Goal: Paint a broad picture, set context for rest of the book.
2 ways to answer: 1) Describe the basic hardware and software that make up the public Internet. 2) Describe the internet in terms of a networking infrastructure that provides services to distributed applications.
A device connected to the internet is a host or end system. These are connected by a network of communication links and packet switches. Different links transmit data at different speeds (transmission rate measured in bits/second). To send data, an end system segments it and adds header bytes to each segment (creating packets, packages of information). Packets are sent through the network to the destination end system, then reassembled.
A packet switch takes a packet on an incoming link and forwards it on an outgoing link. Mostly commonly a router (typically used in the network core) or link-layer switch (typically used in access networks). A packet traces out a route or path across switches as it moves across the network.
End systems access the internet through Internet Service Providers (ISPs) (residential, corporate, university, public). An ISP is itself a network of packet switches and communication links. Lower tier ISPs that provide access to end systems are interconnected through national and international upper tier ISPs. Each is managed independently, runs the IP protocol, and conforms to address and naming conventions.
The pieces of the internet run protocols that control sending and receiving information. The Transmission Control Protocol (TCP) and the Internet Protocol (IP) are two of the most important. Internet Standards are development by the Internet Engineering Task Force, called Request For Comments.
Can also describe the internet as an infrastructure that provides services to applications. The apps are distributed applications because they involve multiple end systems exchanging data. End systems provide an Application Programming Interface. An Internet application must choose one of the Internet's services to use.
All activity in the Internet that involves multiple communicating entities is governed by a protocol. A protocol defines the format and the order of messages exchanged between 2 or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.
End systems are also referred to as hosts. Hosts are sometimes divided into clients and servers.
Today (2011) the most prevalent type of broadband residential access are digital subscriber lines (DSL). Usually obtained from the same local telco that provides wired telephone access. Customer's DSL modem uses the existing telephone line to exchange data with a digital subscriber line access multiplexer (DSLAM), located in the telco's central office. Home modem takes digital data and translates it to high frequency tones for transmission over the wire. Analog signals are translated back to digital at the DSLAM.
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R1. What is the difference between a host and an end system? List several types of end systems. Is a Web server an end system?
A host is another term for an end system. Sometimes classified as a client or a server. A client would be a laptop, phone, iot toaster, etc. Yes, a web sever is an end system.
R2. The word protocol is often used to describe diplomatic relations. How does Wikipedia describe diplomatic protocols?
In international politics, protocol is the etiquette of diplomacy and affairs of state. --Wikipedia.
R3. Why are standards important for protocols?
Without standards, there's no guarantee two end systems are implementing the same protocol in the same way. If they do not, they will be unable to communicate via the protocol.