Internet Tutorial Overview and Definitions - "internet" vs "Internet" - various internets. internet vs Internet (small "i" vs capital "I") internet: a data-communications network built around the TCP/IP family of protocols (as opposed to SNA or Appletalk, etc). Internet: a very large "internet" that connects over 30,000 computers throughout the world. internet - a data-communications network that uses the TCP/IP family of protocols as opposed to SNA, DNA, OSI, X.25, XNS, Novell's protocol, Appletalk, Kermit, or whatever. - is designed around the idea of joining smaller networks to form larger networks. - was originally designed for ARPANET: so ARPANET could be joined with other networks "transparently to the user". - the government was the first big "customer": was originally used to join institutions doing research for the government. - has since spread to other research, university, and technical areas of computing. - made more popular when the University of California at Berkeley used it as the "native protocol" for their version of Unix. internet (continued) - software to support it is now available for virtually all computers. Any computer vendor who wants to sell to the U.S. Government had better offer it. - adopted by the National Science Foundation to build their network to help U.S. researchers. Internet (with a capital "I") - started with ARPANET. - grew as new networks were attached to ARPANET. - now includes more than 30,000 computers on: - ARPANET - MILNET - Wideband - ESNet - DRI - NSFnet - various campus networks of universities and other research institutions (e.g. Syracuse University Internet). - various corporate networks (e.g. Hewlett Packard). - various internets serving other countries. - NSFnet now includes: - BARRNet - CICnet - JVNCNET - Merit - MIDNET - MRNET - NCSANET - NorthwestNet - NYSERNet - PSCNET - SDSCNET - SESQUINET - SURANET - USAN - WESTNET Each of these networks serves a region of the United States and receives funding from the NSF. - NYSERNet interconnects: - NSFnet backbone - ARPANET - Kodak - Clarkson - RADC - SUNY Albany - GE CRD - University of Rochester - Cornell - Syracuse University - RPI - Canadian Defense Research Network - University of Buffalo - SUNY College at Oswego - Skidmore College - SUNY Stonybrook - Columbia - NYU - Brookhaven National Lab - NYNEX - SUNY Binghamton - Alfred - CUNY - Rockefeller University - IBM Syracuse University Internet - part of the Internet. - attached to the rest of the Internet via a connection to NYSERNet. - includes over 200 computers on campus. - serves nearly all large computers on campus. SUMVS and SUAIS are two exceptions. - built out of more than 30 individual local area networks. Internet Tutorial Services to Users - Moving files (FTP) - Signing on to remote computers (TELNET) - Electronic Mail - Other Services Moving Files between computers - you use a "file copy" operation very similar to moving files between disks on a single computer or moving between computers using Kermit. This is different from BITNET where you "send" a file to a username on the receiving-computer. BITNET reassembles the entire file on each computer along the path between the sending- and receiving-computers. - the command (i.e. computer program) to do the copying is usually called FTP (which is also the name of the protocol within the TCP/IP family of protocols used to transfer the data). - FTP usually runs interactively, offering you commands PUT and GET to copy files from your local computer to another and vice versa. - FTP also usually has an array of other commands including DIR to display a file directory on the remote computer. Example FTP Session: % ftp rodan Connected to rodan.acs.syr.edu. 220 rodan.acs.syr.edu FTP server ready. Name (rodan:jw): jmwobus 331 Password required for jmwobus. Password: 230 User jmwobus logged in. ftp> get myfile.data 200 PORT command successful. 150 Opening data connection for myfile.data 226 Transfer complete. local: myfile.data remote: myfile.data 1153 bytes received in 0.18 seconds (6.3 Kbytes/s) ftp>quit % Signing On to Other Systems - a command to your computer makes your keyboard and screen appear to be a terminal on another computer. - the command (i.e. computer program) to do this is usually called TELNET (which is also the name of the protocol within the TCP/IP family of protocols used by a TELNET program to carry out the function). Example TELNET Session: % telnet rodan Trying... Connected to rodan.acs.syr.EDU. Escape character is '^]'. UTX/32 (rodan.acs.syr.edu) login: jmwobus Password: Last login: Tue May 30 10:48:07 from