![]() ![]() A physical Ethernet interface, for example, can have logical interfaces in several virtual LANs defined by IEEE 802.1Q VLAN headers. While routers usually forward from one physical (e.g., Ethernet, serial) to another physical interface, it is also possible to define multiple logical interfaces on a physical interface. Routers forward traffic that enters on an input interface and leaves on an output interface, subject to filtering and other local rules. Information from (dynamic) routing protocols.Information on the status of directly connected hardware and software-defined interfaces.There are three general sources of routing information: In some cases, there may be multiple routes of equal "quality", and the router may install all of them and load-share across them. Several different information sources may provide information about a route to a given destination, but the router must select the "best" route to install into the routing table. IS-IS, OSPF and BGP maintain internal databases of candidate routes which are promoted when a route fails or when a routing policy is changed. ![]() Multicast routing may require an additional routing table for multicast routes. "Main" refers to the table that holds the unicast routes that are active. Building the unicast routing table Ī major function of the control plane is deciding which routes go into the main routing table. ![]() An early example is Unix, where the basic file operations are open, close for the control plane and read write for the data plane. The conceptual separation of the data plane from the control plane has been done for years. The control plane is optimized for customizability, handling policies, handling exceptional situations, and in general facilitating and simplifying the data plane processing. ![]() The distinction has proven useful in the networking field where it originated, as it separates the concerns: the data plane is optimized for speed of processing, and for simplicity and regularity. The data plane is also sometimes referred to as the forwarding plane. By contrast, the data plane is the part of the software that processes the data requests. In computing, the control plane is the part of the software that configures and shuts down the data plane. Control plane logic also can identify certain packets to be discarded, as well as preferential treatment of certain packets for which a high quality of service is defined by such mechanisms as differentiated services.ĭepending on the specific router implementation, there may be a separate forwarding information base that is populated by the control plane, but used by the high-speed forwarding plane to look up packets and decide how to handle them. In most cases, the routing table contains a list of destination addresses and the outgoing interface(s) associated with each. Control plane functions, such as participating in routing protocols, run in the architectural control element. In network routing, the control plane is the part of the router architecture that is concerned with drawing the network topology, or the information in a routing table that defines what to do with incoming packets. Part of the router architecture that maintains the routing table ![]()
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