9 Apr 1995
For the PC to access the Internet over SLIP or PPP, it must first
In a small number of cases, the communications controller will be configured to use only PPP protocol and to exchange Userid, Password, and configuration information automatically. In this case, nothing further is required. Otherwise, there are several possible sequences:
The PC may then have to scan the remaining messages from the controller to extract IP addresses.
In addition, the user may have to supply information provided by the network administrator, including a subnet mask and gateway address. It is also important to define a name server, news server, mail server, and other important service machines.
To supply this information in a way that allows several different people to dial the same network from the same machine, or to allow one person to dial any of several different networks, Warp supplies the "Dial Other Internet Providers" program (actually a module named SLIPPM.EXE).
The main panel of SLIPPM provides lots of useful information. In the middle there is provision for a list of "phonebook entries" for different networks. Two are listed here, Yale and Another. A new line is added by clicking the Add Entry icon and filling in information. Select and entry and click the phone icon to dial the phone. Messages during the initial connection appear in the scrollable box at the bottom. While connected, the window shows the elapsed time of the current connection, and the total time online since the counter was last reset. This allows a user to control cost when the network provider charges by connect time. There is even a nice little box to click when dialing out requires a "9" prefix from the current phone. Clicking the Add or Modify icons brings up a notebook of configuration settings for one of the providers.
The first page of the notebook provides the essential information for this provider. It is given a name "Yale", a phone number, and a Userid and Password is supplied. The user selects either the SLIP or PPP protocol. There is an inactivity timer that will hang up the phone if no data has been transferred for a number of minutes. This eliminates the threat of racking up connect time charges with a commercial Internet vendor if you are unexpectedly called away from your computer.
The Login Sequence in the middle is the most important and most complicated field in the configuration. Note that there is Help for the configuration, so if you have trouble filling out this field, hit F1 or the Help button for more details.
In a few cases, someone will dial a phone number which is dedicated to PPP access. Since most of the configuration can be handled automatically, it may not be necessary to use a Login Sequence.
In other cases, a user will dial a phone that is often busy. The user will want the system to wait a few minutes, then retry the number until it answers. To provide this level of support, one must supply a REXX program to control the line.
Most users will confront a Communications Controller that will prompt in some order for Userid, Password, and the SLIP or PPP command. It will then supply address information. The exact sequence varies from vendor to vendor. For example, some controllers ask for "Username", some for "Userid", and some use other words for the same thing.
The Login Sequence shown above provides an example of the most common sequence. The user supplies a set of lines that alternate between output expected from the Communications Control and input that should be supplied by the PC. Special variables are defined in as "[VARIABLE]". IBM provides one example for the ANNEX (visible) communications controller.
\r
sername:
[LOGINID]
ssword:
[PASSWORD]
annex:
slip
address\sis\s[$IPDEST]\sYour\saddress\sis\[$IPADDR]
The first line is sent from the PC to the Communications Controller after the modem has connected. The special value "\r" asks for the PC to send a Carriage Return. The Controller prompts for "Username" or "username". The script leaves off the first letter and therefore doesn't care if it is capitalized or not. The script now responds with the string configured in the "LOGIN ID" field in the configuration panel. The Controller then prompts for password and the PC supplies the value typed into the password field. The Controller then generates a command prompt ending in "annex:". The PC responds with the command "slip". The Controller types out a line of the form:
Annex address is 130.132.57.20. Your address is 130.132.57.27.
The last line of the script matches this output. The special sequence "\s" matches one or more blanks. The first address "130.132.57.20" is stored as variable $IPDEST which becomes the address that the PC will use for the Gateway. The second address "130.132.57.27" is stored as $IPADDR and becomes the IP address that the PC will assign itself.
Now consider another script used to connect to a Cisco Controller:
[LOGINID]
word:
[PASSWORD]
>
SLIP
IP\saddress\sis\s[$IPADDR]
This particular system doesn't require a starting Carriage return from the remote user, but the IBM script requires the PC to speak first. The Cisco allows the user to typeahead, and will take whatever is sent in as the answer to the first question, so this script sends the userid initially in response to a question that has not yet been asked and then waits for the second prompt for "Password:". Note also that the Cisco controller is one of the "invisible" type and only sends out the address that the PC should adopt. The user needs to obtain information about the Gateway address from the network administrator and enter it in the supplied field of the next panel.
