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Protecting Your Data: A Guide to Windows Firewall


TCP and UDP - What's the Difference?


TCP and UDP are two separate protocol types that perform considerably different networking functions. Both TCP and UDP have unique characteristics that apply to different situations. Some applications on your computer will use TCP, and other applications will use UDP. The Windows Firewall distinguishes between TCP and UDP, and it will independently block or allow traffic from each protocol type.

For the purposes of this guide, it's not particularly important to understand the technical differences between TCP and UDP. However, the basic differences in the two protocols can help gain a better understanding of traffic patterns and the relationships that Windows Firewall has to these traffic patterns.


Transmission Control Protocol (TCP)
TCP is the most-used IP-based protocol on the Internet. Web browsers, email clients, and file transfer programs use TCP as their preferred transport protocol. TCP's popularity is due to a built-in verification system that's used when data is received by a remote device. When a Google search page is requested by your browser, the Google web server sends an message back to your computer that acknowledges that the search request was received. You never see these acknowledgements, but these informational network packets are always working behind the scenes to verify that your data gets from one side of the Internet to the other.


Although this process seems cumbersome, it's extremely useful for programs that transfer pieces of information. With TCP, there's no question that the data sent from one device was received by a remote computer. This data acknowledgment process requires some network overhead, but the data transfer confirmations are well worth the additional bandwidth.