Trafﬁc Rate Limiting, Flow Control | Cabletron Systems 2200 manual

Cabletron Systems 2200 manual Trafﬁc Rate Limiting, Flow Control

Overview

1.1.9Trafﬁc Rate Limiting

The Rate Limiting feature enables the SmartSwitch device to have control over trafﬁc rates on a per-port, per-priority basis. The network administrator can conﬁgure a rate limit (from 100 kbps to 1 Gbps) for a given port with an associated list of IEEE 802.1p priorities (which can include one, some, or all of the eight priority levels deﬁned in 802.1p). Each rate limit is speciﬁed as an inbound or an outbound limit. The combined rate of all trafﬁc on the port that matches the listed priorities cannot exceed the programmed limit. If the rate exceeds the deﬁned limit, frames are dropped until the rate falls below the limit.

Administrators can conﬁgure up to four rate limit rules per port; however, each rule must not include conﬂicting 802.1p priority values. In order to control trafﬁc inbound and outbound on the same port, two rate limit rules must be conﬁgured (one inbound and one outbound). Since the rate limiting operation occurs after the processing of the multi-layer classiﬁcation rules, the two features can be combined to provide application-aware rate limiting.

NOTE

This rate limiting function is not supported on ports connected to SmartTrunk ports.

For more information about the application of rate limiting, refer to SmartSwitch Series 2E253, 2H252, 2H253, and 2H258 Local Management User’s Guide.

1.1.10 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 is accomplished by the transmitting device pausing its transmission while the receiving device processes the frames already received.

The 2E253-49R supports 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. Flow control can be enabled or disabled on a port-by-port basis.

Back pressure ﬂow control is supported on all Ethernet ports operating in the standard mode of operation. Flow control can be enabled or disabled on a port-by-port basis.

Introduction 1-5