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OSPF is a layer 3 protocol. If a layer 2 switch is between the two devices running OSPF, one side may negotiate a speed different from the other side. This can create an asymmetric routing on the link (Router 1 to Router 2 could cost '1' and the return path could cost '10'), which may lead to unintended consequences.
For example, if some host needs a password verification for access and if credentials are provided then for that session password verification does not happen again. This layer can assist in synchronization, dialog control and critical operation management (e.g., an online bank transaction).
Examples of link-state routing protocols include Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS). [2] The link-state protocol is performed by every switching node in the network (i.e., nodes which are prepared to forward packets; in the Internet, these are called routers). [3]
eth0 is the interface name of the network interface card representing an Ethernet port. ppp0 is a PPPoE interface, which is configured as the default route in this example. A default route is recognized by the destination 0.0.0.0 and the flag G. A network router is identified by the network mask 255.255.255.255 and the flag H.
2 Network-LSAs Designated router (DR) area-local Originated for broadcasts and NBMA networks by the Designated Router. This LSA contains the list of routers connected to the network.The link-state ID of the type 2 LSA is the IP interface address of the DR. In OSPFv3 Network-LSAs have no address information and are network protocol independent. 3
Certain additional characteristics such as multilayer interfacing may also be employed as a means of distributing uncompromised networking gateways to authorized ports. [1] This has the added benefit of preventing issues with routing protocol loops. [2] Many routing protocols are defined in technical standards documents called RFCs. [3] [4] [5] [6]
Service definitions, like the OSI model, abstractly describe the functionality provided to a layer N by a layer N−1, where N is one of the seven layers of protocols operating in the local host. At each level N , two entities at the communicating devices (layer N peers ) exchange protocol data units (PDUs) by means of a layer N protocol .
Several authors have attempted to incorporate the OSI model's layers 1 and 2 into the TCP/IP model since these are commonly referred to in modern standards (for example, by IEEE and ITU). This often results in a model with five layers, where the link layer or network access layer is split into the OSI model's layers 1 and 2. [citation needed]