Cabletron Systems 2H253-25R Installation & User Manual

Contents

Cabletron Systems 2H253-25R Installation & User Manual Manual pdf 25 page image

OverviewIntroduction 1-51.1.9 Rate LimitingThe Rate Limiting feature enables the SmartSwitch device to control traffic rates on a per-port,per-priority basis. The network administrator can configure a rate limit (from 100 kbps to 1 Gbs)for a given port with an associated list of IEEE 802.1p priorities (which can include one, some, orall of the eight priority levels defined in 802.1p). Each rate limit is specified as an inbound or anoutbound limit. The combined rate of all traffic on the port that matches the listed priorities cannotexceed the programmed limit. If the rate exceeds the defined limit, frames are dropped until therate falls below the limit.Administrators can configure up to four rate limit rules per port; however, each rule must notinclude conflicting 802.1p priority values. In order to control traffic inbound and outbound on thesame port, two rate limit rules must be configured (one inbound and one outbound). Since the ratelimiting operation occurs after the processing of the multi-layer classification rules, the twofeatures can be combined to provide application-aware rate limiting.For more information about the application of the Traffic Rate function, refer to the SmartSwitchSeries 2E253, 2H252, 2H253 and 2H258 Local Management User’s Guide.1.1.10 Flow ControlFlow control is a method of managing the flow of frames between two devices. It ensures that atransmitting device does not overwhelm a receiving device with data. This is accomplished by thetransmitting device pausing its transmission while the receiving device processes the framesalready received.The 2H253-25R supports the following two types of flow control:• Frame based 802.3x• Back pressureFrame based 802.3x flow control is supported on all Ethernet ports operating in the full duplexmode. 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 ofoperation. Flow control can be enabled or disabled on a port-by-port basis.NOTEThis traffic rate function is not supported on ports configured as SmartTrunk ports.