Restrictions when choosing and registering a new domain. How the domain name system works

Hi all. Relatively recently, two interesting widgets from VKontakte appeared.

These are “Write Us” and “Community Messages”, but many still haven’t heard of them. Today we’ll talk about why they are needed and how to install them on your landing page.

“Write to us” widget

The essence of the “Write to us” widget is that a button (link) is placed on the site, by clicking on which the user enters a dialogue with the community where he can ask questions that interest him.

This widget works for:

• groups;
• communities;
• personal pages.

But groups and communities must be enabled to accept messages. This is done in the settings of the group or public itself.

Installing the “Write to Us” widget

link :

There are just a few options to configure. Button text, size and link to the page from which the dialog will appear.

To install on the site, copy the first script between head tags. And the div and the second squeak are in the place where the widget itself will be displayed.

More interesting option, in my opinion, is the “Community Messages” widget. This is a kind of online consultant. You have a button on your website that, when clicked, opens a window with a dialogue with familiar interface In contact with. At the same time, you can not only write text, but also attach a document or photo.

To add such a widget to your site, you must have a community created and “Community Messages” and “Message Widget” enabled in it. This is where the main settings are made.

• « Greetings" - This automatic message, which will be sent to the user when he opens the dialog.
• « brief information" is the text/greeting that the user will see. You need to try to formulate it in such a way as to encourage a visitor to your site to write to you.
• « Offline status" will be shown to the user if you have not responded to him within 30 minutes.
• « Allowed domains" are the domains on which the widget will be displayed.

Installing the Community Posts widget

In order to get the widget code, you need to follow this

A subdomain is part of a larger domain. For example, mail.google.com, www.google.com and docs.google.com are subdomains of the google.com domain. As a rule, website owners create them to make it easier for users to remember the addresses of sections and services.

Base Domain

Main domain

Additional domain

Domain alias

IP address

An IP address (or Internet Protocol address) is a set of numbers indicating the location of a device on the Internet. Example IP address: 74.125.19.147.

A domain name can have multiple IP addresses associated with it, so Google Email and sites you need to provide additional information.

Domain Registrar

A registrar is a company that sells available domain names. Often these companies also offer services.

You can register for the Google Domains beta version or use the services of our partners and purchase a domain name upon registration in Google Cloud. If you purchased a domain when you signed up for a G Suite account, Gmail and personal web addresses are automatically activated. If you purchased your domain before you subscribed, change your DNS records at your domain registrar.

Domain registrar

A domain registrar maintains your domain's DNS servers and provides tools for managing DNS records, specifically MX records for Gmail settings and CNAME records to create web addresses. Many of them also help you register domain names.

Domain Name Server

The DNS server serves as the reference point for your domain's DNS data and is typically maintained by . A failure on the DNS server can cause problems with mail and website operation. To avoid creating a single point of failure, you must use at least two unrelated DNS servers. In some countries, DNS servers must be located on different IP networks - this increases the reliability of their operation. DNS records for a domain obtained from different servers, must match, but the order in which they are returned does not matter.

WHOIS directory

WHOIS is a publicly available directory of domain names indicating their owners (individuals or legal entities).

For security reasons, some domain owners prefer not to disclose personal information in the WHOIS directory, as some subscribers do not want to place personal number phone number in the city phone book.

Using the WHOIS directory, you can find out who owns domain names and IP addresses. There are many free web directories on the Internet, but the WHOIS publishes, among other things, your mailing address and telephone number.

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Hello, dear readers of the blog site. This blog has detailed information. After or while reading this publication, I advise you to read that article so that a complete picture emerges. I also advise you to read my publications on the topic of what and means.

Today we have a question on our agenda - what is domain or domain name(essentially, these are synonyms). Well, it's actually simple. This is the name for the site, which is assigned to it instead of the difficult-to-remember IP address of the server on which this site is hosted (see). Enter this name in address bar browser and the site opens.

But the difficulties arise precisely in the details. What are they, how does it all work, what domain zones are, how to understand what level domain and which of them can be registered, where this can be done and which zone to choose. There are a lot of questions and I will try to answer them all in this “small note”.

What is a domain?

As I mentioned above, domain is the name for the site..162.192.0. And besides, imagine the situation. You have placed your website on a hosting server (see what this is above) and received an IP address. But, moving to another hosting, the IP will change, which will cause a disaster. But in the case of domain names, this will not happen. Why?

