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In this chapter we will explore three essential concepts in TCP/IP protocol. This includes learning how the TCP/IP protocol suite works, learning how subnetting and CIDR works, and finally we will explore static and dynamic IP addresses as well as their functions. TCP, or Transport Layer Protocol, is another protocol we can use to share files between computers over the internet. TCP is used the most of these protocols, sending information through a three-way secure handshake. UDP operates with what is called datagrams. Protocols like HTTP operate on what is called application layer protocols, and send and receive information through ports. IP, or internet protocol, refers to a set of rules, or protocol suites, that connect computers together. IP can support complex networks and small networks can operate on LAN over ethernet. With IP addressing, devices receive a unique 32-bit value in dotted decimal notation, and knowing the arithmetic behind converting binary numbers to decimal and back is essenti Subnet masks help determine where to send information across the network and are also written in dotted decimal notation. Subnet masks in binary values can describe network and host IDs. Comparing the subnet mask to the IP address, matching 1s become network IDs and matching 0s define the host ID. CIDR is a technology based on subnetting. As we've explored earlier, subnetting splits IP addresses into smaller groups. However, CIDR typically carries out subnetting on an ISP, or Internet Service Provider, before it reaches the user. CIDR and subnetting help to distribute bandwidth and allow you to set up connections for many different computers at once. Even with many devices on the network, the network as a whole is given an ID. Each computer gets its own, separate host ID. Finally, let's examine the difference between static and dynamic IP addresses. Static IP addresses require you to manually enter information for the IP address. With this method, you can choose custom IP addresses and connect to a small network. If you are working with static IPs, remember to write down your IP address numbers for future reference. With ping commands you can test your networks to ensure they are working properly. Dynamic IP hosting, or Dynamic Host Configuration Protocol, is the more widely used version of dynamic IPs. Alternatively, you have the older Bootstrap Protocol, or BOOTP. DHCP automatically assigns an IP. DHCP starts by sending out discovery packets looking for other DHCP servers. If successful, a handshake is performed and a DHCP lease to the client completes the connection. In DHCP, automatic private IP addressing, or APIPA will have DHCP client assigned to them if it cannot find another DHCP server. This technology may give you problems in regards to connections, but the "ipconfig /renew" command in Windows can help you manually re-establish the lease. Doing this on a Macintosh requires opening the network utility under system preferences, and in Linux "sudo ifconfig eth0 down" followed by "sudo ifconfig eth0 up" should accomplish the same thing. Lastly, there are some special types of IP addresses. For example, the loopback address, or 127.0.0.1, automatically references your own device's address. You also have private IP address numbers under Class A, Class B, and Class C licenses.