IP Address

Every device connected to the public Internet is assigned a unique number known as an Internet Protocol (IP) address. IP addresses consist of four numbers separated by periods (also called a 'dotted-quad') and look something like 127.0.0.1.
Since these numbers are usually assigned to internet service providers within region-based blocks, an IP address can often be used to identify the region or country from which a computer is connecting to the Internet. An IP address can sometimes be used to show the user's general location.
Because the numbers may be tedious to deal with, an IP address may also be assigned to a Host name, which is sometimes easier to remember. Hostnames may be looked up to find IP addresses, and vice-versa. At one time ISPs issued one IP address to each user. These are called static IP addresses. Because there is a limited number of IP addresses and with increased usage of the internet ISPs now issue IP addresses in a dynamic fashion out of a pool of IP addresses (Using DHCP). These are referred to as dynamic IP addresses. This also limits the ability of the user to host websites, mail servers, ftp servers, etc. In addition to users connecting to the internet, with virtual hosting, a single machine can act like multiple machines (with multiple domain names and IP addresses).
Two versions of the Internet Protocol (IP) are in use: IP Version 4 and IP Version 6. Each version defines an IP address differently. Because of its prevalence, the generic term IP address typically still refers to the addresses defined by IPv4. The gap in version sequence between IPv4 and IPv6 resulted from the assignment of number 5 to the experimental Internet Stream Protocol in 1979, which however was never referred to as IPv5.

IP version 4 addresses

Main article: IPv4#Addressing

Decomposition of an IPv4 address from dot-decimal notation to its binary value.

In IPv4 an address consists of 32 bits which limits the address space to 4294967296 (2³²) possible unique addresses. IPv4 reserves some addresses for special purposes such as private networks (~18 million addresses) or multicast addresses (~270 million addresses).
IPv4 addresses are canonically represented in dot-decimal notation, which consists of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g., 172.16.254.1. Each part represents a group of 8 bits (octet) of the address. In some cases of technical writing, IPv4 addresses may be presented in various hexadecimal, octal, or binary representations.

IPv4 subnetting

In the early stages of development of the Internet Protocol, network administrators interpreted an IP address in two parts: network number portion and host number portion. The highest order octet (most significant eight bits) in an address was designated as the network number and the remaining bits were called the rest field or host identifier and were used for host numbering within a network.
This early method soon proved inadequate as additional networks developed that were independent of the existing networks already designated by a network number. In 1981, the Internet addressing specification was revised with the introduction of classful network architecture.
Classful network design allowed for a larger number of individual network assignments and fine-grained subnetwork design. The first three bits of the most significant octet of an IP address were defined as the class of the address. Three classes (A, B, and C) were defined for universal unicast addressing. Depending on the class derived, the network identification was based on octet boundary segments of the entire address. Each class used successively additional octets in the network identifier, thus reducing the possible number of hosts in the higher order classes (B and C). The following table gives an overview of this now obsolete system.

IPv4 private addresses

Early network design, when global end-to-end connectivity was envisioned for communications with all Internet hosts, intended that IP addresses be uniquely assigned to a particular computer or device. However, it was found that this was not always necessary as private networks developed and public address space needed to be conserved.
Computers not connected to the Internet, such as factory machines that communicate only with each other via TCP/IP, need not have globally unique IP addresses. Three ranges of IPv4 addresses for private networks were reserved in RFC 1918. These addresses are not routed on the Internet and thus their use need not be coordinated with an IP address registry.
Today, when needed, such private networks typically connect to the Internet through network address translation (NAT).

IANA-reserved private IPv4 network ranges

	Start	End	No. of addresses
24-bit Block (/8 prefix, 1 × A)	10.0.0.0	10.255.255.255	16777216
20-bit Block (/12 prefix, 16 × B)	172.16.0.0	172.31.255.255	1048576
16-bit Block (/16 prefix, 256 × C)	192.168.0.0	192.168.255.255	65536

Any user may use any of the reserved blocks. Typically, a network administrator will divide a block into subnets; for example, many home routers automatically use a default address range of 192.168.0.0 - 192.168.0.255 (192.168.0.0/24).

IPv4 address exhaustion

IPv4 address exhaustion is the decreasing supply of unallocated Internet Protocol Version 4 (IPv4) addresses available at the Internet Assigned Numbers Authority (IANA) and the regional Internet registries (RIRs) for assignment to end users and local Internet registries, such as Internet service providers. IANA's primary address pool was exhausted on February 3, 2011 when the last 5 blocks were allocated to the 5 RIRs. APNIC was the first RIR to exhaust its regional pool on 15 April 2011, except for a small amount of address space reserved for the transition to IPv6, intended be allocated in a restricted process

IP version 6 addresses

Main article: IPv6 address

Decomposition of an IPv6 address from hexadecimal representation to its binary value.