The fact is that there are thousands of DNS (domain name system) servers on the Internet, which will state that the domain site is accessible at the IP address 108.162.192.0. If I move to another hosting, I will go to the domain name registrar panel (where I bought it), change some things in all DNS servers The Internet will indicate that the site needs to be searched at a different IP address. Convenient right?

Convenient, but probably not yet clear. The main thing you need to understand is the name for the site is a very important thing and it is for life (as a rule, although you can transfer the site to another domain if you wish, this is not easy). Whatever you name the boat, that’s how it will float. True, not only the name is important, but also the level of the domain, as well as the zone to which it belongs. Is it unclear again? Well, let's take things in order.

How a domain name works

Let's start with the basics. The domain record (site name) must include all levels of nesting of the domain (all zones it belongs to) so that it is unique and does not cause confusion.

There are two main domain name registration rules:

1. Zones included this domain, are listed from right to left.
2. Dots are used as separators.

It might look like this, for example:

Net.blog.site

We get the fourth level domain net, which is part of domain zone third level “blog”, which is included in the second level zone “ktonanovenkogo” belonging to the first level zone.ru. Nonsense, right? (my wife, who checks errors in the article, will be happy to confirm this).

What domain levels are distinguished?

1. Root domain(level zero) is considered to be an empty entry, denoted simply by a dot (.). In theory, full record domain name should always end with a dot, but in most cases it is omitted (as if meaning) and instead of writing: site.

   They use the already well-established relative notation of domains (without a dot at the end):

2. Next comes the first level - this is usually regional(national) domains (.ru, .su, .ua, .us, .de, .fr, etc.) or thematic(.com, .edu, .org, .net, etc.). But there are also first-level domain names that include national alphabets(for example, .рф).
3. Second level- these are already the same domains that you and I we buy(we register with special registrars). Their prices vary not only depending on their belonging to a particular first-level domain (for example, xxxxxxx.ru is usually cheaper to buy than xxxxxxx.com), but also depending on the registrar (or its reseller - retailer).
4. Third, fourth, etc. — you no longer need to buy them (as a rule) and can be created independently (without registering anywhere) based on the purchased second-level domain. For example, I can create a name like this for a new site - forum..forum..

Let me explain all this again For example:

1. . (dot) - zero (root) level domain
2. ru - first level, also called domain top level or zone
3. website - second level domain name
4. blog.site - third level domain
5. net.blog.site - fourth level

Top (first) level domains

Apart from the zero level (root domain), because this is emptiness, then the base is the so-called zones or top-level domains(the name of any site begins with them, although it seems that it ends with them - but not the point). They can't be bought to an ordinary person, but it is from these zones that we will choose when purchasing a second-level domain (name for our website).

So what are they?

1. First (highest) level domains, assigned to countries, which are usually among a hell of a lot smart people are called by the abbreviation Cctld, meaning country code top-level domain. Russia has two of them:
   1. su - a rudiment left over from Soviet Union and now representing the resource space in Russian
   2. ru - originally assigned to Russia
2. Domains with national alphabets, which are usually abbreviated Idn (internationalized domain name). In Russia it is zone.rf. In fact, their names are still written in English characters (recoding occurs), but this is, as it were, hidden from view. However, if you enter the address in your browser: http://ktonanovenkogo.rf/

   and after going to this site, copy its address from the address bar, you will get completely indigestible nonsense:

   Http://xn--80aedhwdrbcedeb8b2k.xn--p1ai/ It turns out he looks so unpleasant. And it is in this form that it will have to be added to different services(like), and not in the form of someonenew.rf. This needs to be taken into account. Yes, other problems are possible, although not obvious at first.

3. Upper domains common use , usually called Gtld, which means generic top-level domain, are registered (sold) regardless of the country in which the webmaster lives. The most used of them:
   1. .com - for commercial projects
   2. .org - for non-profit websites of various organizations
   3. .net - for Internet-related projects
   4. .edu - for educational institutions and projects
   5. .biz - only commercial organizations
   6. .info - for all information projects
   7. .name - for personal sites
   8. .gov - for US government agencies

How and where you can register (buy) a domain in top-level zones

As a rule, you can’t get second-level domain names just like that (and it’s better not to try, because the name for the site is too important to risk registering it with someone unknown). They cost money. Moreover payment is made annually, and then the domain lease needs to be renewed.

Let me draw your attention once again - buy second level domain names, and everything above - you can create on their basis yourself. This is usually done in the panel of your hoster in the subdomains section - these are third-level and higher-level domains, such as blog..blog.site.

