X.25 Specifications Supported


X.25 Standards
X.25 Line Level Features
X.25 Frame Level Features
X.25 Packet Level Features


  • AT&T compatible interface - Supports the Network Provider Interface (NPI) protocol to the user
  • Full CCITT compliance - Conforms to CCITT X.25 1980, 1984, 1988
  • System administration - Utilities for configuring the software and obtaining statistics and trace information
  • Hardware available from Gcom
Gcom provides protocol solutions to connect legacy systems to TCP/IP networks. Protocols: SNA, X.25, Bisync, Frame Relay, LAPB, LAPD, HDLC, SDLC, and more. Operating systems: Windows, Linux, Unix, Solaris, Solaris Intel, QNX, and more. Hosts: Any TCP/IP/Ethernet-capable host (IBM, Unisys, Tandem, HP mainframes...), PCs, Intel PCs, SPARC or Sun workstations, and more. End-user devices: ATMs, POS, radar terminals, and more.
Streams Model

NPI STREAMS Driver for X.25 Packet Level

  • Implements AT&T NPI Ver. 1.3
  • STREAMS multiplexor driver
  • Compatible with UNIX 5.3 and 5.4, QNX and Linux
  • Network management support
  • Least-cost call routing with retries
  • X.25 packet level facilities supported
  • X.25 virtual circuits can be used as IP interfaces
  • Uses DLPI to interface to frame level below

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DLPI STREAMS Driver for X.25 Frame Level

  • Implements DLPI Ver 2.0.0
  • STREAMS Multiplexor driver
  • Compatible with UNIX 5.3 and 5.4, QNX and Linux
  • Network management support
  • Uses CDI to interface to physical line driver below
  • Supports X.25 LAPB single link and multilink

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CDI STREAMS Driver for Physical Line Driver

  • STREAMS device driver
  • Compatible with UNIX 5.3 and 5.4, QNX and Linux
  • Network management support
  • Drivers for a variety of synchronous boards

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X.25 Standards

  • CCITT X.25 1980, 1984, 1988
  • DDN compatible

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X.25 Line Level Features

  • Maximun frame size
  • Watchdog timer on transmissions
  • Inter-frame delay option
  • Oscillation detection for modem signals
  • Line level may be used directly by user (no frame level)
  • Statistics: CRC errors, underruns, overruns, aborts, number of bytes transmitted/received, others

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X.25 Frame Level Features


  • Frame level window
  • Max frame size
  • T1, T2 and T3 timers supported
  • Retransmission limit (N2)
  • Mod 8/128 sequence numbers
  • Active/passive link setup
  • Use of DISC optional
  • SREJ option
  • Modem signal monitoring
  • Loopback mode for testing
  • Idle RRs optional
  • Trace buffer for frames
  • Frame level may be used directly by user (no packet level)
  • Frame counts by frame type
  • I-fields bytes transmitted/received

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X.25 Packet Level Features

  • All X.25 facilities allowed via registration packets
  • Normal/extended sequence mode
  • Window, packet size negotiated
  • Throughput class negotiated
  • Packet REJ: DTE and DCE
  • Incoming/outgoing calls barred
  • One way logical channels
  • Closed user group
  • Reverse charge acceptance
  • Fast select acceptance
  • Charging Information
  • D-bit support, D-bit modification
  • Local charging prevention
  • Fast select
  • Logical channel range negotiable
  • Diagnostic packet
  • CCITT 1980, 1984, 1988
  • Optional 1988 TOA/NPI addressing using A-bit
  • Default and max packet sizes
  • Default window size
  • Segment size and charging rate parameters
  • Segment size and charging rate parameters
  • Loopback option for testing
  • Restart timer (T20/R20, T10/R10)
  • Call timer (T21, T11)
  • Reset timer (T22/R22, T12/R12)
  • Clear timer (T23/R23, T13/R13)
  • Registration timer (T28/R28)
  • Packet counts by packet type
  • Data byte counts
  • Trace buffer for packets

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