SYRACUSE UNIVERSITY INTERNET HOST ADMINISTRATOR'S GUIDE John M. Wobus Communications & Development Computing & Network Services Syracuse University May 16, 1991 Document Number: HADMIN-5 (c) Syracuse University Computing & Network Services 1991 No warranty is expressed or implied. Permission to copy and use is extended to all. Permission to redistribute is granted under the following conditions: it is not sold for profit; this copy- right notice remains intact; the same permissions extend to the recipient; and if any changes are made, a notice is added so stating. Abstract This guide tells you what you need to know to attach your com- puter to the Syracuse University Internet. This guide is intend- ed for technical people responsible for computers that are attached to the Syracuse University Internet as well as technical people responsible for the local area networks that make up the Syracuse University Internet. This guide does not replace the instructions for installing the device or the network software. It merely fills in gaps with data and procedures specific to Syr- acuse University. This guide deals with computers with only one connection to the Internet. It does not deal with computers that are serving as internet gateways. Abstract ii Contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . ii Syracuse University Internet Host Administrator's Guide . . . . 1 Setting Up Your Host . . . . . . . . . . . . . . . . . . . . 1 Automatic Configuration . . . . . . . . . . . . . . . . . . 2 Network Configuration Information . . . . . . . . . . . . . 3 An Official Internet Address . . . . . . . . . . . . . . 3 An Official Internet Name . . . . . . . . . . . . . . . . 3 Network Characteristics . . . . . . . . . . . . . . . . . 4 LAN Encapsulation . . . . . . . . . . . . . . . . . . 5 ARP . . . . . . . . . . . . . . . . . . . . . . . . . 5 Network Mask . . . . . . . . . . . . . . . . . . . . . 5 Default Gateway . . . . . . . . . . . . . . . . . . . 5 Broadcast Address . . . . . . . . . . . . . . . . . . 6 Trailer Encapsulation . . . . . . . . . . . . . . . . 6 RIP . . . . . . . . . . . . . . . . . . . . . . . . . 6 Names of Other Internet Computers . . . . . . . . . . . . 7 Host Table . . . . . . . . . . . . . . . . . . . . . . 7 Domain Name System . . . . . . . . . . . . . . . . . . 8 Spreading Your Computer's Internet Name . . . . . . . . . 10 Appendix A: Contacts . . . . . . . . . . . . . . . . . . . . 11 Syracuse University Internet Administrator . . . . . . . . 11 Academic Computing Services Macintosh Help . . . . . . . . 11 LAN Administrator . . . . . . . . . . . . . . . . . . . . 12 Departmental Name Administrator . . . . . . . . . . . . . 12 Appendix B: Choosing a Computer or Workstation . . . . . . . 13 Some Approved Implementations . . . . . . . . . . . . . . 14 Some Critical Features . . . . . . . . . . . . . . . . . . 14 Some Desirable Features . . . . . . . . . . . . . . . . . 15 Some Future Desirable Features . . . . . . . . . . . . . . 15 Appendix C: Network Configuration Information Summary . . . 16 Syracuse University Internet Host Administrator's Guide iii Syracuse University Internet Host Administrator's Guide The Internet is a world-wide cooperative network made up of many interconnected smaller networks. The Syracuse University Internet is a portion of the Internet that is located at Syra- cuse University. It is made up of several LANs (Local Area Net- works), each of which serves a portion of the University. A sin- gle LAN might serve a building, a hallway, or a single room. All the LANs are connected together by a campus-wide network which is connected, in turn, to a network which serves our region (NYSER- Net, the New York State Educational and Research Network) which is connected via national networks (such as NSFnet) to other regional networks, and through them to other campuses and their LANs. Not all LANs at Syracuse University are part of the Internet. Network programs can only communicate with others of the same "family"(1) so the various University LANs are intended to sup- port programs of one or another particular "family". These include the "internet family" (or the TCP/IP "family") as well as "families" specific to various individual computer and network vendors. Internet networking software has the advantage of tying your computer with virtually all types of computers, and through the Internet, to other Universities and research institutions throughout the world. Setting Up Your Host Part of the procedure for connecting your computer to the Internet cannot be adequately described by your computer's manu- al. Internet network software has "blanks" to fill which need to be completed in cooperation with the rest of the Syracuse Univer- sity Internet. We shall refer to this information as "network configuration information". This guide supplement's your