1. A method of estimating intra-mode paths, the method comprising the steps of:
receiving in memory at least a partial autonomous system (AS)-level path comprising a first AS and a second AS, the at least partial AS-level path corresponding to a mode of communication between a first endpoint and a second endpoint;
selecting by a processor a first hand off pair comprising an exit point from the first AS and an entry point into the second AS, the exit point being in communication with the entry point, the selection being based on, at least in part, at least one of: (i) a property of the first AS, (ii) a property of the second AS, and (iii) a statistical property of traffic associated with at least one of a proxy to the first endpoint and a proxy to the second endpoint, the traffic passing via the first AS; and
identifying by the processor a set of router-level paths within the first AS, from a first entry point into the first AS to the exit point from the first AS within the first hand off pair.
2. The method of claim 1, wherein the property of the first AS comprises at least one of: (i) a number of router-level hop counts within the first AS on a path from the first entry point into the first AS to the exit point from the first AS within the first hand off pair, (ii) a geographic distance between the first entry point into the first AS and the exit point from the first AS within the first hand off pair, and (iii) a number of points of presence associated with both the first AS and the second AS.
3. The method of claim 1, wherein the selection step comprises maximizing a first distance within the first AS, the distance comprising at least one of: (i) a number of hop counts on a path to the exit point from the first AS within the first hand off pair, and (ii) a geographic distance between the first entry point into the first AS and the exit point from the first AS within the first hand off pair.
4. The method of claim 3, further comprising minimizing a second distance from the exit point from the first AS within the first hand off pair to the proxy to the second endpoint, the second distance comprising at least one of: (i) a number of hop counts on a path from the exit point from the first AS within the first hand off pair to the proxy to the second endpoint, and (ii) a geographic distance between the exit point from the first AS within the first hand off pair and the proxy to the second endpoint.
5. The method of claim 1, wherein the selection of the first hand off pair comprises:
selecting a candidate exist point from the first AS;
selecting a candidate entry point into the second AS such that a frequency of traversal of traffic between the candidate exit point and the candidate entry point is greater than a selected threshold; and
designating: (i) the selected candidate exit point as the exit point within the first hand off pair, and (ii) the selected candidate entry point as the entry point within the first hand off pair.
6. The method of claim 5, wherein the frequency of traversal of traffic comprises a frequency of traffic directed to at least one of the proxy to the first endpoint and the proxy to the second endpoint.
7. The method of claim 1, further comprising selecting a router-level path from the identified set of router-level paths such that a path metric corresponding to the selected router-level path satisfies a specified threshold.
8. The method of claim 7, wherein the path metric comprises at least one of a frequency of traversal of traffic via the selected router-level path, delay, jitter, reliability, and availability.
9. The method of claim 7, wherein at least one router-level path in the identified set comprises an intermediate router node, and the path metric comprises a frequency of traversal of traffic via an intermediate router node.
10. The method of claim 9, wherein the frequency of traversal of traffic via the intermediate router node comprises a frequency of traffic directed to at least one of the proxy to the first endpoint and the proxy to the second endpoint.
11. The method of claim 1, further comprising:
selecting a second hand off pair comprising an exit point from the first AS and an entry point into the second AS, the exit point being in communication with the entry point, the selection being based on, at least in part, at least one of: (i) a property of the first AS, (ii) a property of the second AS, and (iii) a statistical property of traffic associated with at least one of the proxy to the first endpoint and the proxy to the second endpoint, the traffic passing via the first AS; and
identifying a set of router-level paths within the first AS, from a second entry point into the first AS to the exit point from the first AS within the second hand off pair.
12. The method of claim 11, wherein the second entry point into the first AS is the first entry point into the first AS.
13. A system for estimating intra-mode paths, the system comprising:
a memory; and
a processor adapted to:
receive at least a partial autonomous system (AS)-level path comprising a first AS and a second AS, the at least partial AS-level path corresponding to a mode of communication between a first endpoint and a second endpoint;
select a first hand off pair comprising an exit point from the first AS and an entry point into the second AS, the exit point being in communication with the entry point, the selection being based on, at least in part, at least one of: (i) a property of the first AS, (ii) a property of the second AS, and (iii) a statistical property of traffic associated with at least one of a proxy to the first endpoint and a proxy to the second endpoint, the traffic passing via the first AS; and
identify a set of router-level paths within the first AS, from a first entry point into the first AS to the exit point from the first AS within the first hand off pair.
14. The system of claim 13, wherein to select the first hand off pair, the processor is further adapted to maximize a first distance within the first AS, the distance comprising at least one of: (i) a number of hop counts on a path to the exit point from the first AS within the first hand off pair, and (ii) a geographic distance between the first entry point into the first AS and the exit point from the first AS within the first hand off pair.
15. The system of claim 14, wherein the processor is further adapted to minimize a second distance from the exit point from the first AS within the first hand off pair to the proxy to the second endpoint, the second distance comprising at least one of: (i) a number of hop counts on a path from the exit point from the first AS within the first hand off pair to the proxy to the second endpoint, and (ii) a geographic distance between the exit point from the first AS within the first hand off pair and the proxy to the second endpoint.
