U.S. patent application number 09/829413 was filed with the patent office on 2001-11-29 for perspective-based shared scope address resolution method and apparatus.
Invention is credited to Dev, Roger, Jeffords, Jason, Quinn, Martin S..
Application Number | 20010047430 09/829413 |
Document ID | / |
Family ID | 25228383 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010047430 |
Kind Code |
A1 |
Dev, Roger ; et al. |
November 29, 2001 |
Perspective-based shared scope address resolution method and
apparatus
Abstract
A network system includes a hierarchical directory which
includes a plurality of nodes in a tree structure. Each node
contains a set of address mappings relating a first address to a
second address. An address resolution request attempts to resolve a
first address to a target address in a node in which the first
address is located. If the resolution of this first address cannot
be accomplished in this first node, the process moves to a next
higher node in the hierarchy and again attempts to resolve the
request. The address mappings become less specific as the process
moves up the hierarchy and, as a result, more general addresses
will be used to resolve the first address to the target
address.
Inventors: |
Dev, Roger; (Durham, NH)
; Jeffords, Jason; (Lee, NH) ; Quinn, Martin
S.; (Lee, NH) |
Correspondence
Address: |
WOLF GREENFIELD & SACKS, PC
FEDERAL RESERVE PLAZA
600 ATLANTIC AVENUE
BOSTON
MA
02210-2211
US
|
Family ID: |
25228383 |
Appl. No.: |
09/829413 |
Filed: |
April 9, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09829413 |
Apr 9, 2001 |
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08819522 |
Mar 17, 1997 |
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6216168 |
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Current U.S.
Class: |
709/245 ;
709/238 |
Current CPC
Class: |
H04L 61/4552 20220501;
H04L 61/10 20130101 |
Class at
Publication: |
709/245 ;
709/238 |
International
Class: |
G06F 015/16; G06F
015/173 |
Claims
1. A system for resolving a first address type and value to a
target address type and value in a network, comprising a
computer-readable medium encoded with: a data structure comprising
a hierarchical directory including a plurality of nodes in a tree
structure, each node being a directory scope representing a
hierarchical level within the network and address mapping elements
defining address mappings; and a plurality of executable methods
including: a method for attempting to resolve the first address
type and value to the target address type and value in a first node
at a first hierarchical level.
2. The system as recited in claim 1, wherein the plurality of
executable methods further comprises: when the first address type
and value cannot be resolved to the target address type and value
in the first node, a method for attempting to resolve the first
address type and value to a first intermediate address type and
value in the first node; and a method for attempting to resolve the
first intermediate address type and value to the target type and
value in a second node at a second hierarchical level, higher than
the first hierarchical level.
3. The system as recited in claim 2, wherein the plurality of
executable methods further comprises: when the first intermediate
address type and value cannot be resolved to the target address
type and value in the second node, a method for attempting to
resolve the first intermediate address type and value to a second
intermediate address type and value in the second node; and a
method for attempting to resolve the second intermediate address
type and value to the target address type and value in the first
node.
4. The system as recited in claim 3, wherein the plurality of
executable methods further comprises: when the second intermediate
address type and value cannot be resolved to the target address
type and value in the first node, a method for attempting to
resolve the second intermediate address type and value to a third
intermediate address type and value in the first node; and a method
for attempting to resolve the third intermediate address type and
value to the target address type and value in the second node.
5. The system as recited in claim 4, wherein the plurality of
executable methods further comprises: when the third intermediate
address type and value cannot be resolved to the target address
type and value in the second node, a method for attempting to
resolve the third intermediate address type and value to the target
address type and value in a third node at a third hierarchical
level, the third hierarchical level being higher than the first and
second hierarchical levels.
6. The system as recited in claim 5, wherein the method for
attempting to resolve the third intermediate address type and value
to the target address type and value in the third node comprises: a
method for attempting to resolve the third intermediate address
type and value to a fourth intermediate address type and value
where the third intermediate value and the fourth intermediate
value have a common prefix; and a method for attempting to resolve
the fourth intermediate address type and value to the target
address type and value.
7. The system as recited in claim 1, wherein the plurality of
executable methods further comprises: a method for attempting to
resolve the source address type and value to the target address
type and value in a second node at a second hierarchical level
higher than the first hierarchical level when the source address
type and value cannot be resolved to the target address type and
value in the first node.
