Specifications

Niagara Release 2.3
Revised: May 22, 2002 Niagara Networking & Connectivity Guide
Chapter 5 Connecting to an ISP
Niagara Considerations
5–6
With direct dial, there is a restriction in simultaneous user- and application-initiated
data passing. If one host makes an application-initiated call, it cannot also send
user-initiated data. Nor can one host make an application connection and receive
user-connection data. With an ISP connected host, there is no restriction. Hosts can
simultaneously pass data, of any type, just as when on a LAN/WAN.
Design Considerations
You should note the following things about connecting Niagara hosts to an ISP:
• Connection to and from a host dialing an ISP will be slower than connection
on a LAN /WAN.
• If the JACEs will be sending little data (archives and alarms) connecting (even
long distance) with direct dial may be cheaper than the monthly fees for the ISP
and the DDNS provider. However, dial-up has some limitations (see the
“About Dialing between Niagara Hosts” section on page 4-3).
• Many IT departments prohibit setting up Internet connections on hosts
attached to their network. This is considered by many departments to be a
network security violation. Therefore, it is advisable to check with them before
implementing the connection.
• Interstation links were designed to be used across connections that are always
available.
Due to the unreliable nature of connecting to and passing
data on the Internet, we do not recommend using interstation links to
or from hosts connecting through an ISP.
Unlike direct dial, however,
nothing prevents you from setting up the link because hosts are not identified
in the station address book as dial-up hosts.
Because interstation links are not available, if you require BUI access to
remote hosts you must license WebUI services on each remote JACE.
• DDNS is not supported on a JACE-4/5 when connected to an ISP via its
Ethernet port (cable or DSL modem).
• TZO is the only DDNS provider supported on the JACE-4/5 platform. With
other platforms you can use any DDNS provider that provides a client for the
platform.
• You should plan to test functionality when connecting Windows-based hosts,
or connecting any Niagara host via cable or DSL modems as these connections
have not been tested by Systems Engineering.
• If NAT is used to assign a private IP address to our equipment you may not also
be able to use DDNS. See the “Additional Scenarios” section on page 5-3.
• Connecting hosts to the Internet with a public IP address makes them more
vulnerable to attack than connecting them via dial-up or connecting them on a
private LAN/WAN. This is especially true of any host that stays connected to
the Internet virtually full time (as we require of our ISP-connected hosts). For
more information, see the “Security Considerations” section on page 6-1.
• There are limitations with using our equipment with a firewall. See “Using a
Firewall or Proxy Device,” page 6-4.