1. A processor-implemented method of determining link delay in a network comprising a plurality of nodes, the method comprising the steps of:
identifying pairs of nodes associated with a given link;
for each of the identified pairs, setting up a virtually-concatenated group between the nodes of that pair;
utilizing the virtually-concatenated groups to make delay measurements; and
processing the delay measurements to determine delay of the given link;
wherein one or more of the virtually-concatenated groups comprise two-member virtually-concatenated groups; and
wherein for a given two-member virtually-concatenated group C, the group having members M1 and M2 using respective paths P1 and P2, a differential delay measurement \u03b4C is determined as
\u2211
linksL
i
\u2208
P
1
\u2062
D
i
–
\u2211
linksL
j
\u2208
P
2
\u2062
D
j
=
\u03b4
C
,
Di and Dj being delays of respective links Li and Lj.
2. The method of claim 1 wherein a given one of the delay measurements made utilizing a particular virtually-concatenated group comprises a differential delay measurement.
3. The method of claim 1 wherein the virtually-concatenated group that is set up for a particular identified pair comprises at least two diversely-routed members.
4. The method of claim 1 wherein the processing step further includes the steps of:
generating a system of equations based on differential delay measurements made utilizing the virtually-concatenated groups; and
solving the system of equations to obtain information utilizable to determine delay of the given link.
5. The method of claim 1 wherein for a given one of the two-member virtually-concatenated groups, the differential delay measurement is made at a particular one of the associated nodes by comparing frame indicator fields for concurrently arriving frames.
6. The method of claim 5 wherein the frame indicator fields comprise multiframe indicator fields (MFIs) of multiframe headers of the two-member virtually-concatenated group.
7. The method of claim 1 wherein the given link is part of a biconnected component of the network.
8. The method of claim 7 wherein the biconnected component of the network comprises a logical ring.
9. The method of claim 8 wherein the logical ring comprises n nodes (N1, N2, . . . Nn) interconnected by n links (L1,2, L2,3, . . . Ln,1) with delays (D1,2, D2,3, . . . Dn,1), the method as applied to the logical ring comprising the steps of:
setting up for each node a two-member virtually-concatenated group with its neighboring node in the ring such that the routes taken by the two members are along opposite sides of the ring;
measuring a differential delay for each node;
for a given virtually-concatenated group set up between a given one of the nodes and its neighboring node in the ring, formulating an equation for the corresponding delay;
repeating the equation formulation step for each of the other virtually-concatenated groups to obtain a system of n equations;
solving the system of n equations; and
based on a result of the solving step, determining the delay of a particular one of the n links.
10. The method of claim 8 wherein after delays are determined for one or more links of the logical ring, another logical ring of the network is selected and a link delay determination process is repeated for that logical ring.
11. The method of claim 1 wherein delay is determined for a given one of the virtually-concatenated groups by configuring a first node associated with the group to send designated information that is substantially the same as that received from a second node associated with the group, the delay being determined as a function of a round-trip delay measurement made using the designated information.
12. The method of claim 11 wherein the designated information comprises frame indicator bits.
13. The method of claim 1 wherein at least one of the method steps is implemented at least in part in software running on a processor of at least one node of the network.
14. A processor-implemented method of determining link delay in a network comprising a plurality of nodes, the method comprising the steps of:
identifying pairs of nodes associated with a given link;
for each of the identified pairs, setting up a virtually-concatenated group between the nodes of that pair;
utilizing the virtually-concatenated groups to make delay measurements; and
processing the delay measurements to determine delay of the given link;
wherein the method performs the following steps to determine a delay Di,j of a given link Li,j between nodes Ni, Nj in the network:
setting up a first two-member virtually-concatenated group between node Ni and another node Nk such that the routes taken by the two members are disjoint and one of the routes goes over the link Li,j, the two routes forming a ring Ri comprising nodes Ni, Nj and Nk and link Li,j;
computing a differential delay \u03b4i for the first virtually-concatenated group;
setting up a second two-member virtually-concatenated group between node Nj and node Nk such that the two routes are on opposite sides of ring Ri;
computing a differential delay \u03b4j for the second virtually-concatenated group; and
determining the delay Di,j as
D
i
,
j
=
\u03b4
i
–
\u03b4
j
2
.
