High Performance Two Port 10/100 Managed Ethernet Switch with
Datasheet
Table 6.2 Spanning Tree States (continued)
Port State | Hardware Action | Software Action |
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11 - Listening | Received packets on the port are | The MAC Address Table should be programmed |
| discarded. | with entries that the host CPU needs to receive |
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| (e.g. the BPDU address). The static and override |
| Transmissions to the port are blocked. | bits should be set. |
| Learning on the port is disabled. | The host CPU may send packets to the port in this |
|
| state. |
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|
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10 - Learning | Received packets on the port are | The MAC Address Table should be programmed |
| discarded. | with entries that the host CPU needs to receive |
|
| (e.g. the BPDU address). The static and override |
| Transmissions to the port are blocked. | bits should be set. |
| Learning on the port is enabled. | The host CPU may send packets to the port in this |
|
| state. |
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|
|
00 - Forwarding | Received packets on the port are | The MAC Address Table should be programmed |
| forwarded normally. | with entries that the host CPU needs to receive |
|
| (e.g. the BPDU address). The static and override |
| Transmissions to the port are sent | bits should be set. |
| normally. | The host CPU may send packets to the port in this |
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| |
| Learning on the port is enabled. | state. |
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6.4.6Ingress Flow Metering and Coloring
The LAN9312 supports hardware ingress rate limiting 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 approximately 20 nS per byte increments. Typical values are listed in Table 6.3. When a port is receiving at 10Mbps, any setting faster than 39 has the effect of not limiting the rate.
SMSC LAN9312 | 71 | Revision 1.4 |
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