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Firewall Settings > QoS Mapping
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SonicOS 5.8.1 Administrator Guide
An ingress module monitors and records the ingress rate for each traffic class. It also monitors
the egress ACKs and queues them if the ingress rate has to be reduced. According to ingress
BW availability and average rate, the ACKs will be released.
Algorithm for Inbound Bandwidth Management
IBWM maintains eight priority queues, where each priority has one rule that has IBWM enabled.
The IBWM pool is processed from the highest to lowest priority further shaping the traffic. IBWM
employs three key algorithms:
Ingress Rate Update
This algorithm processes each packet from the WAN and updates the ingress rate of the class
to which it belongs. It also marks the traffic class if it has over utilized the link.
a. Determine that the packet is from the WAN zone and is a firewall packet.
b. Add the packet length to the sum of packet lengths received so far in the current time
slice. Deduct the minimum of (GBW, packet length) from link’s credit.
c. If the sum is greater than the class’s credit, mark the class to be over utilizing the link.
d. If the packet length is greater than the link’s credit, mark the link as well as the class to
be over utilized.
Egress ACK monitor
This algorithm depicts how the egress ACKs are monitored and processed.
a. Determine that the packet is to the WAN zone and is a TCP ACK.
b. If class or interface is marked as over utilizing, queue the packet in the appropriate
ingress rule queue.
Non-TCP Packets
Feedback
TCP
Packets
Ingress
Packets
Ingress
Packets
Egress
Packets
Egress Module
CBQ per class/priority
Ingress BWM by controlling
ACK Packets
AckQ per class/priority
Ingress Module
Calculates and Maintains
Link BW and
Available BW for class
Inbound Bandwidth Management Flow