There are not so many such companies (prominent examples include RegRu And WebNames), but they may have a whole network of resellers (partners) who will select and sell domains on their behalf. If you are not satisfied with the current reseller in some way or you have any tension with him, then by contacting the registrar, you can choose another reseller or go directly under the wing of the registrar.

At all no limits You can buy domains in the public zones .com, .net, .org, .info, .biz and .name. In the .edu, .gov and .mil zones, this opportunity is provided only for institutions, as well as state educational and military institutions. There are also a number of specialized first-level domains, for example, .travel, .jobs, .aero, .asia.

Second level domain names in these public areas can be purchased from any registrar(not only national), which, in fact, is what some resources use, which may have conflicts with copyright holders. The same torrent was forced to move to the public zone org, because its resource was blocked in the national domain zone ru.

Second level domains - employment verification and Whois

There are already about half a billion domain names registered on the Internet. different zones, so choosing a good (short, simple, sonorous) name in the right zone is now very not an easy task (just like it's difficult). A third of the registered names are not used at all, because they were purchased for resale (successful domains can be expensive on the secondary market - sometimes many millions of dollars).

Domain name occupancy check

Therefore, the first thing you should do when selecting a suitable domain for your website is . This can be done at different registrars (the result will be the same, since they use a common database).

Below are released in this moment domains(click on price for detailed view):

Good luck to you! Before see you soon on the pages of the blog site

You can watch more videos by going to

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Checking for employment and purchasing a domain name, what is the difference between domain registrars and resellers and what is WHOIS
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According to the guidelines (RFC-1034, RFC-1035), the domain name system consists of three main parts:

• Total set of domain names (domain name space)
• Domain name servers
• DNS Clients (Resolvers)

Many domain names were discussed in detail in the material “Domain addressing. A little history and principles of construction,” so let’s focus on the two remaining components: servers and resolvers.

The domain name system service is built according to the client-server scheme. The client part is an application process that requests information about the correspondence of the name to the address (or vice versa, the address of the name). This software is called a resolver. Acts as a server application program-server.

Most often, Resolver is not any program or system component. This is a set of procedures from the application library software(for example, from the libc library) that allow a program edited with them to make queries to the domain name system and receive responses to them. These procedures contact the domain name server and thus serve requests from the user's application programs.

A number of manufacturers operating systems, for example, Sun or SGI, offered solutions in which the resolver was a separate process, and application programs interacted with DNS through it.

Another example of a resolver implementation is some versions of Nescape browsers, where a separate resolver process was launched to speed up the process of receiving responses to DNS queries.

A standalone resolver can also be compiled in BIND version 9. This is the so-called lightweight resolver. It consists of a rosolver daemon and a library for interacting with this daemon, the procedures of which are linked with application software. This resolver allows you not only to send requests to a domain name server, but also to cache correspondence between a domain name and an IP address.

The most commonly used domain name servers are different versions BIND (Berkeley Internet Name Domain). If the server is implemented on Windows platform, then they use the solution from Microsoft, although there are also BIND versions for this platform.

General interaction scheme various components Domain name systems can be depicted as shown in the following figure:

Fig1. A recursive resolver request and a non-recursive (iterative) procedure for resolving a domain name by a domain name server.

This name resolution scheme (establishing a correspondence between a name and an IP address) is called non-recursive (iterative). How it differs from recursive we will discuss later.

Let us explain the following diagram of a non-recursive query resolution procedure:

1. The application program, through the resolver, requests an IP address by domain name from the local server (the resolver request is recursive, i.e. the resolver asks the server to find the address for it).
2. The local server provides the application with the IP address of the requested name while non-recursively querying domain name servers. Wherein:
   1. if the address is in the area of ​​its (local server) responsibility, it immediately reports it to the resolver,
   2. if the address is in the area of ​​responsibility of another domain name server, then it contacts root server domain name systems behind the TLD server address (top-level domain server),
   3. contacts the TLD server for the address,
   4. receives the remote server address from it,
   5. contacts a remote server for an address,
   6. receives an address from a remote server,

IN in this case we considered the nesting of a second-order domain name, i.e. the host had a name similar to quest.kuku.ru or even kuku.ru.

The latter is important to understand, because corporate postal addresses type [email protected] This is precisely what requires the application software to contact the IP address of the kuku.ru host. The TLD server of the ru domain does not have information about which IP address given name matches, but at the same time it knows which server is responsible for the kuku.ru domain.

If the nesting of the domain name is greater, say the third level (host.department.corp.ru), and this level is supported by another domain name server, different from the one that supports the second level of nesting, then the remote domain name server will transfer to our local server not the host address, but the address of the new domain name server whose area of ​​responsibility is the requested name.

