Cambium Networks PTP 650 Series, Руководство пользователя

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Chapter 1: Product description Ethernet bridging
Ethernet loopback mode
PTP 650 provides a local Ethernet loopback function that can be used to loop traffic between the
Aux Port and one of the other Ethernet ports.
Loopback is intended to assist in the commissioning of a camera or other auxiliary device
collocated with the PTP 650 ODU. For example, when setting up a camera which will ultimately be
connected to the wireless bridge, it may be useful to loop the data back to a second local interface,
to assist in the positioning and alignment of the camera.
When ports are configured for Ethernet local loopback, they are temporarily disconnected from
their allocated function and connected together internally within the PTP 650 ODU. Out-of-band
local management is disconnected from the management agent, and the In-band management
path will also be un-available if one of the loopback ports has been allocated for Data and in-band
management. In this case, it will not be possible to manage the ODU from a local Ethernet port.
For this reason the Ethernet loopback is always disabled when the ODU is rebooted or power-
cycled, restoring the previous port configuration and any associated management paths.
During loopback operation, the same frame size restrictions that apply to management traffic are
present, jumbo frames are not supported and the maximum frame size is restricted to 1536 bytes.
Loopback is able to loop between Ethernet ports operating at different line rates if required, and it
is possible to configure a Loopback between ports operating at 1000BASE-T/LX/SX and
100BASE-TX if needed.
Protocol model
Ethernet bridging behavior at each end of the wireless link is equivalent to a two-port, managed,
transparent MAC bridge where the two ports are Ethernet Port and Wireless Port.
Frames are transmitted at the Wireless port over a proprietary point-to-point circuit-mode link
layer between ends of the PTP 650 link. Ethernet frames received at the Ethernet port, or generated
internally within the management agent, are encapsulated within a lightweight MAC layer for
transmission over the wireless link.
Protocol layers involved in bridging between Ethernet and wireless interfaces are shown in Figure
6 . Protocol layers involved in bridging between external interfaces and the management agent are
shown in Figure 7 . In these figures, the layers have the meanings defined in IEEE 802.1Q-2005.
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