8. The system as recited in claim 1, wherein the plurality of
executable methods further comprises: a method for attempting to
resolve the source address type and value to a first intermediate
address type and value in the first node when the source address
type and value cannot be resolved to the target address type and
value in the first node; and a method for attempting to resolve the
first intermediate address type and value to the target address
type and value; wherein the first intermediate address value and
the target address value have a common prefix.
9. A method of resolving a first address type and value to a target
address type and value in a system including a data structure
comprising a plurality of address types and respective values
mapped to one another in a hierarchical structure including at
least a first hierarchical node at a first hierarchical level, the
method comprising the steps of: (a) attempting to resolve the first
address type and value to the target address type and value in the
first hierarchical node; and (b) when the attempted resolution in
step (a) is not successful at the first hierarchical node,
attempting to resolve the first address type and value to an
intermediate address type and value in the first hierarchical node;
and (c) attempting to resolve the first intermediate address type
and value to the target address type and value in a second
hierarchical node at a second hierarchical level.
10. The method as recited in claim 9, further comprising the steps
of: when the first address type and value cannot be resolved to an
intermediate address type and value in the first hierarchical node,
attempting to resolve the first address type and value to a first
intermediate address type and value in a second hierarchical
node.
11. The method as recited in claim 10, wherein the step of
attempting to resolve the first intermediate address type and value
to the target address type and value in the second hierarchical
node includes the steps of: when the first intermediate address
type and value cannot be resolved to the target address type and
value, attempting to resolve the first intermediate address type
and value to a second intermediate address type and value; and
attempting to resolve the second intermediate address type and
value to the target address type and value in the first
hierarchical node.
12. The method as recited in claim 11, wherein: when the second
intermediate address type and value cannot be resolved to the
target address type and value in the first hierarchical node,
attempting to resolve the second intermediate address type and
value to the target address type and value in the second
hierarchical node.
13. A method of resolving a starting address type and value to a
target address type and value in a system including a hierarchical
directory including a tree structure, the tree structure including
at least a starting hierarchical node at a starting hierarchical
level, each hierarchical node including at least one address
mapping set, the method comprising the steps of: (a) attempting to
resolve the starting address type and value to the target address
type and value in the starting hierarchical node; (b) when the
starting address type and value cannot be resolved to the target
address type in step (a), performing one of the following steps:
(c) resolving the starting address type and value to a first
intermediate address type and value in the starting node; and (d)
attempting to resolve the starting address type and value to the
target address type and value in a second hierarichical node at a
second hierarchical level higher than the first hierarchical
level.
14. The method as recited in claim 13, wherein: (e) when the
starting address type and value have been resolved to the first
intermediate address type and value in step (c), attempting to
resolve the first intermediate address type and value to the target
address type and value in a second hierarchical node at a second
hierarchical level higher than the starting hierarchical level; and
(f) when the first intermediate address type and value cannot be
resolved to the target address type and value in step (e),
performing one of the following steps: (g) resolving the first
intermediate address type and value to a second intermediate
address type and value in the second hierarchical node; and (h)
attempting to resolve the first intermediate address type and value
to the target address type and value in a third hierarchical node
at a third hierarchical level higher than the second hierarchical
node.
15. The method as recited in claim 14, wherein: when the first
intermediate address type and value have been resolved to the
second intermediate address type and value in step (g), attempting
to resolve the second intermediate address type and value to the
target address type and value in the starting hierarchical
node.
16. An apparatus for mapping a first address type and value to a
second address type and value, the apparatus comprising: means for
storing a plurality of address types and respective values mapped
to one another; and first means for mapping the first address to
the second address as a function of the stored address types and
values.
17. The apparatus as recited in claim 16, wherein the storing means
comprises means for storing the address types and values in a
hierarchical directory tree structure including at least a first
hierarchical node at a first hierarchical level.
18. The apparatus as recited in claim 17, further comprising:
second means for mapping the first address type and value to the
second address type and value in the first hierarchical node.
19. The apparatus as recited in claim 18, further comprising: third
means for mapping the first address type and value to a first
intermediate address type and value when the second means for
mapping cannot map the first address type and value to the second
address type and value; and means for mapping the first
intermediate address type and value to the second address type and
value.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a method and apparatus for address
mapping and resolution in a communications network, and more
particularly to a method and apparatus wherein network mappings
that are more specific from the requesting entity's point of view,
perspective of the network, are used before network mappings that
are less specific relative to the requesting entity.
