Broadcast Suppression

Introduction

Cabletron Systems RMON Actions is a vendor-speciﬁc extension of RMON and provides the ability to set an “Action” on any SNMP MIB variable. The Action can be triggered by setting an RMON Event and/or Alarm. An example of an Action would be to turn off a MIB-2 interface if a broadcast threshold is crossed.

Broadcast Suppression enables a user to set a desired limit of receive broadcast frames per port/per second to be forwarded out the other ports on the module up to the set limit. Any broadcast frames above this speciﬁed limit are dropped. In the event that broadcast frames are being suppressed, multicast and unicast frames continue to be switched.

Port Redirect Function

The Port Redirect function, also referred to as “Port Mirroring,” is a troubleshooting tool used to map trafﬁc from a single source port to a destination port within the chassis. This feature allows all packets, including those with errors, to be copied and sent to an analyzer or RMON probe. The analyzer or RMON probe will see the data as if it is directly connected to the LAN segment of the source port.

Flow Control

Flow Control is a method of managing the ﬂow of frames between two devices. It ensures that a transmitting device does not overwhelm a receiving device with data. This enables the receiving device to communicate with the transmitting device, and to have it pause its transmission while the receiving device processes the frames already received. Flow control can be enabled or disabled on a port-by- port basis. Both devices must support the IEEE 802.3x standard for ﬂow control to work.

The 9H531-17 and 9H532-17 support the following two types of ﬂow control:

•Frame based 802.3x

•Back pressure

Frame based 802.3x ﬂow control is supported on all Ethernet ports operating in the full duplex mode.

Back pressure ﬂow control is supported on all Ethernet ports operating in the standard mode of operation.

802.1p Port Priority

The IEEE 802.1p standard is used to assign a default priority to the frames received without priority information in their tag header, and to map prioritized frames to the appropriate transmit queues.

The default priority-to-queue mappings are shown in Table 1-1. This conﬁguration can be changed by the administrator.

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