The following is an example of a subnet IP address you might have on your computer at home if you're using a router (wireless or wired) between your ISP connection and your computer: Show
Besides reserving IP addresses, the IANA is also responsible for assigning blocks of IP addresses to certain entities, usually commercial or government organizations. Your internet service provider (ISP) may be one of these entities, or it may be part of a larger block under the control of one of those entities. When you connect to the internet, your ISP assigns you one of these addresses. You can see a full list of IANA assignments and reservations for IPv4 addresses at IANA's website. If you only connect one computer to the internet, that computer can use the address from your ISP. Many homes today, though, use routers to share a single internet connection between multiple computers. If you use a router to share an internet connection, the router gets the IP address issued directly from the ISP. Then, it creates and manages a subnet for all the computers connected to that router. If your computer's address falls into one of the reserved subnet ranges listed earlier, you're going through a router rather than connecting directly to the internet. IP addresses on a subnet have two parts: network and node. The network part identifies the subnet itself. The node, also called the host, is an individual piece of computer equipment connected to the network and requiring a unique address. Each computer knows how to separate the two parts of the IP address by using a subnet mask. A subnet mask looks somewhat like an IP address, but it's actually just a filter used to determine which part of an IP address designates the network and node. A subnet mask consists of a series of 1 bits followed by a series of 0 bits. The 1 bits indicate those that should mask the network bits in the IP address, revealing only those that identify a unique node on that network. In the IPv4 standard, the most commonly used subnet masks have complete octets of 1s and 0s as follows:
People who set up large networks determine what subnet mask works best based on the number of desired subnets or nodes. For more subnets, use more bits for the network; for more nodes per subnet, use more bits for the nodes. This may mean using non-standard mask values. For instance, if you want to use 10 bits for networks and 22 for nodes, your subnet mask value would require using 11000000 in the second octet, resulting in a subnet mask value of 255.192.0.0. Another important thing to note about IP addresses in a subnet is that the first and last addresses are reserved. The first address identifies the subnet itself, and the last address identifies the broadcast address for systems on that subnet. See the sidebar for a look at how all this information comes together to form your IP address. Originally Published: Jan 12, 2001 The Domain Name System resolves the names of internet sites with their underlying IP addresses adding efficiency and even security in the process.
 The Domain Name System (DNS) is one of the foundations of the internet, working in the background to match the names of web sites that people type into a search box with the corresponding IP address, a long string of numbers that no one could be expected to remember. It's still possible for someone to type an IP address into a browser to reach a website, but most people want an internet address to consist of easy-to-remember words, called domain names. (For example, Network World.) In the 1970s and early 80s, the task of matching domain names and IP addresses was assigned to one person - Elizabeth Feinler at Stanford Research Institute, who maintained a master list of every internet-connected computer. This was obviously unsustainable, given the rapid growth of the internet, and, in 1983, Paul Mockapetris developed DNS, an automated, scalable system that handles domain-name-to-IP-address translation. There are currently more than 342 million registered domains, so keeping all those names in a single directory would be cumbersome. Like the internet itself, the directory is distributed around the world on domain name servers that communicate with each other on a regular basis to provide updates and eliminate redundancies. Another reason for the creation of a distributed system is to boost performance. For example, imagine if all of the requests coming in at the same time all over the world to resolve the domain name Google with the underlying IP address were being handled in a single location. To address this issue, DNS information is shared among many servers. That means a single domain can have more than one IP address. For example, the physical server that your laptop or smartphone reaches when you enter www.google.com is different from the server that someone in another country would reach by typing the same site name into their browser. But DNS still gets you to the right place, no matter where you are in the world. How does DNS work? Recursive resolvers and root, top-level, and name servers When your computer wants to find the IP address associated with a domain name, it first makes its DNS query via a DNS client, typically in a Web browser. The query then goes to a recursive DNS server, also known as a recursive resolver. A recursive resolver is typically operated by an Internet Service Providers (ISP), such as AT&T or Verizon (or some other third-party), and it knows which other DNS servers it needs to ask to resolve the name of a site with its IP address. The servers that actually have the needed information are called authoritative name servers. DNS is organized in a hierarchy. An initial DNS query for an IP address is made to a recursive resolver. This search first leads to a root server, which has information on top-level domains (.com, .net, .org), as well as country domains. Root servers are located all around the world, so the DNS system routes the request to the closest one. Once the request reaches the correct root server, it goes to a top-level domain server (TLD nameserver), which stores information for the second-level domain, which is the words that you type into a search box. The request then goes to a domain nameserver, which looks up the IP address and sends it back to the DNS client device so it can visit the appropriate website. All of this takes mere milliseconds. What is DNS caching? Chances are that you use Google several times a day. Instead of your computer querying the DNS nameserver for the IP address every time you enter the domain name, that information is saved on your personal device so that it doesn't have to access a DNS server to resolve the name with the IP address. Additional caching can occur on the routers used to connect clients to the internet, as well as on the servers of the user's ISP. With so much caching going on, the number of queries that actually make it to the DNS name servers is significantly reduced, which helps with the speed and efficiency of the system. How does the DNS numbering system work? Every device