Most Commonly Asked
Cable Modem and xDSL Questions

Last Updated 11/11/1999

1. Where can I get a Cable Modem?
2. Can I host a server on my cable modem?
3. How Fast is a Cable Modem?
4. What are the most popular Cable ISP's?
5. Which is better, Cable Modems or xDSL Modems?
6. Can I share the Cable Modem Connection with other PC's on my LAN?
7. When my Cable TV Provider will give me Internet Access?
8. What exactly is a Cable Modem and how does it work?
9. How Secure is a Cable Modem Internet Connection?
10. How can I speed up my Cable or xDSL Modem?    
11. Can I hook up a TV to the same line as the Cable Modem?    
12. What are the Options for sharing my Cable or xDSL Modem?    
13. Where do I find more information on Cable and xDSL Modems?    
14. Who Makes Cable Modems, and Can I buy one in the Store?    
15. I am running a Mail Server, but I can't get inbound Mail, Why?    
16. I am running a Mail Server, but I can't send outgoing Mail, Why?    
17. Can I host my own Domain Name and run it from my Cable or xDSL?
18. How do I tell if my Cable Modem or xDSL ISP blocks certain ports?    
19. Can others see my Cable or xDSL modem in Network Neighborhood?
20. How can I find out what IP address my Cable Modem is using?    
21. Where can I find more information on Cable and xDSL Modems?    
22. Can I use Home Networking with my Cable or xDSL Modem?    
23. Can I share my Cable or xDSL Modem using the Built-In Win98 ICS?
24. Can I connect my Cable or xDSL Modem to my PC running Linux?    
25. Can I get a Cable or xDSL Modem installed in my Business?
26. What's the difference between a Static and Dynamic IP address?
27. What is the difference between a 1-Way and a 2-Way Cable Modem?
28. Can I still use my 28.8 or 56K Modem if I have Cable or xDSL?
29. What hardware or software do I need if I get Cable or xDSL?    
30. What exactly does the Specification DOCSIS mean?    
 

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Q: Where can I get a Cable Modem?
A: If you already have Cable TV, your chances of getting a cable modem are decent, but they are still only available in major metropolitan areas. Canada seems to have quite a few ISP/Cable Companies that offer Internet Cable connections. Your best bet is to call your local cable company and ask what their plans are for adding Cable Modem Internet service in the future. You should also check with surrounding towns and other local Cable providers. If Cable Modems are not available, you should also check with your local Phone and Internet providers, since they may offer some form of xDSL connectivity, which is also fairly fast.
 

Q:Can I host a server on my Cable Modem?
A: Typically, most ISP's do not want you to host a server, but usually a small web or personal FTP server will usually be tolerated. Once big issue with hosting on your home cable connection is a Dynamic IP Address. This Dynamic IP may change at any time, and causes problems when people try to connect to your PC. These Dynamic Addresses are given out for two reasons: It makes network administration easier, and it also acts as a deterrent to hosting your own server on your Dynamic IP. Some newer services like Dynamic DNS (http://www.tzo.com) offer a permanent domain name for a Dynamic IP address, allowing ANY user on a Dynamic IP to host a Server.
 

Q: How fast is a Cable Modem?
A: Cable Modems are up to 10-20Mbps download. Typical downloads for the majority are over 300Kbps, or close to 600Kbps, but the speed of the cable modem depends on a few things. First, it depends on how many users are on the system, since the cable technology is a "shared" bandwidth. This "Shared" technology can be drained by too many users using too much throughput. This often happens if a Cable Provider opens up the network and let's everyone run their own server. This causes congestion on the network and slows the connection speed (Upload and Download) to a halt. The second factor to cable modem speed is a throttle or limit on the cable modem itself. Some Cable providers will limit the upload or download speed on the cable modem, and this could affect your connection speed. You may also want to check out the section of this FAQ on increasing the speed of your cable modem.

Q: What are the popular Cable Modem Service Providers? 
A: There are several popular cable modem providers, but the big three are: @Home available at http://www.Home.Com, Mediaone Express available at http://www.MediaoneExpress.com, and Road Runner, a service by Time Warner available at http://www.RR.Com
Most local Cable offerings are some brand of the above companies, for example Cox@Home and Shaw@Home are flavors of the @Home Cable Modem Service.

