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Computing and Networking FAQ


5. DIALIN ACCESS, SLIP/PPP, MODEMS


Note : This FAQ was written before the UQnet web pages were developed. Most of the information in this section can now also be found in the Modem Bank pages [URL : http://www.uq.edu.au/pcc/services/uqnet/modem.html ]

[5.1] How much dialin access time do I get?

Historically, we used to impose a 25 hr per week quota, but currently the situation is that users may exceed this limit as long as the banks are not congested. Rather than having a rigid quota, by default, users now have a "threshold" number of hours per week. The threshold number is subject to change, and varies according to the category of user (contact Client Service for more information). Apart from the peak period of 9pm - midnight, during which time EVERYBODY has a 90 minute limit to the length of time they can stay connected, as long as you are within your allotted threshold, you will not be disconnected. If, however, you have exceeded your threshold, and the banks are defined as being "congested", then you may be disconnected.

As Mark Williams [MIW] explains : Prentice has instituted a system which attempts to ration out modem time fairly. When the modem banks are congested (i.e. when there are fewer than about 6 lines free), the system searches for the people who have used the most time and disconnects them from the system until the banks are no longer congested. If, however, you have not used your "threshold" of hours in the previous 7 days, you will not be disconnected by the system. The exception to this rule is if you are connected at a time when there is a limit to the length of time when you can login, in which case you will be disconnected if your current login has lasted longer than this limit. (Currently, logins are restricted to 90 minutes in length between 9pm and midnight.)

Users can find out their threshold and time remaining (before disconnection may occur) via the "quota" command on the Annex servers, or via the "mquota" command on dingo and student. Sample output from such a session is as follows.


	[4-v1] annex: quota
	Trying...
	Connected to 130.102.2.19.
	Escape character is '^]'.
	
               Prentice Modem Connect Time Threshold Database
	
               This allows you to find out your weekly connection time 
               threshold and how much time you have remaining.
	
	Username: s123456
	Time remaining: 15 hours, 3 minutes, 54 seconds
	Threshold: 25 hours
	CLI: Connection closed.
	[4-v1] annex: 
Users can also check the amount of time they have accrued via an interactive form on the UQNet Connection Time web page ( http://www.uq.edu.au/pcc/services/uqnet/mquota/ ).

[5.2] How are the threshold balance and 90 min peak time limits calculated?

A week is not a fixed 7 day period, and does not begin or end on any particular day. Instead, it should be thought of as a sliding 7 day access "window". Each day, you are entitled to connect for a period of time that is calculated by subtracting the total time you were connected in the preceding 6 days from your allotted weekly "threshold". If you exceed this entitlement, you could get disconnected, but only if the modem bank is congested at the time.

For example, suppose you have a weekly threshold of 10 hours per week, and that you wish to dial in on a Wednesday given that in the preceding 6 days (ie. Thu, Fri, Sat, Sun, Mon, Tue) you were connected for a total of 7 hours. This means you can dialin, and expect to be connected on Wednesday for a total of at least 3 hours. The next day, the balance of your quota is calculated afresh as before, but this time looking at the total time you were connected during the 6 day period Fri,..,Wed.

The 90 minute peak time limit is enforced from 9 pm onwards. Note that if you are already connected when 9 pm comes around, the time used up by this connection will be included in the 90 minute limit. This means, for example, that if you dialin at 8:00 pm, if you are still online at 9:30 pm you will be disconnected immediately.

[5.3] At what times are the modem banks uncongested so I won't get disconnected for exceeding my threshold?

If you wish to use more than your "threshold" number of hours per week, you can connect to the modem banks at times when the banks are uncongested. There are no times when the banks are guaranteed to be uncongested, but it is unusual for all the lines to be all used up between midnight and 4pm on non-vacation workdays and between midnight and 9:30am on days when there are no University classes. [MIW]

[5.4] Can I get a larger threshold?

Yes, but it costs money. When you pay to have your threshold extended, you also gain access to a modem bank that is reserved for paying customers only. Contact the Client Service counter on 3365-4400 or send email to help@cc.uq.edu.au for details. [MIW]

[5.5] Which dialup communications package do you recommend?

