Network Router User Manual

Configuring L2TP Services
1-8
303532-A Rev 00
L2TP Packet Encapsulation
The PC or router at the remote site sends PPP packets to the LAC. The LAC
encapsulates these incoming packets in an L2TP packet and sends it across an IP
network through a bidirectional tunnel. After the LNS receives the packets, it
decapsulates them and terminates the PPP connection.
Figure 1-3
shows how data is encapsulated for transmission over an L2TP
network.
Figure 1-3. Packet Encapsulation Process
PPP IP
LAC
LNS
D ATA
IP/UDP
Layer 2
protocol
IPL2TP
PPP
D ATA
I P D ATA
Remote user places a call
Data packet moves to the corporate network
L2T0005A