MB86977 Datasheet, PDF (14/30 Pages) Fujitsu Component Limited. – IP PACKET FORWARDING ENGINE

MB86977
4. FEF Engine-priority control function
Priority control can be applied to D.M.Z. and WAN connections through the cooperation of the FEF engine,
priority queues in the switch block, and the classifier block. Priority control is best recommended for applications
such as VoIP where small jitter and minimal delay are required. The switch block forms both high and low priority
queues as shown in the figure below. The low priority queue is used for the transmission of packets with normal
priority such as data packets. The high priority queue is used for applications such as VoIP where high trans-
mission quality is required. The classifier block determines the priority of an IP packet by referring the fields of
the packet to the corresponding settings in the priority control table.
Below explains the operation of the classifier block when a packet is transmitted from the D.M.Z. to WAN. First,
the classifier block defines the priority of the packet received at the D.M.Z. interface.If the packet is classified as
high priority, the packet is linked to the high priority queue destined for the host interface block. The high priority
queue is serviced prior to the low priority queue, and FEF processing is carried out on the packet. Since in this
case the NAT/IP forwarding table has defined the WAN High Priority Interface as the packet destination, the FEF
will process the packet and link it to the high priority queue destined for the WAN. This WAN high priority queue
will be serviced at top priority.Packet transmission from the WAN to the D.M.Z. interface is also performed in the
same manner.
DMZ
Input
Ports
DMZ
Output
Ports
Classifier
@D.M.Z port
WAN
Input
Ports
WAN
output
Ports
Classifier
@WAN port
Host Interface Side Queue
High Priority Queue
Low Priority Queue
WAB Interface Side Queue
High Priority Queue
Low Priority Queue
FEF
engine
Priority control in the packet transmission from D.M.Z. to WAN.
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