Detection of asymmetric network routes
View Patent ↗Route asymmetry is detected in a network by running a route tracing program to trace routes between a first element of the network and a second element of the network. The route tracing program need be run at only a single network element, such as the first network element. Forward and reverse routes between the first and second network elements are identified as asymmetric if performance data from the route tracing program indicates a significant deviation from an expected monotonic characteristic as a function of time-to-live values of respective packets transmitted by the route tracing program.
1. A method comprising:
executing a route tracing program, at a first network element, the route tracing program transmitting a sequence of packets with different time-to-live values along a forward route that spans from the first network element to a second network element, wherein the route tracing program specifies the second network element as the destination of the sequence of packets, wherein a reverse route spans from the second network element to the first network element, and wherein the sequence of packets are configured to trigger control messages to be transmitted to the first network element;
in response to executing the route tracing program, calculating performance measurements based on the control messages corresponding to the different time-to-live values, and wherein a first portion of the control messages has been transmitted to the first network element via the forward route and a second portion of the control messages has been transmitted to the first network element via the reverse route;
determining an expected monotonic characteristic that is exhibited by the performance measurements in relation to the different time-to-live values; and
identifying the forward route and the reverse route as being asymmetric with each other when a performance measurement that corresponds to an individual time-to-live value indicates a deviation, over a predetermined deviation threshold, from the expected monotonic characteristic.
2. The method of claim 1 , wherein the route tracing program comprises a traceroute utility.
3. The method of claim 1 , further comprising identifying the forward route and the reverse route as being asymmetric with each other when the performance measurement that corresponds to the individual time-to-live value exceeds a threshold of the expected monotonic characteristic, wherein the expected monotonic characteristic is exhibited by the performance measurements in relation to the different time-to-live values.
4. The method of claim 1 , wherein the route tracing program is executed at least in part on the first network element.
5. The method of claim 1 , wherein the route tracing program runs on a network analysis device coupled to the first network element.
6. The method of claim 1 , wherein at least one of the first network element and the second network element comprises at least one of a router and a switch.
7. The method of claim 1 , wherein the performance measurements comprise delay data.
8. The method of claim 1 , further comprising identifying the forward route and the reverse route as being symmetric with each other when the performance measurements indicate no deviation, over the predetermined deviation threshold, from the expected monotonic characteristic.
9. The method of claim 1 , wherein the route tracing program is executed at least twice, wherein deviations in the performance measurements in a first execution of the route tracing program and, deviations in the performance measurements in a second execution of the route tracing program, are observed for each execution before the forward route and the reverse route are identified as being asymmetric.
10. The method of claim 1 , further comprising utilizing the forward route and the reverse route to determine a location of a performance problem in a network when the forward route and the reverse route are identified as being asymmetric with each other.
11. The method of claim 1 , further comprising transmitting to a network administrator, an indicator of the forward route and the reverse route when the forward route and the reverse route are identified as being asymmetric with each other.
12. The method of claim 1 , further comprising utilizing the forward route and the reverse route to alter operations of a network when the forward route and the reverse route are identified as being asymmetric with each other.
13. A non-transitory computer-readable storage medium storing instructions which, when executed by a processor, implements the method of claim 1 .
14. A processing element comprising a processor and a memory, the memory being coupled to the processor, the processing element being configured to implement the method of claim 1 .
15. A system comprising:
a processor; and
a non-transitory computer-readable storage medium storing instructions which, when executed by the processor, cause the processor to perform operations comprising:
executing a route tracing program, at a first network element, the route tracing program transmitting a sequence of packets with different time-to-live values along a forward route that spans from a first network element to a second network element, wherein the route tracing program specifies the second network element as the destination of the sequence of packets, wherein a reverse route spans from the second network element to the first network element, and wherein the sequence of packets are configured to trigger control messages to be transmitted to the first network element;
in response to executing the route tracing program, calculating performance measurements based on the control messages corresponding to the different time-to-live values, and wherein a first portion of the control messages has been transmitted to the first network element via the forward route and a second portion of the control messages has been transmitted to the first network element via the reverse route;
determining an expected monotonic characteristic that is exhibited by the performance measurements in relation to the different time-to-live values; and
identifying the forward route and the reverse route as being asymmetric with each other when a performance measurement that corresponds to an individual time-to-live value indicates a deviation, over a predetermined deviation threshold, from the expected monotonic characteristic.
16. The system apparatus of claim 15 , wherein the system is implemented within a network analysis device coupled to the first network element.
17. The system of claim 15 , wherein the system is implemented at least in part within the first network element.
18. The system of claim 15 , wherein the first network element comprises one of a router and a switch.
19. A network comprising:
a plurality of interconnected network elements, including a first network element and a second network element interconnected by multiple routes;
wherein a route tracing program is executed at the first network element, the route tracing program transmitting a sequence of packets with different time-to-live values along a forward route that spans from the first network element to the second network element, wherein the route tracing program specifies the second network element as the destination of the sequence of packets, wherein a reverse route spans from the second network element to the first network element, and wherein the sequence of packets are configured to trigger control messages to be transmitted to the first network element;
wherein, in response to executing the route tracing program, the route tracing program calculates performance measurements based on the control messages corresponding to the different time-to-live values, and wherein a first portion of the control messages has been transmitted to the first network element via the forward route and a second portion of the control messages has been transmitted to the first network element via the reverse route;
wherein the route tracing program determines an expected monotonic characteristic that is exhibited by the performance measurements in relation to the different time-to-live values; and
wherein the route tracing program identifies the forward route and the reverse route as being asymmetric with each other when a performance measurement that corresponds to an individual time-to-live value indicates a deviation, over a predetermined deviation threshold, from the expected monotonic characteristic.
20. The network of claim 19 , wherein the route tracing program is run on a network analysis device coupled to the first network element.
21. The network of claim 19 , wherein the route tracing program is executed at least in part on the first network element.