Packet – Collection of data at the “network” layer Router – Device that identifies optimal path for network traffic and “routes” or directs packets down that path. TCP/IP – Transmission Control Protocol/Internet Protocol – These are communication standards that enable information to move across a network from one computer to another. DNS – Domain Name System Resolver – Software that uses the DNS to translate a server name into an IP address. (www.friendscentral.org  65.61.134.112) Bandwidth – Number of bits that pass through a given network interface in a given period of time. baud – bits/second KB – Kilobyte Mbps – Megabit Domain – Highest level name server in the DNS(.com,.org,.gov.edu,etc) Download – Save data from server to local machine Upload – Place data from local machine onto server traceroute – Software utility that traces the path of your packets ping – Software utility that tells you how long it takes packets to reach their destination WAN – Wide area network (Internet) LAN – Local area network (FCS Lab) FTP – File Transfer Protocol Encapsulation – Process of adding more and more data to a network data transmission. Encapsulated data enables your messages to get to the right machine in the right order.

1994 - Time magazine explained why the Internet would never go mainstream… 1995 - Newsweek put the doubts more bluntly in a February headline… By Kevin Kelly, Wired Magazine; August 2005 “The scope of the Web today is hard to fathom. The total number of Web pages, including those that are dynamically created upon request and document files available through links, exceeds 600 billion. That's 100 pages per person alive. How could we create so much, so fast, so well? In fewer than 4,000 days, we have encoded half a trillion versions of our collective story and put them in front of 1 billion people, or one-sixth of the world's population. That remarkable achievement was not in anyone's 10-year plan. Today, at any Net terminal, you can get: an amazing variety of music and video, an evolving encyclopedia, weather forecasts, help wanted ads, satellite images of anyplace on Earth, up-to-the-minute news from around the globe, tax forms, TV guides, road maps with driving directions, real-time stock quotes, telephone numbers, real estate listings with virtual walk-throughs, pictures of just about anything, sports scores, places to buy almost anything, records of political contributions, library catalogs, appliance manuals, live traffic reports, archives to major newspapers - all wrapped up in an interactive index that really works. This view is spookily godlike. You can switch your gaze of a spot in the world from map to satellite to 3-D just by clicking. Recall the past? It's there. Or listen to the daily complaints and travails of almost anyone who blogs (and doesn't everyone?). I doubt angels have a better view of humanity. “

1969 – Birth of The Internet The Advanced Research Projects Agency (ARPA) sponsored research focused on computer communications. A bunch of guys at Cal, Berkley started playing with electronic communication between computers. The result was Arpanet and laid the groundwork for today’s Internet.

Vinton Cerf, Bob Kahn – Developed Transmission Control Protocol/Internet Protocol TCP/IP Tim Berners-Lee – Built the first web server and browser. His developments eventually turned led to Mosaic then to Netscape. He heads the World Wide Web consortium that works to establish web standards.

November, 1993: First official release of Mosaic browser. It is THE popular pioneer in the GUI browser market and one of the main ingredients in the initial overwhelming success of the World Wide Web. It is also the basis for many other popular browsers. It is produced by the National Center for Supercomputing Applications (NCSA), which licenses its code under the name of Spyglass.

Domain Name System (DNS) A set of distributed databases that contain Internet Protocol (IP) addresses and their corresponding domain names — i.e., 65.61.134.112 and www.friendscentral.org. Instead of one computer containing the names of all hosts on the Internet, name servers are spread around the network. If a local server does not recognize a name and address, it will communicate with another server to get the information. The reason for keeping two sets of names is to enable users to use easily understandable names, instead of machine or protocol names. A domain is a hierarchical system use to define an Internet location or set of addressable computers. The first part of a domain name is called the Top Level Domain (TLD). This is typically the last two or three letters that represent the geographical or section of the Internet. Major domain suffixes are: .edu - Educational Institutions; .gov - US Government; .com - Commercial (business); .net - Network Infrastructure Organizations; .org - Non-profit Organizations; .mil - military organizations and there are country codes such as .ca for Canada, .fr for France, and .jp for Japan. The second part of a domain name is called the Low Level Domain (LLD). This is what people commonly refers to as site name or domain name. In our case, our domain name is “friendscentral". The third part is an optional part of a domain called the subdomain. A subdomain allows web site administrators to organize a larger web site into smaller logical unit, such as, "http://mail.friendscentral.org", "http://ourfcs.friendscentral.org", etc. In these examples, “mail" and “ourfcs" are sub domains of “friendscentral". IP Address The four-part numerical address of a computer connected to the Internet. IP addresses have the form xxx.xxx.xxx.xxx where x is a number between 0 and 255. Communications between computers with different IP addresses on the Internet are routed in the way phone numbers are used to route telephone calls. The domain name system translates IP addresses of web servers into names that can be easily remembered by site visitors. A dedicated IP address is used for a single web site. A shared IP address is used by many web sites on a single server. IPV6 is a future Internet protocol that will increase the number of available IP addresses and improve security Top Level Domain In the Domain Name System (DNS), top level domain is the highest level of the hierarchy above second level domains. For instance, the ".com", ".net", ".info", and ".org" are top level domains.

