Westermo ED-20 - Manual (Page 16)

16 6609-2222
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 8.2.
7.1 Application mode
In application mode the ED-20 transfers data between the serial interface (CH1) and the
network interface (10Base-T). 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-, 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 Mbit/100 Mbit maximum theoretical throughput,
whereas an analogue modem operates at speeds up to 56 kbit.
PPP is 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 or 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 interface
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’
7.1.2.2 PPP Network interface
The PPP connection can be established over PSTN, Leased Line or private lines.
ED-20 can act as a PPP Server, PPP Client or both.These functions is set on the ‘Modem
settings’ tab in ED-Tool for ED-20. See application example in chapter 9.
* The IP address must be compliant to the attached network. Ask the network administrator when in doubt.