I certainly do not work for Sling Media or speak for them, but as I understand it, in order to communicate from a computer (PC or Mac) with your Slingbox, the Sling folks need to be able to find your Slingbox out there in Internet Land at any and every time that you attempt to connect to it. They do this by maintaining a database of entries containing your account number, the serial numbers of the Slingbox (or boxes) that you own, and the Internet addresses (both the WLAN address of, say, your cable modem, and the LAN address of the Slingbox on your local area network that is controlled by your router). Your Slingbox provides this information to the Slingbox database the first time you set up or your Slingbox and connect it to the internet, and whenever your do a reset of your Slingbox (I believe this latter is the case).
The key to finding your Slingbox in Internet Land on a day-to-day basis is having confidence that these two addresses -- WLAN and LAN -- have remained the same. But, if you have multiple devices that come and go from connection to your router in your local network, then it is possible (not always, but sometimes) that your router will assign a different dynamic address to your Slingbox from what had previously been assigned to the Slingbox by the router. This could happen, for example, if you have a power outage for several days, or if you change routers, or ...
And if the LAN address for the Slingbox changes, and the Slingmedia folks' directory of addresses doesn't get the word, then you are likely to not be able to connect anymore with your Slingbox (without pushing the reset buttton, or rerunning setup).
So, programming your router to assign a static IP address to the Slingbox in its local area network solves half the address problem. If your Internet Service Provider changes the WLAN IP address assigned to your modem, that would be another way to lose contact with your Slingbox, but I'm guessing here that the ISP folks have a way to keep track of "old WLAN IP addresses" should they ever need to change the one assigned to your modem. Otherwise, I'm guessing that world chaos would ensue if modems were constantly losing touch with their external users because of IP address changes.
HOW, you set a static IP address for your Slingbox depends on what brand and model router that your are using -- the user manual for your router should explain how to assign a static IP address to ANY device in its local network (including a Slingbox). You will need the MAC ID for your Slingbox, which is printed on a sticker on the bottom of the Slingbox and on the shipping box that it came in. But if you provide the name and model of your router here, perhaps another user can provide some simple instructions on how to do the static IP address assignment.
If your Internet Service Provider changes the WLAN IP address assigned to your modem, that would be another way to lose contact with your Slingbox, but I'm guessing here that the ISP folks have a way to keep track of "old WLAN IP addresses" should they ever need to change the one assigned to your modem. Otherwise, I'm guessing that world chaos would ensue if modems were constantly losing touch with their external users because of IP address changes.
No, it isn't done by the ISP. The Slingbox 'phones home' to the Sling servers very regularly to keep the WAN database up-to-date. If you use the following URL:
http://srs.slingmedia.com/getDeviceInfo.asp?id=xxxxxxxx-xxxx-xxxxxxxx-xxxx-xxxxxxxx (Substitue your Finder ID for the xxx) it will tell you when it last told the server.