Digicom ED-20 PPP Functional description, Application mode, About PPP, Network interfaces

7. Functional description

The ED-20 can be in either configuration mode or in application mode. Normally the ED-20 is in application mode, where the serial-to-network data transfer is enabled and all configuration settings are readable.

Change of configuration parameters are done in ED-20 configuration mode. Configurable

parameters are listed in chapter 6.3.

7.1 Application mode

In application mode the ED-20 transfers data between the serial interface (CH1) and the network interface (10BaseT). At the network interface data is transferred using the TCP/IP protocol suit. At the serial interface data is transferred using PPP.

7.1.1 About PPP

PPP(the Point to Point Protocol) is a mechanism for creating and running TCP/IP over a serial link – a direct serial connection or a link made using one of following: Westermo analogue PSTN-, Leased-line-, ISDN-, GSM-, Radio-, Fibre- or Short-haul modem.

Other computers can connect via the ED-20 and communicate over the PPP link using FTP,Telnet,Web, etc. in the same manner as with an Ethernet TCP/IP link. One major difference between a PPP and an Ethernet connection is of course the speed. A standard Ethernet connection operates at 10 Mbs maximum theoretical throughput, whereas an analogue modem operates at speeds up to 56 kbps.

PPPis strictly a peer to peer protocol; there is no difference between the machine that dials in and the machine that is dialed into. However, it is still useful to think in terms of servers and clients.When you dial into a site to establish a PPP connection, you are a considered the client.The machine to which you connect is considered the server. Authentication is provided with the protocols PAP and CHAP.

7.1.2 Network interfaces

ED-20 has two network interfaces, Ethernet and PPP, so the unit can forward IP-packets between these interfaces.

7.1.2.1 Ethernet connection

This interface is a part of the local network and the ‘Local IP Address’* and ‘Subnet Mask’ must be set to the right ‘Network ID’

*The IP address must be compliant to the attached network. Ask the network administrator when in doubt.

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