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... guidelines for network service access point (NSAP) address
assignment. This paper provides guidelines for allocating NSAP
addresses in the Internet (the terms NSAP ...
... 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).
...
... The guidelines presented in this document are quite similar to the
guidelines that are proposed in the Internet for IP address
allocation with CIDR (RFC 1519(-> 4632) ...
... 1519(-> 4632) [19]). The major difference between
the two is the size of the addresses (4 octets for CIDR vs 20 octets ...
... 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
...
... topology of areas or allocate portions of its NSAP
address space; the relationship between topology and addresses
is discussed, but the method of deciding on a particular topology ...
... routers know the level 2 topology and know which
addresses are reachable via each level 2 router. The set of all
level 2 routers ...
...
NSAP addresses provide a flexible, variable length addressing format,
which allows for multi-level ...
... addressing format,
which allows for multi-level hierarchical address assignment. These
addresses provide the flexibility needed to solve two critical ...
... multi-level hierarchical address assignment. These
addresses provide the flexibility needed to solve two critical
problems simultaneously: (i) How to administer a worldwide address
space ...
... addresses provide the flexibility needed to solve two critical
problems simultaneously: (i) How to administer a worldwide address
space; and (ii) How to assign addresses in a manner which makes
routing ...
... critical
problems simultaneously: (i) How to administer a worldwide address
space; and (ii) How to assign addresses in a manner which makes
routing scale well in a worldwide Internet ...
... format and authority responsible for assigning the rest of the
address. The DSP is assigned by whatever addressing authority ...
... addresses are subdivided by IS-IS into the
area address, the system identifier (ID), and the NSAP selector
...
... identifier (ID), and the NSAP selector
(SEL). The area address identifies both the routing domain and the
...
... area within the routing domain. Generally, the area address
corresponds to the IDP plus a high-order part of the DSP ...
... IDI field|
+-----+-----+-------------------------------+--------------+-------+
<----------------Area Address--------------> <-----ID-----> <-SEL->
IDP ...
... 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 ...
... 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 (after truncation of the ID and SEL
...
... NSAP address. The area address can be identified as
the remainder of the address (after truncation of the ID and SEL
fields). It is therefore not necessary for the area address to have
...
... the remainder of the address (after truncation of the ID and SEL
fields). It is therefore not necessary for the area address to have
any particular length -- the length of the area address could vary
...
... fields). It is therefore not necessary for the area address to have
any particular length -- the length of the area address could vary
between different area addresses in a given routing ...
... any particular length -- the length of the area address could vary
between different area addresses in a given routing domain.
...
...
Usually, all nodes in an area have the same area address. However,
sometimes an area might have multiple addresses. Motivations for
...
... nodes in an area have the same area address. However,
sometimes an area might have multiple addresses. Motivations for
allowing this are several:
...
... It might be desirable to change the address of an area. The most
graceful way of changing an area address from A to B is to first
...
... It might be desirable to change the address of an area. The most
graceful way of changing an area address from A to B is to first
allow it to have both addresses A and B, and then after all nodes ...
... graceful way of changing an area address from A to B is to first
allow it to have both addresses A and B, and then after all nodes
in the area have been modified to recognize both addresses ...
... addresses A and B, and then after all nodes
in the area have been modified to recognize both addresses, one by
one the nodes can be modified to forget address ...
... method for accomplishing this is to, one by one, add knowledge of
address B into the A partition, and similarly add knowledge of
address ...
... address B into the A partition, and similarly add knowledge of
address A into the B partition.
...
... of removing a portion of an area). This would be accomplished by
first introducing knowledge of address A into the appropriate
nodes (those destined to become area A), and knowledge of address ...
... address A into the appropriate
nodes (those destined to become area A), and knowledge of address
B into the appropriate nodes, and then one by one removing ...
... route within an area based on the ID
portion of the ISO address. Level 1 routers recognize, based on the
destination address ...
... address. Level 1 routers recognize, based on the
destination address in a packet, whether the destination is within
the area. If so, they route ...
... Level 2 intermediate systems route based on address prefixes,
preferring the longest matching prefix, and preferring internal
routes ...
... routing domain boundary that have advertised external
address prefixes into the level 2 subdomain. A level 2 router may
also be operating as a level 1 router ...
...
A level 1 router will have the area portion of its address manually
configured. It will refuse to become a neighbor with a router ...
... neighbor with a router whose
area addresses do not overlap its own area addresses. However, if a
level 1 router ...
... router whose
area addresses do not overlap its own area addresses. However, if a
level 1 router has area addresses ...
... addresses. However, if a
level 1 router has area addresses A, B, and C, and a neighbor has
area addresses ...
... addresses A, B, and C, and a neighbor has
area addresses B and D, then the level 1 IS will accept the other IS
as a level 1 neighbor.
...
... router as a neighbor,
regardless of area address. However, if the area addresses do not
overlap, the link ...
... neighbor,
regardless of area address. However, if the area addresses do not
overlap, the link would be considered by both routers ...
...
A host may autoconfigure the area portion of its address by
extracting the area portion of a neighboring router's address ...
... address by
extracting the area portion of a neighboring router's address. If
this is the case, then a host will always accept a router ...
... neighbor. Since the standard does not specify that the host *must*
autoconfigure its area address, a host may be pre-configured with an
area address ...
... Confederation Identifier (RDCI). RDCIs are assigned out of the
address space allocated for RDIs -- RDCIs and RDIs are syntactically
indistinguishable. Procedures for assigning and managing RDIs and
RDCIs are outside the scope of the protocol. However, since RDIs are
...
... syntactically nothing more than network layer addresses, and RDCIs
are syntactically nothing more than RDIs, it is expected that RDI and
...
... IDRP doesn't assume or require any particular internal structure for
the addresses. The protocol provides correct routing as long as the
following guidelines are met:
...
... 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.
...
... topology and/or policy information. To provide
maximum benefits, both mechanisms can be used together. This implies
that address assignment that will facilitate route aggregation does
...
... aggregation does
not conflict with the ability to form RDCs, and vice versa; formation
of RDCs should be done in a manner consistent with the address
assignment needed for route aggregation.
...
... IDP and the
HO-DSP) must be globally unique. If the area address of an NSAP
matches one of the area addresses ...
... Level 2 routing acts on address prefixes, using the longest address
prefix that matches the destination address;
...
... Level 2 routing acts on address prefixes, using the longest address
prefix that matches the destination address;
...
... routing acts on address prefixes, using the longest address
prefix that matches the destination address;
...
... A system shall be able to generate and forward data packets
containing addresses in any of the formats specified by
ISO 8348. However, within a routing ...
... IS-IS
routing. End systems with addresses which do not conform may
require additional manual configuration and be subject ...
... domain, level 2 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
...
... 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 ...
... affected only by the number of areas in the domain, and the number of
area addresses assigned to each area.
...
... domain, level 2
routing routes according to address prefixes. In this case, there is
considerable potential advantage (in terms of reducing the amount of
routing information ...
... considerable potential advantage (in terms of reducing the amount of
routing information that is required) if the number of address
prefixes required to describe any particular set of external
destinations can be minimized. Efficient routing ...
... routing with IDRP similarly
also requires minimization of the number of address prefixes needed
to describe specific destinations. In other words, addresses ...
... address prefixes needed
to describe specific destinations. In other words, addresses need to
be assigned with topological significance. This requirement is
...
... bandwidth consumed in
support of routing. This implies that address assignment must serve
the needs of routing, in order for routing ...
...
Level 2 routing is based upon address prefixes. Level 2 routers
(ISs) distribute, throughout the level 2 subdomain, the area
...
... routers
(ISs) distribute, throughout the level 2 subdomain, the area
addresses of the level 1 areas to which they are attached (and any
manually configured reachable address prefixes). Level 2 routers ...
... addresses of the level 1 areas to which they are attached (and any
manually configured reachable address prefixes). Level 2 routers
compute next-hop ...
... routers
compute next-hop forwarding information to all advertised address
prefixes. Level 2 routing is determined by the longest advertised
address prefix ...
... address
prefixes. Level 2 routing is determined by the longest advertised
address prefix that matches the destination address.
...
... routing is determined by the longest advertised
address prefix that matches the destination address.
...
... At routing domain boundaries, address prefix information is exchanged
with other routing domains ...
... authorities (allowing no abstraction), then the boundary prefix
information consists of an enumerated list of all area addresses.
...