The rapid exhaustion of IPv4 address space, despite conservation techniques, prompted the Internet Engineering Task Force (IETF) to explore new technologies to expand the Internet's addressing capability. The permanent solution was deemed to be a redesign of the Internet Protocol itself. This next generation of the Internet Protocol, intended to replace IPv4 on the Internet, was eventually named Internet Protocol Version 6 (IPv6) in 1995^. The address size was increased from 32 to 128 bits or 16 octets. This, even with a generous assignment of network blocks, is deemed sufficient for the foreseeable future. Mathematically, the new address space provides the potential for a maximum of 2¹²⁸, or about 3.403×10³⁸ unique addresses.
The new design is not intended to provide a sufficient quantity of addresses on its own, but rather to allow efficient aggregation of subnet routing prefixes to occur at routing nodes. As a result, routing table sizes are smaller, and the smallest possible individual allocation is a subnet for 2⁶⁴ hosts, which is the square of the size of the entire IPv4 Internet. At these levels, actual address utilization rates will be small on any IPv6 network segment. The new design also provides the opportunity to separate the addressing infrastructure of a network segment — that is the local administration of the segment's available space — from the addressing prefix used to route external traffic for a network. IPv6 has facilities that automatically change the routing prefix of entire networks, should the global connectivity or the routing policy change, without requiring internal redesign or renumbering.
The large number of IPv6 addresses allows large blocks to be assigned for specific purposes and, where appropriate, to be aggregated for efficient routing. With a large address space, there is not the need to have complex address conservation methods as used in Classless Inter-Domain Routing (CIDR).
Many modern desktop and enterprise server operating systems include native support for the IPv6 protocol, but it is not yet widely deployed in other devices, such as home networking routers, voice over IP (VoIP) and multimedia equipment, and network peripherals.

IPv6 private addresses

Just as IPv4 reserves addresses for private or internal networks, blocks of addresses are set aside in IPv6 for private addresses. In IPv6, these are referred to as unique local addresses (ULA). RFC 4193 sets aside the routing prefix fc00::/7 for this block which is divided into two /8 blocks with different implied policies The addresses include a 40-bit pseudorandom number that minimizes the risk of address collisions if sites merge or packets are misrouted.
Early designs used a different block for this purpose (fec0::), dubbed site-local addresses. However, the definition of what constituted sites remained unclear and the poorly defined addressing policy created ambiguities for routing. This address range specification was abandoned and must not be used in new systems.
Addresses starting with fe80:, called link-local addresses, are assigned to interfaces for communication on the link only. The addresses are automatically generated by the operating system for each network interface. This provides instant and automatic network connectivity for any IPv6 host and means that if several hosts connect to a common hub or switch, they have a communication path via their link-local IPv6 address. This feature is used in the lower layers of IPv6 network administration (e.g. Neighbor Discovery Protocol).
None of the private address prefixes may be routed on the public Internet.

IP subnetworks

IP networks may be divided into subnetworks in both IPv4 and IPv6. For this purpose, an IP address is logically recognized as consisting of two parts: the network prefix and the host identifier, or interface identifier (IPv6). The subnet mask or the CIDR prefix determines how the IP address is divided into network and host parts.
The term subnet mask is only used within IPv4. Both IP versions however use the Classless Inter-Domain Routing (CIDR) concept and notation. In this, the IP address is followed by a slash and the number (in decimal) of bits used for the network part, also called the routing prefix. For example, an IPv4 address and its subnet mask may be 192.0.2.1 and 255.255.255.0, respectively. The CIDR notation for the same IP address and subnet is 192.0.2.1/24, because the first 24 bits of the IP address indicate the network and subnet.

IP address assignment

Internet Protocol addresses are assigned to a host either anew at the time of booting, or permanently by fixed configuration of its hardware or software. Persistent configuration is also known as using a static IP address. In contrast, in situations when the computer's IP address is assigned newly each time, this is known as using a dynamic IP address.

Methods

Static IP addresses are manually assigned to a computer by an administrator. The exact procedure varies according to platform. This contrasts with dynamic IP addresses, which are assigned either by the computer interface or host software itself, as in Zeroconf, or assigned by a server using Dynamic Host Configuration Protocol (DHCP). Even though IP addresses assigned using DHCP may stay the same for long periods of time, they can generally change. In some cases, a network administrator may implement dynamically assigned static IP addresses. In this case, a DHCP server is used, but it is specifically configured to always assign the same IP address to a particular computer. This allows static IP addresses to be configured centrally, without having to specifically configure each computer on the network in a manual procedure.
In the absence or failure of static or stateful (DHCP) address configurations, an operating system may assign an IP address to a network interface using state-less auto-configuration methods, such as Zeroconf.

