CECS 474 Computer Network Interoperability Tracy Bradley Maples, Ph.D. Computer Engineering & Computer Science Cal ifornia State University, Long Beach

“May you live in interesting times.” -- Chinese Blessing (or Curse) The Industrial Revolution (c. 1760) The change in social and economic organization resulting from the replacement of hand tools by machine and power tools and the development of large-scale industrial production. The “Digital Revolution” (c. 1990) The change in social and economic organization resulting from the replacement of earlier forms of communication and information storage by a digital format and the development of large-scale networks transmitting digital information.

Definition of Networking net·work (net´würk´) n. 1. any arrangement or fabric of parallel wires, threads, etc. crossed at regular intervals by others fastened to them so as to leave open spaces; netting; mesh 2. a thing resembling this in some way; specif., a) a system of roads, canals, veins, etc. that connect with or cross one another b) Radio and TV a chain of transmitting stations controlled and operated as a unit c) a group, system, etc. of interconnected or cooperating individuals 3. the making of nets or netted fabric Defn: A computer network is a collection of computers interconnected via a transmission medium (e.g., copper wire, optical fiber, microwaves, satellites, WiFi, etc.) The computers can be special-purpose or general-purpose programmable hardware devices.

Types of Networks LAN (Local Area Network) Examples: Ethernet, WiFi, etc. Defn: A LAN is a network that covers a relatively small area (e.g, a home or business) usually characterized by high-speed transmission and primarily connected by switches. A LAN is consists of privately owned and managed components. CAN (Campus Area Network) Examples: CSULB network (wired + BeachNet), Network at the Long Beach Boeing Facilities Defn: A CAN is a network that covers medium-sized area (perhaps 1-10 square miles) and in characterized by medium-to-high transmission speeds and is connected via switches and internally managed routers. A CAN is consists of privately owned and managed components.

Types of Networks (Cont’d) WAN (Wide-Area Network) Examples: The Internet, A Provider Network (e.g., Sprint), etc. Defn: A WAN is a network that typically covers large distances (100+ miles) and utilize leased telecommunication lines to interconnect switches/routers. WANs are typically characterized by lower speeds than LANs or CANs. A WAN is consists of privately owned switches (or routers) and leased transmission links. Other Networks Plain Old Telephone SERVICE (POTS), Cell Phone networks, Cable TV networks, Satellites networks, MAN (Metropolitan Area Network), SAN (System Area Network), PAN (Personal Area Network), etc.

Motivation: Why use Networks? Availability of resources Make resources available to anyone on the network regardless of the physical location of the resource or the user. Load sharing Process a job on the least crowded (or busy) machine. High reliability Have alternate sources of resources (multiple copies). Human-to-human communication Allow humans to communicate through , telephone, teleconferencing, etc.

History of Networking WANs (c. 1970) Driving force behind WANs: The need for government and university researchers located in various parts of the United States to communicate ideas and data between computers. Beginning of the Internet: ARPANET Created in the early seventies Funded by ARPA (DARPA) Prototype for what has evolved into the Internet Created by folks from Berkeley, MIT, AT&T Bell Labs, etc.

History of Networking LANs Driving force behind LANs: The creation of the personal computer in the mid- 70s and its widespread usage in the mid-80s. Evolution of LANs: Sneaker Net  Data Switches  Disk Servers  File Servers

Connectivity A network must provide connectivity among a set of computers. Defn: A link is the physical medium connecting computers on a network. For example, coaxial cable or optical fiber. Defn: The computers connected by the physical medium are called nodes. Note: sometimes these nodes are specialized pieces of hardware sometimes general purpose. Defn: A host is a node running a user application program. Host machines are interconnected by links to form computer networks.

Connectivity (Cont’d) Two Types of Network Links: 1. Point-to-Point (or store-and-forward) links connect only two nodes. The Internet Backbone is a point-to-point network.

Connectivity (Cont’d) 2. Multiple Access (or broadcast or shared) links allow more than two nodes to share a single physical medium. Example 1: Ethernet Busses & Example 2: WiFi Hubs (Generation I & II) NOTE: In a shared link, collisions are possible if the protocol does not prevent them.

Switched Networks Two types of switched networks: 1. Over point-to-point links, Circuit-switched network provide service by setting up a total path of connected links from the origin to the destination host. A control message is first sent to setup a path from the origin to the destination. (A return signal informs the origin that data transmission may proceed.) Once data transmission starts, all channels in the path are used simultaneously, and the entire path remains allocated to the transmission (whether or not it is in use). Example: Plain Old Telephone SERVICE (POTS)

Switched Networks 2. Over point-to-point and multiple access links, Packet-switched networks decompose messages into small pieces called packets. These packets are each numbered and make their way through the net in a store-and-forward fashion. Links are considered busy only when they are currently transmitting packets.

Which Type of Switching Performs Better– Circuit Switching or Packet Switching? The answer is not straightforward. Performance Issues: Header overhead (i.e., the amount of "extra" information that must be sent along with the data to ensure proper transmission) Transmission delay (i.e., the amount of time it takes data from the time it enters the network until it arrives at its' destination) Routing Speed Packet Size Transmission Speed More on these issues later…