[SR-Users] Dispatcher module and xavp_dst

[Julien Chavanton]

Maybe the documentation should be improved, it seems the first bullet point
should say.

"The algorithm will load balance using round-robin prioritizing the
gateways with the highest *adjusted* priority. "



On Thu, Sep 1, 2022 at 9:06 AM Julien Chavanton <jchavanton at gmail.com>
wrote:

> Hi, did you look at the documentation of  algorithm 13 ?
>
> The priority is used in combination with the latency to determine the
> preferred gateway.
> Once you confirm that this is what you want "latency latency optimized
> dispatching", we can help to clarify why and how this may not work as
> expected.
>
>
> Regards
>
>
> https://kamailio.org/docs/modules/devel/modules/dispatcher.html
>
>    -
>
>    “13” - latency optimized dispatching
>
>    - The algorithm will load balance using round-robin prioritizing the
>    gateways with the highest priority.
>
>    - If ds_ping_latency_stats is active the algorithm will adjust the
>    priority of the gateway automatically, the priority will be lowered by 1
>    point every time the latency ms is as high as the priority.
>
>    - If the attribute 'cc=1' is set, the latency used is congestion ms :
>    estimate (current latency ms) - average (normal condition latency ms).
>
>    *Example 1.46. latency_optimized_dispatching usage*
>
>    Using this simple formula :
>        ADJUSTED_PRIORITY = PRIORITY - (ESTIMATED_LATENCY_MS/PRIORITY)
>
>    GATEWAY | PRIORITY | ESTIMATED | ADJUSTED | LOAD
>       #    |          |  LATENCY  | PRIORITY | DISTRIBUTION
>       1    |    30    |    21     |    30    | 33%
>       2    |    30    |    91     |    27    | 0%
>       3    |    30    |    61     |    28    | 0%
>       4    |    30    |    19     |    30    | 33%
>       5    |    30    |    32     |    29    | 0%
>       6    |    30    |    0      |    30    | 33%
>       7    |    30    |    201    |    24    | 0%
>
>
>    With congestion control the formula becomes :
>        CONGESTION_MS = CURRENT_LATENCY_MS - NORMAL_CONDITION_LATENCY_MS
>        ADJUSTED_PRIORITY = PRIORITY - (CONGESTION_MS/PRIORITY)
>
>
>    -
>
>
>
>
> On Thu, Sep 1, 2022 at 2:38 AM Pyry Aaltonen <pyry.aaltonen at cuuma.com>
> wrote:
>
>> Hello,
>>
>>
>>
>> I’m quite new user with kamailio (heard first time about it a year ago
>> and joined the list yesterday) and now wondering how the xavp_dst should
>> work.
>>
>>
>>
>> I had read from the documentation that
>>
>> ”The first XAVP is the current selected destination.”
>>
>>
>>
>> I use ds_select_dst with alg 13. And my kamailio version is kamailio
>> 5.5.3 (x86_64/linux)
>>
>>
>>
>> So when my dispatcher list is like (I have also tried to differ the
>> priority value like 10 and 1, but doesn’t make difference)
>>
>> 10 sip:1.2.3.4;transport=tcp 10 1 type=type1
>>
>> 10 sip:4.3.2.1;transport=tcp 10 1 type=type2
>>
>>
>>
>> If one of the destinations fails (dx/ip), and it happens to be the one
>> with higher priority or the one that just gets higher position in the
>> dispatcher list if the prio Is equal.
>>
>> My xavp_$xavp(dsdst=>attrs) get null value. And, if I try to seek
>> $(xavp(dsdst[0]=>attrs) or $(xavp(dsdst[1]=>attrs) I also got nothing.
>>
>>
>>
>> If both destinations are up with equal priority, it selects them with
>> round-robin, and the xavp_$xavp(dsdst=>attrs) has the type value of the
>> selected destination as expected, also the $(xavp(dsdst[0]=>attrs) or
>> $(xavp(dsdst[1]=>attrs) contains the destinations so that the selected
>> is 0 and the other is at position 1.
>>
>> The $du is updated as I expect so if one fails the other one is selected
>> always, why the xavp_dst isn’t working same way, or am I missing something?
>>
>>
>>
>> If needed I’ll try to provide more information,
>>
>> Thanks already in advance
>>
>>
>>
>> -Pyry
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
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