This is only for non SLIP/PPP modem communications (see [5.6] for SLIP/PPP software), but even if you use SLIP/PPP it's worth having a good comms program for modem troubleshooting and an "if all else fails" method of dialling in. If you bought a new modem recently (ie. in the last 2 years or so) chances are that the software supplied with your modem is quite satisfactory. Otherwise you could download one of the following.

PC

Mac

[5.6] What is SLIP [PPP] and do I need it?

SLIP and PPP are protocols for handling TCP/IP communications over modem and serial lines. SLIP stands for Serial Line Internet Protocol, and PPP stands for Point to Point Protocol.

You need SLIP or PPP if you wish to run TCP/IP applications directly on your PC or Mac [rather than on a remote host] when connected to the UQ network via a modem or serial connection. Your PC/Mac will have its own IP address, and for all intents and purposes behaves just like any Internet host computer which is connected directly to the campus ethernet backbone.

For example, with SLIP/PPP you can run Netscape or some other graphical web browser, and transfer files to and from remote hosts by running an ftp client program on your computer instead of having to send and receive via another host [eg. student, dingo]. Rather than having to open a telnet session and login to your mail server to access email, you can run a POP mail client (eg. Eudora) which handles all message transmissions to/from your mail server for you. Note, however, that use of graphically oriented TCP/IP applications via SLIP/PPP requires a fast modem [at least 9600 bps], although the Annexes are not programmed to bar SLIP/PPP communications with slower modems.

With SLIP [PPP], you dial in to one of the UQ modem banks, login to the Annex server by entering a username and password, and then start a SLIP [PPP] session by issuing the "slip" [or "ppp"] command. From this point on, the SLIP/PPP software runs "in the background", managing all modem communications for your main "foreground" TCP/IP applications.

The alternative to SLIP or PPP is to dialin with a standard modem communications program (eg. Procomm, Telix, QModem, ZTerm, QuickLink, Cooee) and open a telnet session on student, dingo, or some other campus host. Email access is via pine or some other mail program that runs on the campus host. Similarly you can only browse the web, use ftp, etc.. by running programs on the campus host to which you are connected.

The biggest advantage of SLIP/PPP is that it gives you access to a huge range of modern, graphically oriented, TCP/IP applications. In addition, using a multi-tasking operating system such as Windows, Mac OS, or OS/2, you can run a number of TCP/IP applications simultaneously. This makes it possible, for example, to browse the web while an ftp program is downloading files in the background, and your mail program is checking for messages at regular interals.

For more information on SLIP/PPP refer to other questions in this FAQ and Prentice Factsheet 32 [SLIP Information].
[URL : http://www.uq.edu.au/pcc-factsheets/factsheet-32.html]

[5.7] What software do I need for SLIP [PPP] and where can I get it?

For Windows 3.x we recommend Trumpet Winsock, which comprises a TCP manager with support for SLIP and PPP dialup connections. For Macs we recommend InterSLIP, a SLIP modem communications manager. This software is available from the Technology Shop on $10 "SLIP Shareware for Mac/Windows" disks. Mac users should note that InterSLIP requires MacTCP, which is bundled with System 7 and later versions of Mac OS. MacTCP is also included on a $40 "commercial version" of the InterSLIP shareware disk.

The disks also include the Netscape 1.1N web browser, a telnet application, and installation instructions. In addition, the Windows disk comes with a one-step installation and setup program.

Trumpet and InterSLIP are shareware products, and can also be obtained from a number of ftp archives on the Internet, including ftp.uq.edu.au. Responsibility for registration of these products rests with the user.

Windows 95 includes the Microsoft Dial-up Networking suite, which provides support for PPP and TCP/IP connections. Although it is possible to use Trumpet with Win 95, this is not recommended - see [5.13] for details.

There are also a number of commercial packages on the market (eg. Internet in a Box). These generally include a SLIP/PPP dialler & TCP/IP communications manager, a web browser, ftp and email clients, and other TCP/IP applications. It is reasonably straightforward to adapt these packages for the UQ modem and network environment.

