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INFORMATIONAL
Network Working Group                                        V. AggarwalRequest for Comments: 1291                      JvNCnet Computer Network                                                           December 1991Mid-Level NetworksPotential Technical ServicesStatus of this Memo   This RFC provides information for the Internet community. It does not   specify an Internet standard. Distribution of this memo is unlimited.Abstract   This document proposes a set of technical services that each Internet   mid-level network can offer within the mid-level network itself and   and to its peer networks. The term "mid-level" is used as a generic   term to represent all regional and similar networks, which, due to   continuous evolutions and transitions, can no longer be termed   "regional" [MAN]. It discusses the pros and cons of offering these   services, as well as areas in which mid-level networks can work   together.   A large portion of the ideas stem from discussions at the IETF   Operational Statistics (OPstat), User Connectivity Problems (UCP) and   Network Joint Management (NJM) working groups.Table of Contents1. Introduction..................................................22. The Generic Model.............................................23. Technical Services............................................33.1  Domain Name Service.........................................33.2  Public Domain Software......................................43.3  Network Time................................................53.4  Network News................................................53.5  Mailing Lists...............................................64. Experimental Testbeds.........................................65. Network Information Services..................................76. Network Operations............................................77. References....................................................88. Security Considerations.......................................99. Author's Address..............................................9Appendix A Mailing Lists.........................................10Appendix B DNS Architecture Strategy.............................10Aggarwal                                                        [Page 1]

RFC 1291             Potential Technical Services          December 19911. Introduction   Over the past few years, the Internet has grown to be a very large   entity and its dependability is critical to its users. Furthermore,   due to the size and nature of the network, the trend has been to   decentralize as many network functions (such as domain name-service,   whois, etc.) as possible. Efforts are being made in resource   discovery [SHHH90] so that the work of researchers is not lost in the   volumes of data that is available on the Internet.   A side result of this growth has been the logical structure imposed   in the Internet of networks classified by function. Tangible examples   in the present state are the NSFnet national backbone, the mid-   level/regional networks and campus networks. Each of these can be   viewed as hierarchies within an organization, each serving a slightly   different function than the other (campus LANs providing access to   local resources, mid-level networks providing access to remote   resources, etc.). The functions of each hierarchy then become the   "services" offered to the organizational layer below it, who in turn   depend on these services.   This document proposes a set of basic technical services that could   be offered by a mid-level network. These services would not only   increase the robustness of the mid-level network itself, but would   also serve to structure the distribution of resources and services   within the Internet. It also proposes a uniform naming convention for   locating the hosts offering these services.2. The Generic Model   The Internet model that is used as the basis for this document is a   graph of mid-level networks connected to one another, each in turn   connecting the campus/organization networks and with the end users   attached to the campus networks. The model assumes that the mid-level   networks constitute the highest level of functional division within   the Internet hierarchy described above (this could change in the   unforeseen future). With this model in perspective, this document   addresses the objectives of minimizing unnecessary traffic within the   Internet as well as making the entire structure as robust as   possible.   The proposed structure is a derived extension of organizational LANs   where certain services are offered within the organizational LAN   itself, such as nameservice, mail, shared files, single or   hierarchical points of contact for problems, etc.   The following are the services that are discussed as possible   functions of a mid-level network:Aggarwal                                                        [Page 2]

RFC 1291             Potential Technical Services          December 1991     o  Technical services     o  Experimental sites for testing and dissemination of new        software and technology to end sites on the network   In addition, the following services are mentioned briefly which are   discussed in detail elsewhere [SSM91,ML91]:     o  Network Operation services and the interaction between        different mid-level networks in this area     o  Network Information services3. Technical Services   The Internet has grown to be an essential entity because of the   services that it offers to its end users. The list of services is   long and growing, but some services are more widely used and deployed   than others. This section attempts to list and discuss those   technical services that could help a mid-level network provide robust   and improved services to its end sites.3.1 Domain Name Service   According to the NSFnet traffic statistics collected for May 1991,   about 7% of the packets on the NSFnet backbone were domain nameserver   (DNS) packets. This is a significant amount of traffic, and since   most of the other network applications depend on this service, a   robust DNS service is critical to any Internet site.   Proper location of secondary nameservers so that they are located on   different physical networks can increase the reliability of this   service to a large extent [MOC87a,MOC87b]. However, the nature of   the service requires that the nameservers for the next highest level   be available in order to resolve names outline-mode side of one's   domain.  Thus, for "foo.princeton.edu" to resolve "a.mid.net", the   root nameservers which point to mid.net's nameservers have to be   reachable.   To make the service more reliable, the mid-level network could have   at least one nameserver that is able to resolve nameserver queries   for all domains directly connected to it. Thus, in the event that the   entire mid-level network becomes isolated from the rest of the   Internet, applications can still resolve queries for sites directly   connected to the mid-level network. Without this functionality, there   is no way of resolving a name if the root (or higher level)   nameservers become unreachable, even if the query is for a site that   is directly connected and reachable.Aggarwal                                                        [Page 3]

