Issue 2.0
SV9100 Networking Manual 5-19
User Priority - Defines user priority, giving eight priority levels. IEEE 802.1P
defines the operation for these three user priority bits.
CFI - Canonical Format Indicator is always set to zero for Ethernet switches. CFI
is used for compatibility reason between Ethernet type network and Token Ring
type network.
VID - VLAN ID is the identification of the VLAN, which is basically used by the
standard 802.1Q. It allows the identification of 4096 VLANs.
Length/Type - This field indicates either the number of MAC-client data bytes that
are contained in the data field of the frame, or the frame type ID if the frame is
assembled using an optional format.
Data - Is a sequence of bytes of any value. The total frame minimum is 64 bytes.
Frame Check Sequence (FCS) - This sequence contains a 32-bit cyclic
redundancy check (CRC) value, which is created by the sending MAC and is
recalculated by the receiving MAC to check for damaged frames.
Example Ethernet Frame with Layer 2 QoS Enabled
The example below shows an Ethernet Frame containing one RTP (speech)
packet. The Frame is VLAN tagged, has a VLAN ID of 99 and a VLAN Priority of
5. It is also possible to see that the Layer 3 QoS has not been set.
Figure 5-7 Ethernet Frame Example - Layer 2 QoS Enabled
Source Destination Protocol
172.16.0.101 172.16.0.21 RTP
Info
Payload type=ITU-T G.729, SSRC=701655963, Seq=28165, Time=21520
Frame 160 (78 bytes on wire, 78 bytes captured)
Arrival Time: Jan 18, 2005 13:55:44.842738000
Time delta from previous packet: 0.008241000 seconds
Time since reference or first frame: 2.910072000 seconds
Frame Number: 160
Packet Length: 78 bytes
Capture Length: 78 bytes
Ethernet II, Src: 00:60:b9:c6:6e:45, Dst: 00:60:b9:c1:ab:a3
Destination: 00:60:b9:c1:ab:a3 (Nitsuko_c1:ab:a3)
Source: 00:60:b9:c6:6e:45 (Nitsuko_c6:6e:45)
Type: 802.1Q Virtual LAN (0xSV9100)
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