The Physical layer is responsible for the ultimate transmission of data over network communications media. Hubs and other repeaters are standard network devices that function at the Physical layer. Cables and connectors also are a part of the Physical layer. At the Physical layer, data are transmitted using the type of signaling supported by the physical medium.
Data transfer can be measured in three ways:
1. Bandwidth
2. Throughput
3. Goodput
The practical bandwidth of a network is determined by a combination of factors: the properties of the physical media and the technologies chosen for signaling and detecting network signals. Due to a number of factors, throughput usually does not match the specified bandwidth in physical layer implementations such as ethernet. Goodput measures the effective transfer of user data between application layer entities, such as between a source web server process and a destination web browser device.
Basic characteristic of copper, fiber and wireless network media.
When it comes to costs, Fibre optics is always assumed to be much more expensive than copper cabling. UTP is the most widely used cable in telephone and computer networks because it is relatively cheaper than other cables and performs well in normal electrical environment such as inside an office or a house. The electrical properties of copper cabling create resistance and interference problems with transmissions. Signals sent over copper wire are direct current electrical signals. Another medium being discussed for in-building local area networks (LAN) is wireless communication. Wireless has advantages in the mobility it provides. Wireless LAN connections are less messy - it enables computers to move and office space to be reconfigured without LAN administrators having to physically move cabling.
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