In either of these examples, the "SLIP" command can be replaced by "PPP" and the Connection Type button on the configuration panel can be switched to PPP. Once PPP is selected, the last line of the script is not needed, because PPP will obtain the address information at the protocol level. However, the line can be left in if the user expects to switch between SLIP and PPP frequently.
The second page of the configuration notebook allows the user to enter basic network information. These values would be supplied by the network administrator of the network into which you are dialing.
The field Your IP Address can be filled in when a user dials a dedicated phone number and is always assigned the same address each time a connection is made. The Destination IP Address is filled in with the address of the Gateway ("invisible" controller) or of the Communications Controller ("visible" controller). The Netmask indicates the part of the IP address that defines individual workstations and the part that defines the remote network. The MTU is the maximum size of data packets that can be exchanged over the link.
VJ Compression triggers a special algorithm that reduces the size of TCPIP packet headers dramatically. Most Communications Controllers support VJ compression, but they are often configured to remain passive. When they seen the PC sending a compressed header, then they respond by sending compressed headers back. If you know that VJ compression is possible, then it is best to force the issue by checking the box.
Domain Name Servers are used in most large organizations. They are configured with the name and IP address assigned to all of the local machines. They also provide access by local machines to the other name servers on the network. When a Web browser wants to connect to "pclt.cis.yale.edu" it will first send a message to the machine configured as the local name server. That machine uses the "yale.edu" part to contact the name server at yale to locate information on the PCLT server. It passes back an IP address that can be used to send a request to the PCLT server.
Fill in the field named "Your Host Name" with anything. Machines on the LAN have a name when they act as servers. Each dial-in line often is assigned an arbitrary name by the name server, which the dial-in user normally doesn't need to know. The field "Your Domain Name" provides a default suffix that is added to any Internet name that doesn't have any periods. As configured here, the OS/2 command "ftp fred" will be treated as a reference to "fred.cis.yale.edu".
The News Server name identifies a Network News Transfer Protocol (NNTP) server that will be used by the News Reader utility to fetch news. The name configured here works within the Yale environment but will not support requests from outside. Find your own news server.
The Gopher Server identifies a "Home" machine to which the Gopher client program will send its first query when it starts up. YALEINFO is the campus information and bulletin board system.
The WWW server field is not very helpful. To start a Web browser, one needs a URL. Configure the "home page" in Web Explorer after it starts up.
The Mail Server information is supposed to provide a starting configuration for the Ultimail Lite package. It identifies a Post Office Protocol (POP) server that receives mail on your behalf. When requested, Ultimail contacts this server to fetch any new mail. Mail sent by Ultimail or by the News Reader goes out through this server.
The mail configuration is rather complicated. In Ultimail itself there are six panels of parameters to establish a signature field at the end of each mail item, to annotate mail quoted during a reply, and handle other special features. Information provided here many not be successfully transferred. It is best to start Ultimail and check all the settings there directly.
In this example, the mail client contacts a machine named "minerva.cis.yale.edu". It supplies the userid "gilbert" and a password not shown. This would be the same userid and password that I would use to logon to that particular Unix host. Instead of logging on, the POP server uses the userid and password to retrieve any mail received by that host and to send it to my PC.
This is not, however, what appears to be happening in the Reply fields. The two reply fields suggest that return mail should be sent to "Howard.Gilbert@yale.edu". This is a convention adopted by the University to save reprinting business cards every time machines change. No matter how the network is configured, there will be a machine acting as "yale.edu". It will have no users or accounts. Its only function is to receive mail and forward it to another machine. In this particular case, mail arriving for "Howard.Gilbert@yale.edu" gets forwarded to "gilbert@minerva.cis.yale.edu".
The last panel selects a type of modem, a COM port, and modem speed. When the brand of modem is selected, the Initialization Strings in the last two fields are filled in. A speed of 38400 is probably a good choice on a computer with a decent (16550A) serial port. If the computer has an older inadequate chip, then 19200 is the highest recommended modem speed. SLIP or PPP will always run with 8 data bits and no parity.
There is also a section to disable the "call waiting" feature where the line generates a "beep" when someone dials into your phone when another call is active. The "beep" may or may not disconnect the data session. If you do not want to be disturbed, then this option may be used.
Copyright 1995 PC Lube and Tune -- Windows on the World -- H. Gilbert
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