Welcome to “Computer Networks: Packets, IP Addressing, DNS, DHCP, and NAT”. After watching this video, you will be able to: Explain what packets and IP addresses are and how they relate to networking Explain the importance of DNS and DHCP servers and the NAT process Everything you do on the Internet involves packets. Every Web page that you visit arrives as a series of packets, and every e-mail you send leaves as a series of packets. Packets are also called frames, blocks, cells, or segments. There are three data transmission flow types: Simplex, Half-duplex, and Full-duplex. In Simplex mode, the communication is unidirectional, where one of the two devices on a link can only transmit but not receive, and the other only receive but not send. Like a radio or a keyboard. In half-duplex mode, each station can both transmit and receive, but not at the same time. Like a walkie-talkie. In full-duplex mode, both stations can transmit and receive simultaneously. Like a phone, or a messaging app. There are four basic transmission modes for IP packets: Unicast – transmission to a single, specific destination (used for most Internet traffic, such as HTTP, and FTP). Anycast – transmission to the closest of multiple nodes that have had the same unicast address assigned to them. Multicast – transmission to all nodes that have “subscribed” to the destination multicast “group” (address). Multicast transmission is limited to UDP protocol. Broadcast – transmission to all other nodes on the subnet (for example, to find a DHCPv4 server). Broadcast transmission is limited to UDP protocol over IPv4 only. When you send an email, it is broken down into individually labeled data packets. Each packet travels independently over the network And arrives at their destination in no set order. They are then compiled in the correct order to produce the original message. Internet Protocol version four or IPv4 is one of the core protocols for the Internet. It was developed to provide identification for every network device. Internet Protocol Version 6 or IPv6 is the newest version of Internet Protocol. IPv6 solves many of the limitations of IPv4, including address space and security. IPv4 only allows around 4.3 billion IP addresses. With all the smartphones, hotspots, smart speakers, and IoT devices, that’s just not enough anymore. IPv6 allows over 340 undecillion IP addresses (an undecillion has 36 zeroes). IPv6 ensures larger network capacity, with added efficiency and security features. An IP address is used to logically identify each device (or host) on a given network. An IPv4 IP address is a 32-bit binary value. It is broken into four 8-character binary values called octets. Each octet has a decimal value between 0 and 255. Any IP address with any octet higher than 255 is not a valid IP address. An IPv6 IP address is a 128-bit binary value broken into 8 fields, each separated by a colon. Each of the IPv6 binary values are represented by alphanumeric hexadecimal numbers. There are several different types of IP addresses: Static IP addresses: are manually assigned. Network servers or network devices that have specific protocol settings often use Static IP addresses. Dynamic IP addresses: are automatically assigned. They change every time the device connects to a network or changes location. A public IP address is used to communicate publicly outside of the local network. It connects to the internet. A private IP address is used to connect securely within an internal, private network. It does not connect to the Internet. Loopback IP address: is the range of IP addresses reserved for the localhost address. Reserved IP addresses are addresses that have been reserved by the IETF and the IANA for special purposes. The Domain Name System, or DNS, is the phonebook of the Internet. When you type a URL, like www.google.com, into a browser and press enter, the browser sends the URL to the DNS server. The DNS server replies with the proper IP address. Your browser will connect to the IP address provided. Because number-only IP addresses are not as easy for people to remember, DNS translates easy to remember web addresses to number-only addresses and ensures that both network devices and the people that use them know where they’re going. The Dynamic Host Configuration Protocol, or DHCP, automates the configuring of IP network devices. A DHCP server uses a pool of reserved IP addresses to automatically assign dynamic IP addresses or allocate a permanent IP address to a device. DHCP Static allocation: the server uses a manually assigned “permanent” IP Address for a device. DHCP Dynamic allocation: the server chooses which IP address to assign a device each time it connects to the network. DHCP Automatic allocation: the server assigns a “permanent” IP address for a device automatically. Subnetting is the process of taking a large, single network, and splitting it up into individual smaller subnetworks or subnets. Subnetting makes network routing much more efficient where traffic travels a shorter distance passing through fewer routers to reach its destination. Each subnet mask identifies the boundary between the IP network and the IP host. A subnet mask is like an IP address, but for only internal usage within a network. Routers use subnet masks to route data packets to the right place. Automatic Private IP Addressing, or APIPA, is a feature in operating systems like Windows that let computers self-configure an IP address and subnet mask automatically when the DHCP server isn't reachable. If a device can reach the local network but not the Internet, chances are the device was assigned an APIPA address. Find out by typing "ipconfig” into the command prompt. Network Address Translation, or NAT, is a process that maps multiple local private addresses to a public one before transferring the information. Organizations that want multiple devices to employ a single IP address use NAT, as do most home routers. NAT conserves public IP addresses and improves security. When data packets arrive at the public IP address, the NAT instructions send all data packets without revealing the private IP addresses of the intended destinations. That single network device acts as an intermediary between the private network and the Internet. A media access control address, or MAC address, is the physical address of each device on a network. A MAC address usually consists of six sets of two digits or characters, separated by colons. Technologies like Wifi, Bluetooth, and Ethernet use MAC addresses. A universally administered MAC address, or UAA, is uniquely assigned to a device by its manufacturer. A locally administered MAC address, or LAA, is assigned to a device by software or a network administrator, overriding the burned-in address for physical devices. MAC Addresses handle the physical connection from computer to computer while IP Addresses handle logical network connection routes. In this video, you learned: Data packets travel in any order across networks to be reassembled at the receipt point. The three types of data transmission modes are Simplex, Half-duplex, and Full-duplex. IPv4 and IPv6 are core protocols for the internet, with IPv6 being newer, more efficient, and more secure. Different IP address types are assigned and used for different purposes and security levels. Subnetting allows large networks to split into smaller, more efficient subnets.
