LAN9303 datasheet(75/366 Pages) SMSC

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Small Form Factor Three Port 10/100 Managed Ethernet Switch with Single MII/RMII/Turbo MII

Datasheet

SMSC LAN9303/LAN9303i

Revision 1.3 (08-27-09)

DATASHEET

6.4.6

Ingress Flow Metering and Coloring

Hardware ingress rate limiting is supported by metering packet streams and marking packets as either

Green, Yellow, or Red according to three traffic parameters: Committed Information Rate (CIR),

Committed Burst Size (CBS), and Excess Burst Size (EBS). A packet is marked Green if it does not

exceed the CBS, Yellow if it exceeds to CBS but not the EBS, or Red otherwise.

Ingress flow metering and coloring is enabled via the Ingress Rate Enable bit in the Switch Engine

Ingress Rate Configuration Register (SWE_INGRSS_RATE_CFG). Once enabled, each incoming

packet is classified into a stream. Streams are defined as per port (3 streams), per priority (8 streams),

or per port & priority (24 streams) as selected via the Rate Mode bits in the Switch Engine Ingress

Rate Configuration Register (SWE_INGRSS_RATE_CFG). Each stream can have a different CIR

setting. All streams share common CBS and EBS settings. CIR, CBS, and EBS are programmed via

the Switch Engine Ingress Rate Command Register (SWE_INGRSS_RATE_CMD) and Switch Engine

Ingress Rate Write Data Register (SWE_INGRSS_RATE_WR_DATA).

Each stream is metered according to RFC 2697. At the rate set by the CIR, two token buckets are

credited per stream. First, the Committed Burst bucket is incremented up to the maximum set by the

CBS. Once the Committed Burst bucket is full, the Excess Burst bucket is incremented up to the

maximum set by the EBS. The CIR rate is specified in time per byte. The value programmed is in

01 - Blocking

Received packets on the port are

discarded unless overridden.

Transmissions to the port are blocked

unless overridden.

Learning on the port is disabled.

The MAC Address Table should be programmed

with entries that the host CPU needs to receive

(e.g. the BPDU address). The static and override

bits should be set.

The host CPU may send packets to the port in this

state. Only packets with STP override will be

transmitted.

Note:

There is no hardware distinction between

the Blocking and Listening states.

01 - Listening

Received packets on the port are

discarded unless overridden.

Transmissions to the port are blocked

unless overridden.

Learning on the port is disabled.

The MAC Address Table should be programmed

with entries that the host CPU needs to receive

(e.g. the BPDU address). The static and override

bits should be set.

The host CPU may send packets to the port in this

state. Only packets with STP override will be

transmitted.

10 - Learning

Received packets on the port are

discarded unless overridden.

Transmissions to the port are blocked

unless overridden.

Learning on the port is enabled.

The MAC Address Table should be programmed

with entries that the host CPU needs to receive

(e.g. the BPDU address). The static and override

bits should be set.

The host CPU may send packets to the port in this

state. Only packets with STP override will be

transmitted.

00 - Forwarding

Received packets on the port are

forwarded normally.

Transmissions to the port are sent

normally.

Learning on the port is enabled.

The MAC Address Table should be programmed

with entries that the host CPU needs to receive

(e.g. the BPDU address). The static and override

bits should be set.

The host CPU may send packets to the port in this

state.

Table 6.2 Spanning Tree States (continued)

Port State

Hardware Action

Software Action

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