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NSAP Address
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... network service access point (NSAP) address
assignment. This paper provides guidelines for allocating NSAP
addresses in the Internet (the terms NSAP and NSAP address ...
... NSAP
addresses in the Internet (the terms NSAP and NSAP address are used
interchangeably throughout this paper in referring to NSAP
addresses).
...
... NSAP and NSAP address are used
interchangeably throughout this paper in referring to NSAP
addresses).
...
... 20 octets
for CLNP). The larger NSAP addresses allows considerably greater
flexibility and scalability.
...
...
Section 4 addresses the specific relationship between NSAP addresses
and routing, especially with regard to hierarchical routing ...
... these concepts to the Internet environment. Section 6 provides
recommended guidelines for NSAP address allocation in the Internet.
This includes recommendations for the U.S. and European parts of the
...
... Internet. The first is the set of administrative
requirements for obtaining and allocating NSAP addresses; the second
is the technical aspect of such assignments, having largely to do
with routing ...
...
The guidelines in this paper are oriented primarily toward the
large-scale division of NSAP address allocation in the Internet.
Topics covered include:
...
... domain (especially a site) should organize its
internal topology of areas or allocate portions of its NSAP
address space; the relationship between topology and addresses
...
...
NSAP addresses provide a flexible, variable length addressing format,
which allows for multi-level ...
... router is therefore able
to identify the ID and SEL fields as a known number of trailing
octets of the NSAP address. The area address can be identified as
the remainder of the address ...
... Network Entity Title (NET -- i.e., an NSAP address without the
selector) that has been assigned under ISO 8348 [11 ...
... domains originate routes whose
NLRI field contain identical NSAP address prefixes, since this
would imply that the same system(s) is simultaneously located
...
... routing domain which contains a mix of systems which use NSAP
addresses assigned by several different addressing authorities.
...
... routing
treats the entire area address (i.e., all of the NSAP address except
the ID and SEL fields) as if it were a flat field. Thus, the
efficiency of level 2 routing ...
... may use their prefix as the basis for subsequent suballocations,
assuming that the NSAP addresses remain within the overall length and
structure constraints. The flexibility of NSAP addresses ...
... NSAP addresses remain within the overall length and
structure constraints. The flexibility of NSAP addresses facilitates
this form of hierarchical address assignment and routing ...
... hierarchy may become necessary. Again, this requires considerable
flexibility in the addressing scheme, such as is provided by NSAP
addresses.
...
... 1] specifies the structure of
the DSP for NSAP addresses that use an Authority and Format
Identifier (AFI) value of (decimal) 39, which identifies the "ISO ...
... For example, suppose that a given subscriber is trying to decide
whether to obtain an NSAP address prefix based on an AA value from
...
... The discussions in Section 5.3 suggest methods for allocating NSAP
addresses based on service provider connectivity. This allows a
great deal of information reduction to be achieved for those routing ...
... routing domains may select their NSAP addresses from a space
allocated to them by their direct service provider. This allows the
...
... providers, to use a single address prefix to describe a large number
of NSAP addresses corresponding to multiple routing domains.
...
... NSAPs reachable within that organization via a single prefix.
The disadvantage of this approach is that since the NSAP address for
that organization has no relationship to the addresses of any
...
...
There are therefore a number of possible solutions to the problem of
assigning NSAP addresses to multi-homed routing domains. Each of
...
... The discussion up to this point concentrates on the relationship
between NSAP addresses and routing between various routing domains ...
... domains use valid
globally unique NSAP addresses. Suppose that the zero-homed routing
domain ...
...
Allocation of NSAP addresses based on connectivity to providers is
important to allow scaling of inter-domain routing to an internet ...
... initially single-homed, but which is expecting to become multi-homed
in the future, it may be advantageous to assign NSAP addresses based
on the anticipated future topology.
...
...
In general, it will not be practical to transition the NSAP addresses
assigned to a routing domain ...
... routers, or by actively querying the
routers for their NSAP address. If the ID portion of the address is
assigned in a manner which allows for globally unique IDs [18 ...
... assigned in a manner which allows for globally unique IDs [18], then
an end system can reconfigure its entire NSAP address automatically
without the need for manual intervention. However, routers will
...
... Internet. The ability of routing to scale is dependent upon the use
of data abstraction based on hierarchical NSAP addresses. As CLNP
use increases in the Internet ...
... use increases in the Internet, it is therefore essential to assign
NSAP addresses with great care.
...
...
In order for data abstraction to be possible, the assignment of NSAP
addresses must be accomplished in a manner which is consistent with
the actual physical topology ...
... domains (which are expected
to remain zero-homed or single-homed), we recommend that the NSAP
addresses assigned for OSI use within a single routing domain ...
... address prefix assigned to that domain. Specifically, this
allows the set of all NSAP addresses reachable within a single domain
to be fully described via a single prefix ...
...
The general technical requirements for NSAP address guidelines do not
vary from country to country. However, details of address
...
...
NSAP addresses for use within the U.S. portion of the Internet are
expected to be based primarily on two address prefixes ...
...
We recommend that a similar hierarchical model be used for NSAP
addresses using the DCC-based address format. The structure for
...
...
This section contains additional RARE recommendations for allocating
NSAP addresses within each national domain, administered by a
National Standardization Organization (NSO) and national research
...
... Domain Specific Part
Figure 3: NSAP address structure.
...
... network addressing domain consists of all the NSAP
addresses in the OSI environment. Within that environment, seven
second-level addressing ...
... ISO 8348 allows a maximum length of 20 octets for the NSAP address.
The AFI of 47 occupies one octet, and the IDI ...