add html rendering of v5 talk

2022/osmodevcall-advanced_sim/advanced_sim.adoc

@@ -0,0 +1,346 @@
+Advanced SIM topics: ARA-M, SCP02, OTA, ISIM
+============================================
+:author:	Harald Welte <laforge@gnumonks.org>
+:copyright:	2022 by Harald Welte (License: CC-BY-SA)
+:backend:	slidy
+:max-width:	45em
+
+
+== Overview
+
+* Administrative Commands
+* ADF.ISIM
+* DF.5GS
+* ARA-M applet
+* GlobalPlatform SCP02
+* pySim-shell updates
+
+== Recap: Some smartcard terminology
+
+* card filesystem
+** *MF* (Master File): The root directory
+** *DF* (Dedicated File): A subdirectory
+** *ADF* (Application Dedicated File): Directory of an application (like USIM, ISIM)
+** *EF* (Entry File): A regulare file
+*** *Transparent EF*: An unstructured file
+*** *Linear Fixed EF*: An file consisting of fixed-length records
+
+== specs vs. proprietary
+
+* SIM cards are fully specified by a combination of ISU, ETSI and 3GPP specs
+* this covers only the operation after the card has been issued, e.g.
+** reading and writing files accessible without PIN auth, after PIN auth
+** performing GSM authentication or UMTS AKA
+* it does _not_ cover how the card is issued/provisioned
+** secret key material (Ki / K / OP / OPc) is not readable from the card
+** it is an implementation detail on how the card manufacturer writes those to the card
+* this leads to the need for card-specific support / code in software like pySim
+
+== Administrative Commands (TS 102 222)
+
+* most well-known SIM/UICC commands relate to normal operation
+** reflects what happens between phone (ME) and SIM
+** SELECT, {READ,UPDATE} {BINARY,RECORD}, VERIFY CHV, ...
+* there are also standardized _administrative_ commands
+** intended for use by the operator / card issuer
+** usually only work after authentication with ADM PIN or via secure channel
+
+== Administrative Commands (TS 102 222)
+
+* `CREATE FILE`
+* `DELETE FILE`
+* `DEACTIVATE FILE`
+** temporary deactivation (cannot be selected anymore)
+* `ACTIVATE FILE`
+** reactivation of deactivated files
+* `TERMINATE DF`
+** DF can never be used again
+* `TERMINATE EF`
+** EF can never be used again
+* `TERMINATE CARD USAGE`
+** permanently bricks the card
+
+== The ISIM application
+
+The history:
+
+* initial 2G SIM cards had `DF.GSM` + `DF.TELECOM`
+* ETSI UICC was specified as application-independent card
+* 3G/UMTS: 3GPP USIM application specified for UICC
+* 4G/LTE: continues to use USIM
+* IMS/VoLTE: optional ISIM application for UICC
+
+== ISIM application: Entirely optional
+
+* ISIM application is entirely optional
+* IMS (VoLTE, VoWiFi) can be used with pure USIM
+* without ISIM, default / fall-back mechanisms are used
+** P-CSCF address
+** Identities (IPUI derived from IMSI)
+
+== ISIM application: Files in USIM or ISIM
+
+Some files can either be in ADF.USIM **or** in ADF.ISIM
+
+* cards without ISIM might have them in USIM
+* cards with ISIM *must not* have them in USIM
+
+Files:
+
+* `EF.UICCIARI`
+* `EF.FromPreferred`
+* `EF.IMSConfigData`
+* `EF.XCAPConfigData`
+* `EF.MuDMiDConfigData`
+
+== ISIM application: Separate authentication context
+
+While IMS uses the same UMTS AKA Authentication Mechanism as 3G/4G systems,
+the authentication context can be different:
+
+* transport / access network (e.g. LTE) authenticates against USIM
+* IMS core network (e.g. P-CSCF) authenticates against ISIM
+
+At least in theory (and in practice with sysmoISIM-SJA2), one can configure
+different key material and even choose different algorithms for the two
+situations.
