X25 » History » Version 2
laforge, 02/02/2022 09:11 PM
| 1 | 1 | laforge | h1. X.25 |
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| 3 | X.25 is a packet switched technology that falls within the domain of PSPSDN (Packet Switched Public Data Network). Contrary to the circuit-switched telephony network, it is based on packet switching technology. It was the first major vendor-independent / interoperable standard for such networks. |
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| 5 | Interestingly, despite X.25 being packet switched, it has the notion of establishing "calls" over it, and packets are exchanged between the two ends after a conenction setup. Think in terms of of TCP having a connection abstraction over the packet switched IP network. |
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| 7 | The advantages of X.25 compared to using modems in the PSTN / telephony network were mainly: |
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| 8 | * the modems were used only on the _last mile_ to the next digital switch / central office, and not end-to-end, rendering higher line quality and hence higher data rates than possible over long/bad analog lines |
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| 9 | * billing was usually done based on traffic, not on duration of a call/session |
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| 11 | FIXME: more background information. Diagrams. |
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| 13 | h2. Community X.25 networks |
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| 15 | h3. Telebahn / x25.org |
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| 17 | * https://x25.org/ |
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| 18 | * https://groups.io/g/x25 |
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| 20 | h3. BAN AI Systems |
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| 22 | * https://ban.ai/x25/ |
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| 23 | * https://github.com/orgs/BAN-AI-X25/repositories |
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| 24 | 2 | laforge | |
| 25 | h3. X.31 - X.25 over ISDN |
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| 27 | The ITU T-REC X.31 specifies two modes of using X.25 over ISDN: |
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| 28 | * using an ISDN B-channel |
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| 29 | * using the ISDN D-channel |
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| 30 | ** this provided up to 9600 bps and was used heavily in Germany e.g. for burgler alarm systems or banking card acceptance terminals in shops, restaurants and the like |
