IP1718 LF
Preliminary Data Sheet
13/33
January 27, 2005
Copyright © 2003, IC Plus Corp.
IP1718 LF-DS-R05
priority.
Table 4.1 IPv4 Data Format
Destination MAC
Address(6 bytes)
Source MAC
Address(6 bytes)
0800H
IP version =
0110b(4 bits)
Traffic Class(8 bits).
IP1718 LF maps TC[5:0] to 2 levels of
priority.
Table 4.2 IPv6 Data Format
High Priority
Low Priority
802.1Q VLAN tag
Precedence
3’b100 ~ 3’b111
3’b000 ~ 3’b011
IPv6 Traffic Class
Field & IPv4 TOS
6’b101110; 6’b001010; 6’b010010;
6’b011010; 6’b100010; 6’b11x000
Other values
Table 4.3
Forwarding Priority for IP DS and 802.1Q VLAN tag
The IP TOS/DS priority configuration can be set through enabling the corresponding register, ranging
from 27H to 28H.
The port based priority only concerns the physical port location in a switch. By enabling the CoS function
of the corresponding bit in registers 23H and 24H, the IP1718 LF can set each physical port to a “high”
priority.
Please note that for those three CoS functions, the LSB (Least Significant Bit) of the registers
corresponds to the low physical port number for that group.
A data packet dropping mechanism is implemented to prevent the buffer from overrun. Once the packet
buffer reach a specified level, the data packet assigned to the low priority will be dropped to reserve the
buffer space for the high priority data packet.
When multiple CoS schemes are enabled, the data packet is treated as the high priority as long as any
one of three CoS schemes is mapped to “high”.
Take the following example for detailed explanation.
If port 3 is set as a low priority port and it receives a data packet which embeds VLAN tag with high
priority and IP DS field with low priority, this data packet will be forwarded in a high priority. In the other
word, the priority of a data packet would be set to high if any of three CoS schemes is interpreted as the
high priority.
4.2.4 Port_based VLAN
The IP1718 LF provides various port_based VLAN configurations. The overall number of VALN groups
that the IP1718 LF can support is 18. The IP1718 LF implements two registers to describe the routing
table for each port. Thus the total number of registers which defines the port_based VLAN is 52.
Take the following example for the detailed description. The data incoming from port 1 will be forwarded
to the corresponding port defined in register 34H and 35H. Similarly, the forwarding rule for the data
incoming from port 2 will refer to the register 36H and 37H.
Note:
The port ID is counted from 1 to 18.
Chinese ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
