computing. IT staff can easily provide departmental staff, suppliers, or customers with secure access to applications and resources. This approach simplifies and streamlines management, significantly reducing overhead. Redundant data centers provide backup using synchronous and asynchronous data and application replication. The network and devices offer server and application load balancing to maximize performance. This solution allows enterprises to scale without major changes to the infrastructure.
  • Branch architecture: Enables enterprises to extend head-office applications and services, such as security, 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 so that enterprises can deploy new services when they are ready without buying new equipment. This solution provides secure access to voice, mission-critical data, and video applications anywhere, 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 located at remote sites, including tools, such as AutoQoS, that proactively resolve congestion and bandwidth issues before they affect network performance.
  • Teleworker architecture: Allows enterprises to securely deliver voice and data services to remote small or home offices over a standard broadband access service, providing a business resiliency solution for the enterprise and a flexible work environment for employees. Centralized management minimizes 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 into the network over an “always-on” VPN and gain access to authorized applications and services from a single cost-effective platform. The productivity can further be enhanced by adding an IP phone, providing cost-effective access to a centralized IP communications system with voice and unified messaging services.
  • WAN architecture: Offers the convergence of voice, video, and data services over a single IP communications network. This approach enables enterprises to cost-effectively span large geographic areas. QoS, granular service levels, and comprehensive encryption options help ensure the secure delivery of high-quality corporate voice, video, and data resources to all corporate sites, enabling staff to work productively and efficiently from any location. Security is provided with multiservice VPNs (IPSec and MPLS) over Layer 2 and Layer 3 WANs, as well as hub-and-spoke and full mesh topologies.
    • Content 1.1 Introducing Campus Networks 1.1.3 Describing Non-Hierarchical Campus Network Issues The simplest Ethernet network infrastructure is composed of a single collision and broadcast domain. This type of network is referred to as a “flat” network because any traffic that is transmitted within it is seen by all of the interconnected devices, even if they are not the intended destination of the transmission. The benefit of this type of network is that it is very simple to install and configure, so it is a good fit for home networking and small offices. The downside of a flat network infrastructure is that it does not scale well as demands on the network increase. Following are some of the issues with non-hierarchical networks: Figure shows the key network hardware devices in a non-hierarchical network and the function of each.
    Content 1.1 Introducing Campus Networks 1.1.4 Describing Layer 2 Network Issues Layer 2 switches can significantly improve performance in a carrier sense multiple access collision detect (CSMA/CD) network when used in place of hubs. This is because each switch port represents a single collision domain, and the device connected to that port does not have to compete with other devices to access the media. Ideally, every host on a given network segment is connected to its own switch port, thus eliminating all media contention as the switch manages network traffic at Layer 2. An additional benefit of Layer 2 switching is that large broadcast domains can be broken up into smaller segments by assigning switch ports to different VLAN segments. For all their benefits, some drawbacks still exist in non-hierarchical switched networks:
    Content 1.1 Introducing Campus Networks 1.1.5 Describing Routed Network Issues A major limitation of Layer 2 switches is that they cannot switch traffic between Layer 3 network segments (IP subnets for example). Traditionally, this was done using a router. Unlike switches, a router acts as a broadcast boundary and does not forward broadcasts between its interfaces. Additionally, a router provides an optimal path determination function. The router examines each incoming packet to determine which route the packet should take through the network. Also, the router can act as a security device, manage QoS, and apply network policy. Although routers used in conjunction with Layer 2 switches resolve many issues, some concerns still remain:
    Content 1.1 Introducing Campus Networks 1.1.6 Multilayer Switching Multilayer switching is hardware-based switching and routing integrated into a single platform. In some cases, frame (Layer 2) and packet (Layer 3) forwarding operations are handled by the same specialized hardware ASIC and other specialized circuitry. A multilayer switch does everything to a frame and packet that a traditional switch and router do, including the following: