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... Level 2 intermediate systems route based on address prefixes,
preferring the longest matching prefix, and preferring internal
routes ...
... route based on address prefixes,
preferring the longest matching prefix, and preferring internal
routes over external routes. They route towards areas, without
...
... 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 ...
... An NSAP prefix carried in the Network Layer Reachability
Information (NLRI) field for a route ...
... routing domain; that is, no system identified by the prefix
should reside in a different routing domain ...
... NLRI field contain identical NSAP address prefixes, since this
would imply that the same system(s) is simultaneously located
in several routing ...
... 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;
...
... 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 ...
...
Level 2 routing is based upon address prefixes. Level 2 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
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.
...
... At routing domain boundaries, address prefix information is exchanged
with other routing domains ...
... NSAP assignment
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 ...
... addresses based upon it, boundary routing information can
be summarized into the single prefix. This can allow substantial
data reduction and, therefore, will allow much better scaling (as
compared to the uncoordinated area addresses ...
... 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; all
...
... group
of subscribers each to be assigned an address prefix from a shorter
prefix assigned to their provider ...
... subscribers each to be assigned an address prefix from a shorter
prefix assigned to their provider. Each subscriber now "owns" its
...
... provider. Each 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 ...
... address prefix may be assigned to
the provider, which then assigns slightly longer prefixes (based on
the provider's prefix ...
... prefixes (based on
the provider's prefix) to each of the subscribers. This allows the
provider ...
... of routing domains as a single prefix. This approach therefore can
allow a great deal of hierarchical abbreviation of routing
information, and thereby can greatly improve the scalability ...
... Routing domains at any "level" in the hierarchy
may use their prefix as the basis for subsequent suballocations,
assuming that the NSAP addresses remain within the overall length and
...
... 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 ...
... assign RD identifiers underneath their unique address prefix (the
reserved field is left to accommodate future growth and to provide
...
... choice is not significant. The subscriber is still allocated a
prefix from the provider's address space, and the provider ...
... subscriber is trying to decide
whether to obtain an NSAP address prefix based on an AA value from
GSA ...
... reason to choose one approach or the other. The subscriber must use
one prefix or another; the source of the prefix has little effect on
routing ...
... subscriber must use
one prefix or another; the source of the prefix has little effect on
routing efficiency within the subscriber ...
... subscriber in
order to route, regardless of any commonality in the prefixes of its
subscribers.
...
... subscriber's address into its own
prefix; the address must be explicitly listed in routing exchanges,
...
...
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
...
... domains which need to maintain routes to
this domain. There is no common prefix that can be used to represent
these NSAPs and therefore no summarization can take place at the
...
... routing domains would advertise is on the order of the number of
attached areas; the number of prefixes a provider routing domain ...
... subscriber routing domain (that is, site) with a unique prefix
results in the biggest single increase in abstraction, with each
subscriber ...
... subscriber domain assigning area addresses from its prefix. From
outside the subscriber routing ...
... domain under its administrative
authority identifier, rrr. The resulting prefix for the routing
domain ...
... domain would have area addresses
comprising this prefix followed by an Area identifier. The prefix
...
... comprising this prefix followed by an Area identifier. The prefix
represents the summary of reachable addresses within the routing ...
... subscriber domains, based on
a single (shorter length) address prefix assigned to the provider.
For example, given the GOSIP Version 2 ...
... domain. A similar hierarchical address assignment based on a prefix
assigned to each provider may be used for other NSAP ...
... 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 ...
... 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 routing domains ...
... subscriber routing domains willing to accept prefixes derived
from the direct providers? In the supplier/consumer model, the direct
provider ...
... 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 ...
... The mechanics of this scenario are straightforward. Each direct
provider is assigned a unique prefix, from which it allocates
slightly longer routing domain ...
... identifiers under the direct provider's
unique prefix. For example, assume that NIST is a subscriber routing ...
... NSAPs from an
indirect provider's prefix is that the indirect providers and their
attached direct providers are perceived as being independent. Direct
providers may take their indirect provider ...
... 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 ...
... attached. This allows each multi-homed organization to base its NSAP
assignments on a single prefix, and to thereby summarize the set of
all NSAPs reachable within that organization via a single prefix ...
... 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 for
...
... particular provider, the providers to which this organization is
attached will need to advertise the prefix for this organization to
other providers. Other providers (potentially worldwide) will need
to maintain an explicit entry for that organization in their routing
tables ...
... 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.
...
... 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 ...
...
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 ...
... 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
...
... routing domains which are attached to both). Rather
than getting two address prefixes (such as two AA values assigned
under the GOSIP address space ...
... under the GOSIP address space) these organizations could obtain three
prefixes. Those routing domains which are attached to NorthSouthNet
...
... but not attached to SouthNorthNet obtain an address assignment based
on one of the prefixes. Those 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
...
... networks would obtain an address based
on the third prefix. Each of these two providers would then
advertise two prefixes to other providers, one prefix ...
... on the third prefix. Each of these two providers would then
advertise two prefixes to other providers, one prefix for subscriber
...
... prefix. Each of these two providers would then
advertise two prefixes to other providers, one prefix for subscriber
routing ...
... customers with addresses that are not based on
its own address prefix, and how such non-local addresses will be
...
... subscriber RD may use any NSAP address prefix, but that
addresses which are not based on the providers own prefix ...
... 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
provider ...
... provider might accept customers using such non-local prefixes and
agree to exchange them in routing information with a defined set of
...
... 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 ...
... 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 ...
... address abstraction requirements
beyond those inherent in the address prefixes exchanged across the
private link.
...
... routing domain use a
single address prefix assigned to that domain. Specifically, this
allows the set of all NSAP addresses ...
... NSAP addresses reachable within a single domain
to be fully described via a single prefix. We recommend that
single-homed routing ...
... single-homed routing domains use an address prefix based on its
connectivity to a public service provider. We recommend that zero-
...
... 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 ...
... provider. We therefore strongly
recommend that addresses be assigned hierarchically, based on address
prefixes assigned to individual providers.
...
... addresses that are not based on
the provider's own address prefix, and how such non-local addresses
...
... DCC scheme.
Organizations which are not associated with a particular country and
which have reasons not to use a national prefix based on ISO DCC
...
... aggregation of NSAPs at national
boundaries into as few prefixes as possible, we further recommend
that NSAPs allocated to routing ...
... simplicity we recommend that RDIs and RDCIs be assigned based on the
NSAP prefixes assigned to domains and confederations.
...
... A multihomed RD should use one of the NSAP prefixes assigned to it as
its RDI. If a service provider ...
... out of the provider, then the NSAP prefix assigned to the provider
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 should use the address prefix ...
... 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 ...