X.25

• First Packet-Switched PSDN Standard

  • Developed in the 1970s
  • Now obsolete
  • But still used, especially in third-world countries and Europe

• Slow: Usually 64 kbps or slower

  • Some faster X.25 services are available

• Reliable, so costs of switches are high

  • So cost of service is high
  • But works even if transmission lines are poor

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