~~ODT~~
===== ETHERNET DATA =====
==== Type 0x68, Ethernet Data, Format 0 ====
Ethernet Data, Format 0 packets are used to record
Ethernet data frames from an Ethernet network. In general, an Ethernet data packet will contain
multiple captured Ethernet data frames.
The layout of the CSDW is shown in Figure 6-52. The iNumFrames field indicates the
number of Ethernet frames included in this data packet. The iFormat field indicates the format
of the captured Ethernet frames. Format type 0x00 is described in Chapter 10 as “Ethernet
Physical Layer” but in practice is better described as “Ethernet Data Link Layer” because
support for physical layer features such as frame sync preamble and collision events are not
described in the Chapter 10 standard.
struct SuEthernetF0_ChanSpec
{
uint32_t uNumFrames : 16; // Number of frames
uint32_t Reserved1 : 12;
uint32_t uFormat : 4; // Format of frames
};
Type 0x68 Ethernet Data Format 0 CSDW
Individual Ethernet data messages follow the CSDW. The format of the intra-packet data
header is shown in Figure 6-53. The suIntrPckTime value is an eight byte representation of
time in either 48-bit relative time format derived from the RTC (format shown in Figure 6-5) , or
as absolute time. If this time is absolute time, it is in either Chapter 4 weighted 48-bit time
(format shown in Figure 6-6) or IEEE 1588 time format (format shown in Figure 6-7). The
uDataLen field is the length of the Ethernet data in bytes. The uNetID field is used to
uniquely identify the physical network attachment point. The uSpeed field indicates the bit rate
at which the frame was captured by the recorder. Early coaxial cable based Ethernet networks
(10BASE5 and 10BASE2) required all network participants to operate at the same bit rate since
they were sharing the same physical channel. Most modern Ethernet network topologies
(10BASE-T, 100BASE-TX, etc.) are a star configuration with a single point to point link
between the networked device and a network hub. In this case, the network bit rate is the bit rate
negotiated between the device (e.g. the recorder) and the network hub. In this star topology,
different devices can operate at different bit rates on the same Ethernet network. The uSpeed
field only indicates the bit rate of the link the data recorder has with the network hub. It does not
imply the speed of any other devices on the network. The uContent field indicates the type of
data payload. The Media Access Control (MAC) content type (0x00) indicates Ethernet Data
Link Layer frames, including the destination address, source address, type (in the case of
Ethernet II) or length (in the case of IEEE 802.3), data, and frame check sequence. The data link
frame preamble is not included, nor are other features of the physical layer such as collisions or
auto-negotiations. The bFrameError flag indicates an unspecified error has occurred in the
reception of the Ethernet frame.
struct SuEthernetF0_Header
{
uint64_t suIntraPckTime; // Reference time
uint32_t uDataLen : 14; // Data length
uint32_t Reserved1 : 2; //
uint32_t uNetID : 8; // Network identifier
uint32_t uSpeed : 4; // Ethernet speed
uint32_t uContent : 2; // Captured data content
uint32_t bFrameError : 1; // Frame error
uint32_t Reserved2 : 1; //
};
Type 0x68 Ethernet Data Format 0 intra-packet data header
----
==== Type 0x69 - 0x6F, Ethernet Data, Format 1 - Format 7 ====
Reserved for future use.