... Alternatively, should the routing domain "own" an address prefix and
assign area addresses based upon it, boundary routing information ...
... domain "own" an address prefix and
assign area addresses based upon it, boundary routing information can
be summarized into the single prefix ...
... prefix. This can allow substantial
data reduction and, therefore, will allow much better scaling (as
compared to the uncoordinated area addresses discussed in the
previous paragraph).
...
... defined hierarchical relationship, administrators would not be able
to assign area addresses out of some common prefix for the purpose of
data abstraction. The result would be flat inter-domain routing ...
... group
of subscribers each to be assigned an address prefix from a shorter
prefix assigned to their provider ...
... subscriber now "owns" its
(somewhat longer) prefix, from which it assigns its area addresses.
...
... (inter-domain) traffic. A short address prefix may be assigned to
the provider, which then assigns slightly longer prefixes ...
... subscribers. This allows the
provider, when informing other providers of the addresses that it can
reach, to abbreviate the reachability information for a large number
...
... 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 ...
... constraints. The flexibility of NSAP addresses facilitates
this form of hierarchical address assignment and routing. As one
example of how NSAPs ...
... compared to the number of routing domains and address prefixes that
can conveniently and efficiently be handled via dynamic inter-domain
routing protocols. As the Internet ...
... hierarchy may become necessary. Again, this requires considerable
flexibility in the addressing scheme, such as is provided by NSAP
addresses.
...
...
[Note: We are using U.S. GOSIP version 2 addresses only as an
example. It is not necessary that NSAPs be allocated from the GOSIP
...
... the U.S. there may in some cases be strong reasons to prefer a
country- or area-specific format rather than the U.S. GOSIP format.
However, GOSIP addresses are used in most cases in the examples in
this paper because:
...
... registration authority for suballocation of AA
values under the GOSIP address space has already been established at
GSA.]
...
... 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 ...
... assign RD identifiers underneath their unique address prefix (the
reserved field is left to accommodate future growth and to provide
...
...
Given such a mapping, where should address administration and
allocation be performed to satisfy both administrative
decentralization and data abstraction? Three possibilities are
...
... For example, suppose that a given subscriber is trying to decide
whether to obtain an NSAP address prefix based on an AA value from
...
... AA value from
GSA (implying that the first four octets of the address would be
those assigned out of the GOSIP space), or based on an RD value from
...
... RD value from
its provider (implying that the first seven octets of the address are
those obtained by that provider). If considering only their own
...
... address into its own
prefix; the address must be explicitly listed in routing exchanges,
resulting in an additional burden to other providers which must
...
...
In the second case, each other provider sees a single address prefix
for the local provider which encompasses the new subscriber ...
... routing information to identify the
new subscriber's address prefix. Thus, the advantages primarily
benefit other providers which maintain routing information about this
...
... customers. The guidelines discussed below
describe reasonable ways of managing the OSI address space that
benefit the entire community.
...
... routing domain use addresses obtained from a wide variety of
administrations. For routing within the domain ...
... administrations. For routing within the domain, the area addresses
are treated as a flat field.
...
... CIDR.
Areas correspond roughly to networks and area addresses to network
numbers. The result of allowing areas within a routing ...
... authorities is flat routing at the
area address level. The number of address prefixes that subscriber
...
... default routes) the size of the routing tables
would be on the order of the number of area addresses globally. As
the CLNP internet ...
... subscriber routing domain, the set of all addresses
reachable in the domain can then be represented by a single prefix ...
... All areas within this routing domain would have area addresses
comprising this prefix followed by an Area identifier ...
... identifier. The prefix
represents the summary of reachable addresses within the routing
domain ...
... subscriber domains, based on
a single (shorter length) address prefix assigned to the provider.
For example, given the GOSIP Version 2 ...
... provider.
For example, given the GOSIP Version 2 address structure, an AA value
may be assigned to each direct provider ...
... routing
domain. A similar hierarchical address assignment based on a prefix
assigned to each provider ...
... NSAP formats. This
results in direct providers advertising to other providers (both
direct and indirect) a small fraction of the number of address
prefixes that would be necessary if they enumerated the individual
prefixes of the subscriber ...
... service from one or more indirect providers and exchanging routing
information with other direct providers. In general, providers will
want to handle as few address prefixes as possible to keep costs low.
In the Internet environment, subscriber ...
