final version of FOSS cellular talk at netdevconf 1.1
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Running Cellular Network Infrastructure on Linux
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Traditionally, much unlike the Ethernet/IP network, classic telecom
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infrastructure has been running proprietary hardware, operating systems
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and protocol stacks.
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In recent years, some Free Software projects have set out to implement
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some of the related protocol stacks and network elements on top of
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Linux, including the unrelated OpenBTS and OpenBSC projects, as well as
|
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the less known other members of the Osmocom umbrella project: OsmoBSC,
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OsmoNITB, OsmoBTS, OsmoPCU, OsmoSGSN, OpenGGSN, and many more.
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As signalling protocols tend to be complex and in many use cases the
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signalling performance is not super critical, those projects primarily
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implement the protocol stacks and network interfaces in user-space.
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This presentation will cover an overview of the many different projects
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out there, which of the cellular network elements they implement.
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Running FOSS Cellular Networks on Linux
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=======================================
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:author: Harald Welte <laforge@gnumonks.org>
|
||||
:copyright: sysmocom - s.f.m.c. GmbH (License: CC-BY-SA)
|
||||
:backend: slidy
|
||||
:max-width: 45em
|
||||
//:data-uri:
|
||||
//:icons:
|
||||
|
||||
|
||||
== What this talk is about
|
||||
|
||||
[role="incremental"]
|
||||
* Implementing GSM/GPRS network elements as FOSS
|
||||
* Applied Protocol Archeology
|
||||
* Doing all of that on top of Linux (in userspace)
|
||||
* If you expeccted kernel stuff, you'll be disappointed
|
||||
|
||||
|
||||
== Running your own Internet-style network
|
||||
|
||||
* use off-the-shelf hardware (x86, Ethernet card)
|
||||
* use any random Linux distribution
|
||||
* configure Linux kernel TCP/IP network stack
|
||||
** enjoy fancy features like netfilter/iproute2/tc
|
||||
* use apache/lighttpd/nginx on the server
|
||||
* use Firefox/chromium/konqueor/lynx on the client
|
||||
* do whatever modification/optimization on any part of the stack
|
||||
|
||||
|
||||
== Running your own GSM network
|
||||
|
||||
Until 2009 the situation looked like this:
|
||||
|
||||
* go to Ericsson/Huawei/ZTE/Nokia/Alcatel/...
|
||||
* spend lots of time convincing them that you're an eligible customer
|
||||
* spend a six-digit figure for even the most basic full network
|
||||
* end up with black boxes you can neither study nor improve
|
||||
|
||||
[role="incremental"]
|
||||
- WTF?
|
||||
- I've grown up with FOSS and the Internet. I know a better world.
|
||||
|
||||
|
||||
== Why no cellular FOSS?
|
||||
|
||||
- both cellular (2G/3G/4G) and TCP/IP/HTTP protocol specs are publicly
|
||||
available for decades. Can you believe it?
|
||||
- Internet protocol stacks have lots of FOSS implementations
|
||||
- cellular protocol stacks have no FOSS implementations for the
|
||||
first almost 20 years of their existence?
