ccna ptt

ccna ptt.The data communications equipment (DCE) terminates the physical WAN connection, provides clocking and synchronization for the connection between the two field points, and connects to the data terminal equipment (DTE). The CSU/DSU.NT1 and modems described in Chapter 1 are DCEs. o DTEs are end-user devices, such as routers and PCs, that connect to the WAN through the DCE. o In some cases, DCE functionality may be built into the physical interface of the DTE. The terms DTE and DCE are commonly used to describe WAN components, but are sometimes used to describe LAN connections as well. For example, in the LAN, PCs, file servers, and routers are sometimes referred to as DTEs, while switches, bridges, and hubs are referred to as DCEs.Physical layer standards include the following cable types (and numerous others): Category 3, Category 5, and Category 5E; EIA/TIA232, 449, and 530; multimode fiber (MMF) and single-mode fiber (SMF); and Category 1 (Type 1) interface connectors including attachment unit interfaces(AUI), BNC (Bayonet Nut Coupling), DB-9, DB.25, DB-60, RJ-1U RJ.45, etc. Ethernet hubs and transponders are devices that run at the physical layer.The physical layer defines the physical characteristics of connections and communications, including cables (UTP and fiber optic) and connectors (RJ-45 and DB-9) hubs.cWires and transponders are both devices that run at the physical layer Heart transponders are used to increase the coverage of network segments, while hubs (also called multiporttransponders) connect multiple network segments together.228 DevicesTable 2.2 indicates the devices that run at each layer of the OSI reference model.Table 2.2 Devices and the layer in which they run Layer Name Device