Refer to other questions and sections in this FAQ for SLIP/PPP and TCP/IP configuration details.

[5.8] Why don't I get a warning message when I am disconnected because I have exceeded my quota or used up my 90 min peak time limit?

It is tempting to say simply that it is the responsibility of all users to keep track of how much connection time they have used up. Remaining time can be established at the start of each session by entering the "quota" command from the "Annex:" prompt, or at any time thereafter by telnetting to "dingo" or "student" and giving the "mquota" command. Alternatively, this function is available via an interactive form on the UQNet Connection Time web page ( http://www.uq.edu.au/pcc/services/uqnet/mquota/ ). Nevertheless, we do have some sympathy for clients who are abruptly disconnected, especially since it is always difficult to estimate in advance how long file transfers or other tranmsissions are likely to take.

Although it would be nice if it were possible to have some kind of reliable advance warning system, unfortunately it is not quite as simple as one might think. A message is in fact sent if you have an Annex CLI session active - ie. you can see the "Annex:" prompt, and the Annex server is waiting for you to enter a command. This is rarely of use, however, since you will probably be in the middle of a SLIP/PPP or a telnet session when you run out of time.

The first problem is that there is no way to send an unsolicited warning message to someone running a SLIP/PPP session. SLIP/PPP software works in the background as a manager of TCP transmissions. TCP managers - eg. Trumpet TCPMAN - establish communications channels or "ports" between applications running on the local and remote hosts, and transmit information between them. Essentially, they can only pass data on to applications that are waiting for it. Unfortunately (or fortunately, depending on your point of view), the Annex servers have no way of knowing which applications are running on your PC. Furthermore, TCP managers have no way of handling unsolicited messages that are not designated as belonging to a particular port or active application.

Secondly, even for Annex telnet sessions, there is no guaranteed way to send messages without possibly creating many new complaints and problems. If the Annex server were to simply send a character stream to your modem & PC, it could cause disruptions, and may not be displayed in any case. For example, if you were in the middle of a zmodem file transfer to your PC, incoming data would be interpreted as part of the transfer. At best, the comms program would treat the data as garbage and throw it away. At worst, the data could confuse the program so much that it may crash.

One way of dealing with this problem under SLIP/PPP would be to have a TCP/IP application running on your PC that could communicate with an accounting daemon running on an Annex server. It could run in the background during SLIP/PPP sessions, perhaps regularly updating a display of your remaining connection time. Currently, however, there is no such program, though it is something we may wish to consider developing in the future if this continues to be a frequent question/complaint.

[5.9] Do the UQ modem banks support PPP as well as SLIP?

Yes.

[5.10] Which is better - SLIP or PPP?

Depends on the criteria used for comparison. In terms of performance, there is little real difference, with PPP being slightly more reliable at the expense of some small, additional overheads. In terms of standards, PPP is more of an "official Internet" standard than SLIP. Nevertheless, SLIP is well supported within client software (eg. Trumpet Winsock, Novell LAN Workplace for DOS, Mac InterSLIP) and modem bank server software (eg. the UQ Annexes). For Windows '95 Dial-up Networking, however, there is no choice - only PPP support is "built-in". For our own support/maintenance reasons, we recommend that Trumpet Winsock clients use SLIP, and that Macintosh clients use InterSLIP in preference to MacPPP.

[5.11] How do I configure Trumpet Winsock?

From Windows, run the TCPMAN.EXE application. From the File menu, choose Setup. Configure as follows.

         IP address : Your IP address, of form 130.102.x.y
         Net mask   : 255.255.255.0
         Nameserver : 130.102.2.15  130.102.128.43
         Gateway    : 0.0.0.0 
         Domain     : slip.cc.uq.oz.au
         MTU        : 552
         MSS        : 512
         TCP RWIN   : 2048
         SLIP port  : 1,2,3 or 4, depending on your communications
                      card.
         Baud rate : 19200, 38400, or 57600 (see note below).
         Hardware handshaking : see below
         CSLIP compression : unchecked (if checked, set MSS to less than 255)

The other parameters are either not used or aren't critical, and should be left at their defaults.

