Facts About Cable Modems

by jeremy

Is the price of ISDN another word for outrageous?  Are modem speeds rapidly losing their luster due to bandwidth-sucking technology?  Tired of making your friends guess what your IP is so they can get on your system?  Read on - soon your days of frustration may be coming to an end.

Lately you may have noticed cable guys frantically working on your cable lines outside of your home or apartment.  What you may not know is they're actually preparing for you to move into the next step of high-speed, low-cost Internet connectivity.  Some of you may already be using 500 kbps cable access as your means of connection, but most of you have only heard rumors or have gotten promises from your cable company about the high-speed connection.  Don't lose hope yet.  Cable companies around the world are uniting with your local ISPs to bring this connection to your home or business at an affordable cost.

How does this work?  The concept is very simple.  Your cable company uses a special transceiver which takes a dedicated feed, a very high speed connection, anywhere from 1 meg/s on up, and broadcasts this bandwidth over RF transmissions via television cable to smaller transceivers located in your home or office.

The cable providers dedicate a channel, or frequency, to the transmit and receive of the cable modem.  Each modem in the field is then configured to utilize these transmission frequencies which allows them to connect to your cable provider.  Here's the catch, and also the reason why it's probably not available in your area.

In order for you to transmit and receive at 500 kbps, your cable lines have to be replaced with fiber optic cable, as well as amplifiers which allow two-way communication.  Right now most cable only flows in one direction - you never needed anything else.  But now in order to take us into this next step in Internet connectivity, all those lines and amplifiers and other related cable equipment need to be replaced.  The major problem with this is the availability of this new equipment.  The demand for it has overwhelmed cable equipment manufacturers to the point where they have to limit the amount of equipment cable companies can order.

One cable company revealed to me that they are only authorized to order a limited supply of equipment, and can only place an order once a year.  So basically the cable companies are working as fast as possible to replace equipment, but a lot of it has to do with the availability of the equipment.  Producing fiber optic cable is not an overnight project.

The client transceiver (the one that goes in your home) is configured via an RS-232 port on the back of the cable modem.  This allows you to assign an IP address - each cable modem gets its own IP address for remote management and PROM update from your service provider.  This modem setting information is retrieved via SNMP, subnet, gateway, and a setting to lock out the RS-232 port from further configuration.  My service provider does not take advantage of this feature for some reason.

So what are the disadvantages, or rather, what should you expect?  The main thing to keep in mind about your cable network is that it is a shared network.  Meaning that your total given bandwidth is divided by the amount of users on the system.  So, this of course causes problems for you when you have a lot of people on your network who decide to set up their "WaReZ" servers and simply do not care that they are using yours and everyone else's bandwidth so they can trade "GaMeZ."  I'll leave it up to you to decide what to do about the bandwidth suckers on your network.  You will almost never get 500 kbps unless you are the only person on your network, so when your ISP or cable tells you that they have 500 kbps cable modems available, ask them how many people they put on each segment and what total bandwidth is dedicated to the network to get an idea of the actual speeds you can expect.  Some ISPs may actually tell you the truth if you ask them what throughput you can consistently expect.  I get an average of 350 - 450 kbps on my box, which I consider very good considering the amount of people on my network.  500 kbps is a marketing tool.  The cable modems are definitely capable of doing 500 kbps, but first you must have the bandwidth to push it.

Security

You should apply the same security that you would to a machine on a local area network because essentially, that's what the cable network is.  The same security holes that are relevant in area LANs are also present in the cable network.  If you plan on running a UNIX based OS, then I suggest you run cryptographic software such as SSH (secure shell), and CFS (cryptographic file system) on your server.  It is very easy to snoop any machine on your cable network unless your provider is using switch technology to segment devices on your cable network.

If you're using a MicroSlop based OS, well then there's not much I can do for ya.  You will have tons of fun finding all the Microshit 95 people on your cable network who have no clue that they're sharing all their services on their machine.  I think you should perhaps send a message over their printer giving detailed instructions on how to improve their security, or perhaps you just want to send them a message telling them to eat a bag of shit.  It's up to you.

Cost

How much is this?

Well, to me this is the best part.  Remember, this can vary, and I assume it does quite considerably.  For customers in my service area there is a one time $25 setup fee and a monthly $50 dollar charge.  It's about $35 for the service and about $10 to lease the cable modem.  I'd be very interested in how much people pay for their service in other places around the world.  In my opinion, 350 - 450 kbps for $50 a month is a very good price.

Hacking

O.K., by now you all may be saying to yourself, what does this have to do with hacking?

One of the things that makes the hacking community so strong is its willingness to share information.  If we simply keep quiet about the things we know and understand, then our strength and power remains concealed as well.  With this advance in technology, it empowers us to spread the word of technology and the hacker spirit without the suppression from corporate politics and government regulation.

You can be in control of your content without worry that Big Brother is going to pull the plug.  You now have the ability to tell your side of the story, without the constant media exploitation and distortion that so many of us have long since accepted as a part of the hacker life.

Miscellaneous Notes

I'm using a 500 kbps Zenith cable modem.  Zenith also has a one-way version, which allows 500 kbps downstream, and modem upstream.  They also have a 4 MB/s version which I have yet to experience.

RF Modem Transmitter Maximum Power Output: +50 dBmV +3 dB Gain Control Range: 20 dB Frequency Stability: 0.01% Bandwidth: 1 MHz for -40 dBc (LANHWU-5K) 6 MHz for -40 dBc (LANHWU-4M) Spurious and Harmonics: 50 dBc Off-Carrier Isolation: 20 dBmV Frequency Range: 12-108 MHz Output Impedance: 75 ohms nominal RF Modem Receiver Input Range: +10 to -15 dBmV (LANHWU-5K) +10 to -10 dBmV (LANHWU-4M) Input Impedance: 75 ohms nominal Capture Range: 100 kHz LAN HWU-4M 50 kHz LAN HWU-5K C/N Performance: 10-8 for 20 dB C/N (LANHWU-5K) 10-8 for 24 dB C/N (LANHWU-4M) Frequency Range: 50-750 MHz Physical Characteristics Molded Plastic Cabinet: 15.5" W x 11.75" D x 2.75" H Weight: 8 lbs. Connectors: 2 broadband "F" style 2 RS-232 (RJ-11) 2 10BaseT (RJ-45) (1 or 2 port versions available) 1 Power LED Indicators Power: Power On Status: Diagnostics and Message Function Collision: Packet Collisions on Broadband A: Network Activity (RF Carrier) TX: Transmit Data RX: Receive data Link 1 (and 2): 10BaseT Link Light(s) (on rear of unit) Model Numbers LANHWU-5K 500 kb HomeWorks Universal - single port - 110V LANHWU2-5K 500 kb HomeWorks Universal - dual port - 110V LANHWU-5K-I 500 kb HomeWorks Universal - single port - 220V LANHWU2-5K-I 500 kb HomeWorks Universal - dual port - 220V LANHWU-4M 4 Mb HomeWorks Universal - single port - 110V LANHWU2-4M 4 Mb HomeWorks Universal - dual port - 110V LANHWU-4M-I 4 Mb HomeWorks Universal - single port - 220V LANHWU2-4M-I 4 Mb HomeWorks Universal - dual port - 220V Zenith Modem Information www.zenith.com/main/network_systems/data.html