16. The system of claim 13, wherein to select of the first hand off pair the processor is adapted to:
select a candidate exist point from the first AS;
select a candidate entry point into the second AS such that a frequency of traversal of traffic between the candidate exit point and the candidate entry point is greater than a selected threshold; and
designate: (i) the selected candidate exit point as the exit point within the first hand off pair, and (ii) the selected candidate entry point as the entry point within the first hand off pair.
17. The system of claim 13, wherein the processor is further adapted to select a router-level path from the identified set of router-level paths such that a path metric corresponding to the selected router-level path satisfies a specified threshold.
18. The system of claim 13, wherein the processor is further adapted to:
select a second hand off pair comprising an exit point from the first AS and an entry point into the second AS, the exit point being in communication with the entry point, the selection being based on, at least in part, at least one of: (i) a property of the first AS, (ii) a property of the second AS, and (iii) a statistical property of traffic associated with at least one of the proxy to the first endpoint and the proxy to the second endpoint, the traffic passing via the first AS; and
identify a set of router-level paths within the first AS, from a second entry point into the first AS to the exit point from the first AS within the second hand off pair.
19. An article of manufacture, comprising a non-transitory machine-readable medium storing instructions that, when executed by a machine configure the machine, for estimating intra-mode paths, to:
receive at least a partial autonomous system (AS)-level path comprising a first AS and a second AS, the at least partial AS-level path corresponding to a mode of communication between a first endpoint and a second endpoint;
select a first hand off pair comprising an exit point from the first AS and an entry point into the second AS, the exit point being in communication with the entry point, the selection being based on, at least in part, at least one of: (i) a property of the first AS, (ii) a property of the second AS, and (iii) a statistical property of traffic associated with at least one of a proxy to the first endpoint and a proxy to the second endpoint, the traffic passing via the first AS; and
identify a set of router-level paths within the first AS, from a first entry point into the first AS to the exit point from the first AS within the first hand off pair.
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. An exhaust gas purification apparatus for an internal combustion engine, applied to an exhaust purification system including a NOx catalyst adsorbing a reducer and selectively purifying NOx by the reducer, an oxidation catalyst disposed downstream of the NOx catalyst for oxidizing the reducer flowing out from the oxidation catalyst, and an adding means for adding the reducer upstream of the NOx catalyst, the exhaust gas purification apparatus comprising:
a heat value data computing means for computing a heat value data corresponding to a heat value in the oxidation catalyst; and
a reducer detecting means for detecting at least one of an existence or nonexistence of the reducer flowing out from the NOx catalyst and a flowing amount of the reducer.
2. An exhaust gas purification apparatus according to claim 1, wherein
the heat value data computing means computes a differential temperature between a temperature of the exhaust gas flowing into the oxidation catalyst and a temperature of the exhaust gas flowing out from the oxidation catalyst or a temperature of the oxidation catalyst, and
the reducer detecting means detects the reducer based on the differential temperature.
3. An exhaust gas purification apparatus according to claim 1, further comprising;
an exhaust temperature detecting means for detecting a temperature of the exhaust gas flowing into the oxidation catalyst, wherein
as the temperature of the exhaust gas is lower, a threshold of the heat value data for detecting an existence or nonexistence of the reducer is made smaller, or a flowing out amount of the reducer corresponding to the heat value data is made larger.
4. An exhaust gas purification apparatus according to claim 1, further comprising;
a velocity detecting means for detecting a velocity of the exhaust gas flowing into the oxidation catalyst, wherein
as the velocity of the exhaust gas is higher, a threshold of the heat value data for detecting an existence or nonexistence of the reducer is made smaller, or a flowing out amount of the reducer corresponding to the heat value data is made larger.
5. An exhaust gas purification apparatus according to claim 1, further comprising:
a gas sensor detecting NOx and reducer between the NOx catalyst and the oxidation catalyst;
a NOx amount computing means for computing a NOx amount in the exhaust gas flowing out from the NOx catalyst based on a detection value of the gas sensor; and
a NOx amount correction means for correcting a NOx amount based on an amount of the reducer flowing out from the NOx catalyst.
6. An exhaust gas purification apparatus for an internal combustion engine, applied to an exhaust purification system including a NOx catalyst adsorbing a reducer and selectively purifying NOx by the reducer, an oxidation catalyst disposed downstream of the NOx catalyst for oxidizing the reducer flowing out from the oxidation catalyst, and an adding means for adding the reducer upstream of the NOx catalyst, the exhaust gas purification apparatus comprising:
a heat value data computing means for computing a heat value data corresponding to a heat value in the oxidation catalyst; and
a determination means for determining that the reducer flows out from the oxidation catalyst when the heat value data corresponds to a maximum heat value.
7. An exhaust gas purification apparatus according to claim 6, wherein
the heat value data computing means computes a differential temperature between a temperature of the exhaust gas flowing into the oxidation catalyst and a temperature of the exhaust gas flowing out from the oxidation catalyst or a temperature of the oxidation catalyst, and
the determination means for determining whether the reducer flows out from the oxidation catalyst based on the differential temperature.