15. An apparatus for use in determining link delay in a network comprising a plurality of nodes, the apparatus comprising:
a processor; and
a memory coupled to the processor;
wherein the processor is operative to perform the steps of:
identifying pairs of nodes associated with a given link;
for each of the identified pairs, setting up a virtually-concatenated group between the nodes of that pair;
utilizing the virtually-concatenated groups to make delay measurements; and
processing the delay measurements to determine delay of the given link;
wherein one or more of the virtually-concatenated groups comprise two-member virtually-concatenated groups; and
wherein for a given two-member virtually-concatenated group C, the group having members M1 and M2 using respective paths P1 and P2, a differential delay measurement \u03b4C is determined as
\u2211
linksL
i
\u2208
P
1
\u2062
\u2062
D
i
–
\u2211
linksL
j
\u2208
P
2
\u2062
\u2062
D
j
=
\u03b4
C
,
Di and Dj being delays of respective links Li and Lj.
16. The apparatus of claim 15 wherein the apparatus is implemented in a distributed manner within one or more of the network nodes.
17. The apparatus of claim 15 wherein the apparatus is implemented in a centralized manner utilizing a central controller.
18. An article of manufacture comprising a non-transitory machine-readable medium storing one or more programs for use in determining link delay in a network comprising a plurality of nodes, the one or more programs when executed in a processor performing the steps of:
identifying pairs of nodes associated with a given link;
for each of the identified pairs, setting up a virtually-concatenated group between the nodes of that pair;
utilizing the virtually-concatenated groups to make delay measurements; and
processing the delay measurements to determine delay of the given link;
wherein one or more of the virtually-concatenated groups comprise two-member virtually-concatenated groups; and
wherein for a given two-member virtually-concatenated group C, the group having members M1 and M2 using respective paths P1 and P2, a differential delay measurement \u03b4C is determined as
\u2211
linksL
i
\u2208
P
1
\u2062
\u2062
D
i
–
\u2211
linksL
j
\u2208
P
2
\u2062
\u2062
D
j
=
\u03b4
C
,
Di and Dj being delays of respective links Li and Lj.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A marker determination device in which feature points extracted from an image are arranged in a predetermined space, and portions of this predetermine space in which the number of said feature points is equal to or less than a predetermined number are defined as unique features, comprising:
a feature storage that stores these unique features, and the feature points extracted from an existing mark; and
a feature comparator that arranges the feature points extracted from said existing mark in said predetermined space, and determines that said existing mark can be used as a marker that is detectable from said image when the number of the feature points matching with said unique features is equal to or more than a predetermined number.
2. A marker determination device according to claim 1, comprising:
a video image inputting unit that images said image;
a feature extracting unit that extracts the feature points from said image; and
a unique feature selector that arranges said feature points in a feature space, selects as said unique features portions of this feature space in which the number of said feature points is equal to or less than a predetermined number, wherein said feature comparator arranges the feature points extracted from said existing mark in said predetermined space, and determines that said existing mark can be used as a marker that is detectable from said image when the number of the feature points matching with said unique features is equal to or more than a predetermined number.
3. A marker determination device according to claim 1, comprising:
a video image inputting unit that images said image;
a feature extracting unit that extracts the feature points from said image; and
an invariant feature convertor that maps the feature points extracted from said image onto an invariant feature space, and selects as said unique features portions of this invariant feature space in which the number of said feature points is equal to or less than a predetermined number, wherein said feature comparator arranges the feature points extracted from said existing mark in said invariant feature space, and determines that said existing mark can be used as a marker that is detectable from said image when the number of the feature points matching with said unique features is equal to or more than a predetermined number.
4. A marker determination device according to claim 1, comprising a notifying unit that notifies a result of a determination by said feature comparator to the outside.
5. A marker determination detection system comprising a marker determination device and a marker detection device:
wherein said marker determination device comprises:
a first video image inputting unit that inputs an image;
a first arranging unit that extracts feature points from said image inputted by this first video image inputting unit and displays these extracted feature points onto a predetermined space;
a unique feature selector that selects as unique features portions of said space in which the number of said feature points is equal to or less than a predetermined number;
a feature comparator that arranges the feature points based upon an existing mark in said predetermined space, selects the feature points matching with said unique features, and determines that said mark can be used as a marker that is detectable from said image when the number of these selected feature points is equal to or more than a predetermined number;
a marker storage that stores the feature points of said mark; and
wherein said marker detection device comprises:
a second video image inputting unit that inputs the image;
a second arranging unit that extracts the feature points based upon said image inputted by this second video image inputting unit, and displays these extracted feature points onto the predetermined space; and
a collating unit that determines whether or not an arrangement of the feature point based upon said marker exists in an arrangement of a feature point group displayed onto said predetermined space.
6. A marker determination detection system according to claim 5:
wherein said first arranging unit arranges said extracted feature points in a feature space; and
wherein said unique feature selector selects as the unique features portions of said feature space in which the number of said feature points is equal to or less than a predetermined number.
