KS8893ML datasheet(39/106 Pages) MICREL

39 / 106 page

Micrel

KS8893M/ML/MI

June 2005

M9999-063005

For packets from regular ports (port 1 & port 2) to port 3, the port mask is used to tell the processor which port the

packets were received on, defined as follows:

“0001”, packet from port 1

“0010”, packet from port 2

No port mask values, other than the previous two defined ones, should be received in this direction in Special

Tagging Mode. The switch to processor egress rules are defined as follows:

Ingress Packets

Egress Action to Tag Field

Tagged with 0x8100 + TCI

- Modify TPID to 0x810 + “port mask”, which indicates source port.

- No change to TCI if VID is not null

- Replace null VID with ingress port VID

- Recalculate CRC

Not tagged.

- Insert TPID to 0x810 + “port mask”, which indicates source port

- Insert TCI with ingress port VID

- Recalculate CRC

Table 12. STPID Egress Rules (Switch Port 3 to Processor)

IGMP Support

For Internet Group Management Protocol (IGMP) support in layer 2, the KS8893M provides two components:

IGMP Snooping

The KS8893M traps IGMP packets and forwards them only to the processor (port 3). The IGMP packets are

identified as IP packets (either Ethernet IP packets, or IEEE 802.3 SNAP IP packets) with IP version = 0x4 and

protocol version number = 0x2.

Multicast Address Insertion in the Static MAC Table

Once the multicast address is programmed in the Static MAC Table, the multicast session is trimmed to the

subscribed ports, instead of broadcasting to all ports.

To enable IGMP support, set register 5 bit [6] to ‘1’. Also, Special Tagging Mode needs to be enabled, so that the

processor knows which port the IGMP packet was received on. This is achieved by setting both register 11 bit [0]

and register 48 bit [2] to ‘1’.

IPv6 MLD Snooping

The KS8893M traps IPv6 Multicast Listener Discovery (MLD) packets and forwards them only to the processor

(port 3). MLD snooping is controlled by register 5 bit 5 (MLD snooping enable) and register 5 bit 4 (MLD option).

With MLD snooping enabled, the KS8893M traps packets that meet all of the following conditions:

•

IPv6 multicast packets

•

Hop count limit = 1

•

IPv6 next header = 1 or 58 (or = 0 with hop-by-hop next header = 1 or 58)

If the MLD option bit is set to “1”, the KS8893M traps packets with the following additional condition:

•

IPv6 next header = 43, 44, 50, 51, or 60 (or = 0 with hop-by-hop next header = 43, 44, 50, 51, or

60)

For MLD snooping, Special Tagging Mode also needs to be enabled, so that the processor knows which port the

MLD packet was received on. This is achieved by setting both register 11 bit [0] and register 48 bit [2] to ‘1’.

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