[Commotion-dev] FYI: Serval & OpenBTS integration

[Dan Staples]

Also, Jeremy, can Serval use non-numeric DIDs? We were thinking that 
that would make it easier for us to integrate Serval/OpenBTS with 
Commotion...for instance for people who wanted to send a Rhizome bundle 
to a Commotion node by using the node's hostname instead of a telephone 
number for the DID.

Dan

On Tue 13 Nov 2012 07:56:41 AM EST, Dan Staples wrote:
> Thanks for the documentation on integrating Serval with OpenBTS. Here
> in our lab we're on our way to testing that out, using our Range 5150
> for the radio hardware. Our snag right now is that for some reason our
> OpenBTS build isn't talking to the Subscriber Registry db when a
> registration is made...anyone else experienced that?
>
> Everything is working fine on the Range commercial OpenBTS version,
> however, so I may just try to install servald and serval-asterisk
> integration on the commercial version to test it out.
>
> Dan
>
> On Tue 13 Nov 2012 07:09:46 AM EST, Jeremy Lakeman wrote:
>> On Tue, Nov 13, 2012 at 9:51 PM, Alexander Chemeris
>> <alexander.chemeris at gmail.com> wrote:
>>>>> How does an OpenBTS user know his number? Do you send a welcome SMS
>>>>> with a number on registration?
>>>>
>>>> That's something we haven't changed from the default install. This
>>>> setup still uses the same database for local number registrations via
>>>> the web UI or SMS message.
>>>
>>> I.e. BTS allocates phone numbers by itself and just announce them to
>>> the network? I thought originally that Serval DNA allocates phones
>>> numbers for users.
>>
>> With our android app, you assign your own phone number and roll a
>> public key when you use it for the first time.
>> Then an instance of our servald daemon will run in the background to
>> answer phone number lookups.
>> With this BTS solution, a single instance of servald with a single
>> public key, answers phone number lookups by checking the registrations
>> in the database.
>> Then when you place a phone call to that instance of servald, we run
>> the asterisk diaplan for the phone number you dialled.
>>
>>>>> Do you think there are benefits of using Serval DNA in a pure OpenBTS
>>>>> multi-site installations, i.e. without other non-OpenBTS Serval
>>>>> devices?
>>>>
>>>> With no single point of failure, one BTS box could still allow local
>>>> phone calls and any two boxes could form a working network.
>>>> Though we still have a lot of work to do, improving codec support and
>>>
>>> Do you mean codec support in your Android application? I thought
>>> you're using a normal SIP and thus shouldn't have any issues with
>>> codec support.
>>
>> We used to use SIP and asterisk on each phone, but it wasn't really a
>> good fit for all of the other things we wanted to do. And sip has some
>> weird timing failures based on packet loss.
>> So we've built our own session protocol and audio transport, on top of
>> a network layer that provides transparent encryption and routing of
>> payloads, using public keys as network identifiers.
>> Removing asterisk has drastically reduced the size of the application
>> and reduced the number of things that could go wrong. But essentially
>> re-implementing the entire network stack in user-space is taking some
>> time.
>> Are we headed in the right direction? Maybe, time will tell.
>>
>>>> our routing protocol. With servald handling the network routing and
>>>> packet delivery, the network layer has the potential to carry more
>>>> simultaneous calls over a wifi network.
>>>
>>> Do you aggregate packets to increase number of voice calls over WiFi?
>>
>> With a single 2.4Ghz wifi channel, the network tends to top out at
>> around 3,500 packets per second regardless of how small they are. With
>> an rtp packet every 20ms, that would give you maybe 30 usable phone
>> calls over one wifi link. Less if you need to repeat these packets
>> over multiple hops on the same channel.
>> We aggregate any payloads travelling over the same network link
>> between nodes, based on our routing table and QOS flags. With a good
>> audio codec we should be able to beat that number of concurrent calls.
>>
>>>>> Does Serval DNA works well with thousands of users?
>>>>
>>>> Good question, no idea. There will probably be scalability issues
>>>> we'll need to deal with so we don't flood a large network just trying
>>>> to resolve phone numbers. Probably some kind of election process to
>>>> pick a small number of network nodes to collect and search the entire
>>>> phone directory.
>>>
>>> Ok.
>>> GSM network may easily cover thousands of users, even with a single
>>> base station and thus scalability is an issue.
>>
>> The main scalability limits for phone number searches would be based
>> on the number of nodes on the network. If you don't have that many
>> base stations, everything should be fine for now.
>>
>>>>> Does Serval support SMS messages?
>>>>
>>>> We have a text messaging solution for android, where we can assume
>>>> that one identity is only reachable via one instance of the software.
>>>> We'd need to build something a bit different to deliver messages to
>>>> users roaming between BTS boxes. We haven't tackled that yet, but we
>>>> might get around to it eventually.
>>>
>>> Would be a great thing.
>>>
>>> --
>>> Regards,
>>> Alexander Chemeris.
>>> CEO, Fairwaves LLC / ООО УмРадио
>>> http://fairwaves.ru
>>
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>
> --
> Dan Staples
> Open Technology Institute

--
Dan Staples
Open Technology Institute