Uses of dynamic addressing

Dynamic IP addresses are most frequently assigned on LANs and broadband networks by Dynamic Host Configuration Protocol (DHCP) servers. They are used because it avoids the administrative burden of assigning specific static addresses to each device on a network. It also allows many devices to share limited address space on a network if only some of them will be online at a particular time. In most current desktop operating systems, dynamic IP configuration is enabled by default so that a user does not need to manually enter any settings to connect to a network with a DHCP server. DHCP is not the only technology used to assign dynamic IP addresses. Dialup and some broadband networks use dynamic address features of the Point-to-Point Protocol.

Sticky dynamic IP address

A sticky dynamic IP address is an informal term used by cable and DSL Internet access subscribers to describe a dynamically assigned IP address that seldom changes. The addresses are usually assigned with the DHCP protocol. Since the modems are usually powered-on for extended periods of time, the address leases are usually set to long periods and simply renewed upon expiration. If a modem is turned off and powered up again before the next expiration of the address lease, it will most likely receive the same IP address.

Address autoconfiguration

RFC 3330 defines an address block, 169.254.0.0/16, for the special use in link-local addressing for IPv4 networks. In IPv6, every interface, whether using static or dynamic address assignments, also receives a local-link address automatically in the block fe80::/10.
These addresses are only valid on the link, such as a local network segment or point-to-point connection, that a host is connected to. These addresses are not routable and like private addresses cannot be the source or destination of packets traversing the Internet.
When the link-local IPv4 address block was reserved, no standards existed for mechanisms of address autoconfiguration. Filling the void, Microsoft created an implementation that is called Automatic Private IP Addressing (APIPA). Due to Microsoft's market power, APIPA has been deployed on millions of machines and has, thus, become a de facto standard in the industry. Many years later, the IETF defined a formal standard for this functionality, RFC 3927, entitled Dynamic Configuration of IPv4 Link-Local Addresses.

Uses of static addressing

Some infrastructure situations have to use static addressing, such as when finding the Domain Name System (DNS) host that will translate domain names to IP addresses. Static addresses are also convenient, but not absolutely necessary, to locate servers inside an enterprise. An address obtained from a DNS server comes with a time to live, or caching time, after which it should be looked up to confirm that it has not changed. Even static IP addresses do change as a result of network administration (RFC 2072)

Public addresses

A public IP address in common parlance is synonymous with a, globally routable unicast IP address.^{[citation needed]}
Both IPv4 and IPv6 define address ranges that are reserved for private networks and link-local addressing. The term public IP address often used exclude these types of addresses.

Modifications to IP addressing

IP blocking and firewalls

Firewalls perform Internet Protocol blocking to protect networks from unauthorized access. They are common on today's Internet. They control access to networks based on the IP address of a client computer. Whether using a blacklist or a whitelist, the IP address that is blocked is the perceived IP address of the client, meaning that if the client is using a proxy server or network address translation, blocking one IP address may block many individual computers.

IP address translation

Multiple client devices can appear to share IP addresses: either because they are part of a shared hosting web server environment or because an IPv4 network address translator (NAT) or proxy server acts as an intermediary agent on behalf of its customers, in which case the real originating IP addresses might be hidden from the server receiving a request. A common practice is to have a NAT hide a large number of IP addresses in a private network. Only the "outside" interface(s) of the NAT need to have Internet-routable addresses.
Most commonly, the NAT device maps TCP or UDP port numbers on the outside to individual private addresses on the inside. Just as a telephone number may have site-specific extensions, the port numbers are site-specific extensions to an IP address.
In small home networks, NAT functions usually take place in a residential gateway device, typically one marketed as a "router". In this scenario, the computers connected to the router would have 'private' IP addresses and the router would have a 'public' address to communicate with the Internet. This type of router allows several computers to share one public IP address.

How to Fix Internet Embarrassments and Improve Your Online Reputation

Whether you're looking to hide your personal activities from prospective employers or you just don't want last Friday's naked wood-chopping contest making the rounds on the internet, getting rid of embarrassing online photos, videos, and messages can be tough. Here's how you can take action when you want to purge the internet of your shameful content and maintain your upstanding online reputation.
Google executive chairman Eric Schmidt famously said, "If you have something that you don't want anyone to know, maybe you shouldn't be doing it in the first place." His advice probably is your best course of action if you never want to be embarrassed again in your life, but it's also a good way to never have fun again. In fact, for most of us, there are certain embarrassments we're happy to share with certain folks but not others. At some point we've all had something to hide, but the internet makes that difficult. In this post we're going to take a look at how you can retake your privacy (or at least greatly improve it) and control your online reputation.
First we'll take a look at Facebook, the most popular social network on the planet and subsquently home to some of your most embarrassing photos, public arguments, and so on. Then we'll look at controlling what shows up on the web in general.