|
||||
[role="incremental"]
|
||||
- it's the classic conflict
|
||||
* classic circuit-switched telco vs. the BBS community
|
||||
* ITU-T/OSI/ISO vs. Arpanet and TCP/IP
|
||||
|
||||
|
||||
== Enter Osmocom
|
||||
|
||||
In 2008, some people started to write FOSS for GSM
|
||||
|
||||
- to boldly go where no FOSS hacker has gone before
|
||||
[role="incremental"]
|
||||
** where protocol stacks are deep
|
||||
** and acronyms are plentiful
|
||||
** we went from `bs11-abis` to `bsc_hack` to 'OpenBSC'
|
||||
** many other related projects were created
|
||||
** finally leading to the 'Osmocom' umbrella project
|
||||
|
||||
|
||||
== Classic GSM network architecture
|
||||
|
||||
image::Gsm_structures.svg[width=850]
|
||||
|
||||
|
||||
== GSM Acronyms, Radio Access Network
|
||||
|
||||
MS::
|
||||
Mobile Station (your phone)
|
||||
BTS::
|
||||
Base Transceiver Station, consists of 1..n TRX
|
||||
TRX::
|
||||
Transceiver for one radio channel, serves 8 TS
|
||||
TS::
|
||||
Timeslots in the GSM radio interface; each runs a specific combination of logical channels
|
||||
BSC::
|
||||
Base Station Controller
|
||||
|
||||
|
||||
== GSM Acronyms, Core Network
|
||||
|
||||
MSC::
|
||||
Mobile Switching Center; Terminates MM + CC Sub-layers
|
||||
|
||||
HLR::
|
||||
Home Location Register; Subscriber Database
|
||||
|
||||
SMSC::
|
||||
SMS Service Center
|
||||
|
||||
|
||||
== GSM Acronyms, Layer 2 + 3
|
||||
|
||||
LAPDm::
|
||||
Link Access Protocol, D-Channel. Like LAPD in ISDN
|
||||
RR::
|
||||
Radio Resource (establish/release dedicated channels)
|
||||
MM::
|
||||
Mobility Management (registration, location, authentication)
|
||||
CC::
|
||||
Call Control (voice, circuit switched data, fax)
|
||||
CM::
|
||||
Connection Management
|
||||
|
||||
|
||||
== Osmocom GSM components
|
||||
|
||||
image::osmocom-gsm.svg[width=850]
|
||||
|
||||
|
||||
== Classic GSM network as digraph
|
||||
|
||||
[graphviz]
|
||||
----
|
||||
digraph G {
|
||||
rankdir=LR;
|
||||
MS0 [label="MS"]
|
||||
MS1 [label="MS"]
|
||||
MS2 [label="MS"]
|
||||
MS3 [label="MS"]
|
||||
BTS0 [label="BTS"]
|
||||
BTS1 [label="BTS"]
|
||||
MSC [label="MSC/VLR"]
|
||||
HLR [label="HLR/AUC"]
|
||||
MS0->BTS0 [label="Um"]
|
||||
MS1->BTS0 [label="Um"]
|
||||
MS2->BTS1 [label="Um"]
|
||||
MS3->BTS1 [label="Um"]
|
||||
BTS0->BSC [label="Abis"]
|
||||
BTS1->BSC [label="Abis"]
|
||||
BSC->MSC [label="A"]
|
||||
MSC->HLR [label="C"]
|
||||
MSC->EIR [label="F"]
|
||||
MSC->SMSC
|
||||
}
|
||||
----
|
||||
|
||||
== Simplified OsmoNITB GSM network
|
||||
|
||||
[graphviz]
|
||||
----
|
||||
digraph G {
|
||||
rankdir=LR;
|
||||
MS0 [label="MS"]
|
||||
MS1 [label="MS"]
|
||||
MS2 [label="MS"]
|
||||
MS3 [label="MS"]
|
||||
BTS0 [label="BTS"]
|
||||
BTS1 [label="BTS"]
|
||||
MS0->BTS0 [label="Um"]
|
||||
MS1->BTS0 [label="Um"]
|
||||
MS2->BTS1 [label="Um"]
|
||||
MS3->BTS1 [label="Um"]
|
||||
BTS0->BSC [label="Abis"]
|
||||
BTS1->BSC [label="Abis"]
|
||||
subgraph cluster_nitb {
|
||||
label = "OsmoNITB";
|
||||
BSC
|
||||
MSC [label="MSC/VLR"]
|
||||
HLR [label="HLR/AUC"]
|
||||
BSC->MSC [label="A"]
|
||||
MSC->HLR [label="C"]
|
||||
MSC->EIR [label="F"]
|
||||
MSC->SMSC;
|
||||
}
|
||||
}
|
||||
----
|
||||
|
||||
which further reduces to the following minimal setup:
|
||||
|
||||
[graphviz]
|
||||
----
|
||||
digraph G {
|
||||
rankdir=LR;
|
||||
MS0 [label="MS"]
|
||||
BTS0 [label="BTS"]
|
||||
MS0->BTS0 [label="Um"]
|
||||
BTS0->BSC [label="Abis"]
|
||||
BSC [label="OsmoNITB"];
|
||||
}
|
||||
----
|
||||
|
||||
So our minimal setup is a 'Phone', a 'BTS' and 'OsmoNITB'.