+
+== ISIM application: Files in ADF.ISIM
+
+image::adf_isim.png[align="center"]
+
+== ISIM application: Files in ADF.ISIM
+
+* `EV.IMPI` (IMS Private User Identity)
+* `EF.DOMAIN` (Home Network Domain Name)
+* `EF.IMPU` (IMS Public User Identity)
+* `EF.AD` (Administrative Data)
+* `EF.ARR` (Access Rule Reference)
+* `EF.IST` (ISIM Service Table, like EF.UST for USIM)
+* `EF.P-CSCF` (P-CSCF Address
+* `EF.GBABP` (GBA Bootstrapping Parameters)
+* `EF.NAFKCA` (NAF Key Centre Address)
+* `EF.SMS / EF.SMSS / EF.SMSR / EF.SMSP` (SMS like in GSM/USIM)
+* `EF.UICCIARI` (IMS Application Reference Identifier)
+* `EF.FromPreferred`
+* `EF.IMSConfigData`
+* `EF.XCAPConfigData`
+* `EF.WebRTCURI`
+* `EF.MuDMiDConfigData`
+
+
+== BER-TLV files (1/2)
+
+* new file type ('structure') from existing known types
+** transparent
+** linear fixed
+** cyclic
+* BER-TLV files store data in BER-TLV format [surprise!]
+* difference between storing BER-TLV in transparent file:
+** read/write/delete only TLV for a certain specific tag
+** no need to bother with padding
+* supported from sysmoISIM-SJA2v2 onwards (IMSI ending in >= 50000)
+
+== BER-TLV files (2/2)
+
+* USIM Files specified as BER-TLV:
+** `EF.URSP` (UE Route Selection Policies)
+** `DF.GRAPHICS/EF.ICE_graphics` (?)
+** `DF.MULTIMEDIA/EF.MML` (Multimedia Messages List)
+** `DF.MULTIMEDIA/EF.MMDF` (Multimedia Messages Data File)
+** `DF.MCS/EF.MCS_CONFIG` (Mission Critical Services)
+** `DF.V2X/EF.V2X_CONFIG` (V2X configuration Data)
+* ISIM Files specified as BER-TLV
+** `EF.IMSConfigData` (IMS Configuration Data)
+** `EF.MuDMiDConfigData` (Multi-Device / Multi-Identity Config)
+
+
+== 5G SIM / DF.5GS
+
+* 3GPP did not specify a new card application
+* 5G/NR uses the same USIM as 4G/LTE and 3G/UMTS
+* some optional additional files in ADF.USIM/DF.5GS
+** together with their associated _services_ (122-135)
+** `EF.5GS3GPPLOCI` (like EF.LOCI/3G and EF.EPSLOCI/4G)
+** `EF.5GSN3GPPLOCI` (non-3GPP location information)
+** `EF.5GS3GPPNSC` (NAS Security Context)
+** `EF.5GAUTHKEYS` (K_SEAF / K_AUSF, like EF.KEYS/3G)
+** `EF.UAC_AIC` (UAC Access Identities Configuration)
+** `EF.SUCI_Calc_Info` (For SUCI computation in ME)
+** `EF.OPL5G` (5GS Operator PLMN List)
+** `EF.SUPI_NAI` (SUPI as Network Access Identifier)
+** `EF.Routing_Indicator`
+** `EF.URSP` (UE Route Selection Policies per PLMN)
+** `EF.TN3GPPSNN` (Trusted non-3GPP Serving network names list)
+
+== 5G SIM / Files in DF.5GS
+
+image::df_5gs.png[align="center"]
+
+== 5G SIM / Calculation of SUCI on SIM
+
+* 5G introduces the optional SUCI security menchanism
+** SUCI == Subscriber Concealed Identifier
+* prevents IMSI (SUPI) transmission in plain-text
+* two implementation options:
+** SUCI computation on ME (phone) using key from SIM
+** SUCI computation on SIM card
+
+Some high-end cards (like eUICC) support SUCI calculation on the card.
+
+
+== ARA-M and Android Carrier Privileges
+
+* Android specific system to give apps more API access
+** change carrier/operator settings like APN, Roaming, ...
