What is a PPP server, and why do I keep getting disconnected from it?

I am using a Huawei e160 USB modem and I regularly lose connection to the internet with the following error: You have been disconnected from the PPP server.

It has nothing to do with reception, and I am always able to connect immediately back up. Does anyone have any ideas as to why this may be happening? Or at least explain to me what a PPP server is? Thanks.

PPP is the Point to Point Protocol is a data link layer (see the OSI 7-layer model). It's an older protocol that's generally used to connect two points together over a physical link like a phone line. It's been in use as a connection protocol (mostly in the PPPoE -- PPP over Ethernet -- form) for ISPs for quite some time now. Your modem uses this protocol to identify you as a customer to your ISP and create a tunnel to them over some larger network, through which your data will flow. Your modem establishes a PPP connection and then over this connection your Ethernet packets flow.

It sounds like you're disconnecting from your ISP at regular intervals. It could be any number of things causing you to lose your connection. You may have poor signal to the ISP end point and the connection is timing out. You may be overloading the connection and your ISP is dropping the link. Your ISP may be having issues. You may have failing or buggy hardware. Or you may have buggy drivers for your hardware.

It's impossible to tell exactly from what you've written.

If you can check your Console logs, see if there are related console messages about the PPP tunnel, you might be able to find something additionally useful to add to your question.

Have you called your ISP? That's where I'd start.

@Ian C. has provided an excellent answer to this question, but I can add a few thoughts. A few years back I was given a Huawei e160 USB from Vodafone mobile broadband here in the UK. The modem establishes a PPP connection over a 3G network, and since that network is shared with cell phones, Vodafone was aggressive about disconnecting idle devices after a very short time. They could always attribute these "dropped calls" to spotty network coverage.

@joshnh and @Martha may also be experiencing disconnections when their modems are idle for a short period of time. Or they may genuinely have spotty network coverage (sometimes signal strength drops for a few moments due to interference, then quickly recovers). In my experience when there was robust cellular coverage the PPP connection was good, and when the coverage was thin (in the countryside) or at peak times the connection became flakey.

Have either of you noticed that this problem happens more at certain times of day? That would point to your ISP shedding load.

Regardless, the solution is the same that @Ian C. suggested, namely to call your ISP.