For get a good understanding you will need an understanding about OSI model. They then offer protocols such as PPP to the network layer, to allow IP traffic to flow over their links. Modems again operate at Layer 2 (the data link layer), but use different protocols than Ethernet to communicate. Responsible for establishing a digital channel over an analogue medium, most commonly the telephone network. In practice, hubs are found less and less in today's data networks, as they have poor performance (as only one user can transmit at a time) and poor security (anyone connected to the same hub can hear everything all other users transmit and receive). A collision domain represents a set of devices all connected to the same physical transmission medium, such that only one of them can transmit at any given time (ignoring multiplexing technologies like wavelength division multiplexing, frequency-division multiplexing, time-division multiplexing, etc etc.). The point to note here is that hubs are a single collision domain. They can be either unpowered (simply providing a physical connection for the existing signal to propagate along), or powered, where they actually regenerate and/or amplify the signal they receive. Hubs: these are essentially multi-port signal repeaters, operating at Layer 1 (the phyiscal layer) of the OSI model. This is the case where you have multi-layer switched networks (think a Netgear or Belkin switch plugged into your office or university network), or a hub connected to a switch port. This is not necessarily a one-to-one mapping many MAC addresses can be bound to the same physical port. Switches: these maintain forwarding tables which map MAC addresses to physical ports, operating at Layer 2 (the data link layer) of the OSI model. Note that an interface may contain one or more ports (See below). They maintain routing tables which map IP addresses (more correctly, IP prefixes) to an outgoing interface. ![]() ![]() ![]() Routers: these devices connect different networks, operating at Layer 3 (the network layer) of the OSI model.
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