What is the Difference of Resolution between D1 and CIF? bandwidth to access the DVR over the internet?

Resolution (D1 and CIF)

Resolution is the size of the image on the display. The most popular resolutions are D1 or 4CIF (720x480), and CIF (352x240). Nearly all DVRs will display in D1 or 4CIF but CIF is a more popular recording resolution. D1 and 4CIF are larger images, but to record the larger image takes up more hard drive space. In addition, most DVRs need to lower the frame rate dramatically when using these resolutions for recording. A DVR that records at 30 frames per second (real time) in CIF mode will usually only record around 7 frames per second in D1 or 4CIF.
For a DVR to record at 30 frames per second in D1 or 4CIF mode requires special firmware which makes these units very expensive, however improvements in technology has now made these units more affordable.

How much bandwidth do I need to access the DVR over the internet?

For a 4, 8 or 9 channel system at least 1 Mbps upload and download is needed. For a 16 channel system 2 Mbps upload and download is needed, for 32 channels 4 Mbps are needed.