However, over the years, enterprise networks have become more critical to business operations and their structures are more complex. The Cisco Enterprise Architecture, shown in Figure , integrates the entire network—campus, data center, branches, teleworkers, and WAN. This integration provides secure access to all tools, processes, and services across all sectors of the company. Cisco Enterprise Architecture helps companies protect, optimize, and grow their infrastructure to support business processes. From an information technology (IT) staff point of view, the model facilitates planning, designing, implementing, operating, and troubleshooting (PDIOT) networks by focusing on network elements and on relations between those elements. Cisco Enterprise Architecture consists of five elements:

• Cisco Enterprise Campus Architecture: Cisco Enterprise Campus Architecture combines a core infrastructure of intelligent switching and routing with tightly integrated productivity-enhancing technologies including Cisco IP Communications, mobility, and advanced security. The campus architecture provides many features:
  • High availability with a resilient multilayer design and redundant hardware and software features.
  • Automatic procedures for reconfiguring network paths when failures occur.
  • Multicast to provide optimized bandwidth consumption.
  • Quality of Service (QoS) to prevent oversubscription and reduce the likelihood of dropping or delaying real-time traffic, such as voice and video, or critical data.
  • Integrated security to protect against and mitigate the impact of worms, viruses, and other attacks on the network, even at the switch port level. Cisco enterprise-wide architecture extends authentication support using standards such as 802.1x and Extensible Authentication Protocol (EAP).
  • Cisco Enterprise Campus provides the flexibility to add IP security (IPsec) and Multiprotocol Label Switching virtual private networks (MPLS VPNs), identity and access management, and VLANs to compartmentalize access. These features help improve performance and security while also decreasing costs.
• Cisco Enterprise Data Center Architecture: Cisco Enterprise Data Center Architecture is a cohesive, adaptive network architecture that supports the requirements for consolidation, business continuance, and security. At the same time, the Data Center enables emerging service-oriented architectures, virtualization, and on-demand computing. IT staff can easily provide departmental staff, suppliers, or customers with secure access to applications and resources. This capability simplifies and streamlines management, which reduces overhead. Redundant data centers provide backup services using synchronous and asynchronous data and application replication. The network and devices offer server and application load balancing to maximize performance. This solution allows the enterprise to scale without major changes to the infrastructure.
• Cisco Enterprise Branch Architecture: Cisco Enterprise Branch Architecture allows enterprises to extend head-office applications and services, such as security, Cisco IP Communications, and advanced application performance, to thousands of remote locations and users or to a small group of branches. Cisco integrates security, switching, network analysis, caching, and converged voice and video services into a series of integrated services routers in the branch. With this integration, enterprises can deploy new services when they are ready to do so without having to purchase new equipment. This solution provides secure access to voice, mission-critical data, and video applications anywhere and anytime. Advanced network routing, VPNs, redundant WAN links, application content caching, and local IP telephony call processing provide a robust architecture with high levels of resilience for all the branch offices. An optimized network leverages the WAN and LAN to reduce traffic and save bandwidth and operational expenses. Enterprises can easily support branch offices with the ability to centrally configure, monitor, and manage devices that are located at remote sites, including tools, such as AutoQoS or the Cisco Security Device Manager (SDM) QoS wizard, that proactively resolve congestion and bandwidth issues before they affect network performance.
• Cisco Enterprise Teleworker Architecture: Also called the Enterprise Branch-of-One, the Cisco Enterprise Teleworker Architecture allows enterprises to deliver secure voice and data services to remote small or home offices (small office/home office [SOHO]) over a standard broadband access service, providing a business resiliency solution for the enterprise and a flexible work environment for employees. Centralized management minimizes the IT support costs, and robust integrated security mitigates the unique security challenges of this environment. Integrated security and identity-based networking services enable the enterprise to help extend campus security policies to the teleworker. Staff can securely log on to the network over an always-on VPN and gain access to authorized applications and services from a single cost-effective platform. Adding an IP phone to provide cost-effective access to a centralized IP Communications system with voice and unified messaging services enhances productivity.
• Cisco Enterprise WAN Architecture: Cisco Enterprise WAN Architecture provides converged voice, video, and data services over a single IP Communications network. This convergence enables the enterprise to span large geographic areas cost effectively. Granular service levels, QoS, and comprehensive encryption options help ensure the secure delivery of high-quality corporate voice, video, and data resources to all corporate sites to enable people to work productively and efficiently regardless of their location. Security is provided with multiservice VPNs (IPsec and MPLS) over Layer 2 or Layer 3 WANs, hub-and-spoke, or full-mesh topologies.

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Content 1.1 Enterprise Networking 1.1.3 Remote Connection Requirements in a Converged Network A company with multiple sites that vary in size needs a remote network to connect the various locations to each other. In such a network, a large central site is often the corporate headquarters or a major office. Regional offices, small offices/home offices (SOHOs), and mobile workers may need to connect to the central site for data and information. Because users may access the central site via multiple WAN technologies, it is important that the central site accommodate many types of WAN connections from remote locations. The central site is often referred to as headquarters, the enterprise, or the corporate site. Figure describes requirements that the central site must provide to support the various sites in a remote network. Remote locations include these sites:

• Branch office: The branch office generally accommodates employees who have a reason to be located away from the central site. A regional sales office is an example. Branch office users must be able to connect to the central site to access company information. Remote site and remote office are other names for a branch office. Branch offices can benefit from high-speed Internet access, virtual private network (VPN) connectivity to corporate intranets, telecommuting capabilities for work-at-home employees, video conferencing, and economical public switched telephone network (PSTN)-quality voice and fax calls over the managed IP networks.
• SOHO and teleworker sites: The SOHO has a small office with one to several employees or is the home office of a telecommuter. Telecommuters may also be mobile users; that is, users who need access while traveling or who do not work at a fixed company site. Depending on the amount of use and the WAN services available, telecommuters working from home tend to use a dialup connection and broadband services.
• Mobile