Alternate odd/even hunting option in a channel group

Symptom:

When the channel group hunting option in a Dialogic IMG Integrated Media Gateway or Dialogic BorderNet™ 2020 Integrated Media Gateway is set to 'alternate odd' or 'alternate even' the channel selected does not always appear to be an odd numbered or even numbered channel.

Reason for the issue:

For alternate odd or alternate even settings, the IMG Gateway or BorderNet 2020 IMG selects the channel based on the channels within the channel group and not from the channel number.

The following describes how the channels are selected in a channel group when the hunting option is set to either 'alternate odd' or 'alternate even'.

If the first channel in a span is 1 then the odd/even selection will be the channel number for that span. See example 1.
If the range of channels in the span is continuous then the selection will be the same for the entire span. See example 2.
If there are multiple spans in a channel group and the number of channels within a channel group is even then the next span will continue from the same odd/even point. See example 3.

Example 1:

In table 1 the hunting option works as expected for alternate odd/even.
In table 2 the hunting option based on the channel number appears to do the opposite of what is configured, but is correct according to the channel number in the channel group.

Table 1

Channel number in group	Channel number
1	1
2	2
3	3
4	4

Table 2

Channel number in group	Channel number
1	0
2	1
3	2
4	3

Example 2:

In table 3 the channels are continuous and will work as expected with alternate odd/even.
In table 4, channels up to channel 15 work as expected and then, because channel 16 is skipped, the rest of the span does not work as expected.

Table 3

Channel number in group	Channel number
15	15
16	16
17	17
18	18

Table 4

Channel number in group	Channel number
15	15
	SS7 link or ISDN D channel
16	17
17	18

Example 3:

In table 5 the channels in both spans work as expected with alternate odd/even.
In table 6 every other span works as expected with alternate odd/even.

Table 5

Channel number in group	Channel number
29	Span 1: Channel 29
30	Span 1: Channel 30
31	Span 2: Channel 1
32	Span 2: Channel 2

Table 6

Channel number in group	Channel number
29	Span 1: Channel 29
30	Span 1: Channel 30
31	Span 2: Channel 0
32	Span 2: Channel 1

Workaround:
Start a span with an odd numbered channel, skipping the first channel if necessary.

Product List
Dialogic IMG Integrated Media Gateways
Dialogic BorderNet™ 2020 Integrated Media Gateway

Dialogic Integrated Media Gateways

Alternate odd/even hunting option in a channel group

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