comput- er's manual by providing this information, or telling you how to get it. There are three ways your computer gets this information: Pre-configuration At the time you get the software, it is already config- ured with some or all of the network configuration information. ---------------------- (1) Family is not a standard data-communications term. In stan- dard terminology: There are different, incompatible data- communications protocols that any particular piece of network software may support. Syracuse University Internet Host Administrator's Guide 1 Automatic Configuration Your computer gets its network configuration informa- tion by using the network to ask special computers designed to hand out this information. This all hap- pens behind the scenes. Manual Configuration You have to get the network configuration information and configure your network software with it. Depending on your network software, you either have to create a file or you have to run its configuration program. Note: Various parts of this document refer to departments or people to contact. Further information on contacting them is in an appendix. Automatic Configuration Automatic configuration requires: 1. Your computer's network software has the automatic configu- ration feature. 2. Your computer's network configuration information has been added to the network server which will supply this informa- tion to your computer. There are three kinds of automatic configuration in use at Syracuse University: * Macintoshes attached through Localtalk (Phonenet) are precon- figured with some of the network configuration information and get the rest from the Localtalk/Ethernet gateway, which is preconfigured with the rest of the information. * Sun Workstations (such as "diskless" Sun Workstations) that use a "boot server" use a network service called RARP to get their network configuration information. * IBM PCs (and compatibles) as well as Macintoshes and Work- stations may use a network service called BOOTP to get their network configuration information. If your computer is going to use BOOTP, a computer on the network called the "BOOTP server" (which will answer your computer's query for network configuration information) must be prepared with your comput- er's specific network configuration information. In this case, in place of supplying all the network configuration information to your computer, you need only configure it to "use BOOTP". Syracuse University Internet Host Administrator's Guide 2 Network Configuration Information An Official Internet Address Your computer must know its official Internet Address. See your LAN's administrator to get one. The Internet Address is a number that is unique throughout the entire Internet. Each dif- ferent LAN at Syracuse University "owns" a set of addresses. The LAN's administrator keeps track of these addresses, assigning them to the individual computers on the network. +---------------------------------------------------------------+ | | | 128.230.1.55 | | | | | | Figure 1: Example Internet Address | +---------------------------------------------------------------+ An Official Internet Name Your computer may have to know its official Internet Name. Your department might supply them. If not, then you can contact the Syracuse University Internet Administrator. The Internet Name is a name that is unique throughout the entire Internet.(2) Some Syracuse University departments already own sets of official Internet Names and have designated someone to hand them out. These names can be thought of in two parts: a short name, and a string of "qualifiers". ---------------------- (2) It seems redundant to make each computer have both a unique name and a unique address, but that is how they designed the Internet. The number is for internal use by networking soft- ware and includes encoded information to help route the data quickly. The name is for the people that use the network. Syracuse University Internet Host Administrator's Guide 3 +---------------------------------------------------------------+ | | | sugaree.syr.edu - official Internet name of the | | computer. | | | | sugaree - a name agreed upon by the computer's | | administrator and the Syracuse | | University Internet Administrator. | | | | .syr.edu - the "qualifiers", designating | | Syracuse University. | | | | | | Figure 2: Example Internet Name and its parts | +---------------------------------------------------------------+ Normally, you can choose a short name yourself, then check it with the Syracuse University Internet Administrator, to make sure it is not already in use, etc. If your department owns a set of names, then the names look slightly different: +---------------------------------------------------------------+ | | | spider.cns.syr.edu - official Internet name of the | | computer. | | | | spider - a name