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APANA Sydney Technical Notes for Dedicated Connections

Choosing PPP Software for Analog Modem Dedicated Connections

If your machine runs a Unix-like operating system such as Linux, Solaris, or NetBSD (to name a few), the best choice for PPP software is the freeware PPP package from Paul Mackerras at the Australian National University in Canberra.

There's another archive of this software on the Samba FTP site.

This software has a world-wide user base, and is well-supported in the 'comp.protocols.ppp' Usenet newsgroup.

Other operating systems, such as MS Windows and Mac OS have suitable PPP software packages available, some of which are proprietry and/or supplied by the operating system vendor, and some of which are freeware or shareware.

Choosing a Modem

So whats the difference? The Netcomm Smartmodem's are designed to be reliable. In most case, the cheapies aren't. The Netcomm's are really set and forget modems, they crash less often, almost never lose their NV ram settings and hold onto calls very well. You will pay less to Telstra if you use them. The Smartmodems also have a useful 'dumb' mode, where you set the operating mode you want and flip a switch. Nothing that goes over the serial line can change those settings.

The other main reason for using a Netcomm Smartmodem is that the analog modems at the hub are racks of Netcomm ProRack modems, which are basically the same as stand-alone Netcomm Smartmodems, but in a card-cage format (there are 16 ProRack modem cards per cage) which makes them extremely reliable and easy to service.

A quality modem is worth it. Make everybody's life easier - get a Smartmodem! 8-)

What is the Story with 56k (aka V.90) Modems?

Please see The 56k modem home page, if you require more information.

Can I Take Advantage of Data-over-Voice Calls with ISDN?

Telstra's ISDN Home service provides access to untimed voiceband calls just like a normal analog telephone line, and Telstra also allows the use of the DoV (Data-over-Voice) calls which are treated exactly like voice calls for charging purposes.

Because ISDN Home is a residential services from Telstra's point of view, any voice calls which would be untimed if they were made from a normal analog line instead of using an analog phone connected to an analog port of an NT1+ unit, or an ISDN device configured to make DoV calls that's connected to the Sbus port of an NT1+ unit, are still untimed when made via an ISDN Home service.

The means that if you cannot make untimed calls from a normal phone to our hub at Petersham, you will probably not be able to make untimed data-over-voice calls via an ISDN Home service to the same location. There's nothing that can be done to change that. Time-charged DoV calls attract special long-distance rates which are specified on Telstra's ISDN pricing page.

Choosing ISDN Hardware

There are many vendors you can source equipment from, but there are some types of equipment which are better from the point of view of being fairly easy to source, guaranteed to work reliably, and also are guaranteed to support the key 'feature' of Telstra's ISDN Home service offering - namely Data-over-Voice calls.

Some suitable types of equipment are presented below:

• - Traverse Technologies in Melbourne makes two types of ISDN hardware:
  • - internal native ISDN NetJet cards for PCI-based PC-clone systems running Linux and MS-Windows (from 95 up),
    
  • - external serial-connected NetSpider ISDN terminal adaptors which function just like an analog modem except that they use an ISDN line rather than a PSTN line.

  The selection of internal or external ISDN hardware depends on what you want to do with the machine, and if you need to keep internal PCI slots free, you will need to use an external device anyway.

• - Cisco Systems produce high-quality, low-end ISDN routers suitable for use when you'd like to connect directly to an ethernet network instead of using a serial port or internal card.

  Suitable models to look at are the older, but extremely good, 1003, and models in the 1600 series.

  We can arrange on request the supply of RAM and PCMCIA flash cards to upgrade these models so they can run DoV-capable versions of Cisco's IOS software.

Configuration Settings

Now you have the hardware details sorted out, it's time to configure a few parameters in the software on your machine which will be calling in to the hub and running your PPP link. Exactly how to do it depends on the type of machine and software you will be using.

Full-time links are normally allocated a dedicated 3 bit chunk (or sub-net) of APANA's address space, allowing you to hook up 6 machines behind your modem. Your machines also need to be named, and these names put into the APANA DNS (Domain Name Service). It is prefered that your machine handle its own e-mail, if you are running some Unix varient like Linux, SunOS/Solaris, Net/Free/OpenBSD, etc. this means sendmail,smail or similar. Most Linux distributions install either one of these and appropiately configure it for leaf node use. Under Windows 95/NT take a look at slmail or Post.Office (they have a free 10 user version). There are a few different freeware Mac E-mail MTA's around.

Firewall? What's a Firewall and Why do we Need One?

Why have a firewall at all? The firewall is a traffic saving measure. Its effects on traffic are dramatic. Universal use of a large proxy cache can save nearly 50% of external web traffic. This translates into real savings in scarce external bandwidth.

Trouble-Shooting for Problems with Dedicated IP Connections

If the IP address of the machine you use to call into the hub can be successfully pinged, that means your link is up and working fine, but there might still be problems with the routing table on your machine, or in the proxy settings you've configured into your web client (and perhaps other software).

Remember that the Sydney region has a block on port 80 enforced by our main ISDN router, so when you're connected via a dedicated IP connection to the hub you must use the WWW proxy server setting listed above to access any web pages and other multimedia content using your web client.

If your PPP link is not working after your modem has turned on it's carrier detect LED (meaning it and the modem at the hub have reached agreement about the data rate, etc. to use) check the TCP/IP settings in your PPP and associated networking software to ensure they are correct.

Parameters to check are the authentication type (which should be set to PAP, or CHAP/PAP if your software can support both), domain name server settings, and also the way your software learns about it's allocated IP address, IP netmask, etc.

Most PPP software can be configured manually for TCP/IP settings, or it can be told to automatically set them when the PPP link is first established (ie. they are supplied by the remote machine). Since dedicated IP connections provide up to 6 fixed IP addresses to be allocated to your machines, there is no need to use automatic configuration of the TCP/IP settings, but if you do, ensure the values received by your software are correct.