[0003] 2. Discussion of the Related Art
[0004] Resources in a network are located and manipulated according
to their associated network addresses. These resources may be
hardware and/or software, including physical devices (routers,
hubs, end stations, processors, components of larger physical
entities, etc.) and processes. Any one resource may have a number
of different types of network addresses. Each type may be used by a
different network protocol to sustain that protocol's operation.
The different network addresses for a particular resource are
referred to as "aliases".
[0005] An alias can also be considered a mapping from one set,
consisting of an address type and an associated value, to another
set, of a different address type and associated value. For example,
a resource may have an IP (Internet Protocol) address as well as a
MAC (Media Access Control) address. In an application, it is useful
to consider that the IP address maps to the MAC address and that
one address type can be resolved to another address type, as long
as a mapping is set up beforehand. To find a related MAC address of
a known IP resource, the address mapping of the known IP address
can be resolved to its MAC type, thereby obtaining its MAC value.
The MAC value can then be used by the requesting resource
(application).
[0006] Because of their importance to the overall operation of a
network, there is an ongoing need for more efficient mapping
techniques for resolving addresses.
SUMMARY OF THE INVENTION
[0007] According to the present invention, address mapping for
end-stations and their associated processes are resolved as a
function of a requesting end-station's network perspective. A
relationship between one address and another is first established
within a hierarchical directory, i.e., a tree structure. When an
end-station desires to connect to a target end-station or resource,
the tree structure is searched, starting at the lowest scope
(level), i.e., the level at which the requesting end-station is
located.
[0008] In one embodiment of the present invention, a system
resolves a first address type and value to a target address type
and value in a network. The system includes a computer-readable
medium encoded with a data structure, including a hierarchical
directory (tree structure) having a plurality of nodes, where each
node represents a hierarchical level within the network and defines
the address mappings. Further included on the computer-readable
medium is a plurality of executable methods (processes) including a
method for resolving the first address type and value to the target
address type and value in a first node at a first hierarchical
level.
[0009] Another embodiment is a method of resolving a first address
type and value to a target address type and value, including the
steps of: starting at the first node, resolving the first address
type and value to the target address type and value according to a
mapping set and when the first address type and value cannot be
resolved to the target address type, resolving the first address
type and value to the target address type and value in a second
node at a second hierarchical level higher than the first
hierarchical level.
[0010] These and other features and benefits of the present
invention will be more particularly described with the following
detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a representation of an address mapping;
[0012] FIG. 2 is a schematic diagram of a network;
[0013] FIG. 3 is a diagram showing the address mappings for the
network of FIG. 2;
[0014] FIGS. 4-8 are flowcharts representing steps performed in
resolving address resolution requests in a network according to the
present invention;
[0015] FIG. 9 is a flow chart also representing steps performed in
resolving address resolution requests in a network according to the
present invention; and
[0016] FIG. 10 shows a general purpose computer as one example of
implementing the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] In order to determine a relationship between one address and
another, there must be first established some representation of
this relationship. In other words, one address must be "mapped" to
another. Without such a mapping, the routing of messages from one
resource to another could fail. In the present invention, the
mapping of a first address to a target address will depend on the
location of the first address in the network. Therefore, if two
different (first) addresses at two different locations in the
network need to communicate with the same target address, the
mappings from each of the two addresses to the target address could
be different.
[0018] In FIG. 1, the direction of mapping is signified by arrows
101. As can be seen, a series of addresses are mapped, e.g.,
address IP 1.2.3.4 to address MAC 2.3.4.5.6.7 to address NAME
SWITCH5. A NAME is just another type of binding, and as such its
significance is minimal. In this context, NAME is a symbolic
identifier used to store and lookup other attributes of a network
device within the topology subsystem of Cabletron's Virtual Network
Services (VNS) available from Cabletron Systems, Inc., Rochester,
NH, U.S.A. While these attributes are not stored in the directory,
the mapping of the actual network address to its NAME identifier
that this identifier represents is within the directory and enables
one to resolve to the NAME using those network addresses; hence,
the other attributes of this device can be retrieved from other
software using the resolved to NAME.
[0019] The present invention also allows more than one address to
map to the same address. As shown, address IP 3.4.5.6 also maps to
address MAC 2.3.4.5.6.7. The mappings, as shown in FIG. 1,
represent a directory "scope" (or level) and within a directory
scope an address can be resolved from a known type and value to
another value, given a target type.