agreed upon by the computer's| | administrator and the administrator | | of the department's names. | | | | .cns.syr.edu - the "qualifiers" belonging to | | the department. | | | | | | Figure 3: Example Internet Name and its parts | +---------------------------------------------------------------+ In this case, the choice of short name is a matter between the department's administrator of Internet names and the administra- tor of the computer. Network Characteristics There are many different types of LANs which can be used on the Internet. Syracuse University Internet supports only Ether- Syracuse University Internet Host Administrator's Guide 4 net LANs and Phonenet LANs. There are also some conventions which all the computers on the LAN must agree upon if they are to communicate with each other. These are discussed below. LAN Encapsulation The Syracuse University Internet supports two types of LANs: Ethernet/IEEE 802.3 The Syracuse University Internet uses network hardware which adheres to Ethernet and IEEE 802.3 standards. The LAN Encapsulation supported is "Ethernet" or "RFC894".(3) Phonenet The Syracuse University Internet uses Phonenet, a type of LAN that can be plugged into a Macintosh's Localtalk (LAN) jack through the use of a "Phonenet adaptor". The LAN Encapsulation supported is known as "KIP". ARP If your computer is attached to an Ethernet LAN, then it must use ARP. If the software offers it merely as an option, then it must be turned on. Network Mask Your computer should be set to use a network mask of 0xffffff00 (also known as 255.255.255.0). This is the network mask used throughout the Syracuse University Internet. Some older internet software does not allow you to set a net- work mask. Some Ethernets on the Syracuse University Internet provide a service called "Proxy ARP" which allows these computers to work. If you cannot set a network mask on your computer, con- sult with the administrator of your LAN to see if it provides Proxy ARP service. However, this is a stopgap measure--you should acquire software that can use the network mask. Default Gateway ---------------------- (3) The Syracuse University Internet does not use a different encapsulation known as "IEEE 802.3", "RFC948", or "RFC1042". This is designed for the same hardware, but will not interop- erate with the "Ethernet" encapsulation. Syracuse University Internet Host Administrator's Guide 5 You should find out the default gateway of your LAN from your LAN's administrator and set your computer to use it. Some internet software doesn't allow you to set a default gateway. A computer running such software cannot communicate with the entire Internet. You should avoid such computers if possible, otherwise complain to the vendor. Broadcast Address You should find out the broadcast address of your LAN from your LAN's administrator and set your computer to use it. Some old internet software does not allow you to set the broadcast address used on your LAN. This is harmless if your computer doesn't use broadcasts. If you can turn off all servi- ces that use broadcasts, then you can still safely place your computer on the LAN. If not, consult your LAN administrator or the Syracuse University Internet administrator to find out about any other alternatives. Trailer Encapsulation You should turn off trailer encapsulation if your computer offers it as an option. Be careful because many computers use "trailer encapsulation" by default. RIP You should set your computer to not send RIP. You may option- ally set it to listen to RIP. Listening to RIP is of no use to your computer if it is properly configured and if there is only one internet gateway on your LAN. If there are two or more gate- ways on your LAN, then listening to RIP can help your computer perform better when the default gateway for the LAN is down (not perfectly, just better). To make a Berkeley-Unix-derived system listen to RIP but not send it, run the "routed" program with the "-q" option.(4) ---------------------- (4) The reason that some computers allow you to send RIP is that these computers are designed so that they can serve as gate- ways. If your computer will serve as a gateway, then you need a lot more information than this guide provides to set it up properly. Syracuse University Internet Host Administrator's Guide 6 Names of Other Internet Computers You should prepare your computer to recognize the names of other computers on the Internet. There are two different ways to do this. Depending on the software you are running, you may be confined to one or you may have a choice. The older method (which eventually will be phased out) is to install a list of names known as the host table. The newer method is to make your computer use a network service that provides your computer with the name of every computer on the Internet.