KSZ8893MQL Datasheet, PDF (48/116 Pages) Micrel Semiconductor – Integrated 3-Port 10/100 Managed Switch with PHYs

Micrel, Inc.
KSZ8893MQL/MBL
FID+SA found in Dynamic
MAC Table?
No
Yes
Action
Learn and add FID+SA to the Dynamic MAC Address Table
Update time stamp
Table 14. FID+SA Lookup in VLAN Mode
Advanced VLAN features, such as “Ingress VLAN filtering” and “Discard Non PVID packets” are also supported
by the KSZ8893MQL/MBL. These features can be set on a per port basis, and are defined in register 18, 34 and
50 for ports 1, 2 and 3, respectively.
QoS Priority Support
The KSZ8893MQL/MBL provides Quality of Service (QoS) for applications such as VoIP and video conferencing.
Offering four priority queues per port, the per-port transmit queue can be split into four priority queues: Queue 3 is
the highest priority queue and Queue 0 is the lowest priority queue. Bit [0] of registers 16, 32 and 48 is used to
enable split transmit queues for ports 1, 2 and 3, respectively. If a port's transmit queue is not split, high priority
and low priority packets have equal priority in the transmit queue.
There is an additional option to either always deliver high priority packets first or use weighted fair queuing for the
four priority queues. This global option is set and explained in bit [3] of register 5.
Port-Based Priority
With port-based priority, each ingress port is individually classified as a high priority receiving port. All packets
received at the high priority receiving port are marked as high priority and are sent to the high-priority transmit
queue if the corresponding transmit queue is split. Bits [4:3] of registers 16, 32 and 48 are used to enable port-
based priority for ports 1, 2 and 3, respectively.
802.1p-Based Priority
For 802.1p-based priority, the KSZ8893MQL/MBL examines the ingress (incoming) packets to determine whether
they are tagged. If tagged, the 3-bit priority field in the VLAN tag is retrieved and compared against the “priority
mapping” value, as specified by the registers 12 and 13. The “priority mapping” value is programmable.
The following figure illustrates how the 802.1p priority field is embedded in the 802.1Q VLAN tag.
Bytes
8
6
6
2
2
2
46-1500
4
Preamble
DA
SA
VPID TCI
length
LLC
Data
FCS
Bits
802.1q VLAN Tag
16
Tagged Packet Type
(8100 for Ethernet)
3
1
802.1p
12
VLAN ID
Figure 6. 802.1p Priority Field Format
802.1p-based priority is enabled by bit [5] of registers 16, 32 and 48 for ports 1, 2 and 3, respectively.
February 2010
48
M9999-021110-1.6