3Com 7757 Configuration Manual page 661

Overview 661
dropped and the other traffic is permitted. The Ethernet switch adopts a
complicated traffic classification rule to filter the packets based on much
information and to drop these useless, unreliable, and doubtful packets.
Therefore, the network security is enhanced.
The two critical steps in the packet filter operation are:
Step1: Classify the inbound packets to the port by the set classification rule.
Step 2: Perform the filter--drop operation on the classified packets.
The packet filter function can be implemented by applying ACL rules on the port.
Refer to the description in t"ACL Configuration" on page 637 for detailed
configurations.
Rate Limit on Ports Rate limit on ports is port-based rate limit. It limits the total rate of outbound
packets on a port.
TP 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, the traffic can only get its committed
resources in an interval to avoid network congestion caused by excess bursts.
TP (traffic policing) is a kind of traffic control policy to limit the traffic and its
resource usage by supervising the traffic specification. The regulation policy is
implemented according to the evaluation result on the premise of knowing
whether the traffic exceeds the specification when TP or TS is performed. The
token bucket is generally adopted in the evaluation of traffic specification.
Traffic evaluation and the 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.