(5) Host Table Your computer should have directions about how to build its host table. It will require that you provide it with a file which includes the necessary information. There is a standard file format used throughout the Internet to distribute data about hosts. Most computers do not use the standard format directly, but have a utility that converts the standard format to their own preferred format. Computing and Network Services makes some "host table" files available via the Internet: hosts.txt This file contains data about computers all over the world in standard format. An updated copy is placed on a computer named "syr.edu" about once a week. Its data about computers at Syracuse University is sparse. localhosts.txt This file contains data about computers at Syracuse University in standard format. localhosts This file contains the same data as "localhosts.txt" but in a format usable by BSD-derived Unix systems. unix_hosts This is all the data, world and local, pre-prepared for BSD-derived Unix systems. On such systems, it is stored as "/etc/hosts". It is not in the standard for- mat, but in a format specific to BSD. Some other sys- tems also use this same format. These files are stored on syr.edu, and can be retrieved via ftp using username "anonymous" and any password. The files are in a directory called "networks/config". ---------------------- (5) There is a third method which uses a network service called Yellow Pages. It can be used to handle this problem for entire networks of Sun computers. See Sun documentation for details of this method. The Name Domain System has the same advantages plus the advantage of being standard. Syracuse University Internet Host Administrator's Guide 7 Getting Started: To get started, you will need to get this file without the luxury of using a name (since your computer knows none). Use your computer's ftp program to transfer the appropriate files from syr.edu, but use syr.edu's Internet Address rather than its name. Syr.edu's Internet Address is "128.230.1.49". After set- ting the username, password, and directory as described above, you can get whichever of the four files that your computer needs. Domain Name System There is a bit of difference in how a small computer and a large computer use the domain name system. Single-user Computers: Your computer must have a function called the "domain name resolver" which knows how to ask other computers about names. It must be configured with the official Internet Address of one or more other computers that know the names or where to find them. Such computers are known as "name servers". We recommend you configure your resolver with a minimum of three name servers if it allows you to do so. Ideally, your computer's name servers would be on the same LAN as your computer. See the administrator of your LAN to find out if there are any. After those on your on LAN, try to pick names- ervers in your building; then (lastly) those in Machinery Hall. Here are the names of some name servers that Computing & Network Services provides in case you need them. +---------------------------------------------------------------+ | zookeeper.cns.syr.edu 128.230.31.2 (Center for Science | | & Technology) | | lurch.cns.syr.edu 128.230.12.5 (Machinery Hall) | | rodan.acs.syr.edu 128.230.1.55 (Machinery Hall) | | syr.edu 128.230.1.49 (Machinery Hall) | | | | Figure 4: Some name servers for general campus use | +---------------------------------------------------------------+ Default Domain: Your computer might allow you to configure a default domain. The default domain for Syracuse University Internet is "SYR.EDU". Multi-User Computers: Syracuse University Internet Host Administrator's Guide 8 A large computer can be configured to use a resolver, but in the interest of efficiency and failure tolerance, it should real- ly be a "domain name caching-only server" if your internet soft- ware can do this. A caching-only server needs to know the offi- cial Internet Address of one or more computers that know all the names or where to go to get all the names. Such computers are known as "root name servers". Below is the list of root name servers which should be used to configure caching-only name ser- vers. +---------------------------------------------------------------+ | a.isi.edu 26.3.0.103 | | a.isi.edu 128.9.0.107 | | aos.brl.mil 192.5.25.82 | | aos.brl.mil 128.20.1.2 | | c.nyser.net 192.33.4.12 | | gunter-adam.af.mil 26.1.0.13 | | ns.nasa.gov 192.52.195.10 | | ns.nic.ddn.mil 192.67.67.53 | | terp.umd.edu 128.8.10.90 | | | | Figure 5: Root Name Servers for use by caching-only ser- | | vers | +---------------------------------------------------------------+ Note that in some cases the same name is listed with two differ- ent addresses. If your software cannot deal with this, you can just leave out the second entry such entry for the name server. Caching-only