+** change IMS configuration for VoLTE / VoWiFi
+** inject SMS into android from an app
+* hash/cert of key used to sign app stored on SIM
+* if Android detects apps signed with matching key, API access is enabled
+* hash/cert is not stored as normal file in filesytem
+* requires _Secure Element Access Control_ application on card
+
+== ARA-M / Secure Element Access Control
+
+image::ara-m-architecture.png[width=1000,align="center"]
+
+== ARA-M in practice
+
+* minimal open source ARA-M applet: https://github.com/bertrandmartel/aram-applet
+* pre-installed on sysmoISIM-SJA2
+* pySim-shell has support for adding/deleting rules (see user manual)
+* see https://github.com/herlesupreeth/CoIMS_Wiki for more information
+
+== pySim-shell updates since April 2021
+
+* commands
+** more decoders for more files
+** TS 102 222 administrative commands
+** `ust_service_check`
+** `apdu` command
+** `export --json`
+* encoders/decoers
+** TLV definitions for IMS, XCAP and MudMid
+** FCP in `export`
+* BER-TLV file support
+* ARA-M support
+* support for generic, non-sysmocom cards
+* WIP
+** basic GlobalPlatform commands
+** `decode_hex` command
+
+
+== GlobalPlatform
+
+* GlobalPlatform specifies the Javacard universe
+* SIM cards are not required to be Java cards, but in practice they mostly are
+** ... and they mostly only implement ancient GlobalPlatform versions
+* specifies how to install/remove/lock/unlock applets
+* specifies transport layer security protocols (SCP02, SCP03)
+
+== GlobalPlatform APDU commands
+
+* Key Management
+** `PUT KEY`
+** `DELETE KEY`
+* Data
+** `GET DATA`
+** `STORE DATA`
+* Application Locking/Unlocking
+** `GET STATUS`
+** `SET STATUS`
+* Installation / Deletion (Executables, Applets)
+** `INSTALL`
+** `DELETE`
+
+== GlobalPlatform INSTALL / DELETE flavours
+
+* `INSTALL`
+** `INSTALL [for load]`
+** `INSTALL [for install]`
+** `INSTALL [for load, install and make selectable]`
+** `INSTALL [for install and make selectable]`
+** `INSTALL [for make selectable]`
+** `INSTALL [for extradition]`
+** `INSTALL [for registry update]`
+** `INSTALL [for personalization]`
+* `DELETE`
+** Executable Load File
+** Executable Load File and related Applications
+** Application
+
+== GlobalPlatform SCP02 initiation
+
+* mutual authentication between card and external software
+** contains random factor from both sides
+** generates session keys
+* transport-level security established ('secure messaging')
+* protected APDUs between on-card software and off-card software
+
+image::scp02-flow.png[align="center"]
+
+== GlobalPlatform SCP02 APDU commands
+
+* `INITIALIZE UPDATE`
+* `EXTERNAL AUTHENTICATE`
+* `BEGIN R-MAC SESSION`
+* `END R-MAC SESSION`
+
+== C-MAC
+
+* C-MAC (Command Message Authentication Code)
+** either on unmodified APDU or modified APDU
+
+image::scp02_cmac_modified.png[align="center"]
+
+== R-MAC
+
+optional MAC on responses generated by card
+
+image::scp02_rmac.png[align="center"]
+
+
+== Data Field Encryption
+
+optional confidentiality of data field of APDUs
+
+image::scp02_data_field_encryption.png[align="center"]
+
+
+== OTA (Over The Air)
+
+* Mechanism how some software in operator core can talk to SIM in the field
+* traverses the entire 3GPP Core and Radio Access Network, hence _over the air_.
+
+image::ota_overview.png[width=1000,align="center"]
+
+== OTA transport mechanisms
+
+* SMS-PP (SMS as you know it)
+* SMS-CB (Cell Broadcast)
+** would require shared keys, bad idea
+* USSD
+** faster, more responsive than SMS
+* BIP (Bearer Independent Protocol)
+** CSD, GPRS, Bluetooth, IrDA
+* HTTP over TLS-PSK on the card (!)