[0020] As an example, consider a resolution request from either IP
1.2.3.4 or IP 3.4.5.6 to a type NAME. Each resolution, according to
the mapping shown in FIG. 1, would return NAME SWITCH5, after an
intermediate resolution to MAC 2.3.4.5.6.7. In this example, the
MAC address is not the desired type, so the search continues along
the mapping series (scope) until successfully resolved or
terminated. In addition, a resolution request using MAC 2.3.4.5.6.7
to type NAME would also return NAME SWITCH5. On the other hand, a
desired resolution, starting at type NAME to a target type of MAC
would fail since the direction of mappings 101 determines the
direction of resolution. Since the NAME address has no mappings out
of it, i.e., there are no mapping arrows, it cannot be resolved to
any other address in this scope.
[0021] Whenever an address cannot be found in its complete form in
a given scope, a shorter version of it may be searched for. This
extra search is dependent upon whether the address is of a type
that supports prefixing. As an example, MAC addresses do not
support prefixing whereas IP addresses do. A prefix is used to
decrease the number of mappings required in a scope and to indicate
that all addresses in a particular range (i.e., designated by upper
and lower ) map to the same value. In the method of the present
invention, the longest matching prefix, i.e., the more specific
address, is used before any shorter prefix, i.e., less specific,
addresses are used.
[0022] As shown in FIG. 2, two IP subnetworks 202, 204 are
separated by a router 206. The MAC address of the router 206 is
6.e3.44.55.66.al. In order to make connections across the
subnetwork boundary, each subnetwork 202, 204 has to route messages
as if they were destined for the router 206. Each subnetwork can be
identified by its respective IP prefix. As shown, subnetwork 202
has an IP prefix of 134.141 and subnetwork 204 has an IP prefix of
123.111. Any substations on the subnet 202 can connect to any
substations on the subnet 204 by going through the router 206 and
vice-versa. As a result, the subnet 202 directory scope will have a
mapping from IP 123.111 to MAC 6.e3.44.55.66.al, and the subnetwork
204 directory scope will have a mapping from IP 134.141 to MAC
6.e3.44.55.66.al.
[0023] The mappings for the directory scopes associated with
subnetworks 202, 204 are shown in FIG. 3. If a resolution request
is performed in subnetwork 202 to resolve, for example, address IP
123.111.34.54 to a MAC address, it can be seen that no IP
123.111.34.54 alias exists in the directory scope 302 associated
with subnetwork 202. As a result, the next shorter prefix of the IP
address will be searched. The next shorter prefix alias is IP
123.111.34 and it does not have an alias in the directory scope
302, either. So, the next shorter prefix IP 123.111 will be
searched. There is a prefix alias for IP 123.111 and its mapping
series is searched for the target MAC type. The MAC value that will
be returned is the MAC address value of the router 206, i.e.,
6.e3.44.55.66.al, as represented in the directory scope 302. As can
be seen in FIG. 3, a similar prefix mapping is set up in the
directory scope 304 associated with the subnetwork 204 indicating
that address type IP, value 134.141.xx.xx is mapped to resolve to
the MAC address of the router 206.
[0024] The present invention thus defines a hierarchical directory
(tree structure) consisting of a plurality of hierarchically
related nodes with each node containing a set of address mappings.
A node is defined as a directory scope. In the present invention, a
scope at a lower level of the hierarchical tree defines address
mappings that relate to more specific mappings, i.e., a subset of
the network resources. In operation, a more specific mapping may
override a mapping higher in the directory tree structure, i.e., a
more general mapping. The entire hierarchical directory (tree
structure) represents all relevant address mapping information for
a particular network. The tree structure and address mappings are
stored in a software structure known as Directory Services. It uses
object-oriented database technology to persist the data, and
object-oriented methodology to represent and perform operations on
the address mappings. It is accessed through an API (application
programming interface) that provides the functionality as shown
below in Table I:
1TABLE I add mappings - a mapping will be added to a specified
directory scope; the directory scope of the mapping will be created
if it does not already exist; mappings are overwritten. resolve
mapping - resolve from one address to an address of a specified
type. remove mappings - the mapping is removed from the specified
scope if it exists; a wild card remove is provided to remove
whatever a particular address maps to. search mappings - return a
set of specified types of mappings. add directory - a directory of
the specified scope will be added if it does not already exist.
remove directory - the specified directory and all its mappings and
children directories will be removed. move directory - move a
directory to become a child of another directory. rename directory
- renames a directory. insert directory - insert a directory
between a target directory and its child directories. search
directory - return the child directory scope identifiers.
[0025] In one embodiment of the present invention, user end-station
mappings may be contained in a scope associated with a particular
switch to which the user end-stations connect, i.e., a "switch"
scope. In another embodiment, a mapping may be used to determine
which server an end-station connects to for a particular
application or resource.
