L-ET4148-50C-DB LSI, L-ET4148-50C-DB Datasheet - Page 281

• Manufacturer Part Number: L-ET4148-50C-DB
• Manufacturer: LSI

Specifications of L-ET4148-50C-DB

• Lead Free Status / RoHS Status: Supplier Unconfirmed

Preliminary Data Sheet
April 2006
Agere Systems Inc.
Appendix B: Configuration
Access Control Lists
IP and TCP Tables
The IP and TCP tables utilize a cascaded k-ary look-up method. A series of 2-way or 4-way decisions are made via
a series of tables arranged as a balanced tree structure.
All k-ary tables have a look-up entry point (table 0) and a look-up terminus point. The look-up terminus point varies
from table to table and is affected by the type of look-up (binary vs. 4-ary) and the number of keys in the table.
The IP address table operates in either a binary or 4-ary mode, depending on whether it is a mix of IPv4 and IPv6
addresses or exclusively IPv4 addresses being operated on, respectively. For a mix of IPv4 and IPv6, there are a
total of nine stages to the look-up process with the final stage holding 256 keys defining 128 prefixes. Hence, this
type of look-up starts with Acl_Ip_Key_Table_0 and ends with Acl_Ip_Key_Table_8.
For IPv4-only operations, there are a total of six look-up stages with the final stage holding 1,024 keys that define
512 prefixes. Hence, this type of look-up starts with Acl_Ip_Key_Table_0 and ends with Acl_Ip_Key_Table_5.
The TCP/UDP port number look-ups operate in a 4-ary mode and require five stages with the final stage holding
512 keys that define 256 ranges. The look-up entry point is Acl_Tcp_Key_Table_0 and the terminus is
Acl_Tcp_Key_Table_4.
From one look-up stage to the next, there are no pointers embedded in the table that point to the keys to be exam-
ined within the next table in sequence. Rather, it is the progression of match results that forms the address used to
pull the appropriate keys from the next table. Using a 4-ary look-up as an example, at each stage, the address of
the current set of keys is shifted left two bit positions and the results of the current comparisons serve as the new
least significant two bits of the address for the next key table. The following table provides an illustration.
Table 383. Key Address Formation
The records embodied in the last stage of each of the look-up types contain both key values as well as look-up
results. These look-up results are index values that identify which prefix or range (if any) matches the search argu-
ment. For the IP address look-ups, source and destination address look-ups return distinct index values for source
vs. destination address look-ups as well as flow identifier values that are also distinct for source vs. destination
address look-ups.
For details regarding the method used to add and delete table entries, refer to Adding and Deleting Table Entries
on page 273.
argument <= key_0
argument > key_0 and <= key_1
argument > key_1 and <= key_2
else
Comparison Results
(continued)
Single-Chip 48 x 1 Gbit/s + 2 x 10 Gbits/s Layer 2+ Ethernet Switch
(continued)
Agere Systems - Proprietary
New Address Bits
00
01
10
11
2
2
2
2
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