+** Amendmend B GlobalPlatform Card Sepc v2.2
+
+== Further Reading
+
+* https://git.osmocom.org/pysim/about/[pySim source code / git repository]
+* https://media.ccc.de/v/36c3-10737-sim_card_technology_from_a-z[Video of talk "SIM card technology from A-Z"]
+* Specs
+** ETSI TS 102 221 (UICC)
+** ETSI TS 102 222 (Administrative Commands)
+** ETSI TS 102 223 (Bearer Independent Protocol)
+** ETSI TS 102 225 (Secured Packets for OTA)
+** 3GPP TS 31.102 (USIM)
+** 3GPP TS 31.103 (ISIM)
+** GlobalPlatform Card Specification 2.2.1
+** GlobalPlatform Secure Element Access Control v1.0
+
+
+== EOF
+
+End of File

2022/osmodevcall-octoi/octoi.adoc

@@ -0,0 +1,386 @@
+OCTOI - Osmocom Community TDM over IP
+=====================================
+:author:	Harald Welte <laforge@gnumonks.org>
+:copyright:	2022 by Harald Welte (License: CC-BY-SA)
+:backend:	slidy
+:max-width:	45em
+
+
+== Overview
+
+* WTF? Why?
+* History: TDM networks
+* existing TDMoIP technology
+* OCTOI Protocol
+* OCTOI Software
+* Current OCTOI Network
+* WIP / Future Plans
+
+== WTF is this all about?
+
+* enable people to run legacy WAN equipment
+** Modems, Phones (analog, ISDN), PBXs
+** ISDN-Adapters
+** Frame Relay / HDLC / X.25 / routers
+* in a distributed fashion, over the internet
+* allow to run retronetworking tech from mid-1980s to about 2010 at a time where the related transport
+  services are no longer available from public telephone operators / carriers
+
+// ***********************************************************************
+// History: TDM networks
+// ***********************************************************************
+
+== History: analog telephone networks
+
+public switched telephone network (PSTN)
+
+* traditionally used only analog lines
+** base band on twisted pair on last mile
+** base band on twisted pair between exchanges nearby
+** analog modulated carrier wave on coaxial cables or microwave links for long distance
+
+== History: TDM networks + ISDN
+
+* at some point (1970s?), digital PCM technology was introduced between exchanges
+** initially PDH, later SDH (which can transport PDH)
+** see https://media.ccc.de/v/osmodevcall-20211112-laforge-tdm[OsmoDevCall on TDM/PDH/SDH]
+* external interfaces, particularly to subscriber, still analog until mid-1980s
+* ISDN changed that: Introduced digital subscriber lines
+** Basic Rate ISDN (BRI): 2x B, 1x D-Channel
+** Primary Rate ISDN (PRI): 30x B, 1x D-Channel
+
+== Present: TDM networks mostly dead
+
+* Telcos have meanwhile mostly migrated to All-IP telephony
+* PDH/SDH networks mostly shut down, occasionally still in operation for legacy customers or some internal
+  legacy services. Not actively sold anymore.