[0026] As an example, at a particular switch scope, a mapping may
define that all end-stations connected to the particular switch use
SERVER X to connect to a particular application. At the scopes
associated with the end-stations, most do not define an individual
SERVER mapping. Rather, the end-stations will use the SERVER X
mapping at the switch's scope. In the scope for one end-station Q,
however, a mapping may be set to use SERVER Y for the particular
application. It should be noted that the application is not
represented in the hierarchy. An application such as VNS (Virtual
Network Services) uses Directory Services to determine the entry
point into or exit point out of a network for a particular
end-station when connections are being setup. When end-station Q
seeks to resolve to its SERVER type address for the particular
application, it would get Y as a result. In order to find this
mapping for end-station Q, however, the resolve request would have
to supply the scope of end station Q. An end station or user may
have unique mappings defined for it due to any number of
administrative, priority or security needs. When all of the other
end-stations resolve to the SERVER type for the particular
application, they would get X returned as a result.
[0027] Different end-stations may have different address views
(perspectives) of network resources. It is necessary to have
different address views at different times to allow shared
resources. In particular, these shared resources may be accessed
through one address while in one location; however, while in
another location, a different address will be necessary in order to
access the shared resource correctly. Sometimes a device will have
two or more physical addresses to which other devices will connect.
It may also have multiple logical addresses or alias names by which
it can be referenced and accessed. If the same address were to be
used by both end-stations, one of them would not be able to locate
the resource correctly, thereby possibly causing a network or a
connection failure. If a device uses an incorrect address in a
communication protocol, the message will not be delivered.
Depending on the device sending the incorrect address, this could
result in network failure.
[0028] The address mappings are added to the hierarchical directory
(tree structure) by specifying two items: 1) the scope or level at
which the address mapping is to be stored, and 2) the mapping to be
added. The scope takes the form of a hierarchical address called a
"distinguished name," e.g., "durham," that contains at least one
mapping term. The mapping term takes the form of a pair of address
tuples, referred to, for convenience and ease of understanding, as
an rhs tuple and an lhs tuple where "rhs" represents "right-hand
side" and "lhs" represents "left-hand side." The lhs tuple maps to
the rhs tuple, i.e., maps from left to right, and each tuple
consists of an address type and an address value of the form (type,
value). The rhs tuple can be used as the lhs tuple of a subsequent
mapping, thereby creating a series of mappings. In other words, a
first (lhs) tuple is mapped to a target (rhs) tuple.
[0029] According to the present invention, a new mapping resolution
method is provided whereby an initial scope of the requestor is the
starting point for alias resolutions When the lhs alias for the
requestor's address is found within the requestor's scope, the
series of address mappings are searched, looking for the desired
type. If the desired type is not found in the initial scope, then a
next higher scope in the hierarchical directory (tree structure) is
searched using the last alias that was searched for or that was
partially resolved to. The method of the present invention requires
that lower hierarchical level scopes be searched before higher
hierarchical level scopes are searched. As a result, if a mapping
at a higher scope partially resolves an alias, i.e., the alias type
is not the target alias type, the search returns to the original
scope. This is done because the local (lower level) scope may
contain a more specific mapping for that alias and the present
invention is directed to insuring that the resolution occurs at the
lowest possible hierarchical level. The process of searching the
next higher hierarchical scope level is repeated either until the
target alias type is found or there is no resolution. A failure to
resolve can occur when the root (the "top level") of the
hierarchical directory tree structure is reached and there has been
no resolution, i.e., the target type has not been found, or the
process has reached a search threshold limit preventing the further
searching of higher hierarchical scopes.
[0030] In operation, the method of the present invention resolves a
tuple of the form (type, value) to a target address type. As above,
each resolution request starts in a particular directory scope. As
shown in FIG. 4, a hierarchical directory (tree structure) 400
includes a "global/root" scope 402 with a "durham" scope 404
subordinate (at a lower level) to the scope 402, a "3rdfl" scope
406 subordinate to scope 404, and a "switch5" scope 408 subordinate
to scope 406. In other words, each scope, as one proceeds down the
hierarchical tree, i.e., from "top" to "bottom," becomes more
specific. Each of the scopes 402-408 includes at least one mapping
of a tuple having the form (type1, value1) mapped, as represented
by an arrow, to another tuple (type2, value2).