|
||||
|
||||
|
||||
== Which BTS to use?
|
||||
|
||||
* Proprietary BTS of classic vendor
|
||||
** Siemens BS-11 is what we started with
|
||||
** Nokia, Ericsson, and others available 2nd hand
|
||||
* 'OsmoBTS' software implementation, running with
|
||||
** Proprietary HW + PHY (DSP): 'sysmoBTS', or
|
||||
** General purpose SDR (like USRP) + 'OsmoTRX'
|
||||
|
||||
We assume a sysmoBTS in the following tutorial
|
||||
|
||||
|
||||
== OsmoBTS Overview
|
||||
|
||||
image::osmo-bts.svg[]
|
||||
|
||||
* Implementation of GSM BTS
|
||||
* supports variety of hardware/PHY options
|
||||
** `osmo-bts-sysmo`: BTS family by sysmocom
|
||||
** `osmo-bts-trx`: Used with 'OsmoTRX' + general-purpose SDR
|
||||
** `osmo-bts-octphy`: Octasic OCTBTS hardware / OCTSDR-2G PHY
|
||||
** `osmo-bts-litecell15`: Nutaq Litecell 1.5 hardware/PHY
|
||||
|
||||
|
||||
== Configuring Osmocom software
|
||||
|
||||
* all Osmo* GSM infrastructure programs share common architecture, as
|
||||
defined by various libraries 'libosmo{core,gsm,vty,abis,netif,...}'
|
||||
* part of this is configuration handling
|
||||
** interactive configuration via command line interface (*vty*), similar
|
||||
to Cisco routers
|
||||
** based on a fork of the VTY code from Zebra/Quagga, now 'libosmovty'
|
||||
* you can manually edit the config file,
|
||||
* or use `configure terminal` and interactively change it
|
||||
|
||||
|
||||
== Configuring OsmoBTS
|
||||
|
||||
* 'OsmoBTS' in our example scenario runs on the embedded ARM/Linux system
|
||||
inside the 'sysmoBTS'
|
||||
* we access the 'sysmoBTS' via serial console or ssh
|
||||
* we then edit the configuration file `/etc/osmocom/osmo-bts.cfg` as
|
||||
described in the following slide
|
||||
|
||||
|
||||
== Configuring OsmoBTS
|
||||
|
||||
----
|
||||
bts 0
|
||||
band DCS1800 <1>
|
||||
ipa unit-id 1801 0 <2>
|
||||
oml remote-ip 192.168.100.11 <3>
|
||||
----
|
||||
<1> the GSM frequency band in which the BTS operates
|
||||
<2> the unit-id by which this BTS identifies itself to the BSC
|
||||
<3> the IP address of the BSC (to establish the OML connection towards it)
|
||||
|
||||
NOTE: All other configuration is downloaded by the BSC via OML. So most
|
||||
BTS settings are configured in the BSC/NITB configuration file.