7. A marker determination detection system according to claim 5:
wherein said first arranging unit maps said extracted feature points onto an invariant feature space; and
wherein said unique feature selector selects as the unique features portions of said invariant feature space in which the number of said feature points is equal to or less than a predetermined number.
8. A marker determination detection device, comprising:
a first video image inputting unit that inputs an image;
a first arranging unit that extracts feature points from said image inputted by this first video image inputting unit, and displays these extracted feature points onto a predetermined space;
a unique feature selector that selects as unique features portions of said space in which the number of said feature points is equal to or less than a predetermined number;
a feature comparator that arranges the feature points based upon an existing mark in said predetermined space, selects the feature points matching with said unique features, and determines that said existing mark can be used as a marker that is detectable from said image when the number of these selected feature points is equal to or more than a predetermined number;
a marker storage that stores said marker;
a second video image inputting unit that inputs the image;
a second arranging unit that extracts the feature points based upon said image inputted by this second video image inputting unit, and displays these extracted feature points onto the predetermined space; and
a collating unit that determines whether or not an arrangement of the feature point corresponding to said marker exists within an arrangement of a feature point group displayed onto said predetermined space.
9. A marker determination detection device according to claim 8: wherein said first arranging unit arranges said extracted feature points in a feature space; and
wherein said unique feature selector selects as the unique features portions of said feature space in which the number of said feature points is equal to or less than a predetermined number.
10. A marker determination detection device according to claim 8: wherein said first arranging unit maps said extracted feature points onto an invariant feature space; and
wherein said unique feature selector selects as the unique features portions of said invariant feature space in which the number of said feature points is equal to or less than a predetermined number.
11. A marker, wherein said marker is determined to be usable as a marker that is detectable from an image when feature points are extracted from said image, these extracted feature points are displayed in a predetermined space, portions of said predetermine space in which the number of said feature points is equal to or less than a predetermined number are selected as unique features, the feature points are extracted from an existing mark, these feature points are arranged in said predetermined space, the feature points matching with said unique features are selected, and the number of these selected feature points is equal to or more than a predetermined number.
12. A marker according to claim 11, wherein said extracted feature points are arranged in a feature space, and portions of this feature space in which the number of said feature points is equal to or less than a predetermined number are selected as unique features.
13. A marker according to claim 11, wherein said extracted feature points are mapped onto an invariant feature space, and portions of said invariant feature space in which the number of said feature points is equal to or less than a predetermined number are selected as unique features.
14. A marker determination method comprising the steps of:
inputting an image;
extracting feature points from said image, and displaying these extracted feature points onto a predetermined space;
selecting as unique features portions of said space in which the number of said feature points is equal to or less than a predetermined number; and
arranging the feature points based upon an existing mark in said predetermined space, selecting the feature points matching with said unique features, and determining that said existing mark can be used as a marker that is detectable from said image when the number of these selected feature points is equal to or more than a predetermined number.
15. A marker determination method according to claim 14, comprising a step of arranging the feature points extracted from said existing mark in a feature space, and determining that said existing mark can be used as a marker that is detectable from said image when the number of the feature points matching with said unique features is equal to or more than a predetermined number.
16. A marker determination method according to claim 14, comprising a step of arranging the feature points extracted from said existing mark in an invariant feature space, and determining that said existing mark can be used as a marker that is detectable from said image when the number of the feature points matching with said unique features is equal to or more than a predetermined number.
17. A non-transitory computer readable storage medium storing a marker determination program for causing an information processing device to execute the processes of:
inputting an image;
extracting feature points from said image, and displaying these extracted feature points onto a predetermined space;
selecting as unique features portions of said space in which the number of said feature points is equal to or less than a predetermined number; and
arranging the feature points based upon an existing mark in said predetermined space, selecting the feature points matching with said unique features, and determining that said existing mark can be used as a marker that is detectable from said image when the number of these selected feature points is equal to or more than a predetermined number.
18. A non-transitory computer readable storage medium storing a marker determination program according to claim 17, causing the information processing device to execute a process of arranging the feature points extracted from said existing mark in a feature space, and determining that said existing mark can be used as a marker that is detectable from said image when the number of the feature points matching said unique features is equal to or more than a predetermined number.
19. A non-transitory computer readable storage medium storing a marker determination program according to claim 17, causing the information processing device to execute a process of arranging the feature points extracted from said existing mark in an invariant feature space, and determining that said existing mark can be used as a marker that is detectable from said image when the number of the feature points matching said unique features is equal to or more than a predetermined number.