[0031] The hierarchical directory (tree structure) relates directly
to the hierarchical structure of the particular network. Referring
to FIG. 4, which will be discussed in more detail below, the tree
structure 400 represents the actual network where the "global/root"
is the uppermost ("top") level of the network. At a next lower
level is the "durham" level which has below it, a "3rdfl" level
which is above a "switch5" level. In the example of FIG. 4, "3rdfl"
means the third floor, and durham means the town Durham. Each
represents a network location group identifier that could be used
to store related network addresses for devices in that location.
This location, which can be defined to be either physical or
logical, is defined as a concatenation of single word terms.
Durham, 3rdfl, represents a particular scope "3rdfl" whose parent
scope is "Durham." Identifiers like these specify the hierarchial
structure of the directory tree structure. The full identifier is
defined from the root of the tree, i.e., the global scope, down to
a specified scope as its Distinguished Name (DN). As can be seen,
the detail of the network becomes more specific as one proceeds
down the hierarchical levels. The address mappings within each node
are specific to that hierarchical level of the network.
[0032] When it is desired that a resolution from a first resource,
as represented by a lhs tuple, to a target type, or rhs tuple, be
found, a command or resolution request in the form of, for
example,
resolve (scope=switch5, Ihs address=(a, al), rhs type to find=b)
(1)
[0033] will be executed.
[0034] In the example, the command "resolve" is interpreted as
follows: 1) starting from the scope of switch5, 2) find the alias
for the Ihs address tuple (a, al) mapped to a rhs address tuple
with a type equal to "b". Starting at the "switch5" scope 408, the
mappings within the scope 408 are checked to see if there is an
alias for the Ihs address of (a, al). In the directory tree 400 as
shown in FIG. 4, the "switch5" scope 408 includes such an alias for
(a, al) with the desired rhs type, in this case "b" . As a result,
in step 410, the address of (a, al) resolves to a type b with a
value of bl in "switch5."
[0035] In some instances, e.g., in a specific scope, the alias may
not have a mapping to the desired type. In that case, the target
type will be searched for in the next higher hierarchical level.
Consider the resolution request:
resolve (scope=switch5, Ihs address=(a, al), rhs type to find=c)
(2)
[0036] as shown in FIG. 5. The hierarchical directory (tree
structure) 400 is the same as the one shown in FIG. 4. The pending
request starts at the "switch5" scope 408, attempting to find the
alias (a, al) matched to a type "c". There is, however, no match
for the tuple (a, al) to a type "c" in the "switch5" scope 408.
There is, on the other hand, an alias for the tuple (a, al) mapped
to the tuple (b, bl). So, step 502 is performed, resolving (a, al)
to (b, bl), where (b, bl) becomes an intermediate lhs tuple. Since
the desired type "c" is not found in the scope of the entity
requesting the resolution, i.e., "switch5", at step 504, the next
higher level, "3rdfl" scope 406, is searched. At this scope level,
the method of the present invention looks to resolve the
intermediate tuple (b, bl) to a tuple having a type of "c". In the
example shown in FIG. 5, there is a mapping for this tuple and
therefore the address tuple (a, al) in "switch5" scope 408 resolves
to address tuple (c, cl) in the "3rdfl" scope 406, in step 506.
[0037] The method of the present invention endeavors to resolve the
desired address at the lowest possible hierarchical level. In some
cases, this involves going from a lower hierarchical level to a
higher hierarchical level, and then back to a lower hierarchical
level. Consider the following resolution request:
resolve (scope=switch5, lhs address=(a, al), rhs type to find=d)
(3)
[0038] The above request is implemented, as shown in FIG. 6, in the
hierarchical network 600 including scopes 602-608. As above, each
of these scopes includes at leastone address mapping. Starting in
"switch5" scope 602 there is no mapping of the address (a, al) to a
type "d" in "switch5" scope 602. There is, however, a mapping to
the address tuple (b, bl). In step 610 address (a, al) is resolved
to address (b, bl) which becomes an "internediate" lhs tuple. The
process goes up in the hierarchy when it cannot resolve any farther
in a particular scope. Step 612 moves to the next higher scope,
"3rdfl" scope 604, where there is a mapping of the intermediate
tuple (b, bl) to the address (c, cl). So, in step 614, address (b,
bl) is resolved to tuple (c, cl) and this becomes the
"intermediate" lhs tuple. At this point, however, the search goes
back, step 616, to the original specific scope, i.e., "switch5" to
resolve the intermediate address (c, cl) in order to find an
address with type "d". Note that the resolution does not continue
from (c, cl) to (d, dl.in3rdfl). There is only one resolution per
scope. The process returns to the original scope upon any partial
resolution in a higher scope (rather than continuing along the
series of the more general higher scope). As shown in "switch5"
scope 602 there is a mapping of (c, cl) to (d, dl.insw5). In step
618, intermediate tuple (c, cl) is resolved to tuple (d, dl.insw5).
