Beta Draft Confidential
Configuring ATM PVCs
Configuring Frame Relay-to-ATM Interworking Circuits
ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000 1/19/0510-45
Rate Enforcement
Rate enforcement prevents network congestion and allocates network resources to
ensure the commitment of service contracts. Rate enforcement measures the actual
traffic flow across a connection and compares it to the configured traffic flow
parameters for that connection. Traffic outside the acceptable committed information
rate (CIR) is tagged and discarded if congestion develops.
Rate enforcement is implemented on a per-DLCI basis on all circuits on ingress
switches. When the switch receives data over time interval Tc (Tc=Bc/CIR), it
classifies the frame as follows:
• Under the committed burst size (Bc)
• Over the committed burst size but under the excess burst size (Be)
• Over the excess burst rate
Color designators (green, amber, and red) identify packets travelling through the
network. Congested nodes use the designators to determine which frames to discard
first under various congested states or congestion conditions. Table 10-9 describes the
designators (traffic colors) and discard policy.
Table 10-9. Rate Enforcement and Discard Policy
Traffic
Color
Description Discard Eligible
(DE)
Green Accumulated number of bits received up to any
time during the current time interval, excluding the
current frame, less than Bc.
No
Amber Accumulated number of bits received up to any
time during the current time interval, excluding the
current frame, greater than Bc but less than Be.
Frame is eligible for
discard if it passes
through a congested
node.
Red Accumulated number of bits received up to any
time during the current time interval, excluding the
current frame, greater than Be.
All red frames are
discarded.
To Next Page
Loading...
