3、 Wide area communication network

Wan communication foundation

PSTN(public switched telephone network) Public switched telephone network 56K

DTE (data terminal equipment) Data terminal equipment ：PC/ Telephone

DCE (data circuit equipment) Data circuit equipment ： modems /modem

mechanical properties ：RS-232-C  25 The needle D Type connector /9 Pin serial interface

notes ： Router console The port is connected to the computer serial port , Router SFP The interface is connected to the WAN through optical fiber

Electrical characteristics ：RS-232-C  V.28 circuit 20kb/s 15m LAN

features ：RS-232-C  V.24 standard

Traffic and error control

flow control X.25、TCP

Stop waiting for the agreement TFA = 2Tp + Tf

Sliding window protocol

Error control   Error detection code ：CRC   Error correction code ： Haiming code

Stop waiting ARQ agreement

Select retransmission reply frame  SREJ

back off N Frame reply frame   REJ

HDLC (High Level Data Link Control) Advanced data link control

oriented position / The bit Of Data link layer Control agreement / Sync Link control protocol

Before and after 8 position Frame delimiter 01111110

X.25 Frame relay

X.25 Public data network The physical layer , The link layer , Group layer

Connection oriented , Virtual link

Error control and flow control 64kbps

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Frame relay FR Connection oriented

 

ISDN Integrated digital service network replace PSTN

Narrowband ISDN

BRI Interface  144kbps

PRI Interface   2.048M

Broadband ISDN (ATM) Connection oriented Virtual link

Cell exchange 53 byte

150M