mordor % ls myfile.data % ls -a . .. myfile.data % Connection closed by foreign host. % Electronic Mail - internets transfer electronic mail using protocols of the TCP/IP family called SMTP and RFC822. - various computers have their own commands to send and receive electronic mail. If the computer is on an internet, these are usually extended to send and receive electronic mail through the internet. For example, SUVM's EMAIL command sends electronic mail to other SUVM users, to other BITNET computers and to other Internet computers. The software figures out which to do by inspecting the electronic-mail address and by comparing the form of the address with internal tables. Example internet-style electronic mail address: jmwobus@suvm.acs.syr.edu Other internet services: Signing on to (other) IBM mainframes: - There is a "variation" of TELNET which allows IBM fullscreen terminals to use TELNET to reach other systems as fullscreen terminals. If you TELNET from SUVM to another system running VM, it will use this variation automatically. - Other systems (other than IBM mainframes) require a special version of TELNET, typically called TN3270 to use an IBM mainframe in "fullscreen mode". - TN3270 needs to know how to operate the screen and keyboard--thus, for example, when you use it from RODAN, it needs to know what type of terminal you are using. Other Network Services: NFS - allows you to use files on another computer as if they were on your own. NeWS & X-Windows - either NeWS or X-Windows allows your screen, mouse, and keyboard to open windows to other computers running programs on them as if they were running on your own computer. USEnet News - a bulletin-board system allowing people throughout the Internet to post articles by topic and to select a topic & read. WHOIS - a directory program for looking up electronic- mail addresses at other sites. LPR & LPD - allow you to print documents on printers on other computers on the Internet. Internet Tutorial Theory - Some Definitions & Explanations - Names & Addresses of Computers - What you can reach & why - Anatomy of a TELNET session Definitions & Explanations: IP a data-communications protocol to direct individual "packets" of data from one computer to another even if they are on separate networks. "IP" stands for "Internet Protocol". TCP a data-communications protocol to move data byte-by-byte from one computer user to another (who may be on a different computer), making sure that each byte arrives in order. It uses IP to actually move the data between computers. "TCP" stands for "Transmission Control Protocol". Definitions & Explanations: UDP a data-communications protocol to direct "packets" of data from one computer user to another even if they are on different computers on different networks. It uses IP to actually move the data. "UDP" stands for "User Datagram Protocol". Ethernet a data-communications protocol which uses a wire (coaxial cable) to move packets between computers. The word "Ethernet" is also used to designate a network built using this protocol. Ethernets are often used as building-blocks for internets: IP uses Ethernets to move data between computers: IP manages the movement of data from one Ethernet to another. Names & Addresses of Computers - each computer on an internet is given a unique "internet name" for the purposes of the internet. Official Internet names are rather long because they must be unique among the 30,000+ computers on the Internet. Examples: suvm.acs.syr.edu sunrise.acs.syr.edu sutcase.case.syr.edu cornellc.cit.cornell.edu - The short name that most sites give their computers are turned into longer, unique names through the use of "qualifiers". Example qualifiers: .acs .syr .edu .cornell Names & Addresses of Computers - Meaning of qualifiers: The set of names ending in the qualifiers ".syr.edu" belongs to Syracuse University. Such a set of names is called a "domain". Names & Addresses of Computers Normal use of names: telnet suvm.acs.syr.edu email jffowler@icarus.cns.syr.edu ftp rodan.acs.syr.edu Names & Addresses of Computers - Do you have to use qualifiers? Much computer software has been designed to supply a default set of qualifiers which you configure when installing the software. At SU we recommend: .syr.edu - To make this work better, major computers at Syracuse University have been given synonyms using only these qualifiers. For example: SUVM's official Internet name is: suvm.acs.syr.edu but also has the synonym: suvm.syr.edu thus all software which adds ".syr.edu" will take "suvm". Names & Addresses of Computers - internet addresses (i.e. internet numbers) are not normally necessary except when you install your software. The software uses them internally during normal operation, but does not expect the user to know them. - some internet software will take an internet address in place of an internet name if the name has not been "made available" for your use. Names are distributed by passing around a file that holds a long list of names and through an Internet-wide database system which allows each institution to add its own names & all computers to retrieve them automatically. Example internet address: 128.230.1.55 (this happens to be the Internet address of RODAN). What can you reach? - When you use an "interactive" command such as TELNET or FTP, there are two reasons you may not be able to get through: - your computer does not recognize the name of the computer you are reaching. Computers which hold their own list of names "know" significantly fewer names than those that use the Internet-wide distributed database of names. You can often get around this problem by using the Internet address. - some network or a piece of some network is down. - Some network applications have been implemented with "timeouts": they require a response within a certain time or they abort. Thus "network congestion" can also prevent you from reaching a site. Internet-like names for Electronic Mail - some networks which are not part of the Internet have very similar names (with qualifiers not found on the Internet). Some have names identical to the Internet. Examples: suais.bitnet Many BITNET nodes will direct this to SUAIS. It is relatively easy to tell from official Internet names because ".bitnet" is not an official qualifier for the Internet. jimi.cs.unlv.edu This computer is on CSNET but not on the Internet. You cannot tell this by simple inspection: ".edu" is a legal final qualifier for the Internet. - CSNET and BITNET are examples of two networks which allow computer-names indistinguishable from Internet names. Internet-like names for Electronic Mail - Solution to the confusion: A new feature of the TCP/IP protocols allows one computer on the Internet to handle mail directed to a different name: this gives the owners of computers not on the Internet but with Internet- like addresses a mechanism for delivering their mail to a computer of their choice. Presumably they have programmed "the computer of their choice" to complete the delivery through non- internet means. The name of the feature is: MX which stands for mail exchanger. - A further problem: Unfortunately, the new feature requires each computer that SENDS the mail to explicitly ask for a list of "mail exchangers" before delivering any mail, i.e. all Internet mail software needs to be upgraded. Internet-like names for Electronic Mail At present, three computers at Syracuse University look for an Internet-style name's designated mail- exchanger: icarus.cns.syr.edu top.cis.syr.edu logiclab.cis.syr.edu In addition to this, SUVM implements a similar mechanism supported by BITNET to deliver to many of the same addresses (and others), but does not itself look for designated mail-exchangers. Thus, SUVM and ICARUS deliver to more addresses than any other computers at SU. The next release of SUVM's software will support MX, thus making it the best. Within a year, SUNRISE and RODAN will probably also support MX. Anatomy of a TELNET Session: - A user on a PC types the command: telnet sunrise - The PC must figure out what Internet address to use. It tacks the qualifiers ".syr.edu" on the name to yield "sunrise.syr.edu" and (using an IP packet) sends a query on the network to Internet address 128.230.1.49. This number was given to the PC software when it was installed. - 128.230.1.49 is the Internet address of "icarus.cns.syr.edu", which holds a table of all the Internet names and addresses for computers at Syracuse University. It responds with an answer telling the PC to use the Internet address 128.230.1.1 (the Internet address of SUNRISE). - The PC sends an initial IP packet to SUNRISE which holds a request to start a "TCP" session. Then it waits for an acknowledgment from SUNRISE. - SUNRISE receives this initial IP packet and returns an IP packet which acknowledges the request. Anatomy of a TELNET Session: - Upon receiving the acknowledgment from SUNRISE, the PC displays a message to you to the effect that the connection has been completed. It sends back another IP packet to SUNRISE "acknowledging the acknowledgment". This is called a "three-way handshake" and is carried out to help SUNRISE detect some possible problem conditions. - Some