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10.3.1. Load Calculation for Access Points Previous topic Parent topic Child topic Next topic

IMPORTANT:
The estimated bandwidth of 32kBit/s (minimum bandwidth) or 64kBit/s for TCP signaling is sufficient for call processing operation. Initial operation and loading of the boards in an AP shelf (sometimes with large loadware volumes) are also controlled via TCP this can result in very long initial operation times!

Calculation of the high-priority load for an individual access point

Table 56. High-priority load of an access point (G.711/20 ms sample size)

Protocol
Data type
Maximum bit rate/ port
[Kbps]
Total bit rate [Kbps] with
N payload ports
N=30
N=60
N=120
RTP
VoIP
88.8
2,664
5,328
10,656
RTCP
VoIP
0.2
6
12
25
TCP/IP
Signaling
64.0
64
64
64
TCP/IP
Supervisory
(only if signaling supervisory is configured)
0.1
4
8
15
Total load
2,738
5,412
10,760
The requisite bit rate for a supervisory connection depends on the configuration of the keep-alive timer for this connection. The parameter to this end is SUPVTIME in the TIMING branch of the AMO SIPCO. The maximum values are specified in the table.
The load which is generated through signaling and control between the OpenScape 4000 central system and an access point - which is also a high-priority load - has been specified globally as 64 Kbps.
However, the actual load depends on the number of subscriber lines, CO and tie trunks and the actual telephone usage behavior in the access point.
If, however, modules are reloaded, additional load is generated which, in the case of limited bandwidth, can delay the signaling.
The absolute minimum of signaling bandwidth required is 32 kbps. If less than 64 kbps signaling bandwidth is available, traffic shaping must be enabled and set to the actual bandwidth available. See Section 2.7.1, “Restriction of the Available Signaling Bandwidth (Traffic Shaping)”.
In addition to high-priority load, low-priority load portions may also arise in certain situations for the following:
  1. SNMP queries via network management
    • TAP/Service PC access at the access point
    • FTP-loading of a new HG 3575 loadware as a background task

High-priority load of an access point as a function of codec type and sample size

Table 57. High-priority load of an AP as a function of codec and sample size

Codec type
Sample
size
RTP load [Kbps] with
N payload ports
Total Ethernet load [Kbps]
with N payload ports
N=30
N=60
N=120
N=30
N=60
N=120
G.711
20
2,664
5,328
10,656
2,738
5,412
10,760
G.711
30
2,416
4,832
9,664
2,490
4,916
9,768
G.711
60
2,168
4,336
8,672
2,242
4,420
8,776
G.729A
20
984
1,968
3,936
1,058
2,052
4,040
G.729A
40
612
1,224
2,448
686
1,308
2,552
G.729A
60
488
976
1,952
562
1,060
2,056
Note
This appraisal must be treated with caution, as the utility of the G.729A codec is limited by various factors:
  1. The call is transferred uncompressed if one of the subscribers/circuits involved prevents compression
    • Connections with fax, modem and data terminal devices are only transferred uncompressed
    • External music and announcements are mostly transferred uncompressed (depends on the configuration (RCSU-CLASSMRK))
    • Connections to a conference unit are mostly switched without compression (depends on the configuration (ZAND-IPDAVCCF))
    In all of these cases, either G.711 is used, or no codec at all.
    The bit rates for G.711 thus apply.
    In order to guarantee that bottlenecks are never encountered in the available bandwidth, the access point link must be designed for the G.711 bit rate.
By means of statistical appraisals, taking the actual configuration into account (how many fax/data devices are actually deployed, how many compression licenses are available, are all possible subscriber/access circuits configured for compression, how frequently are conferences used), a mixed calculation can be performed.
The load as a function of a sample size can only be used if it is ensured that all IPDA components are configured exclusively for this sample size. Otherwise, the worst value for the respective codec type would have to be used for reasons of reliability.