1. Description of layers - – FYI ONLY Physical layer Layer 1: The physical layer defines all electrical and physical specifications for devices. This includes the layout of pins, voltages, and cable specifications. Hubs and repeaters are physical-layer devices. The major functions and services performed by the physical layer are: establishment and termination of a connection to a communications medium. participation in the process whereby the communication resources are effectively shared among multiple users. For example, contention resolution and flow control. modulation, or conversion between the representation of digital data in user equipment and the corresponding signals transmitted over a communications channel. These are signals operating over the physical cabling -- copper and fibre optic, for example. SCSI operates at this level. Data link layer Layer 2: The Data link layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the Physical layer. The addressing scheme is physical which means that the addresses (MAC address) are hard-coded into the network cards at the time of manufacture. The addressing scheme is flat. Note: The best known example of this is Ethernet. Other examples of data link protocols are HDLC and ADCCP for point-to-point or packet-switched networks and LLC and Aloha for local area networks. This is the layer at which bridges and switches operate. Connectivity is provided only among locally attached network nodes. Network layer Layer 3: The Network layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks while maintaining the quality of service requested by the Transport layer. The Network layer performs network routing, flow control, segmentation/desegmentation, and error control functions. The router operates at this layer -- sending data throughout the extended network and making the Internet possible, although there are layer 3 (or IP) switches. This is a logical addressing scheme - values are chosen by the network engineer. The addressing scheme is hierarchical. Transport layer Layer 4: The purpose of the Transport layer is to provide transparent transfer of data between end users, thus relieving the upper layers from any concern with providing reliable and cost-effective data transfer. The transport layer controls the reliability of a given link. Some protocols are stateful and connection oriented. This means that the transport layer can keep track of the packets and retransmit those that fail. The best known example of a layer 4 protocol is TCP. Session layer Layer 5: The Session layer provides the mechanism for managing the dialogue between end-user application processes. It provides for either duplex or half-duplex operation and establishes checkpointing, adjournment, termination, and restart procedures. This layer is responsible for setting up and tearing down TCP/IP sessions. Presentation layer Layer 6: The Presentation layer relieves the Application layer of concern regarding syntactical differences in data representation within the end-user systems. MIME encoding, encryption and similar manipulation of the presentation of data is done at this layer. An example of a presentation service would be the conversion of an EBCDIC-coded text file to an ASCII-coded file. Application layer Layer 7, the highest layer: This layer interfaces directly to and performs common application services for the application processes. The common application services provide semantic conversion between associated application processes. Examples of common application services include the virtual file, virtual terminal (for example, Telnet), and "Job transfer and Manipulation protocol" (JTM, standard ISO/IEC 8832)

