Another new member of the team. Barry owns his own 'broadband for businesses' consultancy company, and has plenty of rich experience to share with us! Go Barry!!
The phrase "uncapping" refers to the method of increasing the amount of bandwidth assigned to a cable modem by an Internet Service Provider. If a cable modem is assigned more bandwidth then it receives a proportional speed enhancement accross all aspects of the Internet.
Be aware that cable modem uncapping is considered as theft and can lead to very serious consequences. Your ISP will detect your uncapping and will take action. Please treat this article as infromation on the concept of uncapping only as talkbroadband.com strongly suggest that you do not uncap your cable modem!
DSL Uncapping? This cannot be done as the technology that supports xDSL connections will not allow an xDSL connection to be uncapped.
TFTP Emulation DOCSIS is a standard used by most cable modem operators around the world. The system works by transferring a file (a DOCSIS) file to a cable modem as it goes online. This DOCSIS file contains within it the settings necessary for the cable modem to operate on the cable modem operators network. Also embedded in this file are the speeds that the modem is allowed to operate at. The DOCSIS file is produced by the cable modem operator and distributed via a TFTP (Trivial File Transfer Protocol) server. The theory of TFTP emulation is that modem speeds could be increased by modifying the cable modem operators DOCSIS file and therefore increasing the bandwidth available to the modem. Then by emulating a TFTP server using a computer on a LAN attached to the cable modem it is possible to trick the modem into receiving the DOCSIS file locally rather than from the cable modem operators TFTP server. Using this method the speed of the cable modem can be governed by modifying the local DOCSIS file.
How Could I Change a Cable Modem MAC Address? The MAC address is hardware programmed however to save designing each cable modem seperately they are stored within a memory chip inserted during the manufacturing of the equipment - as it is stored in memory it is possible to reprogram this memory chip with a different MAC address. To acheive this access to the debug shell within the cable modem is required however most cable cable modems are supplied with this feature disabled.
What is the debug shell? The debug shell is simply a command line interface that can be accessed via within the cable modem via telnetor in some cases a graphical interface available via a web browser.
Can Your ISP Detect If You Are Using An Uncapped Cable Modem? The simple answer here is yes they can. Due to the fact that uncapping a modem is classed a theft and based on the ease that your ISP would detect your speed increase talkbroadband.com strongly suggest that you do not uncap your cable modem. However feel free to tweak the registry settings on your computer as this is a safe, and legal way to increase your connection speed.
Remember that "Some bandwidth is better than none at all" - As most ISP's will suspend or terminate your connection if you are found stealing bandwidth.
Comment #1
(Posted by Ross L) Rating
I remember when uncapping was a huge issue in the UK... these days with the bandwidth available who would need to cap? I guess uncapping your modem would give you a shed load more bandwidth. I guess it's tempting, but bloody risky! Thanks for the article :)
Comment #2
(Posted by Des UK) Rating
A good read, and a fun topic!!!! If I could get away with it I would, but I reckon thats gotta be hard today!
Comment #3
(Posted by an unknown user) Rating
if you do both change your mac and then host the config file on your own sytem there in no way your isp can find you not that am saying just coz they cant find you is ok to do in fact you are not only stealing your slowing other people connections down
Another new member of the team. Barry owns his own 'broadband for businesses' consultancy company, and has plenty of rich experience to share with us! Go Barry!! 
;) ;) ;)