distributed GSM / some thoughts

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Keith keith at rhizomatica.org
Thu Dec 5 11:11:29 UTC 2019


On 04/12/2019 20:46, Harald Welte wrote:
>
>> We don't envisage a separation between MSC and HLR over unreliable
>> back-haul, but I think I'm missing something here. (I still need to
>> actually implement a local setup and observe)
> In an inbound roaming situation, you have the MSC (VPLMN) in one village and the
> "authoritative" HLR for that subscriber (HPLMN) in another village.
>
Ah, indeed. I do need to setup and play with this. In my head, I was
imagining that an IMSI attach request triggers an mslookup (broadcast)
and that the response message contains what the VLR (msc) needs. I
wasn't imagining TCP connections relating to core GSM over the
unreliable IP network.

I'm wary of TCP. I'm no expert in all the things that can be tuned, so
maybe there's a solution I'm unaware of?

If not, I don't like tcp over tinc-vpn at all where the underlying IP
connection is unreliable. Things tend to stall for a long time. This is
precisely the main problem I was seeing with multi-master distributed
databases. They work fine in theory in a data centre, but add severe
packet loss and it all falls down.

I'm quite possibly still missing something?

Thanks!

k.






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