servers that can give special handling to names ending in "SYR.EDU" may also be configured with the name servers listed above for resolvers. Doing so can make the caching-only server operate more efficiently for such names as well as make them usable even when the Syracuse University Internet cannot reach any of the root name servers. Host Table Too: A computer that uses the domain name system may also require a host table--which is used any time that the name domain service is not functioning. If your computer requires a host table, or allows you to use it as a backup, see the information above on host tables. Syracuse University Internet Host Administrator's Guide 9 Spreading Your Computer's Internet Name You should make the name of your computer available to other computers on the Internet. Tell the Syracuse University Internet administrator about your computer's official Internet Name and Address so who will include them in the local host tables and the domain name system. Thus all Syracuse University computers will handle the name as well as all non-Syracuse University computers that use the domain name service. Upon request, the administrator will also submit the name of large computers (which serve numerous people) for inclusion in the "world-wide" host table, so all non-Syracuse University com- puters will handle the name. Syracuse University as well as oth- er Internet sites are minimizing the number of computers they include in the world-wide host table to keep it to a manageable size. Syracuse University Internet Host Administrator's Guide 10 Appendix A Contacts This guide refers to four contacts. Syracuse University Internet Administrator +---------------------------------------------------------------+ | John Wobus Phone: 443-4324 | | Internet address: jmwobus@suvm.acs.syr.edu | +---------------------------------------------------------------+ Since one person might be on vacation, as a backup, contact: +---------------------------------------------------------------+ | Phil Green Phone: 443-5775 | | Internet address: pmgreen@suvm.acs.syr.edu | +---------------------------------------------------------------+ Academic Computing Services Macintosh Help Two different groups within Academic Computing Services offer help for Macintosh software. If you are a faculty member, con- sult: +---------------------------------------------------------------+ | Faculty Assistance and Computer Education Services | | Phone: 443-1865 | +---------------------------------------------------------------+ If you are a staff member, consult: +---------------------------------------------------------------+ | Office Technology Phone: 443-3989 | +---------------------------------------------------------------+ Syracuse University Internet Host Administrator's Guide 11 In case this changes, the Academic Computing Services Help Line can direct you to whatever services they offer: +---------------------------------------------------------------+ | ACS Help Line Phone: 443-2677 | +---------------------------------------------------------------+ LAN Administrator If you are connecting to a LAN administered by your depart- ment, then you probably know who its administrator is. Other LAN's are administered by the Syracuse University Internet Admin- istrator who can also give you the name of the LAN administrator if you are not sure. Departmental Name Administrator If you are on a departmental LAN, this is very likely to be the same person as the LAN administrator. If not, you can con- tact the Syracuse University Internet Administrator who will tell you who administers names for your department. Contacts 12 Appendix B Choosing a Computer or Workstation This appendix deals only with networking issues. It is not a "complete guide" to choosing a workstation. In order to attach a computer or workstation to the SU Inter- net, your computer must support "IP networking" (also known as TCP/IP) It may have come with such support, or you may have do acquire additional hardware and/or software to give it such capa- bility. IP networking is not well standardized, so you cannot take the vendor's word that it will work. The rules are continually being changed, often making the old rules no longer apply--thus you cannot even be assured that an old implementation which "works in a limited manner" will be sufficient for your needs. It may not work at all or may even cause trouble for other users of the net- work.(6) Ideally, the rules would be periodically "frozen" with a name or number that you can cite to the vendors of computers or soft- ware that you are interested in. Then you might establish exact- ly what it is a vendor claims to support and whether that is suf- ficient to work on the SU Internet. This is not the case.