that connects to the internet needs to have a unique IP address in order to have traffic properly routed to it. DNS translates human queries into numbers using a system known as IPv4 or IPv6. With IPv4, the numbers are 32-bit integers that are expressed in decimal notation. The string of numbers is divided into sections, which include the network component, the host and the subnet, not dissimilar to a telephone number that might have a country code, an area code, etc. The network part of the number designates the class and category of network that is assigned to that number. The host identifies the specific machine on the network. The subnet part of the number is optional but is used to navigate the sometimes extremely large number of subnets and other partitions within a local network. IPv6, which was created to address concerns about the internet running out of IPv4 addresses, uses 128-bit-sized numbers, compared to 32-bit numbers with IPv4. There are 340 trillion trillion possible IPv6 addresses. Who assigns IP addresses? In 1998, the U.S. government handed the task of assigning IP addresses over to the Internet Corporation for Assigned Numbers and Names (ICANN). The not-for-profit organization has managed that function ever since without any notable disruptions. ICANN develops policies on things like the creation of new top-level domains (such as .io). For the most part, ICANN takes a neutral and advisory role. For example, anyone who wants to register a domain on the internet today can go to any number of ICANN-accredited registrars, which basically decentralizes the already decentralized DNS system. Once registered, new domains can populate and be reached worldwide via DNS servers in a matter of minutes. Is DNS secure? Cybercriminals are extremely clever when it comes to identifying vulnerabilities that can be exploited in just about any system, and DNS has certainly come in for its fair share of attacks. A 2021 IDC survey of more than 1,100 organizations in North America, Europe and Asia-Pacific, showed that 87% had experienced DNS attacks. The average cost of each attack was around $950,000 for all regions and about $1 million for organizations in North America. The report noted that organizations across all industries averaged 7.6 attacks during the previous year. The COVID-related shift to off-premises work and the response by companies to move resources to the cloud to make them more accessible have provided new targets for attackers, the report said. The researchers also found a sharp rise in data theft via DNS, with 26% of organizations reporting that sensitive customer information was stolen, compared with 16% in 2020. Common types of DNS attacks include DNS amplification, DNS spoofing or cache poisoning, DNS tunneling, and DNS hijacking or DNS re-direction. What is DNSSec? DNSSec is a security protocol devised by ICANN to help make communication among the various levels of servers involved in DNS lookups more secure. It addresses weaknesses in the communication between DNS top-level, second-level, and third-level directory servers that would allow hackers to hijack lookups. This hijacking allows attackers to respond to requests for lookups to legitimate sites by directing users to a malicious site. These sites could upload malware to users or carry out phishing attacks. DNSSec addresses this by having each level of DNS server digitally sign its requests, ensuring that requests sent by end users aren't commandeered by attackers. This creates a chain of trust so that at each level of the lookup, the integrity of the request is validated. DNSSec also can determine if a domain name really exists, and if it doesn't, prevents a fraudulent domain from being delivered to innocent requesters seeking to have a domain name resolved. What is DNS over HTTPS (DoH)? While DNSSec addresses potential vulnerabilities within the distributed network of DNS servers, it certainly hasn't stopped DNS-based cyberattacks that use some form of deception to inject malicious code into the DNS system. In one of the biggest shifts in the long history of DNS, Google, Mozilla, and others are encouraging a move to DNS over HTTPS or DoH, an IETF standard that encrypts DNS requests in the same way that the HTTPS protocol already protects most web traffic. The shift to DoH, however, is not without controversy. By encrypting DNS requests, DoH could get in the way of enterprise IT being able to monitor the web activity of employees, and parents have complained that it could block them from implementing parental controls over their children's internet usage. Uptake of DNS over HTTPS has been slow. On the client side, DoH comes with the latest version of Google Chrome and Mozilla Firefox, but it can be turned off by the end user. Organizations, that try to have some measure of control over which browsers and browser versions are used by employees, have the option to simply disable it. On the ISP side, many of the leading ISPS have not yet enabled DoH on their end. How to find my DNS server Generally speaking, the DNS server that you use will be established automatically by your ISP when you connect to the internet. If you want to see which servers are your primary name servers, there are web utilities that can provide information about your current network connection, such as browserleaks.com. While your ISP will set a default DNS server, you're under no obligation to use it. Some users may have reason to avoid their ISP's DNS, for example, if the ISP uses their DNS servers to redirect requests for nonexistent addresses to pages with advertising. As an alternative, you can point your computer to a public DNS server that will act as a recursive resolver. One of the most prominent public DNS servers is Google's. The IP address is 8.8.8.8. Join the Network World communities on Facebook and LinkedIn to comment on topics that are top of mind. Copyright © 2022 IDG Communications, Inc. What is a unique text based Internet address corresponding to a computer's unique IP address called?The Domain Name System (DNS) is one of the foundations of the internet, working in the background to match the names of web sites that people type into a search box with the corresponding IP address, a long string of numbers that no one could be expected to remember.
What converts text based addresses to IP addresses?A TCP converts text-based addresses to numeric IP addresses.
Which organization coordinates applications for new TLDs?org. The Internet Corporation for Assigned Names and Numbers (ICANN) is responsible for assigning these top level domain names. ICANN is a nonprofit organization that was formed in 1998.
Which of the following is a network that covers a small area such as a group of buildings or campus?A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a writing lab, school, or building.
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What is a unique text based Internet address corresponding to a computers unique IP address called?
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