home *** CD-ROM | disk | FTP | other *** search
-
-
- Network Working Group Jon Postel
- Request for Comments: 921 ISI
- October 1984
- Updates: RFC 897, RFC 881
-
- Domain Name System Implementation Schedule - Revised
-
-
- Status of this Memo
-
- This memo is a policy statement on the implementation of the Domain
- Style Naming System in the Internet. This memo is an update of
- RFC-881, and RFC-897. This is an official policy statement of the
- IAB and the DARPA.
-
- The intent of this memo is to detail the schedule for the
- implementation for the Domain Style Naming System. The explanation
- of how this system works is to be found in the references.
-
- The Current Situation
-
- There are three aspects to the domain style naming system, (1) the
- names themselves, (2) the method of translating names to addresses,
- and (3) the relationship between the Internet and the rest of the
- world.
-
- Names
-
- The names are being changed from simple names, or globally unique
- strings, to structured names, where each component name is unique
- only with respect to the superior component name.
-
- Simple Names
-
- Until recently, hosts in the DARPA research and DDN operational
- communities were assigned names in a flat or global name space
- of character strings. There are some limits on these names.
- They must start with a letter, end with a letter or digit and
- have only letters or digits or hyphen as interior characters.
- Case is not significant.
-
- For example: USC-ISIF
-
- Hierarchical Names
-
- Because of the growth of the Internet, structured names (or
- domain style names) have been introduced. Each element of the
- structured name will be a character string (with the same
- constraints that previously applied to the simple names). The
-
-
-
-
- Postel [Page 1]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- elements (or components) of the structured names are separated
- with periods, and the elements are written from the most
- specific on the left to the most general on the right.
-
- For example: USC-ISIF.ARPA
-
- The Initial and Temporary Domain
-
- The introduction of these hierarchical names has been very
- limited. Every current name in this new system has the form
- "old-simple-name.ARPA". That is, the all the hosts are in a
- domain called "ARPA". This is a temporary situation. The
- current intention is for the ARPA domain to cease to exist.
- This means that all hosts will change their names as the domain
- style names come into full use.
-
- Name to Address Lookup
-
- Every host in the Internet is expected to have a way of
- translating the name of any other host into its Internet address.
-
- By and large, the name to address translation is done by looking
- up the information in a table of all hosts.
-
- The maintenance of this table is centralized at the Network
- Information Center (NIC). Each host is expected to obtain a
- current copy of the table on a timely basis. This table is called
- "HOSTS.TXT" [8] and is normally accessed via the Hostnames
- Server [9].
-
- Interface to the World
-
- A great deal of mail moves between the Internet and other
- "systems" that somehow transport mail among computers. This is
- currently done by hiding some sort of "other-system" addressing
- information in the local-part of the mail address and using a
- mail-relay host in the host-part of the mailbox.
-
- For example,
-
- OBERST%EDUCOM.MAILNET@MIT-MULTICS.ARPA
- EDMISTON.CIC@CSNET-RELAY.ARPA
-
-
-
-
-
-
-
- Postel [Page 2]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- The Future Situation
-
- Names
-
- Hierarchical Names
-
- The use of the hierarchical names will be greatly expanded
- according to the rules established in the "Domain Requirements"
- memo (RFC-920) [5].
-
- For example: F.ISI.USC.EDU
-
- There are several levels of development for use of the domain
- style names.
-
- First, there is the current simple substitution of the domain
- style names for the old style host names. At this stage all
- domain style names directly translate to host addresses (using the
- NIC tables) and all domain style names have two components. The
- mail system uses addresses of the form "local-part@host", where
- host is a domain style host name.
-
- For example: USC-ISIF.ARPA and Postel@USC-ISIF.ARPA
-
- Here we expect that "USC-ISIF.ARPA" is the name of an Internet
- host and that we can send mail for "Postel" to the SMTP port on
- that host. It may be that some backward host can still fake it
- by ignoring the ".ARPA" and looking up an address for
- "USC-ISIF" in some old style file.
-
- Second, there is an extension to more name components and more top
- level domains. The mail system still uses addresses of the form
- "local-part@host", where host is a domain style host name.
-
- For example: F.ISI.USC.EDU and Postel@F.ISI.USC.EDU
-
- Here we expect that "F.ISI.USC.EDU" is the name of an Internet
- host and that we can send mail for "Postel" to the SMTP port on
- that host. It is likely that the NIC will enter these new
- domain style names in the centrally maintained table (i.e.,
- HOSTS.TXT) during the transition period. It is unlikely that a
- backward host can hack this at all.
