ISSN: 1693-6930
TELKOMNIKA Vol. 14, No. 3A, September 2016 : 98 – 107
101 schedule and process the short-frame packet, but it will be blocked at more once with the being
processed data packets. Therefore, the service curve of short-frame queue is:
2 3
max max
1
8 max l
l t
C t
C
, 1
Where,
2 max
l ,
3 max
l is the maximum frame length of the
2
Q
,
3
Q
queue. When the highest priority
1
Q
queue has multiple virtual link data flows, according to the analysis of the FIFO scheduling algorithm, without considering the end system scheduler
generates a delay jitter, the service curve for the jth VL data flow in the
1
Q
queue:
2 3
1 1
max max
max max
1 1
8 8
i i
i j
j i
j i
max l l
l l
t C
t BAG
C
,
2 Where,
1 max
i
l is the maximum frame length of the ith VL in
1
Q
queue,
1 i
BAG
is the bandwidth allocation interval of the ith VL in
1
Q
queue.
3.2. Service Curves of Relatively Important Task and General Task
According to the combination scheduling strategy, the data flow in the
2
Q
3
Q
queue can be processed just when the data stream of the high priority queue has been processed. The first
delay corresponding to the situation is the frame is being blocked with the high priority queue, so the sum of the service curves obtained by the important task and the general task queue is:
1 1
max max
1 2 3
1 1
max 1
1 1
8 8
8
n i
i n
i Q Q
i n
i i
i i
l l
t C
t l
BAG C
BAG
3 Where, n is the number of virtual link aggregation for the high priority queue.
According to the combined scheduling strategy, the important task and the general task was scheduled by WRR, so the service curves of the
2
Q
,
3
Q
queue are:
1 3
1 2
max 3
max max
2 max
1 2
3 1
1 max
1 max
2 1
1
8 8
8
n i
i n
i i
n m
i i
m m
i i
l l
l l
t C
t l
BAG l
C BAG
4
1 2
1 3
max 2
max max
3 max
1 3
3 1
1 max
1 max
2 1
1
8 8
8
n i
i n
i i
n m
i i
m m
i i
l l
l l
t C
t l
BAG l
C BAG
5 When the important task
2
Q
queue and the general task
3
Q
queue have multiple virtual link data flows, the service curves for the jth VL data flow in the
2
Q
,
3
Q
queue can be get by the FIFO scheduling algorithm.
TELKOMNIKA ISSN: 1693-6930
Short-frame Prior Scheduling with WRR Transmission Strategy in AFDX … Yuanyuan Xu 102
1 2
2 max
2 max
max 2
3 1
1 2
max 2
2 1
3 max
max 3
max 1
1 1
2 max
max 2
max 3
1 1
1 1
max 2
8 8
8 8
8 8
i m
n j
m i
m j i
m m
m n
m i
m j i
i i
n n
m i
i i
i m
m
l l
l t
C BAG
BAG l
l l
l t
l l
l C
C BAG
BAG l
1 3
3 max
3 max
max 3
3 1
1 3
max 2
3 1
2 max
max 2
max 1
1 1
3 max
max 3
max 3
1 1
1 1
max 2
8 8
8 8
8 8
i m
n j
m i
m j i
m m
m n
m i
m j i
i i
n n
m i
i i
i m
m
l l
l t
C BAG
BAG l
l l
l t
l l
l C
C BAG
BAG l
3.3 The Delay Time of VL
i
t
max 1
n i
i
l
Qi
t
i
D
Figure 3. The delay upper bound
ij
D
As shown in Figure 2, the arrival curve of all virtual links in different priority queue
i
Q can be expressed as:
max max
1 i
n i
Qi i
i
l t
l t
BAG
6 From the Figure 3, we know that in order to ensure the real-time and validity when data
transmission, the setting of the parameters such as bandwidth and weight ratio guarantees that the service rate of the virtual link is greater than the rate of its arrival.
Then, we will calculate the delay upper bound
i
D
of
i
Q queue under the combined scheduling algorithm:
2 3
1 1
max max
max 1
8
n i
D max l
l l
C
,
ISSN: 1693-6930
TELKOMNIKA Vol. 14, No. 3A, September 2016 : 98 – 107
103
3 1
3 2
2 max
3 max
2 max
max max
1 2
1 2
1 3
2 max
2 max
max 1
2 1
8 8
n n
i m
m i
m i
i n
m m
i m
i
l l
l l
l D
l C
l l
BAG
3 1
2 3
3 max
2 max
3 max
max max
1 2
1 3
1 3
3 max
3 max
max 1
2 1
8 8
n n
i m
m i
m i
i n
m m
i m
i
l l
l l
l D
l C
l l
BAG
The queue
i
Q is composed of multiple virtual links, the delay upper bound
ij
D
as follows:
2 3
1 1
max max
max 1
max 1
max 1
8 8
8
i i
i j j
i j i
max l l
l l
D l
C BAG
C
,
2 1
3 max
max 3
max 1
2 1
1 2
max max
2 max
3 1
1 1
1 max
2 2
max 1
2 2
max 2
max max
3 1
1 2
max 2
8 8
8 8
8 8
8
n m
i m j
i j
i i
n n
m i
i i
i m
m i
m n
m i
m j i
m m
m
l l
l D
l l
l C
C BAG
BAG l
l l
l l
C BAG
BAG l
3 1
2 max
max 2
max 1
3 1
1 3
max max
3 max
3 1
1 1
1 max
2 3
max 1
3 3
max 3
max max
3 1
1 3
max 2
8 8
8 8
8 8
8
n m
i m j
i j
i i
n n
m i
i i
i m
m i
m n
m i
m j i
m m
m
l l
l D
l l
l C
C BAG
BAG l
l l
l l
C BAG
BAG l
The upper expression shows the delay upper bound has some connection with the physical link bandwidth, the maximum frame-length and weight ratio.
4. Combination Scheduling Compared with other Scheduling Algorithms