RFC 1291             Potential Technical Services          December 1991   Strategies for implementing this architecture are discussed inappendix B.   To locate such a "meta-domain" server within a mid-level network, it   is proposed that a nameserver entry for "meta-dns" exist within the   mid-level network's domain.3.2 Public Domain Software   File transfer traffic constituted 23% of the NSFnet backbone traffic   for May 1991. Public shareware is a very valuable resource within the   Internet and a considerable amount of effort is being put into   developing applications to track all available resources in the   public archives [SHHH90].   It would be difficult, if not impossible to create an up-to-date   repository for every public domain package available on the Internet,   simply because of the volume of software and the rate at which new   software is being developed every day. Some hosts have gained   popularity as good public archives (such as uunet.uu.net, sumex-   aim.stanford.edu, wuarchive.wustl.edu) and new developers tend to   distribute the software to these sites as distribution points. The   economics of maintaining centralized archives is another deterrent to   centralization (the UUnet archives at uunet.uu.net take up roughly   1GB of disk storage).   Recently however, a number of methods for resource discovery have   been developed and are available on the Internet ("ftp-list" file   compiled by John Granose - odin@pilot.njin.net, Archie at   archie.cs.mcgill.ca and Prospero [NEU]).   It is desirable that the mid-level networks be able to provide up-   to-date pointers to the distribution hosts for available public   software archives. Coordinating the distribution of a static list is   difficult (though not impossible) and the use of automated resource   discovery mechanisms such as Archie and Prospero is recommended.   Under ideal conditions, any software that is popular and significant   (e.g., X11, TeX, RFC's) could be archived and distributed within the   mid-level network, but measuring "popularity" and "significance" are   debatable and left for further evaluation. Furthermore, a nameserver   entry for host "swdist" within the domain can provide information on   the various available alternatives for software distribution and   discovery (static file location, pointers to Archie servers, etc.) --   this nameserver entry can be an alias for a CNAME or a TXT entry.Aggarwal                                                        [Page 4]

RFC 1291             Potential Technical Services          December 19913.3 Network Time   An important feature of any computer network providing distributed   services is the capability to synchronize the local clocks on the   various systems in the network. Ideally, the clocks of all the   reference sources would be synchronized to national standards by wire   or radio. The importance and immense popularity of this service makes   Network Time a very useful potential service that can be provided by   a mid-level network. No specific protocol for maintaining time is   proposed, and any available protocol that maintains time with   reasonable accuracy could be used.   Network Time Protocol (NTP) traffic constituted 1% of the NSFnet   traffic during May 1991. The traffic might seem insignificant, but   there have been instances where a particular stratum-1 timeserver   (e.g., one of the stratum-1 servers at University of Delaware) has   reached a point of overload with too many different sites trying to   peer with it.   It is proposed that at least one stratum-1 and two stratum-2 servers   be located within a mid-level network (the selection of three servers   is based on the NTP standards documentation [MIL89]).  Note that the   servers can be located at any of the directly connected sites in the   network as long as they are publicly accessible. All sites connected   to the mid-level network can then coordinate their system times with   the servers within the mid-level network itself. Besides increasing   the reliability of the timekeeping network, this approach would also   limit the load on each timeserver.   For locating the network time servers within a domain, nameserver   entries for "timekeeper-x" (where x= 1,2,3..) can be made within the   domain. The servers are numbered in order of preference and accuracy.   Thus, "timekeeper-1.foo.net" would be the primary timekeeper and   "timekeeper-2.foo.net" would be additional (possibly secondary)   timekeepers within domain "foo.net". If such hosts are not available   within a domain, a TXT entry pointing to other recommended time-   servers could be provided instead.3.4 Network News   Network News (or Usenet News) constituted 14% of the NSFnet traffic   in May 1991. Netnews is an expensive service, both in terms of disk   and CPU power, as well as network bandwidth consumed.   The present structure of Network News consists of several hub sites   which are distributed over the Internet. End sites get news feeds   from other sites, and an article gets injected into the news stream   by sending it to the nearest "upstream" site, which then forwards itAggarwal                                                        [Page 5]

