Priority Marking; Traffic Policing; Protocol Priority - 3Com 5500-EI PWR Install Manual

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Protocol Priority

Protocol packets generated by a switch carry their own priority. You can set a new IP
precedence or DSCP precedence for the specific type of protocol packets to implement
QoS.

Priority Marking

The priority marking function is to reassign priority for the traffic matching an ACL
referenced for traffic classification.
If 802.1p priority marking is configured, the traffic will be mapped to the local
precedence corresponding to the re-marked 802.1p priority and assigned to the output
queue corresponding to the local precedence.
If local precedence marking is configured, the traffic will be assigned to the output
queue corresponding to the re-marked local precedence.
If IP precedence or DSCP marking is configured, the traffic will be marked with new IP
precedence or DSCP precedence.

Traffic Policing

The network will be made more congested by plenty of continuous burst packets if the
traffic of each user is not limited. The traffic of each user must be limited in order to make
better use of the limited network resources and provide better service for more users. For
example, traffic can be limited to get only its committed resources during a time period to
avoid network congestion caused by excessive bursts.
Traffic policing is a kind of traffic control policy used to limit the traffic and the resource
occupied by supervising the traffic. The regulation policy is implemented according to the
evaluation result on the premise of knowing whether the traffic exceeds the specification
when traffic policing is performed. Normally, token bucket is used for traffic evaluation.
Token bucket
The token bucket can be considered as a container with a certain capacity to hold tokens.
The system puts tokens into the bucket at the set rate. When the token bucket is full, the
extra tokens will overflow and the number of tokens in the bucket stops increasing.
802.1p priority Local precedence
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