...
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 ...
... 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
...
... service provider. This allows the
provider, when announcing the addresses that it can reach to other
providers, to use a single address prefix to describe a large number
...
... provider, when announcing the addresses that it can reach to other
providers, to use a single address prefix to describe a large number
of NSAP addresses corresponding to multiple routing ...
... providers, to use a single address prefix to describe a large number
of NSAP addresses corresponding to multiple routing domains.
...
...
One possible solution is to assign 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 ...
... 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
...
... The disadvantage of this approach is that since the NSAP address for
that organization has no relationship to the addresses of any
particular provider, the providers to which this organization is
...
... AA value under the U.S.
GOSIP Version 2 address space. It is likely that outside of the
U.S., a single entry may be maintained in routing tables for all U.S.
...
... U.S., a single entry may be maintained in routing tables for all U.S.
GOSIP addresses. However, within the U.S., every "default-less"
provider will need to maintain a separate address ...
... addresses. However, within the U.S., every "default-less"
provider will need to maintain a separate address entry for MBII. If
MBII is in fact an international corporation, then it may be
necessary for every "default-less" provider ...
... unacceptable load on routers within providers if all organizations
were to choose such address assignments. This solution may not scale
to internets where there are many hundreds of thousands of multi-
homed organizations.
...
... connection to a provider,
and to assign a single address prefix to each area within its routing
domain ...
... providers in Europe, and one in the far east, then MBII may make use
of six different address prefixes. Each area within MBII would be
assigned a single address prefix based on the nearest connection ...
... of six different address prefixes. Each area within MBII would be
assigned a single address prefix based on the nearest connection.
...
... connection to MBII
needs to announce to other providers the ability to reach only those
parts of MBII whose address is taken from its own address space.
This implies that no additional routing information ...
... needs to announce to other providers the ability to reach only those
parts of MBII whose address is taken from its own address space.
This implies that no additional routing information needs to be
...
... provider announces that it can reach
all of the NSAPs based on its own address prefix, which only includes
some of the NSAPs within MBII. If the connection ...
... provider were severed, then the NSAPs within MBII with
addresses based on that provider would become unreachable via inter-
domain ...
...
The second solution also requires that when external connectivity
changes, internal addresses also change.
...
... destination within country X must at all
times stay entirely within the country. With the first solution, it
is not possible to determine from the destination address whether or
not the destination is within the country. With the second solution,
...
... not the 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 discard any traffic that has a destination within MBII's address
space. However, with the first solution this requires one entry;
with the second it requires many entries and may be impossible as a
practical matter.
...
...
There are other possible solutions as well. A third approach is to
assign each multi-homed organization a single address prefix, based
on one of its connections to a provider ...
... With the third approach, each multi-homed organization in the widget
group would make use of an address assignment based on its other
attachment(s) to providers (the attachments not associated with the
widget group ...
... However, since the widget backbone does not inform other general
world-wide providers of what addresses it can reach (since the
backbone is not intended for use by other outside organizations), the
...
... relatively large set of routing prefixes needs to be maintained only
in a limited number of places. The addresses assigned to the various
organizations which are members of the widget group would provide a
...
... routing domains which are attached to both). Rather
than getting two address prefixes (such as two AA values assigned
under the GOSIP address space ...
... address prefixes (such as two AA values assigned
under the GOSIP address space) these organizations could obtain three
prefixes. Those routing ...
... routing domains which are attached to NorthSouthNet
but not attached to SouthNorthNet obtain an address assignment based
on one of the prefixes. Those routing ...
... routing domains which are attached to
SouthNorthNet but not to NorthSouthNet would obtain an address based
on the second prefix. Finally, those routing ...
... domains which are
multi-homed to both of these networks would obtain an address based
on the third prefix. Each of these two providers would then
...
...
There are therefore a number of possible solutions to the problem of
assigning NSAP addresses to multi-homed routing domains. Each of
...
... provider to develop policy on whether and under what
conditions to accept customers with addresses that are not based on
its own address prefix, and how such non-local ...
... customers with addresses that are not based on
its own address prefix, and how such non-local addresses will be
...
... its own address prefix, and how such non-local addresses will be
treated. For example, a somewhat conservative policy might be that
an attached subscriber ...