RFC 1291             Potential Technical Services          December 1991   to its connected news sites, and so on. There is no preset norm for   finding a site willing to provide a news feed, and it usually ends up   being a site with whom the site administrator happens to be   acquainted. However, this could easily result in some sites not being   able to get an economical news feed from within the mid-level network   and actually having to derive the feed from a site located on another   mid-level network.   A mid-level network could alleviate such occurrences by being able to   provide a newsfeed to any or all of its directly connected end sites.   Though an expensive resource, some of the costs can be moderated by   acting as a transit news feeder so that the news needn't be stored   for a long time on disk. The software for providing the news feed is   not specific and depends entirely on the newsfeed provider.3.5 Mailing Lists   Internet mailing lists are another popular source of information in   parallel to Network News. However, like public software, there is no   central repository of all the possible mailing lists available on the   Internet, and it would require considerable effort to compile one (at   the time of writing this document, a fairly comprehensive list is   available on the Internet and mentioned inappendix A.   At this time, there is no clear strategy for distributing or   maintaining mailing lists. However, it can be very expensive for a   site to distribute mail to all individual end users directly, and if   a clear strategy for maintaining a list of mailing-lists can be   devised, then mail exploders can be set up at the mid-level networks,   each of which forwards the mail to exploders at the end sites. This   mechanism would reduce the load on the originating systems, and   provides a clean path for tracking down mailer problems. Also, in   order to prevent bounced mail from propagating back to the originator   of the message, the mailing lists should be set up in a way so that   bounced mail goes to the the "owner" of the list and not to the   originator of the mail message.   A list of major mailing lists for the services discussed in this   document are listed inappendix A.4. Experimental Testbeds   Due to the working relationships that they have with their end sites   and peer networks, the mid-level networks are very good media for   distribution of new ideas and technology. Examples of this function   are the White Pages pilot project [RS90] established by NYSERnet, the   NSAP routing schema for OSI transitioning [CGC91], etc.Aggarwal                                                        [Page 6]

RFC 1291             Potential Technical Services          December 1991   The mid-level networks could establish cooperative experimental   testbeds for testing and deployment of new technologies similar to   the ones mentioned above. Besides deployment and testing of new   technology, this could also serve to provide a "help" service to the   end-sites and to get them started with the new software.   The exact interaction between the mid-level networks in this area is   not very clear. It is complicated by competition for members between   the mid-level networks and needs to be discussed further.5. Network Information Services   There are a variety of new and useful user services available on the   Internet that are difficult to document and provide a comprehensive   list of. Some attempt has been made at documenting such resources   [NNS] and a mid-level network can be the initial point of contact for   distribution of such information on a wide basis. The information can   be disseminated in a more controlled and complete manner using this   hierarchical approach if each mid-level network maintains up-to-date   information about its directly connected sites. Network Information   services (NIC) also make the network easier and more attractive to   end users. Examples of these services are:     o  provide information resources          -  security advisory messages          -  list of library catalogs [GL91]          -  geographical information servers          -  password generators     o  resolve end user problems (user support)   These services are NIC related and discussed in detail elsewhere   [SSM91]. For accessibility information, an entry for "nic" could   exist in the DNS for the domain (this could be a TXT entry listing   email or phone number information for users or other NIC's).6. Network Operations   The Network Operation Center's (NOC's) at the mid-level networks need   to cooperate with each other to resolve network problems.  In the   event of a network problem between two mid-level networks or if an   end-site has trouble getting to any host, the mid-level network NOCs   can serve to be the initial point of contact. The procedures for   interaction among NOCs and the formats for exchange of trouble-Aggarwal                                                        [Page 7]

