Datasheet

____________________________________________________ DS34S101, DS34S102, DS34S104, DS34S108
Rev: 032609 39 of 198
10.6.1.1 VLAN Tag
As specified in IEEE Standard 802.1q, the twelve-bit VLAN identifier's tagged packets, enables the construction of
a maximum of 4,096 distinct VLANs. For cases where this VLAN limit is inadequate VLAN stacking provides a two-
level VLAN tag structure, which extends the VLAN ID space to over 16 million VLANs. Each packet may be sent
without VLAN tags, with a single VLAN tag or with two VLAN tags (VLAN stacking).
Figure 10-11. Single VLAN Tag Format
0
0 1 2 3 4 5 6 7 8 9 0
1
1 2 3 4 5
VLAN Tag Protocol ID (TPID)
User
Priority
CFI
VLAN ID
Figure 10-12. Stacked VLAN Tag Format
0
0 1 2 3 4 5 6 7 8 9 0
1
1 2 3 4 5
VLAN Tag Protocol ID (TPID)
User
Priority
CFI
VLAN ID
VLAN Tag Protocol ID (TPID)
User
Priority
CFI
VLAN ID
The VLAN tag’s Protocol ID (TPID) can be either the typical value of 0x8100 or a value configured in the
vlan_2nd_tag_identifier field in Packet_classifier_cfg_reg7.
• The User Priority field is used to assign a priority level to the Ethernet packet.
• The CFI (Canonical Format Indicator) fields indicate the presence of a Router Information Field.
• The VLAN ID, uniquely identifies the VLAN to which the Ethernet packet belongs.
10.6.1.2 UDP/IPv4 Header
Figure 10-13. UDP/IPv4 Header Format
0
0 1 2 3 4 5 6 7 8 9 0
1
0
2
0
3
1
IPVER
IHL IP TOS TOTAL LENGTH
IDENTIFICATION
FLAGS FRAGMENT OFFSET
TIME TO LIVE PROTOCOL
IP HEADER CHECKSUM
SOURCE IP ADDRESS
DESTINATION IP ADDRESS
SOURCE PORT NUMBER
DESTINATION PORT NUMBER
UDP LENGTH
UDP CHECKSUM
IP
HEADER
UDP
HEADER
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9