-
- Third, there is an extension to domain style names that may
- represent only organizations or administrative entities. Finding
- a host that acts for such entities may require a level of
-
-
-
- Postel [Page 3]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- indirection in the search. The mail system may use
- "local-part@domain-name", where the "domain-name" identifies a
- host (as before) or an organization.
-
- For example: USC-ISI.EDU and Postel@USC-ISI.EDU
-
- Here we don't count on "USC-ISI. EDU" being the name of an
- Internet host. When we want to send mail to "Postel" we ask
- the domain name server about sending mail to "USC-ISI.EDU".
- The server will tell us the name (and address) of a real
- Internet host that handles mail on this organizations behalf,
- for example, "F.ISI.USC.EDU = 10.2.0.52". We then send mail
- for "Postel@USC-ISI.EDU" to the SMTP port on F.ISI.USC.EDU.
-
- Name to Address Lookup
-
- Every host in the Internet will be expected to have a way of
- translating the name of any other host into its Internet address.
-
- By and large, the name to address translation will be done by
- interacting with a lookup server. There will be a number of
- servers that each hold a portion of the name to address
- information.
-
- The maintenance of the translation data base will be subdivided
- and distributed.
-
- The design and implementation details for this service are given
- in RFC-882 [2] and RFC-883 [3].
-
- Interface to the World
-
- Mail will continue to move between the Internet and other
- "systems". This may be done by designating some sort of
- "other-system" representative organization in the domain server
- data bases that can indirect mail to a mail-relay host.
-
- For example,
-
- Oberst@EDUCOM.MAILNET
-
- When we want to send mail to "Oberst" we ask the domain name
- server about sending mail to "EDUCOM.MAILNET". The server will
- tell us the name (and address) of a real Internet host that
- handles mail on this organizations behalf, for example,
- "MIT-MULTICS.ARPA = 10.0.0.6". We then send mail for
- "Oberst@EDUCOM.MAILNET" to the SMTP port on MIT-MULTICS.ARPA.
-
-
- Postel [Page 4]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- For example,
-
- Edmiston@CIC.CSNET
-
- When we want to send mail to "Edmiston" we ask the domain name
- server about sending mail to "CIC.CSNET". The server will tell
- us the name (and address) of a real Internet host that handles
- mail on this organizations behalf, for example,
- "CSNET-RELAY.ARPA = 10.4.0.5". We then send mail for
- "Edmiston@CIC.CSNET" to the SMTP port on CSNET-RELAY.ARPA.
-
- The Transition Situation
-
- Actually, the situation is a bit more complicated, of course. Hosts
- are already using domain style names under the constraint that their
- domain style name is exactly their old style name with the string
- ".ARPA" appended. The first transition step is to ensure that all
- hosts do this, and then to eliminate the use of old style names
- altogether.
-
- Please note carefully that two types of changes are being made:
-
- One is a change in the support mechanism for translating a host
- name to an internet address,
-
- that is from using local copies of a full centrally maintained
- table to dynamically accessing a distributed set of servers
- each posesing a portion of a data base maintained in a
- distributed fashion.
-
- The other is a change in the host names themselves,
-
- from a flat global space of unstructured strings to a
- hierarchical structure of names.
-
- There are two steps to the transition plan.
-
- First, change from old names to domain style names.
-
- Second, change from using central tables to using name servers.
-
- There are two communities that are taking slightly different courses
- in this transition. The DARPA research community is making the full
- transition. The DDN operational community is making the change in
- naming on the same schedule, but is not requiring hosts in the DDN
- operational community make the change to using servers at the same
-
-
-
- Postel [Page 5]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- time (they can if they want to). The DDN PMO will establish a
- schedule for that change at a later time. The NIC will maintain a
- central table of all DDN operational hosts.
-
- Interface to the World
-
- The interchange of mail with "other-systems" will have to continue
- pretty much as it has (except that RELAY-HOST is RELAY-HOST.ARPA)
- until organization names can be used. Then representative
- organizations can be designated for each "other-system" in the
- domain server data bases that will then specify a mail-relay host.
-
- All Hosts Change Names
-
- The impact of introducing the domain style names is that all hosts
- change their names at least once. Hosts that move to new domains or
- subdomains may change their names several times.
-
- Hosts have an official (or primary) name and possibly several
- nicknames. When mail is sent from a host, the official name is used
- in the mail header address fields.
-
- Suppose, that in the old days before domains were thought of, a host
- changed its name. What is the impact on users of changing the name
- of a host?
