1 - 2 - 4 - 8 - A - B - C - D - E - F - G - H - I - L - M - N - O - P - Q - R - S - T - U - V - W - X
NSAP
Click on the red underlined text to get to the source
... routing
protocols. Also required as part of this infrastructure are
guidelines for network service access point (NSAP) address
assignment. This paper provides guidelines for allocating NSAP
addresses in the Internet ...
... network service access point (NSAP) address
assignment. This paper provides guidelines for allocating NSAP
addresses in the Internet (the terms NSAP and NSAP address ...
... address
assignment. This paper provides guidelines for allocating NSAP
addresses in the Internet (the terms NSAP and NSAP address are used
interchangeably throughout this paper in referring to NSAP
addresses ...
... 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
...
...
The Appendix contains a compendium of useful information concerning
NSAP structure and allocation authorities. The GOSIP Version 2 NSAP ...
... NSAP structure and allocation authorities. The GOSIP Version 2 NSAP
structure is discussed in detail and the structure for U.S.-based DCC ...
... DCC
(Data Country Code) NSAPs is described. Contact information for the
registration authorities for GOSIP and DCC ...
... registration authorities for GOSIP and DCC-based NSAPs in the U.S.,
the General Services Administration (GSA ...
... access points. For discussion of OSI NSAP allocation in
this paper, providers are treated as composing a mesh having no fixed
hierarchy. Addressing ...
...
There are two aspects of interest when discussing OSI NSAP allocation
within the Internet. The first is the set of administrative
...
... 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 technical issues in NSAP allocation are mainly related to
routing. This paper assumes that CLNP ...
...
The guidelines in this paper are oriented primarily toward the
large-scale division of NSAP address allocation in the Internet.
Topics covered include:
...
...
It is noted that there are other aspects of NSAP allocation, both
technical and administrative, that are not covered in this paper.
Topics not covered or mentioned only superficially include:
...
... Policy or mechanisms for making registered information known
to third parties (such as the entity to which a specific NSAP
or a portion of the NSAP address space has been allocated);
...
... 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
...
... Procedures for assigning the System Identifier (ID) portion of
the NSAP. A method for assignment of System IDs is presented
in [18 ...
...
Some background information is provided in this section that is
helpful in understanding the issues involved in NSAP allocation. A
brief discussion of OSI ...
... intra-domain and inter-domain protocols in sufficient detail to
understand the issues involved in NSAP allocation. Finally, the
specific constraints that the routing protocols ...
...
This paper examines the technical implications of NSAP assignment
under the assumption that ES-IS, intra-domain ...
...
NSAP addresses provide a flexible, variable length addressing format,
which allows for multi-level ...
... IDP (see Appendix A for more discussion on the top
level NSAP addressing authorities). It is expected that the
...
... area address, the system identifier (ID), and the NSAP selector
(SEL). The area address identifies both the routing ...
... 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.
...
...
The preferred NSAP format for IS-IS is shown in Figure 1. A number
of points should be noted from IS-IS ...
... HO-DSP) must be globally unique. If the area address of an NSAP
matches one of the area addresses of a router ...
... the CLNP packet within the system identified by the rest of the
NSAP (i.e., a transport entity) and is always the last octet of the
...
... domain that conforms to IS-IS,
the lower-order octets of the NSAP should be structured as the ID
and SEL fields shown in Figure 1 to take full advantage of IS-IS
...
... 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 ...
...
When determining an administrative policy for NSAP assignment, it is
important to understand the technical consequences. The objective
behind the use of hierarchical routing ...
...
Abstraction of reachability information dictates that NSAPs be
assigned according to topological routing structures. However,
...
... routing domain are all drawn from distinct NSAP assignment
authorities (allowing no abstraction), then the boundary prefix ...
... 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 ...
... address assignment and routing. As one
example of how NSAPs may be used, the GOSIP Version 2 NSAP structure
...
... example of how NSAPs may be used, the GOSIP Version 2 NSAP structure
is discussed later in this section.
...
... hierarchy may become necessary. Again, this requires considerable
flexibility in the addressing scheme, such as is provided by NSAP
addresses.
...
... NSAP Administration and Efficiency ...