High-priority load of an access point as a function of the maximum number of B-channels

Table 58. High-priority load of an AP as a function of the permissible B-channels

Maximum permissible number of B-channels
Total Ethernet load at G.711/20ms
[Kbps]
Total Ethernet load at
G.711/30ms
[Kbps]
Total Ethernet load at G.711/60ms
[Kbps]
1
153
145
137
2
242
226
209
3
331
306
282
4
420
387
354
5
509
468
427
6
598
549
499
7
687
629
571
8
776
710
644
9
865
791
716
10
954
872
789
11
1,043
952
861
12
1,132
1,033
934
13
1,221
1,114
1,006
14
1,310
1,195
1,079
15
1,399
1,275
1,151
16
1,488
1,356
1,224
17
1,577
1,437
1,296
18
1,666
1,517
1,369
19
1,755
1,598
1,441
20
1,844
1,679
1,514
21
1,933
1,760
1,586
22
2,022
1,840
1,659
23
2,111
1,921
1,731
24
2,200
2,002
1,804
25
2,289
2,083
1,876
26
2,378
2,163
1,948
27
2,467
2,244
2,021
28
2,556
2,325
2,093
29
2,645
2,406
2,166
30
2,734
2,486
2,238
31
2,823
2,567
2,311
32
2,912
2,648
2,383
33
3,001
2,729
2,456
34
3,090
2,809
2,528
35
3,179
2,890
2,601
36
3,268
2,971
2,673
37
3,357
3,052
2,746
38
3,446
3,132
2,818
39
3,535
3,213
2,891
40
3,624
3,294
2,963
41
3,713
3,375
3,036
42
3,802
3,455
3,108
43
3,891
3,536
3,181
44
3,980
3,617
3,253
45
4,069
3,697
3,325
46
4,158
3,778
3,398
47
4,248
3,859
3,470
48
4,337
3,940
3,543
49
4,426
4,020
3,615
50
4,515
4,101
3,688
51
4,604
4,182
3,760
52
4,693
4,263
3,833
53
4,782
4,343
3,905
54
4,871
4,424
3,978
55
4,960
4,505
4,050
56
5,049
4,586
4,123
57
5,138
4,666
4,195
58
5,227
4,747
4,268
59
5,316
4,828
4,340
60
5,405
4,909
4,413
61
5,494
4,989
4,485
62
5,583
5,070
4,558
63
5,672
5,151
4,630
64
5,761
5,232
4,703
65
5,850
5,312
4,775
66
5,939
5,393
4,847
67
6,028
5,474
4,920
68
6,117
5,555
4,992
69
6,206
5,635
5,065
70
6,295
5,716
5,137
71
6,384
5,797
5,210
72
6,473
5,878
5,282
73
6,562
5,958
5,355
74
6,651
6,039
5,427
75
6,740
6,120
5,500
76
6,829
6,200
5,572
77
6,918
6,281
5,645
78
7,007
6,362
5,717
79
7,096
6,443
5,790
80
7,185
6,523
5,862
81
7,274
6,604
5,935
82
7,363
6,685
6,007
83
7,452
6,766
6,080
84
7,541
6,846
6,152
85
7,630
6,927
6,224
86
7,719
7,008
6,297
87
7,808
7,089
6,369
88
7,897
7,169
6,442
89
7,986
7,250
6,514
90
8,075
7,331
6,587
91
8,164
7,412
6,659
92
8,253
7,492
6,732
93
8,342
7,573
6,804
94
8,431
7,654
6,877
95
8,520
7,735
6,949
96
8,609
7,815
7,022
97
8,698
7,896
7,094
98
8,787
7,977
7,167
99
8,876
8,058
7,239
100
8,965
8,138
7,312
101
9,054
8,219
7,384
102
9,143
8,300
7,457
103
9,232
8,380
7,529
104
9,321
8,461
7,601
105
9,410
8,542
7,674
106
9,499
8,623
7,746
107
9,588
8,703
7,819
108
9,677
8,784
7,891
109
9,766
8,865
7,964
110
9,855
8,946
8,036
111
9,944
9,026
8,109
112
10,033
9,107
8,181
113
10,122
9,188
8,254
114
10,211
9,269
8,326
115
10,300
9,349
8,399
116
10,389
9,430
8,471
117
10,478
9,511
8,544
118
10,567
9,592
8,616
119
10,656
9,672
8,689
120
10,745
9,753
8,761
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