Branch Virtualization

Although the WAN optimization and application acceleration techniques provided by Cisco WAAS can certainly enable centralization and ultimately consolidation while providing users with high performance access to centralized applications and data, some applications simply cannot be removed from the branch office. Many of these applications are fundamentally required to allow users access to the network, in helping them find resources they need to interact with, or support their day-to-day tasks. Such applications include IP address assignment, user login and authentication, name resolution, and the simple ability to print. These applications are simply too vital to be removed from the branch office, as they are required to allow workers onto the network, which must occur prior to any productive work. In many cases, removing them from the branch office could be disastrous, as a network outage or device failure in that location could prevent the users from being able to do their jobs.

Techniques exist in these applications to minimize the impact of a network outage. For instance, the Dynamic Host Configuration Protocol (DHCP)—used to assign IP addresses to nodes connecting to the network—issues IP addresses based upon a lease. Should a DHCP server be unavailable, a node is free to continue using an IP address as long as the lease has not expired. Active Directory (AD), a vital component of a Microsoft infrastructure, provides authentication, profile, and policy management. AD profile information can be cached locally on the client, enabling users to login while a domain controller cannot be reached. The Domain Name Service (DNS), used to resolve network names to IP addresses, provides records with expiration, which are reused until they expire.