Layer-3 Ethernet tunnel with L2TPv3

LCOS LX supports the Layer 2 Tunneling Protocol (L2TP) in version 3. With L2TPv3, Ethernet traffic (layer 2) is tunneled over UDP. This allows LANs to be connected across network and site boundaries.

This is particularly useful for bridging WLAN traffic on access points to a central concentrator by means of an L2TPv3 Ethernet tunnel. Without L2TPv3, this would require the use of a WLAN controller operating CAPWAP layer-3 tunnels. L2TPv3 does not require WLAN controllers, and this allows WLAN traffic to be bridged through tunnels to the central site.

Data types

L2TP uses two types of data:

Control data
The control data are used to establish, maintain and tear down the tunnel connections. The control data includes a data-flow control to ensure that the sender and receiver correctly exchange the control data.
Payload data
The payload data are encapsulated in Ethernet frames, which are exchanged between the LAC and the LNS via the tunnel. In contrast to the control data, payload data contains no data flow control. Thus there is no guarantee that the sender and receiver are exchanging data correctly.

Unlike PPTP, which transfers control and payload data via different protocols (TCP and GRE), L2TP only uses UDP for both data types. You also have the option to operate multiple logical payload-data channels on each control-data channel.

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