1.2 The Network Edge

• Computers and other devices connected to the Internet are referred to as end systems.
• End systems are also referred to as hosts because they host application programs
• Hosts sometimes can be divided into two categories: clients and servers
• A data center is a building that houses computer servers and other electronic equipment that are used to store and process data
• An access network physically connects an end system to the first router (also known as edge router) on a path from the end system to any other distant end system.
• The two most prevalent types of broadband residential access are DSL and cable.
• DSL stands for digital subscriber line. It is a type of broadband connection that uses copper wires to transmit data.
• The residential telephone line carries both data and traditional telephone signals simultaneously, which are encoded at different frequencies.
• LAN stands for Local Area Network, which is a network that connects computers within a small geographical area.
• Ethernet is the most prevalent access technology in corporate, universities, and homes networks.
• Physical media falls into two categories: guided media and unguided media.
• How do we connect end systems to edge router?

  residential access nets, institutional access networks, mobile access networks
• Frequency division multiplexing(FDM) are different channels transmitted in different frequency bands
• Cable-based access networks are asymmetric, meaning that the download speed is faster than the upload speed
• With a cable-based access network, homes shared access network to cable headend.
• Wireless local area networks (WLANs) typically have a range within or around, less than 100 feet.
• WiFi has transmission rates of 11, 54, and 450 Mbps.
• Usually companies and universities use enterprise networks with a mix of wired, wireless link technologies, and connecting a mix of switches and routers.
• Ethernet has wired transmission rates at 100 Mbps, 1 Gbps, and 10 Gbps.
• A bit propagates between transmitter/receiver pairs
• A physical link is what lies between transmitter and receiver
• Guided media is wired and has signals that propagate in solid media: copper, fiber, and coax
• Unguided media is wireless and has signals that propagate freely. Examples include LAN(WiFi), wide-area, satellite, and terrestrial microwave.
• Coaxial cables are two concentric copper conductors that are bidirectional and broadband.
• Fiber optic cables is a glass fiber carrying light pulses at a high speed
• Fiber optic cable have a low error rate and are immune to electromagnetic noise.
• Wireless radio is effected by reflection, obstruction by objects, and Interference from other wireless devices.
• Wireless radio signal is carried in various “bands“ in electromagnetic spectrum
• Radio link types include wifi, Bluetooth, terrestrial microwave, and satellite