rayan@ai.toronto.edu.UUCP (11/23/87)
The Canadian Domain: Introduction to CA
Updated November 20, 1987
The Canadian domain has been registered with the Network Information
Center (NIC) for the ARPA-Internet. The registration has been organized
by CDNnet with input from representatives of NetNorth, UUCP, and the
Defence Research Establishment.
Perhaps the most important application of the domain naming scheme
initially is to identify people in order that electronic mail can be
exchanged. Generally, the scheme is intended to be a consistent means
to refer to resources. This note describes the basic structure of the
Canadian domain, and summarizes the information used to arrive at that
structure.
Implications of Registering a Domain
The registration of a Canadian domain with the NIC implies that the
namespace should be structured and managed according to NIC guidelines.
It does not mean that Canada is "joining the ARPANET", and it does not
mean that a host within a registered Canadian subdomain automatically
has the permission to communicate with hosts on the ARPANET, or on any
other network for that matter. These things are separate issues;
registering a domain and deciding on a structure for it only fits us
into the namespace. The issues are closely enough related, however,
that an organization applying for a subdomain under the Canadian domain
will be asked for the names of hosts willing to act as gateways to the
major networks.
Using ARPA guidelines for domain naming does not mean that other ARPA
guidelines and protocols must also be used. This is explicitly
recognized by the designers of the ARPA domain name scheme. This is
just as well, because only a small part of the Canadian community
uses these protocols exclusively. Neither does it follow that there
must be a widespread shift to the use of ARPA protocols, although
discussing this point is well beyond the scope of this note. Suffice
it to say that standards being put forth by bodies such as ISO and
CCITT are becoming widely implemented and used--this is happening in
Canada now--and it would be unwise to plan a namespace that is
incompatible with them.
Naming and Addressing
In choosing a structure for the Canadian namespace, at least four
naming and addressing systems should be taken into account. The first
is the ARPA-Internet domain name system as described in several
documents including RFCs 882, 883, 920, 921, 973, 974, and 1032. (This
is not intended to be a description of the domain name system.
Interested readers should consult the RFCs.) The domain name space is a
tree, and domains are administrative entities. These two facts together
ensure that there is a decentralized means for managing the namespace,
and especially for assigning unique names. Each domain has an
individual who is responsible for the administration of the names
within the domain. Some of this authority and responsibility may be
delegated to subdomain administrators; this achieves further
decentralization.
The second system is the Originator/Recipient address structure of the
CCITT X.400 recommendations on message handling systems. The O/R
address consists of a list of typed attributes and values. No textual
representation for O/R addresses is specified in the recommendations.
Widely used attributes are country, administration management domain
name, private management domain name, organization name, organizational
units, domain defined attributes, and personal name.
The third system is the Originator/Recipient name structure of the
ISO/CCITT collaborative work on directory standards. These standards
are expected to be approved in 1988, and are called the CCITT X.500 and
ISO 9594 series. We are concerned mainly with the structure of the
Directory Information Tree. Here is a simplified description of the
structure:
- Subordinate to the root are organizations and countries.
- Subordinate to a country are organizations and subtrees of
localities.
- Subordinate to a locality are organizations.
- Subordinate to an organization are organizational persons and a
subtree of organizational units.
- Subordinate to an organizational unit are organizational persons.
- Subordinate to a locality are residential persons.
In other words, the tree may be described as geographical with
organizations attached at any level, and with persons attached below
organizations and localities. Note again that this is a simplification
of the actual structure, and of course the entire standard deals with
much more than that structure.
Finally, a way to communicate between X.400 and RFC 822 mail systems is
described in RFC 987 ("Mapping between X.400 and RFC 822"), with an
addendum in RFC 1026. RFC 987 includes a description of mapping
between O/R addresses and RFC 822 addresses. This mapping in general
requires the use of a directory.
In summary, the two main schemes are the ARPA-Internet domain naming
scheme and the CCITT X.400/X.500 naming and addressing scheme. Although
there are differences between them, we should adopt a naming system
that fits into each as naturally as possible. It is likely that a
standard, distributed directory service will be popular outside the
CCITT/ISO world. In particular, it would not be surprising to see work
on gateways to allow access to the directory from the ARPA scheme.
Having some naming compatibility from the outset will be to everyone's
benefit.
Domain Name
The domain CA has been registered. The domain is intended for all of
Canada, although registration of subdomains under CA is voluntary.
Several Canadian subdomains exist under other domains, and there is no
requirement that these other domains (e.g. EDU, COM, MIL, GOV) cannot
be used for new subdomains in Canada. The domain is called CA because
RFC 920 ("Domain Requirements") recommends the use of the two letter
(alpha-2) code for countries according to ISO 3166 ("Codes for the
Representation of Names of Countries"). The same standard is
recommended for use in X.400/X.500, and although each camp allows the
possibility of other names, it makes sense to take the common ground.
(One must always keep in mind that the common ground may be a swamp.)
Domain Structure
In addition to the major standards, the needs of the various
communities should be considered. At present, the major players in the
Canadian networking scene are organizations: universities, government
agencies, companies engaged in research and development, and
progressive companies engaged in other activities. Easy access to
commercial networks may become important, and these are adopting the
CCITT/ISO standards. It is also possible that the individual, not the
organization, will become the major direct force in the future.
However, it is more likely that individuals will fit in under
organizations or will receive services from a service provider such as
a commercial organization. Initially the central administration for CA
will not be able to cope directly with individuals.
The domain should be structured so that the namespace can be
administered easily, and so that names make sense to people. Since a
common unit of administration is the organization and since
organization names are widely used by people when trying to locate
other people, it is reasonable that the namespace should not cut across
organizational boundaries in most cases.
The structure of the CA domain is a hierarchy. The second-level
subdomains under CA are provincial and territorial abbreviations and
the names of national organizations. Similarly, the third-level
subdomains are municipality names and provincial organizations.
Fourth-level subdomains are for municipal organizations. This fits
both major schemes. Since the ARPA scheme does not easily allow for
representing typed information, the two kinds of names are chosen from
the same namespace. One issue with geographical subdomains is finding
responsible people to manage them.
An organization applying for a registration will be required to request
a geographical subdomain that matches its scope of activity, and to
choose a string that encodes the proper name of the organization in a
widely recognized fashion that will be unique to the requested
geographical subdomain. To simplify the introduction of standard
directory services, the organization string should make sense standing
alone. The use of nationally recognized abbreviations is recommended,
especially since subdomain names will be widely distributed and will
appear on letterheads and on business cards.
The substructure within an organization is its own business. However,
it is strongly suggested that it be hierarchical, that it fit the
organization's administrative structure, and that the X.500 naming
scheme be considered.
Current Status
Application forms are available from the registrar and from
participating network administrations. In the future it is possible
that the management of the domain will be taken up by a government
body.
John Demco
CA domain registrar