With the creation of a new breed of ISPs that want to interconnect with one another, offering the required connectivity while maintaining flexibility and control has become more challenging. Each provider has a set of rules, or policies, that describe what to accept and what to advertise to all other neighboring networks. Sample policies include determining route filtering from a particular ISP and choosing a particular path to a specific destination. The potential for variou..
Protocol Independent Multicast
As mentioned above, PIM has two modes of operation. The first, dense mode, is useful for multicast groups that have densely distributed subscribers. The second, sparse mode, is more useful for groups that have widely scattered subscribers. PIM Dense Mode PIM dense mode is a flood-and-prune protocol. As illustrated in Figure 13-2, its operation is relatively simple. Dense mode PIM is automatically used for certain administrative functions, such as aut..
The Cisco PIX and ASA VPN capabilities have their roots in Cisco IOS VPN technologies. VPNs were first introduced in the Cisco IOS router product line and then added to the PIXs in an early 5.x release. Like the routers and the concentrators, Cisco PIXs support many VPN solutions including IPsec, PPTP, and L2TP. Because of their flexibility, they can be used in many different situations. The ASA was introduced in the spring of 2005. The ASA is a unique hybrid security applian..
When mainframe computers dominated the industry, user terminals attached either directly to ports on the computer or to a controller that gave the appearance of a direct connection. Each wire connection was dedicated to an individual terminal. Users entered data, and the terminal immediately transmitted signals to the host. Performance was driven by the horsepower in the hosts. If the host became overworked, users experienced delays in responses. Note, though, that the connec..
Frame Relay Traffic Shaping Explained
Cisco's Frame Relay Traffic Shaping feature provides many parameters for handling users' traffic and managing congestion on Frame Relay networks. With Frame Relay Traffic Shaping, users are able to configure rate enforcement to either the CIR level or to other user-defined values on a per-VC basis. In this way, bandwidth can be flexibly allocated to each VC and tailored to specific requirements. This allows the feature to provide a mechanism for sharing a common Frame Relay c..
