The Domain Naming Convention for Internet User Applications
RFC 819
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(August 1982; No errata)
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2020-11-14
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Network Working Group Zaw-Sing Su (SRI)
Request for Comments: 819 Jon Postel (ISI)
August 1982
The Domain Naming Convention for Internet User Applications
1. Introduction
For many years, the naming convention "<user>@<host>" has served the
ARPANET user community for its mail system, and the substring
"<host>" has been used for other applications such as file transfer
(FTP) and terminal access (Telnet). With the advent of network
interconnection, this naming convention needs to be generalized to
accommodate internetworking. A decision has recently been reached to
replace the simple name field, "<host>", by a composite name field,
"<domain>" [2]. This note is an attempt to clarify this generalized
naming convention, the Internet Naming Convention, and to explore the
implications of its adoption for Internet name service and user
applications.
The following example illustrates the changes in naming convention:
ARPANET Convention: Fred@ISIF
Internet Convention: Fred@F.ISI.ARPA
The intent is that the Internet names be used to form a
tree-structured administrative dependent, rather than a strictly
topology dependent, hierarchy. The left-to-right string of name
components proceeds from the most specific to the most general, that
is, the root of the tree, the administrative universe, is on the
right.
The name service for realizing the Internet naming convention is
assumed to be application independent. It is not a part of any
particular application, but rather an independent name service serves
different user applications.
2. The Structural Model
The Internet naming convention is based on the domain concept. The
name of a domain consists of a concatenation of one or more <simple
names>. A domain can be considered as a region of jurisdiction for
name assignment and of responsibility for name-to-address
translation. The set of domains forms a hierarchy.
Using a graph theory representation, this hierarchy may be modeled as
a directed graph. A directed graph consists of a set of nodes and a
Su & Postel [Page 1]
RFC 819 August 1982;
collection of arcs, where arcs are identified by ordered pairs of
distinct nodes [1]. Each node of the graph represents a domain. An
ordered pair (B, A), an arc from B to A, indicates that B is a
subdomain of domain A, and B is a simple name unique within A. We
will refer to B as a child of A, and A a parent of B. The directed
graph that best describes the naming hierarchy is called an
"in-tree", which is a rooted tree with all arcs directed towards the
root (Figure 1). The root of the tree represents the naming universe,
ancestor of all domains. Endpoints (or leaves) of the tree are the
lowest-level domains.
U
/ | \
/ | \ U -- Naming Universe
^ ^ ^ I -- Intermediate Domain
| | | E -- Endpoint Domain
I E I
/ \ |
^ ^ ^
| | |
E E I
/ | \
^ ^ ^
| | |
E E E
Figure 1
The In-Tree Model for Domain Hierarchy
The simple name of a child in this model is necessarily unique within
its parent domain. Since the simple name of the child's parent is
unique within the child's grandparent domain, the child can be
uniquely named in its grandparent domain by the concatenation of its
simple name followed by its parent's simple name.
For example, if the simple name of a child is "C1" then no other
child of the same parent may be named "C1". Further, if the
parent of this child is named "P1", then "P1" is a unique simple
name in the child's grandparent domain. Thus, the concatenation
C1.P1 is unique in C1's grandparent domain.
Similarly, each element of the hierarchy is uniquely named in the
universe by its complete name, the concatenation of its simple name
and those for the domains along the trail leading to the naming
universe.
The hierarchical structure of the Internet naming convention supports
decentralization of naming authority and distribution of name service
capability. We assume a naming authority and a name server
Su & Postel [Page 2]
RFC 819 August 1982;
associated with each domain. In Sections 5 and 6 respectively the
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