|
||||
|
||||
|
||||
== Configuring OsmoNITB
|
||||
|
||||
* 'OsmoNITB' is the `osmo-nitb` executable built from the `openbsc`
|
||||
source tree / git repository
|
||||
* just your usual `git clone && autoreconf -fi && ./configure && make install`
|
||||
** (in reality, the `libosmo*` dependencies are required first...)
|
||||
* 'OsmoNITB' runs on any Linux system, like your speakers' laptop
|
||||
** you can actually also run it on the ARM/Linux of the 'sysmoBTS' itself,
|
||||
having a literal 'Network In The Box' with power as only external
|
||||
dependency
|
||||
|
||||
|
||||
== Configuring OsmoNITB
|
||||
|
||||
----
|
||||
network
|
||||
network country code 1 <1>
|
||||
mobile network code 1 <2>
|
||||
shot name Osmocom <3>
|
||||
long name Osmocom
|
||||
auth policy closed <4>
|
||||
encryption a5 0 <5>
|
||||
----
|
||||
<1> MCC (Country Code) e.g. 262 for Germany; 1 == Test
|
||||
<2> MNC (Network Code) e.g. mcc=262, mnc=02 == Vodafone; 1 == Test
|
||||
<3> Operator name to be sent to the phone *after* registration
|
||||
<4> Only accept subscribers (SIM cards) explicitly authorized in HLR
|
||||
<5> Use A5/0 (== no encryption)
|
||||
|
||||
|
||||
== Configuring BTS in OsmoNITB (BTS)
|
||||
|
||||
----
|
||||
network
|
||||
bts 0
|
||||
type sysmobts <1>
|
||||
band DCS1800 <2>
|
||||
ms max power 33 <3>
|
||||
periodic location update 6 <4>
|
||||
ip.access unit_id 1801 0 <5>
|
||||
codec-support fr hr efr amr <6>
|
||||
----
|
||||
<1> type of the BTS that we use (must match BTS)
|
||||
<2> frequency band of the BTS (must match BTS)
|
||||
<3> maximum transmit power phones are permitted (33 dBm == 2W)
|
||||
<4> interval at which phones should send periodic location update (6 minutes)
|
||||
<5> Unit ID of the BTS (must match BTS)
|
||||
<6> Voice codecs supported by the BTS
|
||||
|
||||
|
||||
== Configuring BTS in OsmoNITB (TRX)
|
||||
|
||||
----
|
||||
network
|
||||
bts 0
|
||||
trx 0
|
||||
arfcn 871 <1>
|
||||
max_power_red 0 <2>
|
||||
timeslot 0
|
||||
phys_chan_config CCCH+SDCCH4 <3>
|
||||
timeslot 1
|
||||
phys_chan_config TCH/F <4>
|
||||
...
|
||||
timeslot 7
|
||||
phys_chan_config PDCH <5>
|
||||
----
|
||||
<1> The RF channel number used by this TRX
|
||||
<2> The maximum power *reduction* in dBm. 0 = no reduction
|
||||
<3> Every BTS needs need one timeslot with a CCCH
|
||||
<4> We configure TS1 to TS6 as TCH/F for voice
|
||||
<5> We configure TS6 as PDCH for GPRS
|
||||
|
||||
|
||||
== What a GSM phone does after power-up
|
||||
|
||||
* Check SIM card for last cell before switch-off
|
||||
** if that cell is found again, use that
|
||||
** if not, perform a netwok scan
|
||||
*** try to find strong carriers, check if they contain BCCH
|
||||
*** create a list of available cells + networks
|
||||
*** if one of the networks MCC+MNC matches first digits of 'IMSI', this is
|
||||
the home network, which has preference over others
|
||||
* perform 'LOCATION UPDATE' (TYPE=IMSI ATTACH) procedure to network
|
||||
* when network sends 'LOCATION UPDATE ACCEPT', *camp* on that cell
|
||||