... NSAP address prefix, but that
addresses which are not based on the providers own prefix might not
be advertised to other providers. In a less conservative policy, a
...
... The discussion up to this point concentrates on the relationship
between NSAP addresses and routing between various routing domains ...
... router M) within MBII. It is
therefore necessary to configure router X to know which addresses can
be reached over this link (specifically, all addresses ...
... addresses can
be reached over this link (specifically, all addresses reachable in
MBII). Similarly, it is necessary to configure router M to know
...
... MBII). Similarly, it is necessary to configure router M to know
which addresses can be reached over this link (specifically, all
addresses ...
... addresses can be reached over this link (specifically, all
addresses reachable in XYZ Corporation).
...
... single
connection to a service provider, and has therefore received an
address allocation from the space administered by that provider.
Similarly, let's suppose that MBII, as an international corporation
...
... connections to six different providers, has chosen the second
solution from Section 5.4, and therefore has obtained six different
address allocations. In this case, all addresses reachable in the
XYZ Corporation can be described by a single address prefix ...
... solution from Section 5.4, and therefore has obtained six different
address allocations. In this case, all addresses reachable in the
XYZ Corporation can be described by a single address prefix (implying
...
... address allocations. In this case, all addresses reachable in the
XYZ Corporation can be described by a single address prefix (implying
that router M only needs to be configured with a single address
prefix ...
... address prefix (implying
that router M only needs to be configured with a single address
prefix to represent the addresses reachable over this point-to-point
link). All addresses ...
... that router M only needs to be configured with a single address
prefix to represent the addresses reachable over this point-to-point
link). All addresses reachable in MBII can be described by six
...
... address
prefix to represent the addresses reachable over this point-to-point
link). All addresses reachable in MBII can be described by six
address prefixes (implying that router ...
... point-to-point
link). All addresses reachable in MBII can be described by six
address prefixes (implying that router X needs to be configured with
six address prefixes ...
... address prefixes (implying that router X needs to be configured with
six address prefixes to represent the addresses reachable over the
point-to-point link ...
... router X needs to be configured with
six address prefixes to represent the addresses reachable over the
point-to-point link).
...
... RD at the other
end of the link. Thus, there are no address abstraction requirements
beyond those inherent in the address prefixes ...
... address abstraction requirements
beyond those inherent in the address prefixes exchanged across the
private link.
...
... domains use valid
globally unique NSAP addresses. Suppose that the zero-homed routing
domain ...
... Address Transition Issues ...
...
Allocation of NSAP addresses based on connectivity to providers is
important to allow scaling of inter-domain routing to an internet ...
... containing millions of routing domains. However, such address
allocation based on topology also implies that a change in topology ...
...
This need to allow for change in addresses is a natural, inevitable
consequence of any method for routing ...
... notion of routing data abstraction is that there is some
correspondence between the address and where a system (i.e., a
routing domain ...
... routing domain, area, or end system) is located. Thus if the system
moves, in some cases the address will have to change. If it were
possible to change the connectivity between routing domains ...
... routing domains without
changing the addresses, then it would clearly be necessary to keep
track of the location of that routing domain ...
... Internet, it is possible that the topology may be relatively
volatile. This implies that planning for address transition is very
important. Fortunately, there are a number of steps which can be
taken to help ease the effort required for address ...
... address transition is very
important. Fortunately, there are a number of steps which can be
taken to help ease the effort required for address transition. A
complete description of address transition issues is outside of the
...
... taken to help ease the effort required for address transition. A
complete description of address transition issues is outside of the
scope of this paper. However, a very brief outline of some
transition issues is contained in this section.
...
...
Also note that the possible requirement to transition addresses based
on changes in topology imply that it is valuable to anticipate the
...
... topology imply that it is valuable to anticipate the
future topology changes before finalizing a plan for address
allocation. For example, in the case of a routing domain ...
... 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 ...
... assigned to a routing domain in an instantaneous "change the address
at midnight" manner. Instead, a gradual transition is required in
which both the old and the new addresses ...
... address
at midnight" manner. Instead, a gradual transition is required in
which both the old and the new addresses will remain valid for a
limited period of time. During the transition period, both the old
...
... valid for a
limited period of time. During the transition period, both the old
and new addresses are accepted by the end systems in the routing
domain ...
... routing
domain, and both old and new addresses must result in correct routing
of packets to the destination ...
