Ip Port Traffic Classification; Traffic Queues - 3Com SuperStack 3 3812 Implementation Manual

56 C 6: U
HAPTER SING
IP Port traffic
classification

Traffic Queues

T M
RAFFIC ANAGEMENT
Figure 13 DSCP Service Level Mapping
Classification
Ingress Port
Figure 13 illustrates how DiffServ code point (DSCP) service levels are
mapped to the eight Traffic Queues.
The Switch supports classification of traffic from legacy devices by
classifying traffic by its IP port number.
When an IP packet is transmitted it is always tagged with an IP port
number. This number represents the type of application that created the
packet and can be used to prioritize traffic originating from different
applications.
The transmitting endstation tags a packet with a port number. When the
packet is received, the Switch places the packet in the queue that
corresponds to the IP port number of the packet. If there is no priority set
against the IP port number then the packet will be sent out with the
default priority.
It is the multiple traffic queues within the Switch hardware that allow
packet prioritization to occur. Higher priority traffic can pass through the
Switch without being delayed by lower priority traffic. As each packet
arrives in the Switch, it passes through any ingress processing (which
includes classification, marking/remarking or dropping), and is then
sorted into the appropriate queue. The Switch then forwards packets
from each queue. Note that each egress port has its own set of queues,
so that if one port is congested it does not interfere with the queue
operation of other ports.
Switch
802.1D
Service Levels
Background
Spare
Best Effort
Business Critical 3
DSCP
(1-64)
Multimedia
Video
Voice
Network Control 7
Traffic Queues
1 Queue 1 Low Priority ( )
2 Queue 2
Queue 0
0
Queue 3
Queue 4
4
Queue 5
5
Queue 6
6
Queue 7 (High Priority)
Egress Port