... There is a balance that must be sought between the requirements on
NSAPs for efficient routing and the need for decentralized NSAP
...
... NSAPs for efficient routing and the need for decentralized NSAP
administration. The NSAP structure from Version 2 ...
... routing and the need for decentralized NSAP
administration. The NSAP structure from Version 2 of GOSIP (Figure
2) offers one example of how these two needs might be met. The AFI ...
... responsible for defining the DSP structure and allocating values
within it (see the Appendix for more information on NSAP structure).
...
... version 2 addresses only as an
example. It is not necessary that NSAPs be allocated from the GOSIP
Version 2 authority ...
... 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 ...
... identifiers may be obtained from ANSI. The technical considerations
applicable to NSAP administration are independent of whether a GOSIP
Version 2 or an ANSI ...
...
Similarly, although other countries make use of different NSAP
formats, the principles of NSAP assignment and use are the same. The
...
... Similarly, although other countries make use of different NSAP
formats, the principles of NSAP assignment and use are the same. The
NSAP formats recommended by RARE WG4 for use in Europe ...
... formats, the principles of NSAP assignment and use are the same. The
NSAP formats recommended by RARE WG4 for use in Europe are discussed
in Section 6.2.
...
...
In the low-order part of the GOSIP Version 2 NSAP format, two fields
are defined in addition to those required by IS-IS. These fields, RD ...
... IS-IS. These fields, RD
and Area, are defined to allow allocation of NSAPs along topological
boundaries in support of increased data abstraction. Administrations
assign RD ...
... For example, suppose that a given subscriber is trying to decide
whether to obtain an NSAP address prefix based on an AA value from
...
...
If areas take their area addresses from a myriad of unrelated NSAP
allocation authorities, there will be effectively no data ...
... domain. There is no common prefix that can be used to represent
these NSAPs and therefore no summarization can take place at the
routing domain ...
... path between an area and the rest of the internetwork. It is
reasonable that this relationship also extend to include a common
NSAP addressing authority. Thus, the areas within the subscriber ...
... routing domains should be the common authority for assigning NSAPs
from a unique prefix to the subscriber ...
... prefix
assigned to each provider may be used for other NSAP formats. This
results in direct providers advertising to other providers (both
direct and indirect) a small fraction of the number of address
prefixes ...
... and indirect). The efficiencies gained in routing clearly warrant
the adoption of NSAP administration by the direct providers.
...
...
A similar scheme can be established using NSAPs allocated under
DCC=840. In this case, a direct provider ...
... There does not appear to be a strong case for direct service
providers to take their address spaces from the NSAP space of an
indirect provider (e.g. backbone ...
...
An additional factor that discourages allocation of NSAPs from an
indirect provider's prefix ...
... providers can be thought of the same way as long-distance telephone
carriers). Having NSAPs derived from the indirect providers is
inconsistent with the nature of the relationship.
...
... 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.
...
... addresses to each multi-homed
organization independently from the providers to which it is
attached. This allows each multi-homed organization to base its NSAP
assignments on a single prefix, and to thereby summarize the set of
...
... assignments on a single prefix, and to thereby summarize the set of
all NSAPs reachable within that organization via a single prefix.
The disadvantage of this approach is that since the NSAP address ...
... 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
...
...
A second possible approach would be for multi-homed organizations to
be assigned a separate NSAP space for each connection to a provider,
...
... solution, each provider, in announcing the ability to reach MBII,
specifies that it is able to reach all of the NSAPs within MBII.
With the second solution, each provider announces that it can reach
...
... With the second solution, each provider announces that it can reach
all of the NSAPs based on its own address prefix, which only includes
some of the NSAPs ...
... NSAPs based on its own address prefix, which only includes
some of the NSAPs within MBII. If the connection between MBII and
one particular provider ...
... connection between MBII and
one particular provider were severed, then the NSAPs within MBII with
addresses based on that provider ...
... destination is within the country. With the second solution,
a separate address may be assigned to those NSAPs which are within
country X, thereby allowing routing policies to be followed.
...
...
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 ...
... The important observation to be made here is that such private links
may be ignored for the purpose of NSAP allocation, and do not pose a
problem for routing. This is because the routing information ...
...
