Cambium PTP 670 Series, User Manual

Page: 62 / 594

Chapter 1: Product description Ethernet bridging
Page 1-38
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.
Further reading
For information about… Refer to…
How to configure Ethernet loopback LAN Configuration page on page 6-43
Protocol model for PTP topology
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 a wired Ethernet port allocated to
the Data Service, Second Data Service, Out-of-Band Management Service, and the Wireless
port.
Frames are transmitted at the Wireless port over a proprietary point-to-point circuit-mode link
layer between ends of the PTP 670 link. The Wireless Port provides two distinct service access
ports (SAPs) where the first is always used for the Data Service, while the second is used by
either the Second Data Service or Out-of-Band Management Service.
Ethernet frames received at the Ethernet ports, 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 4 . Protocol layers involved in bridging between external interfaces and the management
agent are shown in Figure 5 . In these figures, the layers have the meanings defined in IEEE
802.1Q-2005.