Notes :

  1. To change the value in the "Gateway" field you will need to make sure the SLIP and PPP checkboxes are unchecked. Trumpet should use the default gateway if this is set to 0.0.0.0, and we suggest leaving it at this setting. After changing the gateway field, check the SLIP box or the PPP box, depending on which protocol you wish to use. We recommend using SLIP in the interests of simplifying maintenance, and since there are a number of login scripts in circulation that are not configured to use PPP.

  2. The IP address field will be filled in for you if you use one of the "official" UQ login scripts, so this can be left at 0.0.0.0.

  3. The nameserver field should contain BOTH of the ip addresses given above (separated by a space). Note that this is a scrollable text entry box, so you can only see both entries by scrolling with the cursor arrow keys.

  4. Values for MTU, MSS and TCP RWIN should be assigned as follows. MTU should be divisible by 8, and should be between 216 and 1024. MTU = MSS + 40. TCP RWIN should be a multiple of MTU, typically 2 to 4 times its value.

  5. Hardware handshaking should be on for high-speed modems (9600 baud or higher)

  6. Baud rate refers to the speed at which your computer communicates with your modem. It must be higher than the maximum connection speed supported by the modem. For 9600 baud or slower modems, it should be set to 19200. For 14.4K modems, set it to 38400. For 28.8K modems, set it to 57600.

  7. If using a 28.8K external modem, you will need a 16550 UART in your comms card. If using Windows 3.1, also note that ALL 28.8K modems require a replacement for comm.drv, the Windows communications driver. This is provided with some modems - for example, the setup program for QuickLink II that ships with Banksia fast modems installs rhsicomm.drv, the Rockwell chipset comms driver, in place of comm.drv. To check which driver you are using, look in the [boot] section of system.ini, and see if you have the line
       comm.drv=comm.drv
    If so, you should obtain the Cybercom shareware comms driver for Windows 3.1
    [ URL ftp://ftp.uq.edu.au/pub/windows/net/cybercom.zip ]

    Note that a replacement driver is only necessary with Windows 3.1, NOT Win 3.11 or Win 95. Follow the instructions in the readme file included in the cybercom zip file. Installation is simple, and only requires copying cybercom.drv to the windows\system directory, changing the line in the [boot] section to comm.crv=cybercom.drv, and adding a COMnFIFO=1 line to the [386Enh] section in system.ini (where n is the number of the com port your modem is using).

For an excellent guide to setting up Trumpet Winsock and SLIP/PPP in general, refer to Cosmic's SLIP/PPP FAQ
[URL : http://www.uq.edu.au/~zzcprows/slip-ppp.html ]

[5.12] Where can I get a Trumpet login script for the UQ modem banks?

ftp://ftp.uq.edu.au/pub/windows/net/Winsock/login.cmd

The script is also included in Appendix 1 of this FAQ. Note that this script assumes that your modem initialization string is stored in the trumpwsk.ini file in a variable called $modeminit. At the bottom of the trumpwsk.ini, you should have a section titled [default vars], something like the following.

    [default vars]
    $modeminit="&f\n5%c1 &d0 S10=100 S30=255"
If you installed Trumpet from the Prentice SLIP Shareware for Windows disk, there may be other data in this section. In any case, make sure that $modeminit contains the correct initialization string for your modem.

[5.13] Can I use Trumpet Winsock with Windows 95?

Yes. Note, however, that Win95 PPP/Dial-up Networking installs the Microsoft winsock.dll, so you will have problems if you try to use Trumpet as well as Win95 PPP. It is usually not a good idea to have multiple winsock.dll files installed, but as long as you know what you are doing, problems can be avoided. Win95 setup installs the Microsoft winsock.dll in the windows\system directory, but as long as you don't try to store the Trumpet files there, or in the \windows directory, Trumpet should work. Note that once you run Trumpet TCPMAN, the Trumpet winsock is loaded, so attempts to use Win95 Dial-up Networking will fail (and vice-versa) until you restart Win95.

