Process and system evaluating deterministic behavior of a packet switching network
View Patent ↗A process and system for evaluating the deterministic behavior of a packet switching network including subscriber stations connected to each other through at least one switch, the behavior defined as deterministic if any packet sent on the network from a source subscriber station joins the destination subscriber station(s) within a limited time. The process and system determines if each output port from each switch on the network satisfies the relationship: i number of virtual links passing through the buffer [ 1 + int ( ( Jitter In ) i i + max Latency BAGi ) ] * ( max frame duration ) ≤ latency in which: the max latency value is a maximum residence time in an output buffer of a switch, this value may be different for each switch in the network, BAGi is a minimum time between two consecutive frames belonging to a virtual link i, before they are transmitted, (Jitter In) i is Jitter associated with a virtual link i that represents a time interval between a theoretical instant at which a frame is transmitted, and its effective transmission that may be before or after the theoretical instant, and (max frame duration) i is a duration of a longest frame on the virtual link i.
1. A method for communication between subscriber stations via a packet switching network, said process comprising:
evaluating deterministic behavior of the packet switching network, the behavior being defined as deterministic if any packet sent on the network from a source subscriber station reaches a destination subscriber station within a duration that is limited in time, said evaluating comprising:
determining a latency value, the latency value being a residence time in an output buffer of a switch,
determining a max latency value, the max latency value being a maximum residence time in an output buffer of a switch,
determining a BAG i value, the BAG i value being a minimum time between two consecutive frames belonging to a virtual link i, before they are transmitted,
determining a (Jitter In) i value, wherein the (Jitter in) i is jitter associated with a virtual link i that represents a time interval between a theoretical instant at which a frame is transmitted, and its effective transmission that may be before or after the theoretical instant,
determining a (max frame duration) i value, the (max frame duration) i value being a duration of a longest frame on the virtual link i, and
determining for each output port from each switch on the network if the following relation is satisfied:
∑
i
=
number
of
virtual
links
passing
through
the
buffer
[
1
+
int
(
(
Jitter
In
)
i
i
+
max
Latenc
y
BAG
i
)
]
*
(max frame duration)
i
≤
latency,
wherein, if the relation is not satisfied, a user is notified that said packet switching network is not deterministic.
2. A method according to claim 1 , further comprising adding the virtual links one by one, and the determining of each output port is performed after each addition of a virtual link.
3. A method according to claim 1 , wherein the packet switching network is located on an aircraft.
4. A method according to claim 3 , wherein the packet switching network includes a first switch connected to a first graphic screen and a second graphic screen.
5. A method according to claim 4 , wherein the packet switching network includes a second switch connected to a flight parameters generator and an aircraft maintenance computer.
6. A method according to claim 5 , wherein the first graphic screen displays flight parameters and the second graphic screen displays flight and maintenance parameters.
7. A method according to claim 1 , wherein the jitter refers to max jitter.
8. A method according to claim 1 , further comprising the step of aggregating a number of the virtual links without causing any loss of segregation.
9. A system for communication between subscriber stations via a packet switching network, said system configured to evaluate deterministic behavior of the packet switching network, the behavior being defined as deterministic if any packet sent on the network from a source subscriber station reaches a destination subscriber station within a duration that is limited in time, the system comprising:
a latency value determining unit configured to determine a latency value;
a max latency value determining unit configured to determine a max latency value;
a BAG i value determining unit configured to determine a BAG i value;
a (Jitter In) i value determining unit configured to determine a (Jitter In) i value;
a (max frame duration) i value determining unit configured to determine a (max frame duration) i value; and
a control unit configured to determine for each output port from each switch on the network if the following relation is satisfied:
∑
i
=
number
of
virtual
links
passing
through
the
buffer
[
1
+
int
(
(
Jitter
In
)
i
i
+
max
Latenc
y
BAG
i
)
]
*
(max frame duration)
i
≤
latency,
in which:
the max latency value is a maximum residence time in an output buffer of a switch,
the latency value is a residence time in an output buffer of a switch,
BAG i is a minimum time between two consecutive frames belonging to a virtual link i, before they are transmitted,
(Jitter In) i is jitter associated with a virtual link i that represents a time interval between a theoretical instant at which a frame is transmitted, and its effective transmission that may be before or after the theoretical instant, and
(max frame duration) i is a duration of a longest frame on the virtual link i; and
a user notification unit configured to notify a user that said packet switching network is not deterministic if the relation is not satisfied.
10. A system according to claim 9 , in which the virtual links are added one by one, and the determining is performed after each addition of a virtual link.
11. A system according to claim 9 , wherein the packet switching network is located on an aircraft.
12. A system according to claim 11 , wherein the packet switching network includes a first switch connected to a first graphic screen and a second graphic screen.
13. A system according to claim 12 , wherein the packet switching network includes a second switch connected to a flight parameters generator and an aircraft maintenance computer.
14. A system according to claim 13 , wherein the first graphic screen displays flight parameters and the second graphic screen displays flight and maintenance parameters.
15. A press-method for communication between subscriber stations via a frame switching network, said process comprising:
evaluating deterministic behavior of the packet switching network, the behavior being defined as deterministic if any packet sent on the network from a source subscriber station reaches a destination subscriber station within a duration that is limited in time, said evaluating including:
determining a latency value, the latency value being a residence time in an output buffer of a switch,
determining a max latency value, the max latency value being a maximum residence time in an output buffer of a switch,
determining a BAG i value, the BAG i value being a minimum time between two consecutive frames belonging to a virtual link i, before they are transmitted,
determining a (Jitter In) i value, wherein the (Jitter In) i is jitter associated with a virtual link i that represents a time interval between a theoretical instant at which a frame is transmitted, and its effective transmission that may be before or after the theoretical instant,
determining a (max frame duration) i value, the (max frame duration) i value being a duration of a longest frame on the virtual link i, and
determining for each output port from each switch on the network if the following relation is satisfied:
∑
i
=
number
of
virtual
links
passing
through
the
buffer
[
1
+
int
(
(
Jitter
In
)
i
i
+
max
Latenc
y
BAG
i
)
]
*
(max frame duration)
i
≤
latency,
and notifying a user, if the relation is not satisfied that said packet switching network is not deterministic.
16. A method according to claim 15 , further comprising adding the virtual links one by one, and wherein the determining of each output port is performed after each addition of a virtual link.
17. A method according to claim 15 , wherein the packet switching network is located on an aircraft.
18. A method according to claim 17 , wherein the packet switching network includes a first switch connected to a first graphic screen and a second graphic screen.
19. A method according to claim 18 , wherein the packet switching network includes a second switch connected to a flight parameters generator and an aircraft maintenance computer.
20. A method according to claim 19 , wherein the first graphic screen displays flight parameters and the second graphic screen displays flight and maintenance parameters.