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Old 14th August 2015
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jggimi jggimi is offline
More noise than signal
 
Join Date: May 2008
Location: USA
Posts: 7,977
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Garry,

I know, it's confusing. I'll try to net out how the pieces of the puzzle all fit together. As I don't have a PPP connection myself, some of the puzzle pieces may not be completely clear when I'm done. Please forgive me, also, if any of this is dull, useless review.

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The umsm(4) driver that appears in your dmesg is for serial modems that have a Qualcomm MSM chipset. These are found found in a variety of cellular devices, including yours. The umsm(4) man page warns that multiple devices may appear in your dmesg, and it is not always clear if it is device number 0 that is an active modem, or if it is one of the other device numbers. Your dmesg shows 4 different umsm devices, so some experimentation might be needed.

PPP (Point-to-Point Protocol) is a way to exchange authentication (userid/pw) and IP address assignments over a serial connection, such as the umsm modem.

The pppd(8) daemon is the tool that uses PPP to authenticate a connection, negotiate IP addressing and routing information, and maintain and manage the connection.

The chat(8) command is used to script commands for serial modems.

The ppp(4) driver is the network interface for PPP.

The ifconfig(8) command is the provisioning and management tool for network interfaces. For example, a ppp(4) device can be created or destroyed by ifconfig. For other devices, such as Ethernet NICs, ifconfig may be used to set IP addresses, but for ppp(4) devices this is done with pppd(8).

The hostname.if(5) files are used to configure network interfaces, used by netstart(8) at boot time. The example from the misc@ mailing list used "up" to create a ppp(4) device during boot.

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In the example scripts in the umsm(4) man page, we see a chat(8) script containing modem commands, a pppd(8) provisioning file, and a pppd(8) authentication file using CHAP -- Challenge Handshake Authentication Protocol -- the protocol required by Cingular Wireless when the example was written. (Cingular Wireless is now AT&T Mobility -- the example was written prior to 2007.)

The first record in the example pppd file uses /dev/cuaU0, which would correspond with the first umsm device, umsm0. The second record is 115200 -- the speed of the modem being used. The third record enables debug, and from the fourth option downward ... are all settings needed for connection with Cingular, and for behavior of the connection: The ISP does not need to authenticate itself with the client. Hardware flow control is disabled. A recommended remote IP address was defined, which can be altered by the ISP, Cingular. The connection will be the default route to the Internet. The userid for this user at the ISP is defined. The connection will ignore NTP packets as a measure of demand or idle activity. Break the link after 10 minutes of idle activity. Remain running and re-establish the link if demand returns. Connect with the chat(8) script.

The chat(8) script includes a blend of chat commands and modem commands. The chat commands are documented in the man page. The modem commands are not -- but they are the "AT" commands (or extensions) written for the Hayes modems in 1981, used by all modem manufacturers since the mid-1980s.

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As you can see, the specifics for PPP connections are partially under your control, and partially under the control of the ISP. This is why I recommended contacting your vendor. Only they can tell you what their requirements are.
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