
Configuring ATM Services
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SVC Access Methods
SVCs use signaling messages to dynamically establish, maintain, and clear a
switched virtual connection at the UNI. These messages (as defined by the Q.2931
standard for signaling protocol) allow the router to assess the availability of an
ATM endpoint (device), establish a connection with that device, maintain that
connection for the duration of data transfer, and then clear the connection when
the transfer is complete.
ATM Traffic Parameters
The ATM User-Network Interface Specification defines several traffic parameters
including
• Peak Cell Rate (PCR) -- The upper traffic rate limit for an individual VC
• Sustainable Cell Rate (SCR) -- The upper bound on the conforming average
rate of an individual PVC or Control VC
where
Average rate = The number of cells transmitted over the link divided by the
duration of the connection
Duration of the connection = The total amount of time it takes from
connection setup to connection release
• Maximum Burst Size (MBS) -- The maximum length of a cell stream allowed
on a particular VC
These parameters help to prioritize and control the traffic on each VC. For more
information about each of these traffic parameters and how to customize them,
refer to Chapter 7.
How you assign your ATM traffic parameters depends on
• The characteristics of the individual connections that you want to set up (for
example, the desired maximum cell rate, average cell rate, and burst size)
• The bit-rate method -- variable or available -- that the ATM ILI pair uses
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