-
- Mail that was sent before the name was changed can not be answered
- using mail program commands that automatically fill in the return
- address. While it may be possible to use special tricks to fix up
- the "From" or the "To" users addresses, the "Cc" addresses are
- very difficult to correct.
-
- Suppose one host changed its name from FOO to BAR. Mail that
- was sent from FRED@FOO to JOE@ABC can not be answered unless
- the change of name is known to the user or the mail program at
- ABC and the host name BAR substituted for FOO. Mail that is
- sent to JOE@ABC from SAM@DEF with a cc to FRED@FOO can not be
- answered easily.
-
- Any mailing lists that have mailboxes with the host that changed
- names will now have incorrect entries.
-
- The point is that while the host that changed names may be able to
- use special tricks for a while to fix things up for the users, it is
- difficult for other hosts to do this.
-
-
-
-
- Postel [Page 6]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- A general trick is to make the old name a nickname for the host for
- some period of time.
-
- The introduction of domain style names means that all hosts change
- their names essentially at the same time.
-
- To lessen the havoc, there will be a period of time when both the old
- and the new names are allowed. That is, the old names will be
- nicknames for a while.
-
- Primary Names
-
- Currently, host have an official or primary names and may have
- several nicknames. For example,
-
- Primary Name Nicknames
-
- USC-ISIF.ARPA USC-ISIF ISIF
-
- ADA-VAX.ARPA ADA-VAX ISI-VAXB AJPO VAXB
-
- The data base is such than given any of the names for a host one can
- find the address, and given the address one can find the primary
- name.
-
- In the new domain style name system this property must be maintained.
- That is, given the Internet address of a host one must be able to
- find the primary name of that host. This calls for careful
- management of the distributed database by those in charge of the
- domains and zones.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Postel [Page 7]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- The Revised Time Table
-
- There are three major phases to the implementation of the domain
- names system: (1) putting the machinery in place (servers,
- resolvers), (2) getting the data base installed, (3) changing the
- user programs (mailers, etc.).
-
- The machinery is now (at last) well along, there is a server for
- TOPS-20, and two different servers for Unix. The data base now
- contains the ARPA domain and is initialized for the other top
- level domains. Little has been done to change user programs to
- use the new procedures.
-
- Done
-
- Service Design and Specification: The design and specification
- for the protocol and data base were published (RFC-882, RFC-883).
-
- Domain Requirements Specification: The requirements for
- establishing a new domain are published as an RFC (RFC-920).
-
- Domain Style Names in Table: Hosts are using their domain style
- names as their official and primary names. The standard table of
- host names contains domain style names as the official and primary
- name.
-
- Servers for ARPA Domain: Several domain name servers are in
- operation to supply host name to internet address translations,
- one of these servers is at the NIC.
-
- 15 Dec 84 Domain Table
-
- A master table of top level domain names and their associated
- servers is established at the NIC. Probably this information will
- be added to the HOSTS.TXT file as a new entry type.
-
- 15 Jan 85 Begin New Domain Registration
-
- New domains may register according to the procedures and
- restrictions described in RFC-920 [5].
-
- 15 Feb 85 Major Machinery Completed
-
- The principal servers are up and running, there are resolvers
- programmed and tested for the most popular systems (Unix 4.2bsd,
- TOPS-20).
-
-
-
- Postel [Page 8]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- 15 May 85 Significant Use of Resolvers and Servers
-
- Programs (e.g., Mailers, Telnet, FTP) begin regular use of the new
- mechanisms (resolvers and servers). This may be done by changing
- the programs to act as resolvers themselves and call on servers
- directly, or to provide system calls that include the resolver
- function to replace old system calls that accessed the host table.
-
- 15 Jul 85 Implementation of the Domain Naming System Completed
-
- The goal is to complete the switch over to the domain style names
- and the use of the servers by this date. All programs that
- translate host name to Internet addresses should now use
- procedures based on the use of the domain style names system of
- resolvers and servers and the distributed data base.
-
- 15 Sep 85 Decommission Host Table
-
- At this point the master host table maintained by the NIC need no
- longer be complete for the DARPA research community. A full table
- of the DDN operational hosts will be maintained by the NIC.
-
- 15 Oct 85 DDN Plan for Domains Name Service
-
- The DDN PMO may establish a plan for the future support of name to
- address translations in the DDN community.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Postel [Page 9]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- Appendix : The Old Time Table
-
- Here we present the time table from the previous schedule (RFC-897)
- with some comments on what was and was not accomplished.