Get Embarrassing Content Removed from Facebook

Facebook wants to be the place where you share everything, but there are some moments in life you'd probably rather keep private. You can certainly prevent yourself from posting embarrassing drunk photos or a love letter you sent to a crush in high school, but you can't control other people. When a friend, family member, or enemy posts content you don't want anyone to see, here are the steps you need to take to get it removed.

Stage One: Use Facebook's Built-in Content Removal Tools

While Facebook won't let you delete content uploaded by another person, it will allow you to ensure it doesn't show up anywhere on your profile, wall, or photo stream. It's very easy to un-tag yourself in wall post by clicking the little gear icon that appears when you hover over a particular message. This gear's drop-down menu will give you three useful choices: remove from profile, remove tag, and remove/mark as spam. The differences between these three options are relatively minor. If a post is only showing up on your wall because you were tagged in it, removing the tag is enough to make it disappear from your page. If someone posted to your wall, specifically, you'll want to remove the post from your profile. If the post or tagged message on your wall is an ad or something that very much doesn't belong on your profile and comes from somebody you don't know, you'll want to mark it as spam instead. You could also use this option to get back at someone who deliberately tried to embarrass you, because they can get in trouble with Facebook if they have enough messages designated as spam, but that's not a very nice thing to do.
If you want to remove a photo from your profile and/or wall, the process is very similar. Just click on the embarrassing photo so you can view it and look for the options on the bottom right. If the photo is on your profile, you'll see a check mark and some text to let you know. Beside that text is a subtle link that says "Remove." Clicking it will keep this photo out of your profile's photo albums and photo stream. Further down you'll also see an option call "Report/Remove Tag." This is what you want to click to prevent this photo showing up as one of the photos you're tagged in and anywhere on your wall. You can remove the tag for no reason at all, but you'll also be asked if the photo is harassing you or a friend. Additionally, you can use this same function to report nudity, hate speech, and more. Basically, this one link is designed to handle reporting any photo that breaches Facebook's terms of use and/or your desire for personal privacy.
In the event that the problem photo is not terribly extreme, however, and you just don't want it showing up as one of the top five photos on your profile, you can remove it very easily. Just hover over that photo's thumbnail on your page and click the little "X" that appears in the top right corner.
These are the most common types of embarrassing content you'd want to remove and report, but Facebook provides similar tools for just about anything on the site. For instructions on dealing with embarrassing groups, fake profiles, and more, check out Facebook's content reporting FAQ.

Stage Two: Ask Your Friend to Remove the Embarrassing Content

Once you've done everything you can using Facebook's privacy tools, your next step should be to talk to the person who posted the embarrassing content regardless of your relationship. Even if you don't get along with the poster, s/he may be willing to remove it if you make a simple, kind request. Send them a polite message on Facebook requesting removal. Even if you get no response or a refusal, asking kindly demonstrates that you made a reasonable effort to get the content removed yourself. Be sure to take screenshots of the message should you need a copy sometime down the road.

Stage Three: Contact Facebook

Full size

There are many reasons a friend, enemy, or family member will want to keep the embarrassing content on their profile. If you've tried to reason with them and this content still upsets you greatly and Facebook's automated methods have gotten you nowehere, you can try to contact Facebook with a complaint. Unfortunately, Facebook does not provide an official means of actually contacting a human and doesn't promise a response. That said, you still have a few options:

1. Post in the help discussions to get advice from other Facebook users and occassionally from Facebook staff.
2. Submit a complaint via the Facebook Intellectual Property Infringement Form. In the event the offending content is a photo, you can report that you did not give the person posting this photo permission to use your likeness in any way and want it removed.
3. Submit a complaint via the Facebook Terms Violation Reporting Form. This form was designed to help people who can't access their accounts and need a means of getting help. You're supposed to use the aforementioned help discussions in the event you can still log in. If you're having issues with content removal, however, the help discussions may not be too helpful. Rather than give up, open a private browsing session or log out of your Facebook account to access this page and submit your issue.
4. Call Facebook headquarters at (650) 543-4800. If you press 1 for customer support, you'll just be notified that they do not offer it. (Thanks a lot, Facebook.) If you know a law enforcement officer that can call for you, they can press 2 and get a response in a couple of days. If you don't, try pressing 7 for "all other inquiries" and leaving a message. Chances are you won't hear back, but if you have an extreme situation that you can't take to the police this is worth a shot.
5. Send an email to info@support.facebook.com. Back when Facebook provided proper email support you'd reach them via this address. This address seems to be active, but few people have had any success in using it. If you're completely out of options, use it as a last-ditch effort.