Q: Which is better, Cable Modems or xDSL Modems? 
A: This is a long debated topic, but there is one major advantage that xDSL has over Cable Modems. Cable Modems use a shared networking technology, where all the cable modems share a single pipe to the Internet. This pipe speed will fluctuate depending on the number of subscribers on the network. When you use xDSL, the pipe to the Internet is "yours", and is not shared along the way to the C/O or Central office. This allows a more consistent speed, and this speed does not typically fluctuate like Cable Modem networks.

Q:Can I share the Cable Modem Connection with other PC's on my LAN?
A: Yes, and it is very easy to share the cable or xDSL modem with other PC's. You should always check with your Cable Providers Terms of Service agreement to make sure that this is legal to do under their agreement. Do this at your own risk. You typically need 2 network cards, or a Cable Modem that you can plug directly into a hub. For Software, Sygate is simple, easy and powerful, and for hardware, the Umax Ugate is simple as well. Check out the CableModemInfo.Com for more info on Hardware and Sharing solutions.
 

Q:How do I find out when my Cable TV Provider will be able to give me Internet Access? 
A: You need to call your Cable TV provider or local ISP and ask them about Cable or xDSL modems. Some ISP's will take advanced sign-ups, or place you on a call or mail list and let you know when the service is available in your area. Be Patient, you will get faster access soon!


Q:What exactly is a Cable modem and how does it work? 
A: A Cable Modem is a digital modem that uses a coaxial cable connection (Same line as Cable TV, except filtered) for the data. This data connection is received by a Cable Modem, that decodes the signal into your PC. This Cable Line is typically filtered and separate from the rest of the Cable TV lines in your house. For More info on Cable Modem Basics, check out http://www.CableModem.Com


Q:How secure is a Cable Modem Internet Connection? 
A: Cable connections, like any other connection on the Internet are not 100% secure in any instance. Although most cable providers block ports 137-139, Cable Modems are likely to be generated in any case where a user has file and print sharing turned on, or possibly other services like SMTP, Web Servers and Telnet services can all be exploited in certain ways. A General rule of thumb is to keep your passwords long and with letters and numbers, and turn off any service that you don't absolutely need running. You should also invest in a NAT or Firewall type application to keep your network as secure as possible.


Q:How can I speed up my Cable or xDSL Modem? 
A: There are methods to speeding up your Cable or xDSL download speed, and mainly they involve tweaking the windows registry. This method seems to work for some, and it's worth giving it a shot. If you want to test the speed, try and download a large file before and after the tweak, and see what you get for an improvement. You can get more info at http://www.Speedguide.Net or you can also check out at John Navas' Speed Tweak website


Q:Can I hook up a TV to the same cable line as the Cable Modem? 
A: Yes, in most cases it will work, but it's not recommended. When my first cable modem was installed by Mediaone, I put a splitter in from the wall jack (The filtered wall jack designed for the Cable Modem Connection) and the Television worked fine off of the splitter. The Cable modem worked exactly as it did when it was hooked up directly. There may be cable systems where this will not work.


Q:What are the Hardware and Software options for sharing my Cable or xDSL Modem? 
A: In order to share your cable modem with other PC's in the house, you typically need a Hub and some RJ45 Ethernet Cables, as well as some sort of Internet Sharing Software (Proxy, Firewall, NAT) or a Hardware Based sharing solution. A software solution is easy to set up, and you typically need another network card in the PC connected to the Cable or xDSL modem. After Installing another Network card, you can install something like Sygate (http://www.Sygate.com), and be sharing your Internet Connection in minutes. A hardware solution like a router from Netopia, or the Ugate from Umax can offer a quicker, easier solution. These hardware solutions offer a quick and easy way to share your Internet connection with your home or office.


