VPN Support for the ISP Environment

In addition to using the ISP as the conduit for access to the Internet, an enterprise may also want to use it as the provider that interconnects its various sites. If an ISP can promise adequate security for this communication, it can provide VPN offerings to its customers.

VPN support over the ISP network can be done in one of two modes of operation. In the first mode, the enterprise trusts that the ISP will perform the appropriate security functions needed for its communication. In the second case, the enterprise doesn't trust the ISP, asking the ISP for only plain IP connectivity and using IPsec-enabled routers under the enterprise's own control. The architecture chosen for enabling this communication might ...

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