Interphase iSPAN, Руководство пользователя

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D
iSPAN Serial WAN Adapter Users Guide
185
D Protocols Overview
This appendix provides a short overview of the following
protocols used by the
i SPAN
-Serial WAN adapter:
• X.25
• Frame Relay
• Point-to-point
For detailed information, refer to relevant network protocol
documentation.
X.25 Protocol
X.25 packet switched networks allow remote devices to
communicate across high-speed digital links without the
expense of individual leased lines. Packet switching is a
technique whereby the network routes individual packets of
HDLC data between different destinations based on
addressing within each packet. The X.25 protocol
encompasses the first three layers of the OSI 7-layered
architecture defined by the International Standards
Organization (ISO).
Layer 1: Physical Layer
The Physical Layer is concerned with electrical or signaling. It
includes several standards such as V35, RS232, and X.21.