, the Internet); virtual LANs are addresses that can be dynamically changed and reconfigured to accommodate changes in the network; IPv6 is the next generation of IP addresses; and network address translation is the mapping of IP addresses from one realm to another. Typically this is between public and private address space. In terms of forwarding, switching and routing are common forwarding mechanisms; default route propagation is a technique used to inform the network of the default route (or route of last resort); CIDR is routing based on arbitrary address mask sizes (classless); multicasts are packets targeted toward multiple destinations; mobile IP is providing network (IP) connectivity for devices that move, roam, or are portable; route filtering is the technique of applying filters (statements) to hide 222 CHAPTER 5 Network Architecture networks from the rest of an autonomous system, or to add, delete, or modify routes in the routing table; peering is an arrangement between networks or autonomous systems (peers) to mutually pass traffic and adhere to routing policies, which are highlevel statements about relationships between networks or autonomous systems; and IGP and EGP selection and location entail comparing and contrasting IGPs, in order to select the appropriate protocols for the network and where to apply them in the network. Two types of interactions between mechanisms are predominant within this component architecture: tradeoffs between addressing and routing mechanisms, and tradeoffs within addressing or within routing. Addressing and routing mechanisms influence the selection of routing protocols and where they are applied. They also form an addressing hierarchy upon which the routing hierarchy is overlaid. Areas of the network where dynamic addressing, private addressing, and network address translation mechanisms are applied impact how routing will (or will not) be provided to those areas. The addressing component architecture is discussed in detail in Chapter 6. 5.3.2 Network Management Component Architecture Network management is providing functions to control, plan, allocate, deploy, coordinate, and monitor network resources. Network management is part of most or all of the network devices. As such, the network management architecture is important as it determines how and where management mechanisms are applied in the network. It is likely that the other architectural components (e.g., IT security) will require some degree of monitoring and management and will interact with network management. The network management component architecture describes how the system, including the other network functions, is monitored and managed. This consists of an information model that describes the types of data used to monitor and manage each of the elements in the system, mechanisms to connect to devices in order to access data, and the flows of management data through the network.