Note that the relationship between routing and NSAP addressing
described in other sections of this paper is concerned with problems
...
... routing domains.
However, for the purpose of NSAP allocation, private point-to-point
links which interconnect only a small number of private routing
...
... domains use valid
globally unique NSAP addresses. Suppose that the zero-homed routing
domain ...
... distinguish between the zero-homed routing domain's NSAPs and any
other NSAPs that it may need to route ...
... domain's NSAPs and any
other NSAPs that it may need to route to. The only way this can be
guaranteed is if the zero-homed routing ...
...
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.
...
... It is in the best interests of the internetworking community that the
cost of operations be kept to a minimum where possible. In the case
of NSAP allocation, this again means that routing data abstraction
must be encouraged.
...
...
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
...
... General NSAP Structure ...
... CDP leaves space for the U.S. GOSIP Version 2
NSAP model (Appendix A.1) by the reserved CFI /8, nevertheless it is
not recommended for use in the European Internet.
...
...
Further, in order to allow aggregation of NSAPs at national
boundaries into as few prefixes as possible, we further recommend
...
... boundaries into as few prefixes as possible, we further recommend
that NSAPs allocated to routing domains should be assigned based on
...
... domains (confederations) they depict, for the sake of
simplicity we recommend that RDIs and RDCIs be assigned based on the
NSAP prefixes assigned to domains and confederations.
...
... should be used as the RDCI of the confederation. In this case the
provider may use a longer NSAP prefix for its own RDIs. In all other
cases a provider ...
... The authors would like to thank the members of the IETF OSI-NSAP
Working Group and of RARE WG4 for the helpful suggestions made during
...
... DSP) of the OSI Network Service Access Point (NSAP) Address", American National Standard X3.216- 1992. ...
... A. Administration of NSAPs ...
... ISO 8348 defines the
semantics of the NSAP and the abstract syntaxes in which the
semantics of the Network ...
... domain
specific part (DSP). The initial domain part of the NSAP consists of
an authority and format identifier (AFI ...
... 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 ...
...
GOSIP Version 2 makes available for government use an NSAP addressing
subdomain with a corresponding address format ...
... value which has been assigned to the U.S. Government. Although GOSIP
Version 2 NSAPs are intended primarily for U.S. Government use,
requests from non-government and non-U.S. organizations will be
considered on a case-by-case basis.
...
... ISO 8348 allows a maximum length of 20 octets for the NSAP address.
The AFI of 47 occupies one octet, and the IDI ...
... Domain, two octets for Area, six octets for the System Identifier,
and one octet for the NSAP selector. Note that two octets have been
reserved to accommodate future growth and to provide additional
flexibility for inter-domain routing ...
... flexibility for inter-domain routing. The last seven octets of the
GOSIP NSAP format are structured in accordance with IS-IS [14], the
...
... physical address (SNPA) or a logical value. Address
resolution between the NSAP and the SNPA may be accomplished by an
ES-IS protocol [10 ...
... ES-IS protocol [10], locally administered tables, or mapping
functions. The NSAP selector field identifies the end user of the
network layer ...
...
The steps required for an agency to acquire an NSAP Administrative
Authority identifier under ICD ...
... If accepted, GSA will send a return letter to the agency head
indicating the NSAP Administrative Authority identifier as-
...
... A.1.2 Guidelines for NSAP Assignment ...
...
Recommendations which should be followed by an administrative
authority in making NSAP assignments are given below.
...
... The authority should make sure that portions of NSAPs that it
specifies are unique, current, and accurate.
...
... The authority should ensure that procedures exist for
disseminating NSAPs to routing domains and to areas within
...
... 12].
Information that enables next-hop determination based on NSAPs
is gathered and maintained by each intermediate system through
routing protocol ...
... A.2 Data Country Code NSAPs ...
... responsibilities of each Registration Authority are to assure that
NSAPs within the domain are unambiguous and to advertise them as
applicable.
...
...
NSAPs must be globally unique, and an organization may assure this
uniqueness for OSI addresses ...
... registration authority for its domain and can register NSAPs or
delegate the authority to do so.
...
...
In the case of GOSIP Version 2 NSAPs, the complete DSP structure is
given in GOSIP Version 2 ...