... IS-IS. As
described in Section 3, IS-IS allows multiple addresses to be
assigned to each area specifically for the purpose of easing
transition.
...
... OSI for the autoconfiguration of
area addresses. This allows OSI end systems to find out their area
addresses ...
... addresses. This allows OSI end systems to find out their area
addresses automatically, either by passively observing the ES-IS IS-
Hello packets transmitted by routers ...
... 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 ...
... routers for their NSAP address. If the ID portion of the address is
assigned in a manner which allows for globally unique IDs [18], then
...
... 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
...
... without the need for manual intervention. However, routers will
still require manual address reconfiguration.
...
...
During the transition period, it is important that packets using the
old address be forwarded correctly, even when the topology has
changed. This is facilitated by the use of "best match" inter-domain
routing ...
... domain assignment based on the AA value obtained by the
NorthSouthNet under the GOSIP address space. However, for a variety
of reasons, the XYZ Corporation decided to terminate its association
...
... NewCommercialNet public data network. Thus the XYZ Corporation now
has a new address assignment under the ANSI address assigned to the
...
... has a new address assignment under the ANSI address assigned to the
NewCommercialNet. The old address for the XYZ Corporation would seem
...
... ANSI address assigned to the
NewCommercialNet. The old address for the XYZ Corporation would seem
to imply that traffic for the XYZ Corporation should be routed to the
...
... (NewCommercialNet) are adjacent and cooperative, then this transition
is easy to accomplish. In this case, packets routed to the XYZ
Corporation using the old address assignment could be routed to the
NorthSouthNet, which would directly forward them to the
NewCommercialNet, which would in turn forward them to XYZ
...
... NewCommercialNet, which would in turn forward them to XYZ
Corporation. In this case only NorthSouthNet and NewCommercialNet
need be aware of the fact that the old address refers to a
destination which is no longer directly attached to NorthSouthNet.
...
... NSFNET backbone would need to maintain a special entry for XYZ
corporation so that traffic to XYZ using the old address allocation
would be forwarded via NewCommercialNet. However, other routing
...
... traffic destined for NorthSouthNet, but may choose
to add one additional (more specific) entry to ensure that packets
sent to XYZ Corporation's old address are routed correctly.
...
...
Whichever method is used to ease address transition, the goal is that
knowledge relating XYZ to its old address that is held throughout the
...
... method is used to ease address transition, the goal is that
knowledge relating XYZ to its old address that is held throughout the
global internet would eventually be replaced with the new
...
... and will be accomplished through the distributed directory system.
Discussion of the directory, along with other address transition
techniques such as automatically informing the source of a changed
address ...
... address transition
techniques such as automatically informing the source of a changed
address, are outside the scope of this paper.
...
... 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 ...
... administrative boundaries are not
related to actual network topology, address assignment based on such
organization boundaries is not recommended.
...
... 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 ...
... routing domain use a
single address prefix assigned to that domain. Specifically, this
allows the set of all NSAP addresses ...
... 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 ...
... single-homed routing domains use an address prefix based on its
connectivity to a public service provider. We recommend that zero-
...
...
The general technical requirements for NSAP address guidelines do not
vary from country to country. However, details of address
...
... requirements for NSAP address guidelines do not
vary from country to country. However, details of address
administration may vary between countries. Also, in most cases,
network topology ...
...
NSAP addresses for use within the U.S. portion of the Internet are
expected to be based primarily on two address prefixes ...
... NSAP addresses for use within the U.S. portion of the Internet are
expected to be based primarily on two address prefixes: the ICD=0005
format used by The U.S. Government, and the DCC ...
... (for the foreseeable future) small enough to allow addressing of this
set of providers via a flat address space. These providers will be
used to interconnect a wide variety of routing domains ...
... domains will be
attached to only one of the providers. This will permit hierarchical
address abbreviation based on provider. We therefore strongly
recommend that addresses ...
... address abbreviation based on provider. We therefore strongly
recommend that addresses be assigned hierarchically, based on address
prefixes assigned to individual providers.
...
... provider. We therefore strongly
recommend that addresses be assigned hierarchically, based on address
prefixes assigned to individual providers.
...
... Routing Domain Confederation. That, combined with hierarchical
address assignment, would provide significant reduction in the volume
of routing information that needs to be handled by IDRP ...