As a final result, the address (a, al) resolves to a "d" type with
a value of "dl.insw5" in scope "switch5".
[0039] In the present method, the use of prefixes can help to
resolve an address resolution request. Consider, therefore, the
resolution request:
resolve (scope=switch5, lhs address=(a, al), rhs type to find=e)
(4)
[0040] As shown in FIG. 7, the hierarchical directory (tree
structure) 400 is the same as that of FIG. 4. Starting in "switch5"
scope 408 there is no mapping of the address (a, al) to an address
with the type "e". Step 702 resolves address (a, al) to address (b,
bl) as an intermediate lhs tuple. Step 704 then moves to the next
higher scope, "3rdfl" scope 406. The tuple (b, bl) is
intermediately resolved to an address (c, cl) in the "3rdfl" scope
406 in step 706. Since the method always tries to resolve at the
lowest scope level, step 708 moves back to scope 408. The
intermediate address (c, cl) is checked in the "switch5" node 408
where a resolution, step 710, from address (c, cl) to address (d,
dl.insw5) is performed. Since the desired type "e" is still not
found, the search moves up to the "3rdfl" node 406, step 712, where
there is also no mapping of the intermediate address (d, dl.insw5)
to an address with a type of "e". Moving up to the next higher
hierarchical "durham" scope 404, step 714, there is no mapping for
the intermediate address (d, dl.insw5). There is, however, a
mapping for the address (d, dl). As between the address (d,
dl.insw5) and the address (d, dl), they have the same type, i.e.,
"d", and the values have the same prefix, i.e., "dl". A mapping of
address (d, dl) to (e, el) is present in "durham" scope 404. In
step 716, intermediate address (d, dl) is resolved to address (e,
el) based on the common "dl" prefix. As a result, the address of
(a, al) in scope "switch5" resolves to an address (e, el) in the
"durharm" scope.
[0041] For each instance that a particular lhs address is mapped to
an rhs address which is not of the desired type, the method goes
back to the lowest scope in the hierarchical directory structure
from which the present resolve request has originated. Consider the
following resolution request:
resolve (scope=switch5, ,lhs address=(a, al), rhs type to find=f)
(5)
[0042] As shown in FIG. 8, the above resolution request is
implemented in the same hierarchical directory (tree structure) 400
as found in FIG. 4. Starting in the "switch5"scope 408, the method
looks for a mapping of address (a, al) to an address tuple having a
type of "f". There is no such mapping, although there is a mapping
of the (a, al) address to an address (b, bl). As a result, in step
802, an intermediate resolution resolves the address (a, al) to
intermediate address (b, bl). In step 804, the next higher level of
hierarchy, i.e., "3rdfl" scope 406, is checked to see if there is a
mapping from address (b, bl) to an address having a type of "f".
Since such a mapping does not exist, step 806 intermediately
resolves the address (b, bl) to the intermediate address (c, cl)
and step 808 returns to the "switch5" scope 408.
[0043] There is no mapping for the address (c, cl) to the desired
type, so in step 810 an intermediate resolution of the address (c,
cl) to the address (d, dl.insw5) is performed. Step 812 moves to
the next higher "3rdfl" scope 406 where there is no mapping of
address (d, dl.insw5), so step 814 moves to the next higher
"durham" scope 404. At this scope level, there is a mapping of the
address (d, dl) to the address (e, el). Relying on the common
prefix between "dl .insw5" and "dl", step 816 intermediately
resolves to the address (e, el).
[0044] Returning to the lowest scope level, i.e., "switch5" scope
408, step 818 looks for a match but cannot find one, so in step 820
this search is done in the next higher scope level, i.e., "3rdfl"
scope 406. Here, once again, there is no match, so step 822 moves
to the "durham" scope 404. Again, there is no match so step 824
moves to the next highest level of "global/root" scope 402.