|
||||
-> let's check if we can perform 'LOCATION UPDATE' on our own network
|
||||
|
||||
|
||||
== Verifying our network
|
||||
|
||||
* look at stderr of 'OsmoBTS' and 'OsmoNITB'
|
||||
** 'OsmoBTS' will terminate if Abis cannot be set-up
|
||||
** expected to be re-spawned by init / systemd
|
||||
* use MS to search for networks, try manual registration
|
||||
* observe registration attempts `logging level mm info`
|
||||
|
||||
-> should show 'LOCATION UPDATE' request / reject / accept
|
||||
|
||||
* use the VTY to explore system state (`show *`)
|
||||
* use the VTY to change subscriber parameters like extension number
|
||||
|
||||
|
||||
== Exploring your GSM networks services
|
||||
|
||||
* use `*#100#` from any registered MS to obtain own number
|
||||
* voice calls from mobile to mobile
|
||||
* SMS from mobile to mobile
|
||||
* SMS to/from external applications (via SMPP)
|
||||
* voice to/from external PBX (via MNCC)
|
||||
* explore the VTY interfaces of all network elements
|
||||
** send SMS from the command line
|
||||
** experiment with 'silent call' feature
|
||||
** experiment with logging levels
|
||||
* use wireshark to investigate GSM protocols
|
||||
|
||||
|
||||
== Using the VTY
|
||||
|
||||
* The VTY can be used not only to configure, but also to interactively
|
||||
explore the system status (`show` commands)
|
||||
* Every Osmo* program has its own telnet port
|
||||
|===
|
||||
|Program|Telnet Port
|
||||
|OsmoPCU|4240
|
||||
|OsmoBTS|4241
|
||||
|OsmoNITB|4242
|
||||
|OsmoSGSN|4245
|
||||
|===
|
||||
* ports are bound to 127.0.0.1 by default
|
||||
* try tab-completion, `?` and `list` commands
|
||||
|
||||
== Using the VTY (continued)
|
||||
|
||||
* e.g. `show subsciber` to display data about subscriber:
|
||||
----
|
||||
OpenBSC> show subscriber imsi 901700000003804
|
||||
ID: 12, Authorized: 1
|
||||
Extension: 3804
|
||||
LAC: 0/0x0
|
||||
IMSI: 901700000003804
|
||||
TMSI: F2D4FA0A
|
||||
Expiration Time: Mon, 07 Dec 2015 09:45:16 +0100
|
||||
Paging: not paging Requests: 0
|
||||
Use count: 1
|
||||
----
|
||||
|
||||
* try `show bts`, `show trx`, `show lchan`, `show statistics`, ...
|
||||
|
||||
|
||||
== Extending the network with GPRS
|
||||
|
||||
Now that GSM is working, up to the next challenge!
|
||||
|
||||
* Classic GSM is circuit-switched only
|
||||
* Packet switched support introduced first with GPRS
|
||||
* GPRS adds new network elements (PCU, SGSN, GGSN)
|
||||
* tunnel for external packet networks like IP/Internet
|
||||
* tunnel terminates in MS and on GGSN
|
||||
|
||||
|
||||
== Extending the network with GPRS support
|
||||
|
||||
[graphviz]
|
||||
----
|
||||
digraph G {
|
||||
rankdir=LR;
|
||||
MS0 [label="MS"]
|
||||
MS1 [label="MS"]
|
||||
MS2 [label="MS"]
|
||||
MS3 [label="MS"]
|
||||
BTS0 [label="BTS"]
|
||||
BTS1 [label="BTS"]
|
||||
MSC [label="MSC/VLR"]
|
||||
HLR [label="HLR/AUC"]
|
||||
MS0->BTS0 [label="Um"]
|
||||
MS1->BTS0 [label="Um"]
|
||||
MS2->BTS1 [label="Um"]
|
||||
MS3->BTS1 [label="Um"]
|
||||
BTS0->BSC [label="Abis"]
|
||||
