Even in Silicon Valley, the choices for high-speed Internet access are limited. 56k modems are available, but there are multiple implementations of 56k technology (K56 Flex, X2, and the new ITU-approved V.90 standard) and you and your ISP needs to be using the same type. The reports I've heard from people using these modems is that the speed increase is anything from nonexistent to marginal, but only in one direction. The new V.90 standard will make it easier to get online at 56k, but it will take a year or so before the standards are widely implemented.
Cable modems are available, but the areas where they are available are extremely limited. Depending on how the cable modems are implemented and how many people in your neighborhood are using the cable modem at the time, the speed can be anything from phenomenal to about 56k speeds. Radio modems are available in some areas, but they too are somewhat speed limited. One of the satellite TV providers allows high-speed Internet access through it's dish, but the "upstream" connection is still a 33.6k modem. DSL (Or Digital Subscriber Line) is starting to become available in some areas, but again, it is not available in all areas, and is somewhat expensive.
Of all the technologies available for the average consumer to get high-speed Internet access, ISDN has been around the longest. ISDN is a digital telephone line that can be used for, among other things, high-speed Internet access. Each ISDN line has 2 B channels and a D channel. The D channel is used to establish a connection and negotiate the communications methods used. The upshot is that it takes far less time to negotiate a connection using ISDN as compared to your typical analog modem. The B channels can be used for voice, data, fax, or whatever. One B channel can be used for an outgoing phone call and the other can be used for access to the Internet, and you can dynamically mix and match.
You can transmit 64k/sec over a B channel. For data applications such as accessing the Internet, the B channels can be "bonded" together to give you one huge 128k channel. In some cases, compression can be implemented to give you even faster speeds. For a single person accessing the Internet, the speed is quite acceptable and far better than an analog modem.
ISDN is more generally available than other technologies, but it is not available everywhere and it requires a bit more coordination between you and the phone company. Before committing to ISDN, make sure you can get ISDN in your area, there is an ISP in your area that can serve ISDN customers, and that it's not going to be prohibitively expensive for you to have ISDN.
In general, when thinking about going the ISDN route, do the following first so you know what you're getting into.
Now, what kind of ISDN modem shall you get, internal or external? Usually, with analog modems, I recommend external modems so you can see the blinking lights, easily power-cycle the modem and move it from computer to computer. I still feel the same way about ISDN modems, but there is an additional cost you must factor in with external ISDN modems: your serial ports.
Most computers these days come with serial ports with 16550 UARTs in them. These chips allow your serial ports to transmit data at speeds up to 115.2k/s. The problem is that ISDN without any data compression easily goes up to 128k. To get the most use out of your external ISDN modem, you will most likely need to purchase a serial port capable of at least 230.4. This will most likely come as an ISA or PCI expansion card and can cost anywhere from $20 on up. The one I ended up using came from Dolphin Peripherals, LLC, though I know of others who have used cards from ByteRunner Technologies as well as Pacific CommWare. The main thing you need to look for in a high-speed serial card is a 16650 or 16750 UART chip. Cards with these chips will be able to keep up with the data stream much better than a 16550 UART will.
On the other hand, by using an Internal ISDN modem, you don't have to purchase a faster serial board because the ISDN modem will build it onto the card. The problem with internal modems in general is that it is difficult to move the modem from one computer to another and resetting the modem without shutting off the computer can sometimes be an excerise in futility. Not to mention problems with "Plug and Play" ISDN modems. And you don't get blinking lights, either. ;-)
For those people who are LAN-enabled, there is a third option: an ISDN
router. While they usually cost a bit more than an internal or external
modem, they give you the benefit of allowing your entire lan to take advantage
of ISDN-enabled Internet access without having to set up one of your PCs
as a router or firewall. This option should only be explored by the rich
uber-geeks among us as configuring a router of any sort is no easy task,
for me. ;-)
The software that came with my 3Com Impact IQ (my sources tell me that most of the local phone companies support this modem) made installing my ISDN line quite painless. Even the DOS program worked pretty well, though it lacked the status information of the Windows program. The main problem I had was that I didn't know what kind of switch my phone company was using, so when I came to that choice in the DOS program, I didn't know which one to pick and wasn't given a lot of feedback as to whether I was sucecssful or not. When I broke down and ran it through the Windows program, it was able to tell me pretty immediately if everything was working right or not. Once I got it configured properly, everything started working beautifully.
The point is: make sure that the modem comes with software that will allow you to configure the modem. Though I probably could have done it manually (the 3Com manual is pretty straightforward, assuming you are familiar with configuring modems), I was thankful the program was there to help.
The other thing that's important is whether or not your software and ISDN ISP support MultiLink PPP. If you bought a Windows 95 computer recently, you're in luck as those versions of Windows 95 include support for MultiLink PPP. If not, you will need to go download the Dial Up Networking Update (Version 1.2) that will support MultiLink PPP.
What about other operating systems? Unfortunately, I don't know which dialers and PPP client support MultiLink, though you can probably get it to work anyway if you do two things:
Occasionally, I need to send and receive faxes as well. I now have a dedicated fax number that is used for sending and receiving faxes. If I happen to be connected to the Internet at the time, one of the B channels will be reallocated for analog and allow me to fax out while remaining connected to the Internet. If an incoming fax comes in, the same thing happens. When I am done, the B channel is bonded back into my connection to the Internet connection and life goes on.
There's also the occasional need to dial out with an analog modem. I
can also do this on the ISDN line without incident and regularly get 31.2
or 33.6k connections.