
ATM Features and Implementation Notes
5-3
• Classical IP and ARP over ATM functions as defined in RFC 1577
• LAN emulation (LANE) functions as defined in the ATM Forum LAN
Emulation Over ATM specification (Version 1.0)
• ATM signaling functions as defined in the ATM Forum ATM User-Network
Interface specification (Version 3.0)
• Signaling AAL functions as defined in the ATM Forum ATM User-Network
Interface specification (Version 3.0)
• Error checking
• Broadcasting and simulated multicasting support
• The Segmentation and Reassembly (SAR) sublayer of the AAL
• The ATM layer defined in the B-ISDN reference model
Multiprotocol Encapsulation
Multiprotocol encapsulation enables the router to multiplex (combine) and
demultiplex (separate) bridged or routed protocol data units (PDUs).
For transmission, the encapsulation process adds a header between two and eight
octets in length to the PDU to allow decoding. The decoding process determines
the proper service access point (SAP).
When receiving information, the encapsulation method evaluates the header to
determine whether the PDU is a valid routed or bridged cell. If it is valid, the
encapsulation method then strips the header from the cell and passes it to the
appropriate SAP for routing or bridging.
Depending on the VC type, ATM allows you to use either LLC/SNAP, NULL, or
LANE 802.3 encapsulation.
Note: Bay Networks routers currently provide only Ethernet (IEEE 802.3)
emulated LAN connectivity.
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