How A Packet Moves Through A Dial Vpn Network - Bay Networks Baystream 7 Configuration And Troubleshooting Manual

How a Packet Moves Through a Dial VPN Network

A data packet moves from a remote node to the Dial VPN service provider's
network through a tunnel created for the remote node to a gateway, which sends
the data to the remote user's home network through a frame relay connection.
Here are the steps involved in this process.
1.
2.
Note: The checksum, control, tunnel flag, and version fields should be set to
zero.
3.
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The remote node sends a PPP packet to the NAS to establish a
connection.
The PPP packet contains flag fields to indicate the beginning and end of a
frame, an address field to indicate the device that originated the frame, a
control field to indicate the type of frame (information or administrative), a
protocol field that indicates the operative network layer protocol, the data, and
the Frame Check Sequence that shows the sequence order of the frame. Refer
to the BayStream manual, Configuring Dial Services, for more information
about the PPP packet.
The NAS strips off the PPP protocol-specific fields and encapsulates the
data into a GRE packet. The GRE packet can move through the IP tunnel
to the gateway.
The GRE packet contains checksum information and flag bits to indicate that
a routing and a key field are present; a control field to indicate the type of
frame; a tunnel flag to indicate that there is a tunnel ID present; a version field
to indicate the version of IP (or IPX) running on the Internet; the protocol type
used (IP or IPX); the tunnel identifier; and the original data from the data
packet. Refer to IETF RFC 1701 or RFC 1490 for more information about the
GRE packet.
The gateway decapsulates the GRE packet information and puts the data
into a frame relay packet.
BayStream Multiservice Software Version 7.2
Dial VPN Network Concepts
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