Baumer VisiLine, Руководство пользователя

Страница: 51 / 68

51
10.3 Packet Size and Maximum Transmission Unit (MTU)
Network packets can be of different sizes. The size depends on the network components
employed. When using GigE Vision
®
- compliant devices, it is generally recommended
to use larger packets. On the one hand the overhead per packet is smaller, on the other
hand larger packets cause less CPU load.
The packet size of UDP packets can differ from 576 Bytes up to the MTU.
The MTU describes the maximal packet size which can be handled by all network com-
ponents involved.
In principle modern network hardware supports a packet size of 1500 Byte, which is
specified in the GigE network standard. " Jumboframes" merely characterizes a packet
size exceeding 1500 Bytes.
Baumer VisiLine IP cameras can handle a MTU of up to 65535 Bytes.
10.4 Inter Packet Gap
To achieve optimal results in image transfer, several Ethernet-specific factors need to be
considered when using Baumer VisiLine IP cameras.
Upon starting the image transfer of a camera, the data packets are transferred at maxi-
mum transfer speed (1 Gbit/sec). In accordance with the network standard, Baumer em-
ploys a minimal separation of 12 Bytes between two packets. This separation is called
"inter packet gap" (IPG). In addition to the minimal IPG, the GigE Vision
®
standard stipu-
lates that the IPG be scalable (user-defined).
IPG:
The IPG is measured in
ticks.
An easy rule of thumb is:
1 Tick is equivalent to 4 Bit
of data.
You should also not forget
to add the various ethernet
headers to your calculation.