Q:Where do I find more information on Cable and xDSL modems? 
A: You can get more info by calling your local Cable Provider, or Telephone provider, or you can use the Internet to find more information. Your best starting point would be www.CableModemInfo.Com, www.CableModemHelp.Com, and www.Catv.Org


Q:Who makes Cable Modems and can I buy one in the Store? 
A: There are many cable modem brands, and the most common are from Com21, Motorola, Bay Networks, RCA, Cisco, Toshiba, 3Com, and Terayon. For more information on Cable Modem Manufacturers, please visit http://www.catv.org
In some areas, Mediaone and Circuit City actually sell cable modems/service in a nice little take home bundle. This allows you to take home the cable modem and drool on it until the cable modem installer comes over to hook it up a few days later. I have seen these bundles in Circuit City locations in the Northeast (Boston Area)


Q:I am Running a Mail server on my Cable Modem, and I can't receive Incoming Email, Why? 
A: If you are running a Standard SMTP Mail Server, most likely this is due to a misconfiguration of the mail server, or a possibility that you are with an ISP that blocks port 25, the standard SMTP port. This port must be open by the provider for you to receive Email on the standard SMTP port 25. Check with your provider to see what ports they block, or you can try http://www.PortDetective.com for Windows, and that describes what ports are open, closed or in-use. If you decide that a port 25 block is in effect, you can still run a mail server with the store and forward service from TZO.Com


Q:I am Running a Mail server on my Cable Modem, and I can't send outgoing Email, Why? 
A: If you are running a Standard SMTP Mail Server, most likely this is due to a Dynamic IP and Reverse lookup. There may be an SMTP server that won't allow mail from a server it can't do a reverse lookup on. This is a common Anti-Spam issue, and is needed in some most cases or this world would be overrun by spammers! You can use a Relay Server that will allow a relay from your IP address range, and some ISP's provide this service. Some SMTP servers will accept your mail, and some may happen to reject it due to the Dynamic IP address or Host Name unable to resolve back to your IP. Check with your ISP and see if they will relay mail for you.


Q:Can I host my private domain (MyDomain.Com) and run it from my Cable or xDSL Modem? 
A: Some Cable or xDSL ISP's will allow domain hosting, but most will not. You should check with your Cable Company or go with a DNS host that can host your domain and point it to your Cable or xDSL modem. TZO.COM works with Static and Dynamic IP address and has a unique Dynamic DNS system to host your domain.


Q:How do I tell if my Cable or xDSL ISP blocks certain ports? 
A: Check with your provider to see what ports they block, or you can try http://www.PortDetective.com for Windows, and that describes what ports are open, closed or in-use. You can also use TELNET as a reliable source to tell if your ISP is blocking. You should set up your server, then use telnet from an outside ISP and telnet back to your server:port. For example, if you were running a Mail Server, You should telnet to the server like this (Telnet MyName.Com:25) - and if the server answers, the port is open. This must be performed from a remote ISP. If you ISP blocks ports, you can get another ISP or check out some services from http://www.Tzo.com that relay Mail or Web requests to other ports.


Q:Can others see my Cable or xDSL modem in Network Neighborhood? 
A: Yes and No. You may or may not be able to see Workgroups, Printers in the Windows Network Neighborhood. Mediaone service I could see some Workgroups, PC's and Printers on my segment, but ports 137-139 are blocked from the outside world. In most cases, it's best if you disable any Microsoft File and Print Sharing, and make sure you use good password protection to keep things secure.


Q:How can I find out what IP Address my Cable or xDSL modem is currently using? 
A: In Windows, the utility WINIPCFG is quick and easy, or using Linux/Unix, Netstat should do the trick for you. TZO or ICQ also have quick and easy methods for finding out your IP address, and TZO offers a domain name that virtually eliminates the need for remembering an IP address. You can get more info on TZO at http://www.tzo.com


Q:What other websites are available with more information about Cable and xDSL Modems? 
A: There are many other websites available with some great information. You should take a look at the CableModemInfo.Com website for links and information to other websites.


Q:Can I use Home Phoneline Networking with my Cable or xDSL modem? 
A: Home Phoneline Networking or HomePNA technology can be used to share your Cable or xDSL Connection. In most cases, these HomePNA products are bundled with some Internet Connection sharing software like Sygate. Even xDSL modems, which use a section of the Phoneline for it's connection, do not usually interfere with these HomePNA products, and can be used at the same time. For more information about Home Phoneline Networking or HomePNA, please see HomePNA.Com


Q:Can I share my Cable or xDSL modem using the built-in Windows 98 ICS software? 
A: The latest version of Microsoft Windows 98 includes a NAT (Network Address Translator) based Internet Connection Sharing software called ICS. This ICS software can be used to share your Internet connection, but you may be better off looking at some commercial sharing packages such as Sygate, or a Hardware solution like the UMAX Ugate.