[0045] In scope 402, there is a mapping of the address (e, el) to
the address (f, finglobal). This latter address is an address of
the desired type "f". Therefore, step 826 resolves the intermediate
address (e, el) to the address (f, finglobal). In the end, the
result of resolution request set forth in (5) above is the address
"finglobal" in the "global/root" scope. It should be noted that
although the mapping found in the hierarchal structure 400 at the
"global/root" scope 402 was a series of mappings, the resolution
finctions in the direction of the mapping and, therefore, can be
started at any point along the mapping. In this example, the
mapping of the address (e, el) to the address (f, finglobal)
started at a point other than what might be considered a "starting
point" of the mapping representation, i.e., tuple (j, jl).
[0046] As set forth in the flow chart of FIG. 9, the steps as
described above with regard to FIGS. 4-8 are summarized
therein.
[0047] Starting with a resolution request in the form of:
resolve (first_scope, first_Lhs_tuple, type_to_find) (6)
[0048] In step 901, a variable Lhs is set equal to first_Lhs_tuple,
in step 903 a variable present scope is set equal to first_scope,
and in step 905 a variable scope_level is set equal to zero. In
step 907, it is determined whether there is a mapping for variable
Lhs at scope level present_scope. If there is a mapping found in
step 907, control passes to step 909 where the rhs tuple is
retrieved. At step 911, the determination is made as to whether or
not the rhs tuple type is equal to the type_to_find. If this
condition is true, control passes to step 913 where the resolution
of the address is completed and it is reported that first_Lhs tuple
in first_scope resolves to rhs tuple at a scope level of
present_scope.
[0049] Returning to step 911, if the rhs tuple type is not equal to
type_to_find, then control passes to step 915 where the variable
Lhs is set equal to rhs tuple. At step 917, it is determined
whether or not the scope_level value is greater than zero. If
scopelevel is greater than zero, control returns to step 903.
[0050] If the determination of step 917 finds that the scope_level
is not greater than zero, control passes to step 919. At step 919,
it is determined if there is a next higher scope level. If there is
not a next higher scope level, control passes to step 921 and a
report that no resolution is found is returned. When, on the other
hand, there is a next higher scope level, control passes from step
919 to step 923 where the variable scope_level is incremented and
at step 925 the system moves to the next higher scope then at step
927, the variable present_scope is set equal to next_scope. Control
then returns to step 907 where the analysis will begin again to
determine if there is a mapping for the value to which the variable
Lhs has been set.
[0051] As can be seen, the process as described by the flowchart in
FIG. 9, will move back down to the first_scope level each time
there is an intermediate mapping of an Lhs tuple to an rhs tuple
which does not have an rhs tuple type equal to the type_to_find. In
addition, if a resolution passed through the process does not
result in finding an rhs tuple having an rhs tuple type equal to
the type_to_find, then the next higher scope will be searched and
an attempt to resolve the address resolution request will be made
at that level.
[0052] It is clear that the process as set forth in FIG. 9 could be
modified to limit the number of higher scopes which are searched in
order to conserve processing resources. In addition, prefixes could
be easily supported in this process, where at least steps 907 and
911 would be modified to equate and/or calculate prefixes. As
disclosed by the specification above, this would be well within the
abilities of one of ordinary skill in the art to incorporate.
[0053] The present invention is preferably implemented on a Virtual
Networking Services System available from Cabletron Systems, Inc.,
Rochester, N.H., U.S.A.; this system includes a SunSparc 20
computer running the Solaris operating system. Of course, the
present invention could be adapted to run on any set of
communicating processes and/or processors appropriately connected
to one another and each capable of performing the required
functions.
[0054] The perspective-based shared scope system of the present
invention may be implemented as software on a floppy disk, compact
disc or hard drive which controls a computer, for example a general
purpose computer such as a workstation, mainframe, or personal
computer, to perform the steps of the processes disclosed in FIGS.
1-9. The software would then include a program having a data
structure for providing general purpose computer instructions and
data for carrying out the functions of the previous embodiments.
Such a general purpose computer 70, as shown in FIG. 10, typically
includes a central processing unit 72 (CPU) coupled to random
access memory 74 (RAM) and program memory 76 via a data bus 78. The
general purpose computer 70 may be connected to the network in
order to receive and provide address mappings and resolutions to
other devices on the network.
[0055] Alternately, the invention may be implemented as special
purpose electronic hardware. Additionally, in either a hardware or
a software embodiment, the functions performed by the different
elements may be combined in various arrangements of hardware and
software.
[0056] Having thus described various illustrative embodiments of
the invention, various modifications will occur to those skilled in
the art that are intended to be within the scope of the present
invention. Thus, this description and accompanying drawings are
provided by way of example and are not intended to be limiting. The
invention is defined by the following claims.
* * * * *