Stage Four: Beef Up Your Privacy Settings

If you don't want embarrassing content posted on your profile page or wall, take preemptive measures and block it in advance. Facebook allows you to prevent others from posting to your wall and more, so if you're concerned about a particular individual or group of people just block certain privileges in advance.
To do this, you need to start by accessing your Privacy Settings. These are easy to find by going to the top right part of any page and clicking on the downward facing triangle (pictured to the right). This will reveal a menu where you can click Privacy Settings. From there you have a few relevant options.
 
How You Connect is the first and possibly only section you're going to need. Towards the bottom you'll find options allowing you to limit who can post on your wall and see wall posts by the people you allow. Setting this to "Friends" is often a safe bet, so only your public messages are visible and only you can see content contributed by others. Alternatively you can choose "Custom" and give access to only people in a specific Facebook List. While this won't remove the content, it'll make it much harder for people to actually find.
The How Tags Work section provides you with several options to help prevent unwanted tagging of photos, messages, and more. You can turn on "Profile Review" and "Tag Review" so that you get to approve every tag before it's allowed to become active.
Finally, the Manage Blocking section will allow you to block users from interacting with you in any way. You'll find this option at the bottom of the page and will only want to use it in extreme circumstances. It's important to remember that while it will prevent them from tagging you in embarrassing content, it won't prevent them from posting it.

Remove or Bury Unwanted Search Results

The fastest way to drudge up embarrassing information about anyone—whether they're on Facebook or not—is by hitting up your search engine of choice (although there are plenty of other methods). When your own shameful content shows up in Google, you can't always get it removed but there is plenty you can do to bury it.

Step One: Attempt to Get the Content Officially Removed

When you want embarrassing content out of a search engine, it helps to start at the source. Contact the web site where the content resides and simply ask them to remove it. Once it's off the site it'll fall out of the search results in due time. In the event the web site won't comply or you just want to be doubly sure your content won't show up, you can send a request to the search engine to have it removed. Most search engines offer this service. Here are instructions for Google, and Google Images, Bing. Some smaller search engines, like Duck Duck Go, have a standard contact form for all issues. If the page with embarrassing content is actually one you made, however, Bing has a support document that shows you how to tell search engines to avoid indexing it. When it's your pages that you don't want showing up in search results, follow those instructions.
In extreme situations, you can submit a legal complaint to Google. Google tends to respond to these legal complaints with quick removal, not taking much effort to investigate. This can be good for you if you want something removed, but bad for the person whose page is being removed as the appeal process can take a long time. You don't want to go this route unless someone is using your likeness without your consent, using your work without permission, defaming you, or potentially breaking the law in another way.

Step Two: Bury the Unwanted Content So Nobody Can Find It

When it comes to hiding something you don't want others to see, "noise" can be your best friend. One embarrassing photo is very easy to see when you're staring right at it, but when it's beside tons of other photos it gets lost pretty quickly—especially if you have to scroll on and on just to figure out where it is. If you can't get rid of something in a search engine, your best bet is to create more interesting and legitimate content to push it down and out of the way.

One of the easiest way to make this happen is to create profiles and pages on popular social sites like Twitter, YouTube, Vimeo, Flickr, Google+, Blogger, and so on, so your content will be indexed and show up in search results. Just be sure to use your real name so that the videos, photos, messages, or whatever you post are associated with that name.
As we've previously discussed, registering your name as a domain name and putting up a name plate web site can help you reclaim what shows up in your search results. Just be sure to add links to your web site on other social sites to help increase its page rank.
You'll need to actually manage your online reputation once you have it set up so your content rises above the embarrassing stuff you can't destroy. This doesn't require much more than actually using the services you sign up for and posting only things you want others to see. If you have a problem posting responsibly, install Internet Shame Insurance to get a warning before you post content you'll regret.

How About You?

Personally, I like to keep my embarrassments alive and well on the internet but I have quite a few friends who have struggled with the problem of eliminating theirs. It can be a long process to cover up the stuff you don't want others to see even if you do know what you're doing. Have you gone through the trouble of keeping your online persona pristine and shame-free? If you have any additional tips or stories to share, you know where to post them! (If you don't, actually, that place would be the comments.)