Network Protocols – FYI ONLY We have already noted that networks must have a set of rules, called protocols, to transmit data in an orderly fashion that will be understood by other computers. Recall that a protocol is embedded in the network software. There are four layers of protocols that are widely used in the ISO model: The Data Link Layer - The Data Link Layer determines how digital data is pulsed over the communication like: how many bits at one time, when to pulse, how often to pulse, etc. There two most prevalent Data Link Layer protocols are ethernet and Point-To-Point Protocol (PPP). Ethernet is used on local area networks and cable modems, and PPP is used for phone modem connections and DSL. Ethernet uses a bus topology and is inexpensive and relatively simple. Since all the nodes (computers) in a LAN use the same cable to transmit and receive data, the nodes must follow a set of rules about when to communicate; otherwise, two or more nodes could transmit at the same time, causing garbled or lost messages. Operating much like a party line, before transmitting data a node "listens" to find out if the cable is in use. If the cable is in use, the node must wait. When the cable is free from other transmissions, the node can begin transmitting immediately. This transmission method is called by the fancy name of carrier sense multiple access with collision detection, or CSMVCD. If, by chance, two nodes transmit data at the same time, the messages collide. When a collision occurs a special message, lasting a fraction of a second, is sent out over the network to indicate that it is jammed. Each node stops transmitting, waits a random period of time, and then transmits again. Since the wait period for each node is random, it is unlikely that they will begin transmitting at the same time again Unlike ethernet, PPP is a direct connection from one modem to another modem over a phone line. There are no collisions when data is transmitted. Most Internet Service Providers (ISPs), like America On-line or Edgenet (in Rhode Island) will expect to interact with their customers using PPP. Windows 95/98/ME/2000 have PPP built in to their dial-up adapter software that most people use to call into their ISP. The Internet Layer - The Internet Layer allows computers of different networks to talk to each other - essentially forming the large multi-faceted network that we know as the Internet. The key to the Internet Layer is that each computer that participates is assigned a unique 32 bit address called an IP Address (Internet Protocol Address). IP addresses are usually shown in four three digit numbers. For instance, the Web server for this text, homepage.cs.uri.edu has IP address 131.128.81.37 . Every computer that does anything on the Internet (send and receive email, serve a Web page, browse a Web page etc) must have an IP address. If your computer is on a LAN, the IP address is probably fixed. For instance, students in URI's dorm rooms with their computers attached to the campus network were given an IP Address by URI for their room. They had to enter this address into their computer using the Network Control Panel on either Windows 95, 98, or a Macintosh. If your computer dials an ISP to gain access, then the IP address is assigned to your computer by the ISP for the duration of your connection to the ISP's modem. ISPs have a large pool of IP Addresses that they temporarily assign to customers while they are connected. You could have a different IP Address every time you use America Online, for instance. With 32 bits, there about 4 billion possible IP Addresses - and the world is running out! A new IP address format is being designed to allow many more IP addresses. The IP protocol software adds bits to all messages that the computers sends indicating the IP address for the destination of the message. The Transport Layer - The Transport Layer Protocol checks messages that are sent and received to make sure that they are error free and received in the right order. If the Transport Layer software of the receiving computer detects errors, it sends a message to the original sending computer asking it to re-transmit the message. The Transport Layer protocol used on the Internet is called TCP (Transmission Control Protocol). On the Internet IP and TCP are used together so you often see the protocol referred to as TCP/IP. TCP/IP software is usually part of the operating system. Other than occasionally setting an IP address via the Network Control Panel, you probably will not directly notice or interact with the TCP/IP software. The Application Layer. The Application Layer provides protocols for specific tasks like sending email or obtaining a Web page. For instance the Simple Mail Transfer Protocol (SMTP) is used on the Internet to format email messages. It is the SMTP that requires the fields we are familiar with: to, from, subject, etc, as well the date of the message and all of the other information we see in email headers. Here are some common Application Layer Protocols in the Internet: SMTP - protocol for transmitting email messages; POP - protocol for retrieving email message from a server to a local disk (Eudora uses this protocol). IMAP - protocol for viewing email via a Web browser where the email is stored on the server (URI's WebMail uses this protocol). HTTP - protocol for a client (e.g. Netscape) to ask for a Web page from a Web server (e.g. from einstein.cs.uri.edu). FTP - protocol for a remote computer to ask for any file to be transferred to or from it. Telnet - protocol to allow one computer to act as a terminal for remotely logging into another computer. This is how you can access URI's or Brown's library catalog from a remote computer. SSL - protocol to allow secure transmission of data. This protocol scrambles messages on the sending end and de-scrambles them on the receiving end. There are other protocols too. Application Layer protocols are usually hidden in an application program like Netscape or Eudora. In fact, the most important thing programs like Netscape does is to be able to "talk" these protocols to other computers on the Internet. Each protocol layer adds bits to a message. For instance, say you wanted to send "HI" in email to a friend. The 'H' and 'I' each take eight bits for their ASCII representation, so you want to transmit 16 bits. However when the email leaves your email program, the SMTP protocol requires that to, from, subject, etc fields be added - all of which add on a few hundred more bits. The IP protocol software in the operating system then adds 32 bits for the IP address of the destination computer and 32 bits for the IP address of the sending computer (and some other Bits) - for another 100 or so bits added. The TCP protocol software adds bits to allow error checking and sequencing. Ethernet or PPP protocol software also add bits to control the pulsing on the communication link. Thus, a simple 16 bit "HI" message gets transmitted as several hundred bits! This seems wasteful, but is necessary to get computers from all over the world to understand each other.