(7) All we can offer you is a list of implementations that we know work, and a list of features that are sometimes missing. ---------------------- (6) Why do the rules change? Mostly to accommodate expansion way beyond what the original rules were designed to handle. Without many of these changes, Syracuse University would nev- er have had the opportunity to join the Internet. Some of these changes might have been avoided by better planning, but others deal with the technical problems of large networks that seem hard to predict even with hindsight. In general, the designers did no worse than the designers of most comput- er systems and by acting quickly while "remaining flexible", they have a working international network whereas the purve- yors of "carefully worked-out standards" are still years away from such a thing. (7) There are people currently formulating a statement of exactly what a computer must do to claim the ability to interoperate with other internet computers. It will probably be completed by the end of 1989, at which time you will be able to cite it to vendors. Syracuse University Internet Host Administrator's Guide 13 Some Approved Implementations Many computers, both Unix and non-Unix use internet networking software either adapted from that included with Berkeley Unix or written to mimic Berkeley Unix's networking software. Berkeley's latest release (known as BSD 4.3) is as good as any internet net- working software available. Berkeley's previous release (BSD 4.2) works but lacks configurable network masks and broadcast addresses. Vendors sometimes use the phrase "including the Berkeley enhancements" (or a similar phrase citing the version number) to describe their system. Unfortunately, some will use the phrase to mean they wrote their own internet implementation for their own Unix, or (in the case of "BSD 4.3 enhancements") because they have added some internet feature which Berkeley did not include until their BSD 4.3 version. In either case, this is no assur- ance that their implementation works as well as Berkeley's. Specific approved implementations: Sun 3 SunOS 4.0, SunOS 4.0.1, SunOS 4.0.3, SunOS 4.1. Sun 4 SunOS 4.0, SunOS 4.0.1, SunOS 4.0.3, SunOS 4.1. VAX/VMS 5.0 Wollongong WIN/TCP for VMS 5.0, Multinet 2.1. Macintosh (MacOS) Apple MacTCP 1.0.1. IBM PC NCSA/TELNET 2.2, Stanford University PC/IP 3.1. Stanford University MAC/IP 4.0 has been announced and is likely to be approved when we have tested it. Some Critical Features This is a list of some critical features that we have found missing in some implementations of IP networking. It is not comprehensive enough to guarantee that software incorporating these features will work well on the Internet. * The ability to route data through Internet gateways to other networks. * The ability to configure a default route. * The ability to handle ICMP redirect messages. * The ability to handle long names. The true length limit is 255 characters, but 20 characters is a practical minimum. Your computer's software must allow its own name to be at least 20 characters. Choosing a Computer or Workstation 14 * The ability to route by means of a configurable network mask.(8) * On Ethernets, adherence to the Ethernet encapsulation stan- dard(9) (rather than the use of the IEEE 802.3/802.3 encapsu- lation standards). * On Ethernets, use of the ARP protocol.(10) Some Desirable Features This is a list of some desirable features that are not abso- lutely necessary but are recommended. * Support for the Domain Name System. * If it uses a resolver, the ability to search through a list of domain name servers to find one that is working. * If it uses broadcasts, the ability to send and receive "one- filled" broadcasts, receiving both 255.255.255.255 and 128.230.X.255, and sending broadcasts in one of these forms. * If it delivers mail, the ability to look for mail exchangers. * If it uses the domain name system, the ability to try more than one internet address when starting a connection. Some Future Desirable Features These are features that you simply cannot get now, but promise to be desirable: * Compliance with the Host Requirements RFCs (Internet RFC 1122 and Internet RFC 1123). ---------------------- (8) This is described in Internet RFC 950. (9) This is described in Internet RFC 894. (10) This is described in Internet RFC 826. Syracuse University Internet Host Administrator's Guide 15 Appendix C Network Configuration Information Summary * Internet Address (i.e. Internet Number): _______________ * Default Gateway: _______________ * Name servers: ________________, __________________, * Internet Name (optional): ______________ * Broadcast Address (optional): ________________ * LAN Encapsulation: Ethernet (a.k.a. RFC894) for Ethernets; KIP for Phonenets * Network Mask: 255.255.255.0 (a.k.a. ffffff00) * ARP: yes * Trailer Encapsulation: no * RIP: no (except in special cases) Network Configuration Information Summary 16