I am not sure what do you mean upgrade to 100mbps. What I know is that a standard CAT5 has a specification that can handle a speed of 100Mbps, frequency of up to 100MHz, and with the expense of a maximum cable length of 100meters. If you need a much higher data transmission a CAT5e or CAT6 or even CAT7 will do the job for you.
All this is just a medium. The data capacity depends totally with your network provider. Contact them.
