3Com CoreBuilder 7000, Руководство по эксплуатации

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228 A
PPENDIX
B: P
ROTOCOLS AND
I
NTERFACES
This layer does not retransmit lost or corrupted information. The ATM
layer also provides the capability to indicate the loss priority of the data
carried in each cell (CLP).
The ATM layer relies on the physical layer to provide for the transport of
ATM cells between communicating ATM entities.
The ATM layer performs the following functions at the UNI:
Multiplexing among different ATM connections
Cell rate decoupling (unassigned cells)
Cell discrimination based on pre-defined header field values
Payload type discrimination
Loss priority indication and selective cell discarding
Traffic shaping
The ATM layer supports fault management, including alarm surveillance
and connectivity verification functions. OAM cells exchange
operation-related information. ATM cells with valid VPI/VCI values are
discarded and Layer Management is informed. Traffic management at the
public UNI monitors traffic on each connection and takes the proper
action to protect the network resources and to ensure that the
user-network traffic agreements are respected.