further IP packets are exchanged to "negotiate TELNET options". The TELNET protocol is designed to support "optional characteristics": if the software on one side requests a certain option and the other side supports it, they exchange messages to discover this. A good example is the "fullscreen support" for IBM mainframes: it only happens if both ends support it. Anatomy of a TELNET Session: - Further IP packets hold the data "bytes of data" that you type and to be displayed on your screen. TCP numbers the bytes and makes certain that they are all received, in order, even if an IP packet is dropped, duplicated, or one IP packet "passes" another on the way. - Finally, you type "LOGOFF" to SUNRISE. After it has displayed all the "final output", it sends an IP packet to the PC that signals the end of the session. - Upon receipt of this packet, the PC displays a message to the effect that the session has been terminated by SUNRISE and sends an IP packet back to SUNRISE to acknowledge the end of the session as well as state that the PC is also done. - Upon receipt of this acknowledgment, sends one more IP packet to acknowledge it: another 3-way handshake. The final 3-way handshake did little good here, but is useful in some internet applications to make sure that the final data in each direction gets through. Internet Tutorial PCs and Macintoshes on the Internet - Single User Systems in General - Macintosh Capabilities - Putting a Macintosh on the SU Internet - PC Capabilities - Putting a PC on the Internet Single User Systems In General - Are likely to run one of the following systems: - MSDOS or PCDOS - MAC-OS - UNIX or some flavor (SunOS, AU/X, etc) - VMS (i.e. MicroVAX systems) - Generally do not automatically receive & store electronic mail through the Internet. Reasons: - Mail waiting for a system that is turned off requires the sending computer to hold the mail and periodically attempt to send the mail, thus using disk space as well as network capacity. - Single-user systems are generally less secure than multi-user systems. - Electronic mail is a bit problem-prone and the services of a "system administrator" can help it continue to work smoothly. Macintosh Capabilities - At SU, we recommend a software package called "Stanford University MAC/IP" for use on Macintoshes. - Macintoshes on the SU Internet are generally attached to Appletalk networks which are, in turn, connected to the SU Internet through Appletalk-to-internet gateways. - This software is available on the SU-wide Appletalk file server: Macintoshes on SU-Internet-connected Appletalk networks can load it. - Capabilities include: - FTP - TELNET - TN3270 Putting a Mac on the SU Internet - The easiest way is to attach it to an SU-Internet- connected Appletalk. With the proper Appletalk Software, it is ready to use the Internet. - The "configuration" work is shifted to the administrator of the Appletalk & its gateway to the SU Internet. PC internet Capabilities - At SU, we recommend a software package called NCSA/TELNET for use on PCs. - With NCSA/TELNET and a PC "Ethernet" card, you have the following internet services: - TELNET (with multiple simultaneous sessions) - FTP - Other PC software packages also offer: - TN3270 - NFS Putting a PC on the SU Internet - You need an Ethernet "Card" (the choice depends partly on your PC's "BUS"). Examples: - 3COM 3C501 Etherlink - MICOM N15210 - Ungermann-Bass PC-NIC - Western Digital WD8003E EtherCard PLUS - Ungermann-Bass NICps/2 - 3COM 3C523 Etherlink/MC - You need a connection to one of the Ethernets that makes up the SU Internet. - You need a copy of NCSA/TELNET (presumably on Floppy). Putting a PC on the SU Internet - Upon installing NCSA/TELNET, you will have to set various "configuration parameters", some of which depend upon the fact that your PC is at Syracuse University: - An official Internet address for your PC. You must get this from the person administering the LAN you are attached to. - A "Subnet mask". This is the same throughout the SU Internet: 255.255.255.0 - A "default domain", i.e., a default set of qualifiers to add to names which you enter without qualifiers. On the SU Internet, PCs use "syr.edu". - The official Internet address of an internet gateway for the LAN you are attached to. You must get this from the person administering the LAN you are attached to. - The official Internet address of a "name server" (i.e., a computer which can tell your PC what Internet address to use when you type and Internet name): you can use 128.230.1.49 or the person administering your LAN might know of a closer one.