BTS1->BSC [label="Abis"]
|
||||
BSC->MSC [label="A"]
|
||||
MSC->HLR [label="C"]
|
||||
MSC->EIR [label="F"]
|
||||
MSC->SMSC
|
||||
|
||||
BTS0->PCU
|
||||
subgraph cluster_gprs {
|
||||
label = "GPRS Add-On"
|
||||
PCU->SGSN [label="Gb"]
|
||||
SGSN->GGSN [label="GTP"]
|
||||
}
|
||||
}
|
||||
----
|
||||
|
||||
* 'PCU': Packet Control Unit. Runs RLC+MAC
|
||||
* 'SGSN': Serving GPRS Support Node (like VLR/MSC)
|
||||
* 'GGSN': Gateway GPRS Support Node (terminates tunnels)
|
||||
|
||||
|
||||
== GPRS Signalling basics
|
||||
|
||||
* GPRS Mobility Management (GMM)
|
||||
** just like GSM Mobility Management (MM)
|
||||
*** 'GPRS ATTACH', 'ROUTING AREA UPDATE', 'AUTHENTICATION'
|
||||
* GPRS Session Management (SM)
|
||||
** establishment, management and tear-down of packet data tunnels
|
||||
*** independent from IP, but typically IP(v4) is used
|
||||
*** 'PDP Context' (Activation | Deactivation | Modification)
|
||||
|
||||
|
||||
== GPRS Protocol Stack
|
||||
|
||||
image::gprs_user_stack.svg[width=850]
|
||||
|
||||
|
||||
== GPRS Acronyms, Protocol Stack
|
||||
|
||||
* Layer 3
|
||||
** 'SM': Session Management (PDP contexts)
|
||||
** 'GMM': GPRS Mobility Management (like MM)
|
||||
* Layer 2
|
||||
** 'MAC': Medium Access Control
|
||||
** 'LLC': Link Layer Control (segmentation, compression, encryption)
|
||||
** 'RLC': Radio Link Control
|
||||
** 'SNDCP': Sub-Network Dependent Convergence Protocol
|
||||
|
||||
[role="incremental"]
|
||||
- Scotty to the bridge: 'You have to re-modulate the sub-network dependent convergence protocols!'
|
||||
|
||||
|
||||
== Simplified OsmoNITB network with GPRS
|
||||
|
||||
[graphviz]
|
||||
----
|
||||
digraph G {
|
||||
rankdir=LR;
|
||||
MS0 [label="MS"]
|
||||
BTS0 [label="OsmoBTS"]
|
||||
BSC [label="OsmoNITB"]
|
||||
PCU [label="OsmoPCU"]
|
||||
SGSN [label="OsmoSGSN"]
|
||||
GGSN [label="OpenGGSN"]
|
||||
MS0->BTS0 [label="Um"]
|
||||
BTS0->BSC [label="Abis"]
|
||||
BTS0->PCU
|
||||
subgraph cluster_gprs {
|
||||
label = "GPRS Add-On"
|
||||
PCU->SGSN [label="Gb"]
|
||||
SGSN->GGSN [label="GTP"]
|
||||
}
|
||||
}
|
||||
----
|
||||
|
||||
* 'OsmoPCU' is co-located with 'OsmoBTS'
|
||||
** connects over unix-domain PCU socket to BTS
|
||||
* 'OsmoSGSN' can run on any Linux machine
|
||||
* 'OpenGGSN' can run on any Linux machine
|
||||
** `tun` device is used for tunnel endpoints
|
||||
* circuit-switched and packet-switched networks are completely separate
|
||||
|
||||
We need to configure those additional components to provide GPRS
|
||||
services.
|
||||
|
||||
== Simplified OsmoNITB network with GPRS
|
||||
|
||||
image::osmocom-gprs.svg[width=750]
|
||||
|
||||
//* show IP addresses at nodes
|
||||
//* show GSM functional elements, Osmocom programs and hardware
|
||||
|
||||
|
||||
== Configuring OsmoPCU
|
||||
|
||||
We assume we have obtained and compiled the `osmo-pcu` from
|
||||
git://git.osmocom.org/osmo-pcu
|
||||
|
||||
* 'OsmoPCU' runs co-located with 'OsmoBTS' to access/share the same PHY + Radio
|
||||
* 'OsmoPCU' is primarily configured from 'OsmoBTS'
