Altera 10-Gbps Ethernet MAC MegaCore Function - Manual (Page 154)

A–2 Appendix A: Frame Format
VLAN and Stacked VLAN Tagged MAC Frame
10-Gbps Ethernet MAC MegaCore Function User Guide February 2014 Altera Corporation
A.2. VLAN and Stacked VLAN Tagged MAC Frame
The extension of a basic frame is a VLAN tagged frame, which contains an additional
VLAN tag field between the source address and length/type fields. VLAN tagging is
defined by the IEEE 802.1Q standard. VLANs can identify and separate many groups'
network traffic in enterprises and metro networks.VLAN tagged frames have a
maximum length of 1522 bytes, excluding the preamble and the SFD bytes. In carrier
Ethernet network applications based on IEEE 802.1ad provider bridge standard
(QinQ) for scaling the network, frames can be tagged with two consecutive VLAN
tags (stacked VLAN). Stacked VLAN frames contain an additional 8-byte field
between the source address and length/type fields.
Figure A–2 shows the VLAN frame format.
Figure A–3 shows the stacked VLAN frame format.
Figure A–2. VLAN Frame Format
Figure A–3. Stacked VLAN Frame Format
first octet
second octet
first octet
second octet
user priority CFI
Pad
Frame Check Sequence
Destination Address
VLAN Identifier (VID, 12 bits)
Source Address
Tag Control Information
MAC Client Length/Type
Payload Data
Length/Type = 802.1Q TagType
6 Octets
6 Octets
2 Octets
2 Octets
2 Octets
0..1500/9600 Octets
4 Octets
8 7 6 5 4 3 2 1
0 0 0 0 0 0 0 0
1 0 0 0 0 0 0 1
0..42 Octets
Pad
Frame Check Sequence
Destination Address
Source Address
Tag Control Information
MAC Client Length/Type
Payload Data
Length/Type = 802.1Q TagType
6 Octets
6 Octets
2 Octets
2 Octets
2 Octets
4 Octets
Tag Control Information
Length/Type = 802.1Q TagType 2 Octets
2 Octets
Stacked VLANs
0..1500/9600 Octets
0..42 Octets