match, then the frame is most likely the

concatenation of two frames.

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Avaya Configuring ATM DXI Services Manual de usuario Pagina 29