|
||||
* 'OsmoBTS' receives relevant config via A-bis OML
|
||||
* 'OsmoNITB' sends those OML messages to OsmoBTS
|
||||
** we thus need to set the PCU configuration in the NITB config file!
|
||||
|
||||
|
||||
== BTS config for GPRS (in OsmoNITB)
|
||||
|
||||
----
|
||||
bts 0
|
||||
gprs mode gprs <1>
|
||||
gprs nsei 1234 <2>
|
||||
gprs nsvc 0 nsvci 1234 <3>
|
||||
gprs nsvc 0 local udp port 23000 <4>
|
||||
gprs nsvc 0 remote ip 192.168.1.11 <5>
|
||||
gprs nsvc 0 remote udp port 23000 <6>
|
||||
----
|
||||
<1> enable `gprs` or `egprs` mode
|
||||
<2> NSEI for the NS protocol layer (unique for each PCU in SGSN)
|
||||
<3> NSVCI for the NS protocol layer (unique for each PCU in SGSN)
|
||||
<4> UDP port on PCU side of Gb connection
|
||||
<5> IP address of SGSN side of Gb connection
|
||||
<6> UDP port on SGSN side of Gb connection
|
||||
|
||||
|
||||
== Configuring OsmoSGSN (Gb and GTP)
|
||||
|
||||
----
|
||||
ns
|
||||
encapsulation udp local-ip 192.168.100.11 <1>
|
||||
encapsulation udp local-port 23000 <2>
|
||||
sgsn
|
||||
gtp local-ip 127.0.0.2 <3>
|
||||
ggsn 0 remote-ip 127.0.0.1 <4>
|
||||
ggsn 0 gtp-version 1 <5>
|
||||
apn * ggsn 0 <6>
|
||||
----
|
||||
<1> SGSN-local IP address for Gb connection from PCUs
|
||||
<2> SGSN-local UDP port number for Gb connection from PCUs
|
||||
<3> SGSN-local IP address for GTP connection to GGSN
|
||||
<4> remote IP address for GTP connection to GGSN
|
||||
<5> GTP protocol version for this GGSN
|
||||
<6> route all APN names to GGSN 0
|
||||
|
||||
|
||||
== Configuring OsmoSGSN (subscribers)
|
||||
|
||||
'OsmoSGSN' (still) has no access to the 'OsmoNITB' HLR, thus all IMSIs
|
||||
permitted to use GPRS services need to be explicitly configured.
|
||||
|
||||
----
|
||||
sgsn
|
||||
auth-policy closed <1>
|
||||
imsi-acl add 262778026147135 <2>
|
||||
----
|
||||
<1> only allow explicitly authorized/white-listed subscribers
|
||||
<2> add given IMSI to the white-list of subscribers
|
||||
|
||||
|
||||
== Setting up OpenGGSN
|
||||
|
||||
In `ggsn.cfg` we need to set:
|
||||
|
||||
----
|
||||
listen 172.0.0.1 <1>
|
||||
net 10.23.24.0/24 <2>
|
||||
dynip 10.23.42.0/24 <3>
|
||||
pcodns1 8.8.8.8 <4>
|
||||
----
|
||||
<1> IP address to bind GSN to.
|
||||
<2> network/mask of `tun` device
|
||||
<3> pool of dynamic IP addresses allocated to PDP contexts
|
||||
<4> IP address of DNS server (communicated to MS via signalling)
|
||||
|
||||
|
||||
== Testing GPRS
|
||||
|
||||
* Check if `osmo-pcu`, `osmo-sgsn`, `openggsn` are running
|
||||
* Check if NS and BSSGP protocols are UNBLOCKED at SGSN
|
||||
** If not, check your NS/BSSGP configuration
|
||||
* Check for GPRS registration using `logging level mm info` in SGSN
|
||||
|
||||
|
||||
== Osmocom beyond GSM/GPRS RAN + NITB
|
||||
|
||||
* Smalltalk implementation of SIGTRAN + TCAP/MAP
|
||||
* Erlang implementation of SIGTRAN + TCAP/MAP
|
||||
* Lots of special-purpose protocol mangling
|
||||
** `bsc-nat` to introduce NAT-like functionality on A (BSSAP/BSSMAP)
|
||||
** `mgw-nat` to transparently re-write MAP/ISUP/SCCP
|
||||
* GSMTAP pseudo-header for feeding non-IP protocols into wireshark
|
||||
* SIM card protocol tracer hardware + software
|
||||
* Lots of non-GSM projects from hardware to protocol stacks (TETRA, GMR, DECT, OP25)
|
||||
* check http://git.osmocom.org/ for full project list
|
||||
|
||||
|
||||
== So... I heard about OpenBTS?