+* You cannot get a real PRI line anymore to connect your ISDN PBX or your Cisco router
+* Idea: Create community network of people who want to play with ISDN / TDM stuff
+* Naive approach: Use existing, off-the-shelf TDMoIP devices
+
+
+== Wanted: TDMoIP network
+
+[graphviz]
+----
+graph G {
+  hub [shape=box, label="TDMoIP hub\ncross-connect\nin public internet"];
+  subgraph cluster_1 {
+    label="Hobbyist A";
+    ad1 [label="Access Device\n"];
+    pbx1 [label="PBX"];
+    phone1a [label="Phone"];
+    modem1b [label="Modem"];
+    ta1c [label="ISDN TA"];
+    pbx1 -- ad1 [label="E1"];
+    phone1a -- pbx1 [label="POTS"];
+    modem1b -- pbx1 [label="POTS"];
+    ta1c -- pbx1 [label="ISDN-BRI"];
+  }
+  subgraph cluster_2 {
+    label="Hobbyist B";
+    ad2 [label="Access Device\n"];
+    pbx2 [label="PBX"];
+    phone2a [label="Phone"];
+    modem2b [label="Modem"];
+    ta2c [label="ISDN TA"];
+    pbx2 -- ad2 [label="E1"];
+    phone2a -- pbx2 [label="POTS"];
+    modem2b -- pbx2 [label="POTS"];
+    ta2c -- pbx2 [label="ISDN-BRI"];
+  }
+  subgraph cluster_3 {
+    label="Hobbyist C";
+    ad3 [label="Access Device\n"];
+    pbx3 [label="PBX"];
+    phone3a [label="Phone"];
+    modem3b [label="Modem"];
+    ta3c [label="ISDN TA"];
+    pbx3 -- ad3 [label="E1"];
+    phone3a -- pbx3 [label="POTS"];
+    modem3b -- pbx3 [label="POTS"];
+    ta3c -- pbx3 [label="ISDN-BRI"];
+  }
+  ad1 -- hub [label="TDMoIP\nInternet"];
+  ad2 -- hub [label="TDMoIP\nInternet"];
+  ad3 -- hub [label="TDMoIP\nInternet"];
+}
+----
+
+// ***********************************************************************
+// Existing TDMoIP technology
+// ***********************************************************************
+
+== Existing TDMoIP: SAToP / CESoPSN
+
+So we just get some of these and all is good?
+
+image::RAD_IPmux-1_front.jpg[width=1200,align="center"]
+
+== Existing TDMoIP: SAToP / CESoPSN
+
+Examples for _transparent_ TDMoIP technologies
+
+* SAToP (Structure Agnostic TDM over IP)
+** RFC 4553
+* CESoPSN (Circuit Emulation Service over Packet Switched Network)
+** RFC 5086
+* transport of raw E1 frames over MPLS or UDP
+* designed for use in LAN or carrier backbone networks
+* waste a lot of bandwidth, even if TDM circuits are completely idle
+** > 2Mbps plus header/packet overhead, bi-directional
+* typically no support for dynamic IP addresses
+
+== Existing TDMoIP: SIGTRAN IUA, EL2TPD
+
+Examples for _non-transparent_ TDMoIP technologies
+
+* SIGTRAN IUA (ISDN User Adaptation)
+** RFC 3057
+** works only for ISDN BRI/PRI with Q.921 as Layer 2 on signaling channel
+** uses SCTP as transport (might not pass all middleboxes in public internet)
+** no specification how the B-channels are handled, pure signaling solution
+* Ericsson L2TP / PacketAbis over IP
+** proprietary, but FOSS implementation in @osmo-el2tpd@
+** makes specific assumption of use of E1 as Ericsson Abis (GSM BTS back-haul)
+
+// ***********************************************************************
+// OCTOI TDMoIP protocol
+// ***********************************************************************
+
+== The case for a new TDMoIP protocol
+
+There's room for a new protocol based on the following goals:
+
+* *transparent*.  Should work for ISDN and other use cases (Frame Relay, Abis, SS7, ATM, ...)
+* *efficient*. Should not waste a lot of bandwidth on an otherwise idle/unused link
+* *dynamic IP*. End-user internet access normally has dynamic IP addresses
+* *nat friendly*. Should work through any number of NATs and CG-NAT without special ALG/helper
+* *IPv6 support*. Should support IPv6 just like IPv4
+* *authentication*.  Should have built-in mutual authentication
+
+== OCTOI Protocol: Bandwidth
+
+* Timeslot Suppression
+** Transmitter has history of 1 TDM frame
+** Before Tx, to-be-transmitted frame is compared with last frame
+** only those timeslots with value != that of last frame are transmitted
+* Batching
+** Batch 32 (up to 40) E1 frames per UDP packet
+*** 8000 frames/s / 32 => 250 packets/s
+
+Result: About 70 kbit/s (including UDP + IPv4 overhead) on idle E1 link
+
+== OCTOI Protocol: dynamic IP / NAT-friendly
+
+* Classic client/server approach
+* Server currently requires fixed IP (no STUN/ICE/...)