RFC 1291             Potential Technical Services          December 1991   tickets between the NOCs are described elsewhere [JOH91,ML91].   It is important for cooperating NOCs to have contact information for   their directly connected campus/organizational sites and also about   their peer mid-level networks. A distributed mechanism for   maintaining contact information could be implemented by using a   nameserver TXT entry for "noc" or by maintaining "finger" information   for user "noc@domain" or "noc@noc.domain". A NOC "phonebook" listing   the contact information for the various NOCs can be used as a static   non-distributed mechanism (it is understood that the phonebook can   contain outdated information, but the distributed mechanisms can   provide correct and updated NOC information provided that the hosts   are reachable at the desired time).  If it is undesirable to publish   the phone number or email address of the NOC for any reason, an entry   saying "unpublished" (or words to that effect) could exist in the   nameserver or "finger" entry instead.7. References   [BOG]     Dunlap, K., and M. Karels, "Nameserver Operations Guide             for Bind Release 4.8", CSRG, Department of Electrical             Engineering and Computer Sciences, University of             California, Berkeley, California.   [CCI88]   CCITT Blue Book, "X.500 Series Recommendations", ITU,             1989.   [CGC91]   Collela, R., Gardner, E., and R. Callon, "Guidelines for             OSI NSAP Allocation in the Internet'',RFC 1237,             NIST, Mitre, DEC, July 1991.   [SSM91]   Sitzler, D., Smith, P., and A. Marine, "Building a Network             Information Services Infrastructure", RFC in             preparation.   [GL91]    George, A., and R. Larsen, "Internet Accessible Library             Catalogs & Databases", Aug 1991.             Available via anonymous FTP from ariel.unm.edu.   [JOH91]   Johnson, D., "NOC TT Requirements", RFC in             preparation.   [MAN]     Mandelbaum, R., and P. Mandelbaum, "The Strategic Future             of the Mid-Level Networks", University of Rochester,             NY, 1991.   [MOC87a]  Mockapetris, P., "Domain Names - Implementation and             Specification",RFC 1035, USC Information SciencesAggarwal                                                        [Page 8]

RFC 1291             Potential Technical Services          December 1991             Institute, November 1987.   [MOC87b]  Mockapetris, P., "Domain Names - Concepts and             Facilities",RFC 1034, USC Information Sciences             Institute, November 1987.   [MIL89]   Mills, D., "Network Time Protocol",RFC 1129, UDel,             October 1989.   [ML91]    Mathis, M., and D. Long, "User Connectivity Problems             Working Group", RFC in preparation.   [NEU]     Neuman, B., "The Virtual System Model: A Scalable             Approach to Organizing Large Systems", Department of             Computer Science, University of Washington, FR-35,             Seattle, WA, May 1990.   [NNS]     NSF Network Service Center, "Internet Resource Guide",             Cambridge, MA.             Available via anonymous FTP from nnsc.nsf.net.   [RS90]    Rose, M., and M. Schoffstall, "The NYSERnet White Pages             Pilot Project", NYSERnet, Inc., Mar 1990.   [SHHH90]  Schwartz, M., Hardy, D., Heinzman, W., and G.             Hirschowitz, "Supporting Resource Discovery Among             Public Internet Archives", Department of Computer             Science, University of Colorado, Boulder, CO.,             September 1990.8. Security Considerations   Security issues are not discussed in this memo.9. Author's Address   Vikas Aggarwal   JvNCnet   6 von Neumann Hall   Princeton University   Princeton, NJ 08544   Phone: +1-609-258-2403   Email: vikas@jvnc.netAggarwal                                                        [Page 9]

RFC 1291             Potential Technical Services          December 1991Appendix A - Mailing Lists   The following is a list of popular mailing lists for the services   listed in this document. To subscribe to a particular mailing list,   send a request to "mailing-list-request" (do not send a request to   the entire mailing list).  o  ietf@isi.edu: The general mailing list for the Internet     Engineering Task Force. This group is concerned with the evolution     and development of Internet related protocols and standards. Old     mail is archived at "venera.isi.edu" in directory ftp/irg/ietf.  o  ntp@trantor.umd.edu: For discussions on the Network Time     Protocol (NTP).  o  namedroppers@nic.ddn.mil: Mailing list for discussions on DNS     topics. Old mail is archived at "nic.ddn.mil".   At the time of writing this document, a list of mailing lists on the   Internet is available via anonymous FTP from host "ftp.nisc.sri.com"   in the file "netinfo/interest-groups".Appendix B - DNS Architecture Strategy   This section discusses practical strategies for implementing a   nameserver architecture within a mid-level network, so that it can   resolve nameserver queries for all domains directly attached to it.   In order to resolve queries for all directly connected networks, a   host that is authoritative for all directly attached domains will   need to exist within the mid-level network. Nameservers at the end   sites would then treat this "group-of-domains" nameserver as a   forwarding server to resolve all non-local queries.   This can be done by adding a line to the named.boot file on the end   site nameservers such as:              forwarders 128.121.50.7 128.32.0.4   This method has the added advantage that the forwarding server builds   up a very rich cache of data [BOG] and acts like a metacache that all   hosts can benefit from. Note that the forwarding server is queried   only if the end-site server cannot service a query locally -- hence   the "meta-domain" server is not overloaded with queries for all   nameserver lookups.Aggarwal                                                       [Page 10]

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