[asterisk-ss7] At what interval should FISUs be sent?

[Marcelo Pacheco]

I've seen one certified switch for Brazilian ISUP/SS7 (MTP is identical
to ITU-T) the switch is from Digitro that delivers FISUs only 25% of
link idle time, 75% of idle octets (considering FISUs idle octets) are
flags. That switch talked with sucess with Ericsson AXE, Nortel DMS,
Vectura (operating as an STP), Tropico RA and some others, without link
instability.

Anyhow, libss7 using dahdi mtp2 shouldn't suffer from this issue, as
well as chan_ss7, as both generate FISUs not stop correctly.

Regards,

Marcelo Pacheco

Kristian Nielsen wrote:
> "Gustavo Marsico [Gmail]" <gustavomarsico at gmail.com> writes:
>
>   
>> It's talking about Japan:
>>
>> Note: In the ITU-T Japan variant, signaling link quality is checked by the
>> continuous transmission of flag octets (8-bit bytes) rather than FISUs;
>> FISUs are sent only at predefined timer intervals (e.g., once every 150
>> milliseconds).
>>
>> If you live in Japan can make sense that, but in ITU world it's just like as
>> Kristian's said.
>>     
>
> Yes, I meant ITU SS7. Forgot about the multiple variants ...
>
> Here is the relevant quote from ITU Q.703:
>
> 11.2.2 For the basic error control method, the priorities are:
> Highest    1. Link status signal units.
>            2. Message signal units which have not yet been acknowledged and for which a
>                negative acknowledgement has been received.
>            3. New message signal units.
>            4. Fill-in signal units.
> Lowest     5. Flags.
>
> So fill-in signal units are sent unless some serious error prevents sending
> anything but flags.
>
> Don't know about any other variants of SS7.
>
>  - Kristian.
>
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