Process for checking the deterministic behavior of a packet switching network
View Patent ↗The invention relates to a process for checking the deterministic behavior of a packet switching network comprising subscriber stations connected to each other through at least one switch, this behavior being said to be deterministic in the sense that every packet sent on the network from a source subscriber station joins the destination subscriber station(s) within a limited time, characterized in that the following relation is satisfied for each output port on each switch on the network: ∑ [ 1 + int ( ( Jitter In ) i i + max Latency BAGi ) ] * ( max frame duration ) ≤ max latency i = number of virtual links passing through the buffer in which: the max latency value is the maximum residence time in the output buffer of a switch, this value may be different for each switch in the network. BAGi is the minimum time between two consecutive frames belonging to a vertical link i, before they are transmitted on the physical support. (Jitter In) i is the Jitter associated with a virtual link i that represents the time interval between the theoretical instant at which a frame is transmitted, and its effective transmission which may be before or after the theoretical instant. (max frame duration) i is the duration of the longest frame on the virtual link i.
1. In a packet switching network in avionics comprising at least a source subscriber station and a destination subscriber station connected to each other through at least one switch having at least one output port, a method for checking a particular service quality in terms of information routing guarantee in said network, said method comprising:
a) determining for each output port of each switch:
1) a maximum latency comprising a maximum residence time in an output buffer of the switch; and
2) a value defined by the relationship:
∑
[
1
+
int
(
(
Jitter
In
)
i
i
+
max
Latency
BAGi
)
]
*
(
max
frame
duration
)
≤
max
latency
i
=
number
of
virtual
links
passing
through
the
buffer
wherein;
BAGi is a minimum time between two consecutive frames belonging to a vertical link i, before said frames are transmitted on a physical support,
(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 which may be before or after the theoretical instant,
(max frame duration) i is a duration of the longest frame on the virtual link i,
b) comparing said value with said maximum latency; and
c) guaranteeing that such a network has a deterministic behavior, in the sense that any packet sent on the network from a source node reaches the destination node(s) within a duration that is limited in time, if, for each switch, said value does not exceed said maximum latency.
2. In a packet switching network in avionics comprising at least a source subscriber station and a destination subscriber station connected to each other through at least one switch having at least one output port, a method for checking a particular service quality in terms of information routing guarantee in said network, said method comprising:
A) For a number i of virtual links which are added one by one:
a) determining, for each output port of each switch:
1) a maximum latency comprising a maximum residence time in an output buffer of the switch; and
2) a valued defined by the relationship:
∑
[
1
+
int
(
(
Jitter
In
)
i
i
+
max
Latency
BAGi
)
]
*
(
max
frame
duration
)
≤
max
latency
i
=
number
of
virtual
links
passing
through
the
buffer
wherein;
BAGi is a minimum time between two consecutive frames belonging to a vertical link i, before said frames are transmitted on a physical support,
(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 which may be before or after the theoretical instant,
(max frame duration)i is a duration of the longest frame on the virtual link i, b) comparing said value with said maximum latency; and
c) guaranteeing that such a network has a deterministic behavior, in the sense that any packet sent on the network from a source node reaches the destination node(s) within a duration that is limited in time, if, for each switch, said value does not exceed said maximum latency;
B) step A is done again if the number of virtual links is not completed.