Data Communication and Networking

• Hosts or end systems are devices that are being hooked up to the internet
• End systems are connected together by a network of communication links and packet switches.
• What is a transmission rate?


  The rate at which data is transmitted over a network.
• What is transmission rate measured in?

  Bits per second (bps)
• What are packets?


  Units of data that are transmitted over a network.
• The two most prominent packet switches in today's Internet are routers and link-layer switches.
• The sequence of communication links and packet switches traversed by a packet from the sending end system to the receiving end system is known as a route or path through the network.
• Packets can be compared to trucks.

  Communication links can be compared to highways and roads.

  Packet switches can be compared to intersections.

  End systems can be compared to buildings.
• End systems access the Internet through Internet Service Providers (ISPs)
• End systems, packet switches, and other pieces of the Internet run protocols that control the sending and receiving of information within the Internet.
• The Transmission Control Protocol (TCP) and the Internet Protocol(IP) are two of the most important protocols in the internet.
• The IP protocol specifies the format of the packets that are sent and received among routers and end systems.
• The Internet's principal protocols are collectively known as TCP/IP.
• Internet standards are developed by the IETF.
• The IETF documents are called RFCs (Request for Comments)
• Internet applications are known as distributed applications, since they involve multiple end systems that exchange data with each other.
• Internet applications run on end systems - they do not run in the packet switches in the network core.
• Packet switches facilitate the exchange of data among end systems, they are not concerned with the application that is the source or sink of the data.