Let me explain how this Works. I wish I could find a picture. I'll be typing this awhile, so I'm posting this now and will edit it as I go.
Lets say you have 4 Wireless Devices in your home, plus an ISP. You bring home your Aircard(GSM Modem) and it happens to have a Wireless Antenna on it, from Cellphone company Pizzazz. Pizzazz sold you 1,000 minutes for Cheaper than your ISP. You've gone over your BitCoin allowance on your ISP and don't want to pay overage fees on your bill...
You Decide To...
Use Your GSM modem as a Stopgap because you've used none of your 1,000 minutes. A GSM works like so:
Cellphone connects to GSM, Laptop Connects to GSM, Ipad Connects to GSM like so, using the Wireless Antenna:
++++++++++++++++
+ Cellphone +
+ IPad + => GSM
+ Laptop +
++++++++++++++++
But You Ask...
How does the GSM, connect to the Internet:
++++++++++++++++++++++
+ GSM +
+ ----- + => Internet
+ Username/Password +
++++++++++++++++++++++
Now when we Bridge both networks together we get:
++++++++++++++++ ++++++++++++++++++++++++++
+ Cellphone + => + GSM +
+ IPad + + ----------- + => Internet
+ Laptop + + Username/Password +
++++++++++++++++ ++++++++++++++++++++++++++
Now, the Interface names in Linux also tell what they are:
wwan0
- Wireless Wide Area Network Zero
ppp0
- Point to Point Protocol Zero
Updating my Stick Photo:
wwan0 ppp0
++++++++++++++++ ++++++++++++++++++++++++++
+ Cellphone + => + GSM +
+ IPad + + ---------------- + => Internet
+ Laptop + + Username/Password +
++++++++++++++++ ++++++++++++++++++++++++++
In other words the GSM behaves just like any network would. The problem is that the GSM has no DNS Server to allow you to route, until after it negotiates with a Dial-up/PPPoE Authentication Server. Once connected to the negotiation server, your minutes are deducted from your 1,000 and you are billed. The IP Address is connected to ppp0
because the negotiation was sucessful, and the Point to Point Protocol manages the connectivity aspect:
- Has this connection been Terminated?
- Is it time for me to ask for a new IP Address from the DHCP Server?
- Am I creating a new connection?
- How long is my lease time?
The wwan0
on the other hand only manages the connected devices. It also asks itself questions like those above, but it isn't allowed to interfere with ppp0
because it knows "Hey I'm not the one in charge of that device. I should keep watch over my devices though. Since I dunno what it's for, I better leave it alone."
Of course, that last paragraph was the simplified version, but if you like I can list the Actual Standards and Protocols used by each device.