DM8203
2-port switch with MII / RMII Interface
The DM8203 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.
9.2.14.1 Port-Based Priority
Port based priority is the simplest scheme and as
default. Each port has a 2-bit priority value as index
for splitting ingress packets to the corresponding
transmit queue. This value can be set in bit 0 and 1 of
register 6Dh.
Received packet will forward to destination port
without modification.
9.2.14 Priority Support
9.2.14.2 802.1p-Based Priority
802.1p priority can be disabled by bit 2 of register
6Dh, it is enabled by default.
The DM8203 extracts 3-bit priority field from
received packet with 802.1p VLAN tag, and maps this
field against VLAN Priority Map Registers (D0h~D1h)
to determine which transmit queue is designated. The
VLAN Priority Map is programmable.
The DM8203 supports Quality of Service (QoS)
mechanism for multimedia communication such as
VoIP and video conferencing.
The DM8203 provides three priority classifications:
Port-based, 802.1p-based and DiffServ-based priority.
See next section for more detail. The DM8203 offers
four level queues for transmit on per-port based.
The DM8203 provides two packet scheduling
algorithms: Weighted Fair Queuing and Strict Priority
Queuing. Weighted Fair Queuing (WFQ) based on
their priority and queue weight. Queues with larger
weights get more service than smaller. This
mechanism can get highly efficient bandwidth and
smooth the traffic. Strict Priority Queuing (SPQ)
based on priority only. The Packet on the highest
priority queue is transmitted first. The next
highest-priority queue is work until last queue empties,
and so on. This feature can be set in bit 5 of register
6Dh.
9.2.14.3 DiffServ-Based Priority
DiffServ based priority uses the most significant
6-bit of the ToS field in standard IPv4 header, and
maps this field against ToS Priority Map Registers
(C0h~CFh) to determine which transmit queue is
designated. The ToS Priority Map is programmable
too. In addition, User can only refer to most
significant 3-bit of the ToS field optionally, see bit 7 of
register 53h.
Preliminarydatasheet
DM8203-15-DS-P05
October 23, 2008
47
DAVICOM [ DAVICOM SEMICONDUCTOR, INC. ]
