TNETX4090GGP datasheet(50/78 Pages) TI1

50 / 78 page

TNETX4090

ThunderSWITCH II™ 9-PORT 100-/1000-MBIT/S ETHERNET™ SWITCH

SPWS044E – DECEMBER 1997 – REVISED AUGUST 1999

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

aging algorithms

time-threshold aging

When learning addresses, the IALE adds the address to the table and tags it with a time stamp. If another frame

is received with this address, the time stamp is refreshed. If the aging counter expires before another frame is

received from this source address, the address is deleted from the table. If the table is full, the oldest address

is deleted to make room for a new address, even if the age for this address has not expired.

table-full aging

In table-full aging, the oldest address (or one of the oldest addresses if there is more than one) automatically

is deleted from the IALE records only if the table is full, and a new address must be added to the table. In this

mode, the age stamp for the addresses is not refreshed.

frame-routing determination

When a frame is received, its 48-bit destination and source addresses are extracted and the VLAN index is

determined as described in

VLAN Support. The destination address and VLAN index are then looked up in the

IALE records to determine if they exist. If a match is found, the information associated with the record is passed

on to the frame-routing algorithm. Figure 11 provides a flow diagram of the routing algorithm. For details of the

TNETX4090 Programmer’s Reference Guide, literature

number SPAU003.

The source address and VLAN index combination also are looked up in the IALE records to determine if they

exist. If a match is found, additional information is provided to the routing process (for details see the

TNETX4090 Programmer’s Reference Guide, literature number SPAU003).

TNETX4090GGP 数据表(PDF) 50 Page - Texas Instruments