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DM9006 Datasheet(PDF) 59 Page - Davicom Semiconductor, Inc. |
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DM9006 Datasheet(HTML) 59 Page - Davicom Semiconductor, Inc. |
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59 / 76 page 
DM9006 2-port Switch with Processor Interface Preliminary datasheet 59 DM9006-13-DS-P01 September 1, 2009 9.2.13 VLAN Support 9.2.13.1 Port-Based VLAN The DM9006 supports port-based VLAN as default, up to 16 groups. Each port has a default VID called PVID (Port VID, see register 6Fh). The DM9006 used LSB 4-bytes of PVID as index and mapped to register B0h~BFh, to define the VLAN groups. 9.2.13.2 802.1Q-Based VLAN Regarding IEEE 802.1Q standard, Tag-based VLAN uses an extra tag to identify the VLAN membership of a frame across VLAN-aware switch/router. A tagged frame is four bytes longer than an untagged frame and contains two bytes of TPID (Tag Protocol Identifier) and two bytes of TCI (Tag Control Information). Dest. Src. Length/Type Data Dest. Src. TPID Data TCI Length / Type Priority CFI VID Standard frame Tagged frame 0x8100 2 bytes 3 bits 1 bits 12 bits The DM9006 also supports 16 802.1Q-based VLAN groups, as specified in bit 1 of register 53h. It’s obvious that the tagged packets can be assigned to several different VLANs which are determined according to the VID inside the VLAN Tag. Therefore, the operation is similar to port-based VLAN. The DM9006 used LSB 4-bytes VID of received packet with VLAN tag and VLAN Group Mapping Register (B0h~BFh) to configure the VLAN partition. If the destination port of received packet is not same VLAN group with received port, it will be discarded. 9.2.13.3 Tag/Untag User can define each port as Tag port or Un-tag port by bit 7 of register 6Dh in 802.1Q-based VLAN mode. The operation of Tag and Un-tag can explain as below conditions: (1). Receive untagged packet and forward to Un-tag port. Received packet will forward to destination port without modification. (2). Receive tagged packet and forward to Un-tag port. The DM9006 will remove the tag from the packet and recalculate CRC before sending it out. (3). Receive untagged packet and forward to Tag port. The DM9006 will insert the PVID tag when an untagged packet enters the port, and recalculate CRC before delivering it. (4). Receive tagged packet and forward to Tag port. Received packet will forward to destination port without modification. 9.2.14 Priority Support The DM9006 supports Quality of Service (QoS) mechanism for multimedia communication such as VoIP and video conferencing. The DM9006 provides three priority classifications: Port-based, 802.1p-based and DiffServ-based priority. See next section for more detail. The DM9006 offers four level queues for transmit on per-port based. The DM9006 provides two packet scheduling algorithms: Weighted Round-Robin Queuing and |
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