FreeCalypso > hg > themwi-system-sw

annotate README @ 124:7e04d28fae8b

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
sip-in: default use-100rel to no BulkVS servers act badly when we send a reliable 180 Ringing response to an incoming call, even though they advertise 100rel support in the Supported header in the INVITE packet, and we probably won't be implementing 100rel for outbound because doing per-the-spec PRACK as a UAC is just too burdensome. Therefore, we need to consider 100rel extension as not-really-supported in themwi-system-sw.
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 01 Oct 2022 15:54:50 -0800
parents 97317ede320a
children b7cd66acb123
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
29
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
1 This Hg repository contains a work-in-progress named Themyscira Wireless system
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
2 software. Themyscira Wireless (ThemWi) is an experimental GSM network operated
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
3 by Mother Mychaela of FreeCalypso at a semi-urban/semi-rural location in
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
4 Southern California, USA; this GSM network is operated with Osmocom CNI software
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
5 components, all running on a single Slackware Linux server. ThemWi system sw
88
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
6 is a suite of daemon processes and command line tools that run on the same
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
7 machine as all those Osmocom sw components and provide some additional
29
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
8 functionality that is not provided "out of the box" by Osmocom, most important
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
9 of which is outside connectivity to USA PSTN.
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
10
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
11 We are currently experimenting with using bulkvs.com as our USA PSTN
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
12 connectivity provider. Like most low-cost PSTN connectivity providers, they
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
13 provide the interface to PSTN in the form of a SIP trunk - while I would
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
14 absolutely love to get a traditional TDM trunk instead, with SS7 signaling,
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
15 such a toy would be far beyond my budget, hence I have to settle for SIP.
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
16 Our current status is:
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
17
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
18 * We have already obtained a block of USA phone numbers (NANP, chosen numbers
88
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
19 from an exchange area local to us) from BulkVS.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
20
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
21 * These BulkVS-sourced real NANP numbers have been entered as MSISDNs into
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
22 OsmoHLR records for our test SIMs operating on ThemWi GSM.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
23
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
24 * We can successfully dial calls from one ThemWi GSM phone to another, with our
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
25 themwi-mncc switch understanding all dialing formats that are considered
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
26 standard for cellular phone networks in USA (full international, or 11 digits
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
27 starting with '1' but no '+', or 10 digits only), as well as our own non-
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
28 standard shorthand dialing method with only 4 digits.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
29
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
30 * Whenever someone dials one of our NANP numbers from the outside world, BulkVS
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
31 servers send UDP SIP INVITE packets to our server. Our inbound call gateway
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
32 process is themwi-sip-in; this daemon process listens on UDP port 5060,
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
33 accepts SIP calls from BulkVS (ultimately coming from global worldwide PSTN)
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
34 and turns them into GSM MT calls in MNCC format, going through themwi-mncc
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
35 and ultimately to OsmoMSC.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
36
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
37 The following functionality remains to be implemented:
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
38
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
39 * As a counterpart to themwi-sip-in, there will be another process named
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
40 themwi-sip-out that will serve as a gateway for outbound calls, going from
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
41 GSM MO MNCC to outside PSTN via SIP. The outbound SIP call functional part
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
42 is already implemented in test prototype form in sip-manual-out.
29
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
43
88
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
44 * themwi-mgw will be our transcoding RTP bridge, speaking GSM codecs (FR and
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
45 EFR are currently of most interest) on the side toward Osmocom components and
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
46 G.711 (PCMU or PCMA) on the PSTN side. Right now themwi-mgw is a working
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
47 skeleton that allocates endpoints with RTP & RTCP UDP port pairs, but doesn't
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
48 pass any traffic yet.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
49
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
50 Differences from osmo-sip-connector
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
51 -----------------------------------
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
52
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
53 In the Osmocom community, the "standard" (or generally accepted) way to connect
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
54 a GSM voice network to the outside world is via osmo-sip-connector, an Osmocom
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
55 process that connects to OsmoMSC's MNCC socket on one end and talks SIP on the
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
56 other end. Our combination of themwi-mncc, themwi-sip-in and themwi-sip-out
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
57 effectively takes the place of osmo-sip-connector. Here are the principal ways
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
58 in which our solution differs from osmo-sip-connector:
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
59
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
60 * o-s-c is designed to connect to a local instance of a SIP PBX such as Asterisk
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
61 or FreeSWITCH, as opposed to interfacing directly to an outside SIP trunk
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
62 from/to a PSTN-via-SIP connectivity provider. themwi-system-sw is different
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
63 in this regard: we do NOT use Asterisk or FreeSWITCH or any other similar
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
64 software of "spaceship" complexity, instead our themwi-sip-in and
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
65 themwi-sip-out processes interface directly to our PSTN-via-SIP connectivity
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
66 provider.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
67
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
68 * o-s-c has no internal call switching function for calls from one local GSM
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
69 phone to another, instead such switching is punted to the required Asterisk
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
70 or FreeSWITCH etc. With o-s-c, the calling phone's MO call is converted to
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
71 SIP, then Asterisk or other PBX hairpins it back to o-s-c, and then o-s-c
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
72 handles the destination call leg as a separate conversion from SIP back to
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
73 GSM MNCC. In our solution such local calls are switched internally inside
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
74 themwi-mncc, staying native within GSM MNCC land and never turning into SIP.