|
||||
|
||||
* OpenBTS is completely unrelated to the Osmocom stack
|
||||
* was independently developed by David Burgess & Harvind Simra
|
||||
** Kestrel Signal Processing -> Range Networks
|
||||
* doesn't follow GSM system architecture at all
|
||||
** no Abis, BSC, PCU, SGSN, GGSN
|
||||
* is a bridge of the GSM air interface (Um) to SIP
|
||||
* Osmocom follows classic GSM interfaces / system architecture
|
||||
* 'OsmoTRX' forked 'OpenBTS' SDR code to use 'OsmoBTS' with SDR hardware
|
||||
|
||||
|
||||
== Outlook on FOSS 2.75G (EDGE)
|
||||
|
||||
* EDGE extends GPRS with higher data rates
|
||||
** 8PSK instead of GMSK modulation
|
||||
** lots of new MAC/RLC features (larger windows, incremental redundancy)
|
||||
** No changes required in 'OmsoSGSN' and 'OsmoGGSN'
|
||||
* 'OsmoPCU' is extended with EDGE support
|
||||
* First working minimal subset published last week
|
||||
|
||||
|
||||
== Outlook on FOSS 3G (UMTS/WCDMA)
|
||||
|
||||
* UMTS very similar to GSM/GPRS in principle
|
||||
** still, almost every interface and protocol stack has changed
|
||||
** all elements have been renamed -> more acronyms to learn
|
||||
* UMTS is ridiculously complex, particular PHY + Layer 2
|
||||
** however, control plane L3 (MM/CC/CM/SM/GMM) mostly the same
|
||||
* Implementing all of that from scratch is a long journey
|
||||
* We've already reached 'Peak 3G'
|
||||
* Osmocom 3G support strategy
|
||||
** Implement Iu interface in NITB and SGSN
|
||||
** Implement HNB-GW to offer Iuh interface
|
||||
** Use existing femtocell / small cell hardware with proprietary PHY, RLC and MAC
|
||||
** Status: Started in October 2015, WIP. Overall completion > 50%.
|
||||
|
||||
|
||||
== Outlook on FOSS 4G (LTE)
|
||||
|
||||
* LTE has nothing in common with 2G/3G
|
||||
* various FOSS activities
|
||||
** 'OpenAirInterface' has some code for a software eNodeB
|
||||
*** but they switched from GPLv3 to 'non-free' license :(
|
||||
** 'srsLTE' (main focus on UE side, but large parts usable for eNodeB side)
|
||||
** 'OpenLTE' is another active FOSS project
|
||||
* No Osmocom involvement so far
|
||||
** team is small, project scope of cellular infrastructure is gigantic
|
||||
** most customer funding currently still on GSM/GPRS/EDGE
|
||||
** if we'd start, we'd start implementing MME + S-GW and use existing LTE cells
|
||||
|
||||
|
||||
== The End
|
||||
|
||||
* so long, and thanks for all the fish
|
||||
* I hope you have questions!
|
||||
|
||||
[role="incremental"]
|
||||
* have fun exploring mobile technologies using Osmocom
|
||||
* interested in working with more acronyms? Come join the project!
|
||||
|
||||
* Check out http://openbsc.osmocom.org/ and openbsc@lists.osmocom.org
|
||||
|
||||
== Thanks to
|
||||
|
||||
* Pablo for running netdevconf and inviting me
|
||||
* the entire Osmocom team for what they have achieved
|
||||
** notably Dieter Spaar, Holger Freyther, Andreas Eversberg, Sylvain Munaut
|
||||
* last but not least: CEPT for making the GSM specs English
|
||||
** (who'd want to read French specs anyway?)
|
||||
|
||||
|
||||
|
||||
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