[5.14a] How do I configure Windows '95 PPP dial-up networking?

For instructions, refer to the Modem Bank Windows 95 Support page [URL : http://www.uq.edu.au/pcc/services/uqnet/os/win95/index.html ], or Sen Hwei CHAN's excellent Setting up Windows 95 PPP web page [ URL : http://student.uq.edu.au:80/~s320367/win95ppp.html ].

[5.14b] Where can I find a dial-up/login script for Windows '95 PPP?

Refer to Appendix 1 for Xiang Du's Win 95 script that uses the Microsoft Plus Dialup Networking Scripting Tool/Manager (available with Microsoft Plus). More information is also available via the UQ Modem Bank Windows 95 Support pages [URL : http://www.uq.edu.au/pcc/services/uqnet/os/win95/scripts/index.html ]

There is also a shareware dialup networking script manager called "RoboDun" available from the dingo ftp archive
[ ftp://ftp.uq.edu.au/pub/windows/win95/internet/robodun6.zip ].
Download the zip file to a new subdirectory, unzip, and view the readme file. The program is installed via Control Panel's "Add Program", and associates (initially blank) scripts with each existing connection in the Dialup Networking group. To add or edit scripts, you run the RoboDun script manager. A sample script for UQ dialin is included in Appendix 1.

[5.15] How do I configure InterSLIP or MacPPP for dial-up networking?

For MacPPP and InterSLIP, you also need MacTCP. In both cases, open the MacTCP Control Panel, and make sure the InterSLIP or MacPPP icon is selected (depending on which you are using). Then click the "More..." button, and enter the following settings.

InterSLIP

Check that the InterSLIP Folder is in the Preferences folder (in the System folder). Within InterSLIP, create a new connection for each modem bank. For each of these, all of the configurable items will be the same, apart from the phone number. Most items are fairly self explanatory. You can use the standard InterSLIP redial script, but the gateway script must be customized for UQ. Refer to Appendix 1 for a sample script.

MacPPP

In the Config PPP dialogue window, use the following settings : Make sure you have a PPP Server entry for each Annex server (use the "New.." button if necessary). Name them Annex1, Annex2, etc.., or by the phone numbers for ease of reference.

Each of the PPP Servers should have the following settings (entered by click the New button, or the Config button to change settings).

Each PPP Server must also have a Connect Script. This is set up via the Connect Script button as follows.
          Wait timeout : 40 seconds

          Radio Button            Text Box Contents         CR check
          -------------------------------------------------------------
             Wait                   username:                 
             Out                    your Annex username        X
             Wait                   password:           
             Out                    your Annex password        X
             Wait                   annex          
             Out                    ppp                        X

[5.16] What are "comms overrun" errors, and how can I prevent them?

Refer to the Navas 28800 Modem FAQ [URL : http://web.aimnet.com/~jnavas/modem/faq.html ].

[5.17] I can dial in and establish a SLIP/PPP session ok, but Netscape and other TCP/IP applications (eg. telnet, Eudora) won't work. What's wrong?

This usually means there is a problem with your TCP/IP setup. The critical fields to check are IP address, gateway and (DNS) nameservers. Note that most SLIP/PPP dialler software is capable of obtaining your IP address from the Annex server, but this may not be implemented in your login script, or if you perform a "manual login". Therefore it's always a good idea to make sure the "IP address" field is correct in your TCP/IP setup. For details on TCP/IP setups for SLIP/PPP, refer to other questions in this section.

[5.18] Do I really need a high speed modem?

"High speed" is defined here as 14.4K baud or higher. If you intend to use SLIP/PPP, the answer is definitely YES. 9600 baud modems can provide good functionality for telnet and email, but are painfully slow for browsing the web or transferring large files. Likewise, slower modems can still be useful for basic communications (telnet, email), and can be picked up for a song in secondhand shops and in the Trading Post.