29
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
75
88
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
76 * o-s-c is based on Sofia-SIP, which in turn uses glib - a very unpleasant
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
77 dependency in this Mother's opinion. In contrast, our implementation of SIP
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
78 is 100% from scratch, written in plain C in the traditional Falconian coding
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
79 style.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
80
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
81 The need for RTP voice transcoding
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
82 ----------------------------------
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
83
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
84 In the context of GSM voice codecs, the term "transcoding" is used in two
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
85 significantly different meanings:
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
86
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
87 * Transcoding from one lossy GSM codec to another effectively constitutes two
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
88 lossy speech codecs running in tandem, and is a highly undesirable condition.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
89
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
90 * Running a single GSM codec (not two in tandem), decoding from GSM to G.711 in
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
91 one direction and encoding from G.711 in the other direction, is a standard
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
92 required function for traditional voice gateways between GSM and PSTN.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
93
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
94 In themwi-system-sw, we need to do transcoding in the second sense above.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
95 BulkVS SIP call interface to PSTN does not support any of GSM codecs, they only
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
96 support G.711 and G.729, and the same situation is expected to hold with other
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
97 PSTN-via-SIP connectivity providers. We certainly don't want to use G.729 - we
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
98 don't want to run two lossy speech codecs in tandem, first GSM and then G.729 -
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
99 hence the only codecs we speak on the PSTN-via-SIP side of our gateway are PCMU
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
100 and PCMA. Therefore, we need to perform RTP transcoding in our themwi-mgw,
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
101 very similar to a traditional GSM TRAU.
29
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
102
88
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
103 On the GSM side, the two codecs of most interest to us at the present time are
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
104 the original FR and EFR - hence they will be the first to be supported. Note
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
105 the big difference from other Osmocom-using GSM community networks which
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
106 typically prefer or even strictly require AMR instead! Our reasons for focusing
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
107 on FR and EFR instead of AMR are:
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
108
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
109 * Our OsmoBSC time slot configuration is full rate channels only, no half rate
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
110 channels. HR channels are needed only for greater capacity of simultaneous
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
111 calls, but with the total number of people *on the planet* who actively want
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
112 GSM/2G as opposed to LTE or 5G being no more than maybe 10, the thought of
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
113 exceeding the limit of 6 simultaneous call legs per cell (meaning 6 separate
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
114 GSM phone handsets talking *at the same time*) is preposterous.
29
dffcae9bc8a3 add README
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
115
88
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
116 * Without any HR channels in OsmoBSC config, AMR means AMR-FR specifically, not
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
117 AMR-HR. The highest level of AMR-FR is identical with EFR - thus if we
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
118 support EFR, do we really need AMR?
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
119
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
120 * The whole point of Themyscira Wireless is to provide service to *vintage*
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
121 mobile phones. Our current collection of vintage phones includes models that
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
122 only support FR1 and EFR (Ericsson I888, Nokia 5190) and Calypso C05 which
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
123 supports FR1, EFR and HR1, but not AMR.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
124
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
125 * EFR is desirable because it gives better voice quality than FR1, but we must
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
126 support FR1 too, so we can serve the very oldest of phones which support only
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
127 FR1 and nothing else.
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
128
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
129 Voice codec restriction (forcing GSM phones to use EFR instead of AMR, or
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
130 forcing all the way down to FR1) is done in OsmoBSC config, with codec-list
97317ede320a README: update for current status
Mychaela Falconia <falcon@freecalypso.org>
parents: 29
diff changeset
131 setting under 'msc 0'.