+* Clients can have dynamic IPs
+* All messages (control plane + TDM user plan) in one UDP flow
+
+// ***********************************************************************
+// OCTOI Software
+// ***********************************************************************
+
+== E1oIP: osmo-e1d + icE1usb
+
+* osmo-e1d was the first (libusb, userspace) driver for the icE1usb hardware
+* traditionally, it sits between icE1usb hardware and applications using E1 like osmo-bsc
+* instead of a local application, it can now interface icE1usb to OCTOI
+** `octoi-server` mode
+** `octoi-client` mode
+
+First 4 OCTOI users were connected to the hub that way
+
+[graphviz]
+----
+graph {
+  rankdir=LR;
+  subgraph cluster_L {
+     label="Site L";
+     PBX_L [label="PBX"];
+     icE1usb_L [label="icE1usb"];
+     GW_L [label="GW L"];
+     PBX_L -- icE1usb_L [label="E1"];
+     icE1usb_L -- GW_L [label="USB"];
+  }
+  subgraph cluster_R {
+     label="Site R";
+     PBX_R [label="PBX"];
+     icE1usb_R [label="icE1usb"];
+     GW_R [label="GW R"];
+     PBX_R -- icE1usb_R [label="E1"];
+     icE1usb_R -- GW_R [label="USB"];
+  }
+  Internet;
+  GW_L -- Internet [label="IP"];
+  GW_R -- Internet [label="IP"];
+}
+----
+
+== E1oIP: osmo-e1d + dahdi-trunkdev
+
+* having one icE1usb per peer/user doesn't scale at the hub
+* this triggered the development of `dahdi-trunkdev`
+** virtual E1 _span_ for DAHDI without any real hardware
+** simply provides stream of E1 frames on a character-device
+** can be used to implement any virtual TDM interface/protocol
+* osmo-e1d was extended to open dahdi-trunkdev instead of icE1usb
+
+Next 4 OCTOI users were connected to the hub that way; will become standard for all users
+
+[graphviz]
+----
+graph {
+  rankdir=LR;
+  subgraph cluster_L {
+     label="Site L";
+     PBX_L [label="PBX"];
+     icE1usb_L [label="icE1usb"];
+     GW_L [label="GW L"];
+     PBX_L -- icE1usb_L [label="E1"];
+     icE1usb_L -- GW_L [label="USB"];
+  }
+  subgraph cluster_R {
+     label="Site R";
+     PBX_R [label="PBX\n(Virtual DAHDI)"];
+  }
+  Internet;
+  GW_L -- Internet [label="IP"];
+  PBX_R -- Internet [label="IP"];
+}
+----
+
+// ***********************************************************************
+// Current OCTOI Network
+// ***********************************************************************
+
+== Current OCTOI network hub
+
+* Debian 11 with `dahdi-trunkdev`, `osmo-e1d` and `yate`
+* since physical machine died recently: migrated into qemu-kvm
+** SRV-IO for NIC, USB Host Controller and DADHI card (TE820)
+* TE820 8-port E1 card, attaches to
+** LaF0rge's local PBX (Auerswald COMmander 2 basic)
+** Livingston PortMaster 3 RAS
+** 4x icE1usb
+** Cisco AS5400
+
+== Current OCTOI participants
+
+The hub currently has the following clients / participants:
+
+* using icE1usb at hub side
+** manawyrm
+** gruetzkopf
+** roox
+** cquirin
+* using `dahdi-trunkdev` at hub side
+** drdeke
+** tmwawpl
+** tom/sirtux
+** tnt
+
+== Current OCTOI services
+
+* E1 / TDM as "transport" layer
+* ISDN network as "routing" layer
+** hub simulates the network / central office / switch side
+** client devices implement the "user" side, just like when attaching to ISDN/PSTN
+* Services on top of ISDN
+** Audio Telephony
+** Video Telephony (T-View 100 / H.320)
+** ISDN Data Calls
+** Analog Modem Calls
+
+== OCTOI ISDN / Modem calls
+
+* hub currently has a https://osmocom.org/projects/retronetworking/wiki/Livingston_Portmaster_3[Livingston Portmaster 3] RAS
+** up to 30 ISDN data or analog modem calls (up to V.90)
+* services can be created in RADIUS, identified by Called Party Number
+** PPP dial-up locally terminated