Transmission Control Protocol (TCP) – A “Segment” contains data about number and order of packets. Internet Protocol – The “Packet” contains information about the sending IP address and the destination IP address.

Packet – Collection of data at the “network” layer Router – Device that identifies optimal path for network traffic and “routes” or directs packets down that path. TCP/IP – Transmission Control Protocol/Internet Protocol – These are communication standards that enable information to move across a network from one computer to another. DNS – Domain Name System Resolver – Software that uses the DNS to translate a server name into an IP address. (www.friendscentral.org  65.61.134.112) Bandwidth – Number of bits that pass through a given network interface in a given period of time. baud – bits/second KB – Kilobyte Mbps – Megabit Domain – Highest level name server in the DNS(.com,.org,.gov.edu,etc) Download – Save data from server to local machine Upload – Place data from local machine onto server traceroute – Software utility that traces the path of your packets ping – Software utility that tells you how long it takes packets to reach their destination WAN – Wide area network (Internet) LAN – Local area network (FCS Lab) FTP – File Transfer Protocol Encapsulation – Process of adding more and more data to a network data transmission. Encapsulated data enables your messages to get to the right machine in the right order.

9th Grade Computer Science Rotation Mr. Fedder/Mr. Crowley

Networking History of Computers Computer Architecture Hardware & Networking Software

Networking History How networking works Layers Communication Protocols DNS Tools Internet Growth

Networking: Terms Domain Download Upload traceroute ping WAN/LAN FTP Encapsulation Packet Router TCP/IP DNS Bandwidth Baud KB Mbps

History of Networking 1994 - Time magazine: “It was not designed for doing commerce, and it does not gracefully accommodate new arrivals.” 1995 –Newsweek: “BAH!” … “baloney.” “THE INTERNET?”

History of Computers – Networking Arpanet - 1969

History of Computers – Networking

Internet Timeline Mosaic Browser 1993 DarpaNet 1969 Berners-Lee 1989

Internet Connectivity - Growth

Networking - Addressing URL http://www.friendscentral.org/default.asp mfedder@friendscentral.org E-Mail

Networking – Domains Domain Hierarchy

Networking – Domains http://www.friendscentral.org org org

Networking - Types

Networking - Internet 1 2 3 5 4 “Network of Networks”

Networking – Routing Single Point of Failure

Networking – Routing

IP: 192.168.2.161 IP: 192.168.1.5 63.139.238.193 192.168.100.100 216.239.49.214 www.google.com 64.233.161.99 64.233.161.99 Name Server

Traceroute 192.168.100.100 63.139.238.193 216.239.49.214 64.233.161.99

Networking – Hardware Network Interface Card (NIC)

Networking – Hardware HUB

Networking – Communication Stack Open Systems Interconnection

Networking – Communication Stack (cont.) Open Systems Interconnection

Networking – Data Communication

Networking – Data Encapsulation Data: Network: Name, Address, Phone, Visa, 0231234490987111 Transport: TCP info Name, Address, Phone, Visa, 0231234490987111 TCP info Address Address Transmission Control Protocol Internet Protocol

Address Hub Networking – Packet Transmission Data Encapsulation TCP info TCP info Address DATA TCP info TCP info Address Address DATA DATA SOURCE DESTINATION

Networking – Communication

Networking: Terms Domain Download Upload traceroute ping WAN/LAN FTP Encapsulation Packet Router TCP/IP DNS Bandwidth Baud KB Mbps