Network interconnection over VPN/SIP

Matthew Johnson matt9j at cs.washington.edu
Mon Oct 22 18:51:32 UTC 2018


Hello naif,
There is an open source project here: https://github.com/co-cell/ccm that
attempts to provide a system for doing the kind of coordination between
independent community networks. It is based on Osmocom under the hood, but
uses the older osmo-nitb stack (before components were split). The networks
are able to operate independently offline, and use a combination of sip
call routing as suggested by Neels above, SMPP, and a web api to
synchronize usage when connected to the cloud for centralized billing and
to interconnect through the cloud for community to community, or community
to public voip network communication. The project was originally run by the
Telecom Infra Project, but was abandoned by them last year after they moved
to a new (unfortunately private) internal tool
https://github.com/facebookarchive/CommunityCellularManager . CCM is still
actively used by the PCARI Vbts project (
https://www.up.edu.ph/index.php/up-globe-sign-moa-for-village-base-station-project/)
with a number of local communities in the Philippines, and they run and
maintain their own instance of the CCM cloud. It might be something to look
at as a potential starting point, or something to learn from if you want to
make different architectural decisions when connecting the networks!
Regards,
-Matt J.

On Wed, Oct 17, 2018 at 6:06 AM Neels Hofmeyr <nhofmeyr at sysmocom.de> wrote:

> Hi naif,
>
> your requirements sound a lot alike those that Rhizomatica are solving in
> Oaxaca.
>
> Running independent GSM networks is the easy part, the hard part is to
> connect
> them to each other in a failure-tolerant way.
>
> The basic concept is, usually you would have one MSC+HLR for all of your
> cells,
> and calls would easily get routed between the different cells. But if the
> connection to the MSC fails, then all is lost. So you want completely
> separate
> network infrastructure for each location. I'm not closely familiar with
> this
> aspect, but I imagine using SIP call routing between the otherwise
> independent
> networks is one solution (think osmo-sip-connector and an external call
> router
> program). The other problem space is that if you want to manage a common
> subscriber database (HLR), so that e.g. one SIM (phone) can travel freely
> around and use any of the network cells and always be reachable by the same
> number wherever it happens to be, then you need some synchronization of
> the HLR
> databases. To illustrate, if I want to be reachable by one given phone
> number
> in all the cells, something has to know which cell to route that number
> to. If
> I show up in a cell, we need to tell the previous cell that I am now over
> here
> instead...  You would have an easier time if each network is managed
> separately
> with its own HLR on-location, in the sense that a SIM card can have a
> different
> phone number in each of them.
>
> I'm making this up as I go, I hope Rhizomatica folks can flesh out some
> more
> details.
>
> Note, we're currently working on improving the network setup for
> Rhizomatica,
> and you're likely to benefit from that, sooner or later.
>
> Either way it would be excellent if you stay in touch and contribute
> documentation and/or patches back to Osmocom. Also possible would be to
> book
> support hours from a professional support vendor, if you have some grant
> that
> allows you to, so that your specific needs can be addressed with higher
> priority than volunteer work can provide (which would also benefit Osmocom
> at
> large, to pay for maintenance etc.). None of this is required, of course,
> but
> Free Software lives by contribution. All kinds of contribution are welcome.
>
> Looking forward to hearing more about your progress!
>
> ~N
>
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