+** PPP dial-up with forwarding of data via L2TP to remote LAC
+** telnet or TCP clear forwarding to remote BBSs
+* Cisco AS5400 with much higher capacity is waiting to be provisioned
+
+== Challenges: Clocking
+
+* TDM networks need a stable bitclock at all parts of the network
+* everyone must transmit and receive at the same rate of bits / frames
+* we use GPS disciplined oscillators (GPS-DO) to ensure same clock everywhere
+** this avoids overruns / underruns resulting in cycle slips that would create phase discontinuity for
+any modem signals carried over the network
+
+== Challenges: Packet Re-ordering
+
+* It seems like particularly on DOCSIS there is quite a bit of UDP packet re-ordering
+* Initially, osmo-e1d used a FIFO and dropped all out-of-order packets
+* later, we introduced a RIFO (Random In, First Out) to support re-ordering without loss
+
+== Challenges: Packet Loss
+
+* There is quite a bit of packet loss on the public internet
+* People probably don't generally notice much, as most services use TCP or retransmit UDP
+* Surprisingly, I couldn't find any comprehensive studies / research papers on packet loss behaviour of
+  consumer internet that are less than 10 years old?
+* Right now we just accept it exists
+* Some early thoughts and experiments on FEC (Forward Error Correction)
+
+== Challenges: Latency
+
+* intercontinental public IP can easily reach >= 200ms RTT
+* ISDN timers in Q.921 and Q.931 are luckily working just fine over that kind of RTT
+* some suspicion that the high latency might have negative impact on Fax (T.30 timers) and modems (buffer
+  sizes). I'm personally not yet convinced it is really an issue.
+
+
+// ***********************************************************************
+// Future Plans
+// ***********************************************************************
+
+== Future Plans
+
+* migrate OCTOI hub to co-location / data centre
+** higher capacity, better reliability, less packet loss
+* ISDN BRI (S/T) access to OCTOI network
+** more end-user friendly; many people have S0 equipment and no E1/S2M PBX at home
+* Frame Relay switch / hub
+** second, additional service, completely independent of the current ISDN service
+** initial testing has confirmed HDLC / FR over OCTOI works without problems
+* exhibits at hacker and vintage computing events
+
+== ISDN BRI (S/T) access to OCTOI
+
+* BRI (ISDN basic rate aka "S/T" aka "S0") support in OCTOI protocol
+* BRI hardware with 2x S/T interface and GPS-DO
+** unlike icE1usb: Ethernet/IP support, not USB
+** complete _appliance_ for OCTOI client mode: no need for computer
+** Status: design of first break-out / evaluation board for ISDN BRI side complete
+** Software not even started yet. Idea is to use Nuttx on Atmel SAMV71
+
+== Longer-Term Future Plans
+
+* improve FOSS soft-modem situation (linmodem, spandsp)
+* investigate somewhat limited V.90 performance so far
+* investigate somewhat limited throughput of PM3 in tcp-clear/telnet-forwarding
+* support for other Q.931 dialects than DSS1 (like 1TR6 or even NI1)
+* X.25 / X.31 support
+
+== Thanks
+
+Thanks to
+
+* Sylvain "tnt" Munaut for icE1usb and all his help
+* All of the early OCTOI network participants manawyrm, gruetzkopf, roox, DrDeke, tmwawpl, cquirin
+
+== Further Reading
+
+* https://osmocom.org/projects/octoi/wiki[OCTOI Project Homepage/Wiki]
+* https://osmocom.org/projects/octoi/wiki/Proposed_efficient_TDMoIP[OCTOI Protocol Description]
+* https://osmocom.org/projects/retronetworking/wiki[Retronetworking Wiki]
+* https://osmocom.org/projects/osmo-e1d/wiki/Wiki[osmo-e1d software]
+* https://osmocom.org/projects/octoi/wiki/Proposed_efficient_TDMoIP[icE1usb hardware]
+
+== EOF
+
+End of File