Nortel BCM 3.7, Manual

Page: 753 / 1004

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Programming Operations Guide
Chapter 39
Virtual Private Networks (VPN)
Business Communications Manager uses the Internet and tunneling protocols to create secure
extranets. These secure extranets require a protocol for safe transport from the Business
Communications Manager to another device through the Public Data Network (PDN). Business
Communications Manager uses the PPTP (
“PPTP” on page 754 ) and IPSec ( “IPSec” on page 765 )
tunneling protocols. Both of these protocols have encryption, but IPSec has a slightly more secure
hashing algorithm for negotiating keys.
Extranets can connect:
• mobile users to a fixed private network at their office over the PDN
• private networks in the two branch offices of the same corporation over PDN
• two divisions of the same corporation over the corporate intranet
When connecting two branch offices, the use of a VPN over the public data network is very
efficient if the connection is required only intermittently or a dedicated point-to-point link is
considered too expensive. Also, with the advent of business-to-business solutions, VPNs can be
deployed to provide secure connections between corporations.
PPTP tunnel notes
PPTP tunnels are used when a mobile user wishes to connect securely to a Business
Communications Manager. PPTP client software is required to use a PPTP tunnel. This client
software is available for all personal computer operating systems from Microsoft. This client is
included in Windows 98.
PPTP tunnels are created from a client to a server or from a server to a server. To form an extranet
using PPTP, a mobile, remote user does the following:
• Establishes a connection with the public data network’s point-of-presence (POP), typically
through an Internet service provider (ISP) using dial up links.
• After the Internet connection is up, the remote user launches a second connection which is a
VPN tunnel to Business Communications Manager. The Business Communications Manager
public IP address is used to establish the tunnel.
• On the Business Communications Manager, the user id of the incoming user is enabled for
dial-in access.