-
- -- Nov 83 Plan and Schedule
-
- At this point the overall plan for the implementation of domain
- style names and name servers, and a schedule of events was
- published (RFC-881). Also the design and specification for the
- protocol and data base were published (RFC-882, RFC-883).
-
- <This was done, but the schedule did not work.>
-
- -- Nov 83 Initial Domain Style Host Name Table
-
- At this point a version of the host table which includes the
- domain style names is made available (DHOSTS.TXT).
-
- <This was done, on schedule.>
-
- -- Feb 84 Domain Requirements Specification
-
- At this point the requirements for establishing a new domain are
- published as an RFC.
-
- <This topic was much discussed in the Namedroppers mailing
- list, but no RFC was published until Oct84 [5].>
-
- 14 Mar 84 Begin using Domain Style Names
-
- At this point all hosts should start using their domain style
- names as their official and primary names. The standard table of
- host names contains domain style names as the official and primary
- name (DHOSTS.TXT becomes HOSTS.TXT).
-
- <This was done, on schedule.>
-
- 04 Apr 84 Server for ARPA Domain
-
- At this point several domain name servers are in operation to
- supply host name to internet address translations, one of these
- servers is at the NIC.
-
- <This was done, not on schedule, but by Sep84.>
-
-
-
-
- Postel [Page 10]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- 04 Apr 84 Domain Table
-
- At this point a master table of top level domain names and their
- associated servers is established at the NIC.
-
- <Not done yet.>
-
- 02 May 84 Stop using old style Names
-
- At this point the use of old style names must be completely phased
- out.
-
- <I think this is done. Except that some hosts still use the
- OHOSTS.TXT file.>
-
- 02 May 84 Certain New Domains
-
- At this point a few new domains may be established, in particular
- the DDN domain.
-
- <Not done yet. Well, "DDN" won't be a top level domain
- according to the new rules (see [5]).>
-
- 06 Jun 84 General & Multilevel Domains
-
- At this point additional new domains may be established, if they
- meet the requirements. Domain style names may have more than two
- segments.
-
- <Not done yet.>
-
- 18 Jul 84 Organizational Domains
-
- Domain style names may identify organizations. Finding an address
- for a host may involve a level of indirection.
-
- <Not done yet.>
-
- 05 Sep 84 Decommission Host Table
-
- At this point the master host table maintained by the NIC need no
- longer be complete for the DARPA research community. A full table
- of the DDN operational hosts will be maintained by the NIC.
-
- <Not done yet.>
-
-
-
-
- Postel [Page 11]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- 03 Oct 84 DDN Plan for Domains Name Service
-
- At this point the DDN PMO will establish a plan for the future
- support of name to address translations in the DDN community.
-
- <Not done yet.>
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Postel [Page 12]
-
-
-
- RFC 921 October 1984
- Domain Implementation Schedule - Revised
-
-
- References
-
- [1] Postel, J., "The Domain Names Plan and Schedule", RFC-881, USC
- Information Sciences Institute, November 1983.
-
- [2] Mockapetris, P., "Domain Names - Concepts and Facilities",
- RFC-882, USC Information Sciences Institute, November 1983.
-
- [3] Mockapetris, P., "Domain Names - Implementation and
- Specification", RFC-883, USC Information Sciences Institute,
- November 1983.
-
- [4] Postel, J., "Domain Name System Implementation Schedule",
- RFC-897, USC Information Sciences Institute, February 1984.
-
- [5] Postel, J., and J. Reynolds, "Domain Requirements", RFC-920, USC
- Information Sciences Institute, October 1984.
-
- [6] Mockapetris, P., "The Domain Name System", Proceedings of the
- IFIP 6.5 Working Conference on Computer Message Services,
- Nottingham, England, May 1984. Also as ISI/RS-84-133,
- June 1984.
-
- [7] Mockapetris, P., J. Postel, and P. Kirton, "Name Server Design
- for Distributed Systems", Proceedings of the Seventh
- International Conference on Computer Communication, Sidney,
- Australia, October 1984. Also as ISI/RS-84-132, June 1984.
-
- [8] Feinler, E., K. Harrenstien, Z. Su, and V. White, "DoD Internet
- Host Table Specification", RFC-810, Network Information Center,
- SRI International, March 1982.
-
- [9] Harrenstien, K., V. White, and E. Feinler, "Hostnames Server",
- RFC-811, Network Information Center, SRI International,
- March 1982.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Postel [Page 13]
-
-