Siemens SIMATIC NET SCALANCE S615 Configuration Manual page 23

Tag Control Information (TCI)
The 2 bytes of the Tag Control Information (TCI) contain the following information:
CoS prioritization
The tagged frame has 3 bits for the priority that is also known as Class of Service (CoS). The
priority according to IEEE 802.1p is as follows:
CoS bits
000
001
010
011
100
101
110
111
The prioritization of the data packets is possible only if there is a queue in the components in
which they can buffer data packets with lower priority.
The device has multiple parallel queues in which the frames with different priorities can be
processed. First, the frames with the highest priority ("Strict Priority" method) are processed.
This method ensures that the frames with the highest priority are sent even if there is heavy
data traffic.
Canonical Format Identifier (CFI)
The CFI is required for compatibility between Ethernet and the token Ring.
The values have the following meaning:
Value
0
1
VLAN ID
In the 12-bit data field, up to 4096 VLAN IDs can be formed. The following conventions
apply:
VLAN ID
0
1 - 4094
4095
SCALANCE S615 Web Based Management
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Non time-critical data traffic (less then best effort [basic setting])
Normal data traffic (best effort [background])
Reserved (standard)
Reserved ( excellent effort )
Data transfer with max. 100 ms delay
Guaranteed service, interactive multimedia
Guaranteed service, interactive voice transmission
Reserved
Meaning
The format of the MAC address is canonical. In the canonical representation of the MAC
address, the least significant bit is transferred first. Standard-setting for Ethernet switches.
The format of the MAC address is not canonical.
Meaning
The frame contains only priority information (priority tagged frames) and no valid
VLAN identifier.
Valid VLAN identifier, the frame is assigned to a VLAN and can also include priori-
ty information.
Reserved
Type of data
Technical basics
2.2 VLAN
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