Obviously though, when it comes to modems, faster is usually better, so if you can afford it, buy a 28.8K V.34 modem. UQ has one modem bank that supports the alternative 28.8K V.FAST "standard", but the problem with V.FAST is that it's not really a standard. Different modem manufacturers provide different implementations, some of which are incompatible with the UQ V.FAST (Rockwell based) bank. This does not mean, however, that your V.FAST modem may be unuseable at UQ, but simply that our modem banks may not always be able to deal with your modem's communication protocols. In practice, this means that some V.FAST modems can only connect to UQ at speeds up to 14.K baud. The moral of this story is that unless you intend to buy a 28.8K V.34 modem, you should consider saving a few dollars and buying a 14.4K modem instead.

There is also an argument for selecting 14.4K on grounds other than price anyway. The argument goes like this. With a good 14.4K modem (eg. Banksia) you can always force a reliable 14.4K connection regardless of which bank you dial, and there is usually no need to mess around with complex initialization strings. 28.8K modem protocols, however, are necessarily more complex, and this makes troubleshooting and support more difficult, and increases the likelihood of connection problems. Line quality becomes a much more important issue, and in practice it is commonplace to only achieve connection speeds of around 20K baud anyway. In addition, the limiting factor for data throughput is very often not connection speed, but volume of network traffic. Even with reliable 26000 baud connections, much time is spent downloading data from remote hosts at rates of below 1K cps, which would be achievable even with a 9600 baud modem.

[5.19] Which modem should I buy?

We recommend Banksia, Netcomm, or Avtek. These brands are all supplied by the University Technology Shop, and supported by Prentice.

[5.20] Why do I keep losing my dialin connection, or why does my modem keep "dropping carrier"?

Possible causes include :-
Possible solutions :-

[5.21] Why can I only get a 20-26K bps connection even though I have a 28.8K modem?

This is a line quality issue. V.FC/V.34 modems negotiate with each other, and theoretically agree on the maximum line speed sustainable under the given line conditions. 28800 bps connections are fairly rare, with line speeds of 26400, 24000, or 21600 bps being more the norm.

[5.22] What is the best initialization string to use for my modem?

Refer to the Prentice Network Services web page http://www.uq.oz.au/pcc/services/modems/modem-index.html for a list of modems and initialization strings.

[5.23] Where can I find more information on troubleshooting modem and dialup communications problems?

One of the best references is the Navas 28800 Modem FAQ [URL : http://web.aimnet.com/~jnavas/modem/faq.html ].

UQ dialin clients can also attend one of the Prentice Centre "SLIP clinics", held in Room 529, Prentice Centre, on Mon, Wed, Fri (1pm - 3pm) and Sat (10am - 12noon). Bring your modem manual and modem if possible, and your notebook computer if you have one.

[5.24] How can I access the Library CD-ROM databases from home?

You need to dial in over SLIP/PPP, and run an erl client on your Mac or PC. The erl (Electronic Reference Library) software can be downloaded from the Library ftp server mercury.library.uq.edu.au (see the subdirectory /software/erl-clients).

Your erlclnt.cfg file should be as follows (the cfg file supplied with some of the library archives is incorrect).

       /* Your ERL Server's server_addr1 line
       /* server_addr1 = /2/your_server_name_or_IP_address_here/416

       server_addr1 = /2/mercury.library.uq.oz.au/416
       server_type1 = 3
       server_addr2 = /2/saturn.library.uq.oz.au/416
       server_type2 = 3
Note that the erl client software allows you to access the Library's Silverplatter databases over TCP/IP from any computer in the UQ domain. Not all CD-ROM databases are in Silverplatter format, however. Some CD-ROMs are mounted only on Library Netware file servers. Currently there is no way to access these from home. For a complete list of available Silverplatter CD-ROMs, as well as more detailed instructions on how to obtain and setup the erl software, refer to the Library web page [URL http://www.library.uq.edu.au/library.uq/database/access.html].

[5.25]Where can I find a PPP script for Linux?

Refer to Appendix 1 for Robert Brockway's PPP script for linux.
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Document last revised : 3 Jun 1997 [MM]