L-ET4148-50C-DB LSI, L-ET4148-50C-DB Datasheet - Page 35

• 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.
Functional Description
VLAN Encapsulation
Prior to transmission, the VLAN encapsulation of the packet is updated as necessary. VLAN tags may be added,
removed, or modified. Similarly, if a packet had its priority demoted by an ingress policer, its priority values (CoS
and DSCP) may need to be replaced prior to transmission.
An optional mode is available whereby the VLAN encapsulation of the packet is not updated. If the packet is not
updated, the packet will be transmitted with the same layer-2 header. If the packet was tagged, it will be transmit-
ted with the same VLAN tag, and the COS will not be updated. If the packet was untagged, it will be transmitted
without a VLAN tag. In both cases, the IP DSCP will not be updated.
REMOVE VLAN ID
Y
PACKET VLAN
TAGGED?
N
Single-Chip 48 x 1 Gbit/s + 2 x 10 Gbits/s Layer 2+ Ethernet Switch
(continued)
Figure 14. VLAN Encapsulation Process
N
Agere Systems - Proprietary
UPDATE DSCP
ADD VLAN ID
TRANSMIT PORT
TRUNK PORT?
HEADER?
UPDATE
PACKET
START
Y
N
Y
PACKET TRANSMISSION
Y
N
DELIVER PACKET TO
REPLACE VLAN ID
PACKET VLAN ==
PACKET VLAN
PORT VLAN?
IP PACKET?
TAGGED?
DONE
N
Y
N
Y
N
REMOVE VLAN TAG
STRIP MATCHING
PACKET VLAN
TAGGED?
VLAN ID?
Y
Y
N
ET4148-50
35