...
We recommend that all providers explicitly be involved in the task of
address administration for those subscriber routing domains ...
... provider should develop policy on whether and under what
conditions to accept customers using addresses that are not based on
the provider's own address prefix ...
... addresses that are not based on
the provider's own address prefix, and how such non-local addresses
...
... provider's own address prefix, and how such non-local addresses
will be treated. Policies should reflect the issue of cost
associated with implementing such policies.
...
...
We recommend that a similar hierarchical model be used for NSAP
addresses using the DCC-based address format. The structure for
...
... We recommend that a similar hierarchical model be used for NSAP
addresses using the DCC-based address format. The structure for
...
... domains which are not attached to any publically-
available provider, no urgent need for hierarchical address
abbreviation exists. We do not, therefore, make any additional
recommendations for such "isolated" routing ...
... between the two domains that they interconnect, no additional
technical problems relating to address abbreviation is caused by such
a link, and no specific additional recommendations are necessary.
...
...
This section contains additional RARE recommendations for allocating
NSAP addresses within each national domain, administered by a
National Standardization Organization (NSO) and national research
...
... CDP identifies an organization within a country and the CDSP is
then available to that organization for further internal structuring
as it wishes. Non-ambiguity of addresses is ensured by there being
the NSO a single national body that allocates the CDPs.
...
... organizations with different requirements and giving different
amounts of the total address space to them, and that it conveniently
enables a substantial amount of address space to be reserved for
...
... amounts of the total address space to them, and that it conveniently
enables a substantial amount of address space to be reserved for
future allocation.
...
...
Organizations are classified into large, medium and small for the
purpose of address allocation, and one CFI is made available for each
category of organization.
...
... similarly to that specified within the U.S. and Europe no matter
whether the addresses are based on DCC or ICD format.
...
...
While RDIs and RDCIs need not be related to the set of addresses
within the domains (confederations) they depict, for the sake of
...
... with some of its subscribers and the subscribers take their addresses
out of the provider, then the NSAP ...
... prefix for its own RDIs. In all other
cases a provider should use the address prefix that it uses for
assigning addresses to systems within the provider ...
... provider should use the address prefix that it uses for
assigning addresses to systems within the provider as its RDI.
...
... Authors' Addresses ...
... Callon, R., "TCP and UDP with Bigger Addresses (TUBA), A Simple Proposal for Internet Addressing ...
... Domain Routing (CIDR): an Address Assignment and Aggregation Strategy", RFC 1519(-> 4632), BARRNet, cisco ...
... ISO/IEC JTC1/SC6, "Addendum to ISO 9542 Covering Address Administration", N6273, March 1991. ...
... 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 ...
... NSAP addressing
subdomain with a corresponding address format as illustrated in
Figure 2 in Section 4.2. The "47" signifies that it is based on the
ICD ...
... ISO 8348 allows a maximum length of 20 octets for the NSAP address.
The AFI of 47 occupies one octet, and the IDI ...
... names a unique system within an area. The value of the system field
may be a physical address (SNPA) or a logical value. Address
resolution between the NSAP and the SNPA may be accomplished by an
...
... may be a physical address (SNPA) or a logical value. Address
resolution between the NSAP and the SNPA may be accomplished by an
ES ...
...
- Electronic Mail Address(es), and,
- Reason Needed (one or two paragraphs explaining the intended
...
... DSP under its control. Further delegation of address assignment
authority (resulting in additional levels of hierarchy in the
...
... administrator must determine whether a logical or a
physical address should be used in the System Identifier field
(Figure 2, Section 4.2). An example of a physical ...
... Identifier field
(Figure 2, Section 4.2). An example of a physical address is a
48-bit MAC address ...
... address is a
48-bit MAC address; a logical address is merely a number that
meets the uniqueness requirements ...
... 48-bit MAC address; a logical address is merely a number that
meets the uniqueness requirements for the System Identifier
field ...
... meets the uniqueness requirements for the System Identifier
field, but bears no relationship to an address on a physical
subnetwork ...
... The network address itself contains information that may be
used to aid routing, but does not contain a source route ...
... NSAPs must be globally unique, and an organization may assure this
uniqueness for OSI addresses in two ways. The organization may apply
to GSA for an Administrative Authority ...