Q:Can I connect my Cable or xDSL modem to my PC running Linux? 
A: Many Cable or xDSL providers have very little experience with Linux, and refuse to install the Cable or xDSL modem into a PC running Linux. You should investigate with the ISP and see if they allow Linux Installs, or if they are "Linux-Friendly". You can find out more info on the newsgroups, or by checking out the Linux Cable Modem Section on http://www.CableModemInfo.com


Q:Can I get a Cable or xDSL modem installed in my Business? 
A: In some cases you can, such as with the @Work service by Home.Com. Many Cable or xDSL providers are targeting the home user, and have not focused on a business plan for installing into businesses. Mediaone and many other Cable Modem ISP's will not install into a business address at all. Typically, xDSL providers are more likely to offer a business connection.


Q:What's the difference between a Static and Dynamic IP Address? 
A: An IP Address is essential to using the Internet, and since each PC needs one to get on the Internet, having an IP address is a must. Typically, most cable and xDSL ISP's do not want you to host a server. One big issue with hosting on your home cable connection is a Dynamic IP Address. This Dynamic IP may change at any time, and causes problems when people try to connect to your PC. These Dynamic Addresses are given out for two reasons: It makes network administration easier, and it also acts as a deterrent to hosting your own server on your Dynamic IP. Some newer services like Dynamic DNS (http://www.tzo.com) offer a permanent domain name for a Dynamic IP address, allowing ANY user on a Dynamic IP to host a server. A Static IP Address never changes (Not unless you change ISP's usually), and can always be found on the Internet. If you have a static IP address, they typically cost more, or some ISP's won't even allow you to have a static IP Address.


Q:What's the difference between a 1-Way and a 2-Way Cable Modem? 
A: In some cases, a Cable ISP may not have the proper Cable network to provide Upstream and Downstream data. In this case, the Cable provider has a 1-way "Broadcast" of data, and all requests for the data are done over a Phone or Wireless Network (CDPD). These requests must be made over an alternate connection, since the cable company can only send data to the user. This 1-Way Network can be a burden, since most often a customer still ties up the Phoneline when using the Internet. This is also similar to the Hughes DirecPC Satellite systems, which only Receive data, and cannot send it. a Two-Way system has both up and down Internet Data flow, and customers can use the Cable TV Line (Coax) connection to send and receive data.


Q:Can I still use my Analog 28.8 or 56K Modem if I have a Cable or xDSL modem? 
A: Usually, if you have a 2-Way Cable Modem or xDSL modem installed, you will never use your analog modem again! Most Cable systems will use the Cable or xDSL connection to send and receive data, thus eliminating the need for an Analog modem. You should keep the modem, and keep it plugged in, just in-case your Cable or xDSL Provider goes offline for any reason, you may need the analog modem as a backup. The 2 technologies can exist on the same PC without any problems, You should only use your analog modem if you have to (Online Banking in some cases, Faxing, etc)


Q:What hardware or software do I need if I get a Cable or xDSL Modem? 
A: In most cases, you need at least an ISA 16 Bit Ethernet card with a RJ45 Ethernet port. This is usually a PCI Card in most cases, but an ISA card can be used. Typically these Network cards cost around $30 or more, sometime bargains can be found and prices can be as low as $10-$15 per card. There are some types of Cable Modems that install in the PC, with everything on-board, inside the PC. You should not need any special software unless your Cable Provider requires a Login Script such as Road Runner. You should also keep in mind that some Cable or xDSL providers will NOT install the cable modem connection if your PC does not run a compatible Operating System. Most Cable Companies will not Install on Linux, Windows NT Server, or another OS. Your best bet is to install Windows 95/98 or Windows NT Workstation for the install. Since most people with a cable modem or xDSL will eventually share their connection with other PC's in the house, you should look into a Internet Sharing solution such as Sygate or Maybe a hardware device like the Umax Ugate.


Q:What exactly does the specification DOCSIS mean? 
A: DOCSIS is a Cable Modem Standard that stands for Data Over Cable Service Interface Specification (DOCSIS), and it defines the interface requirements for cable modems involved in high-speed data transmission over cable television networks. These standards and testing will help inter-operability between Cable Modems and Cable Networks. You can see http://www.CableLabs.com for more information.

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