As you can see from the above diagram, obtaining information from the domain name system is a multi-step process that is not implemented instantly. The following example shows how DNS works in practice.

When entering the mode remote terminal to the computer polyn.net.kiae.su using the command:

/usr/paul>telnet polyn.net.kiae.su

We receive in response:

/usr/paul>telnet polyn.net.kiae.su trying 144.206.130.137 ... login: .....

The line indicating the IP address of the computer polyn.net.kiae.su shows that by this time the domain name was successfully resolved by the domain name server and the application program, in this case telnet, received an IP address for its request. Thus, after entering the command from the console, and before the IP address appeared on the monitor screen, the application program made a request to the domain name server and received a response to it.

Quite often you may encounter a situation where, after entering a command, you have to wait quite a long time for a response from the remote machine, but after the first response remote computer begins to respond to commands at the same speed as your own Personal Computer. In this case, the domain name service is most likely to blame for the initial delay.

Another example of the same sort is the traceroute program. Here, the delay in requests to the domain name server is manifested in the fact that the response time from the gateways on which ICMP packets “die”, indicated in the report, is small, and the delays in displaying each line of the report are quite large.

It is curious that in Windows system 3.1, some tracing programs first showed the IP address of the gateway, and only then, after allowing the “reverse” request, replaced it with the domain name of the gateway. If the domain name service worked quickly, then this substitution was almost unnoticeable, but if the service worked slowly, then the gaps were quite significant.

You can check how sensitive traceroute requests are from the point of view of displaying a trace to the use of a domain name server by specifying a trace search using the server:

>traceroute www.w3.org

and without using a server:

>traceroute -n www.w3.org

If in the example with telnet and ftp we considered only “direct” requests to the domain name server, then in the example with traceroute we first mentioned “reverse” requests. In a "direct" request, the application program asks the domain name server for an IP address, telling it the domain name. In a "reverse" request, the application program requests a domain name by providing the domain name server with an IP address.

It should be noted that the speed of resolving "forward" and "reverse" requests in general case will be different. It all depends on where the “forward” and “reverse” zones are described in the databases of the domain name servers serving the corresponding domains (forward and reverse).

We will touch on this issue in more detail when discussing the named program configuration files.

However, let's return to discussing how the domain name system works. Actually, the query discussed above is non-recursive only from the server’s point of view. From the resolver's point of view, the request resolution procedure is recursive, since the resolver has entrusted the local domain name server with the task of searching necessary information. According to RFC-1035, the resolver itself can query remote domain name servers and receive answers to its requests from them.

In this case, the resolver contacts the local domain name server; if it does not receive an address from it, then it queries the server root domain, receives from it the address of the remote TLD server, queries this server, receives the address of the remote server, queries the remote server and receives the IP address if it sent the so-called “direct” request.

Fig.2. Non-recursive resolver query.

As you can see from this diagram, the resolver itself found the required IP address. However general practice is such that the resolver does not generate non-recursive queries, but forwards them to the local domain name server.

The local server and resolver do not perform all requests according to the specified procedure. The fact is that there is a cache that is used to store information received from a remote server.

The smartest resolvers, such as the Windows 2000 Server resolver and BIND 9, are able to maintain a cache in which they save not only successfully established name-address matches (positive response), but also the so-called “negative” response results ) for inquiries. In addition, these resolvers organize responses about server addresses in accordance with their (resolver) preference algorithms, which are based on server response time.

Fig.3. Request resolution scheme with response caching.

If a user accesses the same network resource within a short time, the request is not sent to the remote server, and the information is looked up in the cache.

Generally speaking, the order of request processing can be described as follows:

1. searching for the answer in the local cache
2. searching for an answer on the local server
3. searching for information on the Internet.

In this case, both the resolver and the server can have a cache.

There is a difference between a domain and a zone that can be difficult to find, but should always be kept in mind. A domain is all the sets of machines that belong to the same domain name. For example, all machines that have the postfix kiae.su in their name belong to the kiae.su domain. A zone is the “area of ​​responsibility” of a specific domain name server, i.e. The concept of a domain is broader than the concept of a zone. If a domain is divided into subdomains, then each of them can have its own server. At the same time, the server’s area of ​​responsibility is more than high level there will be only that part of the domain description that is not delegated to other servers. Splitting a domain into subdomains and organizing a server for each of them is called delegation of zone management rights to the appropriate domain name server, or simply zone delegation.

When setting up a server, you can directly enter the addresses of zone servers in its configuration files. In this case, calls to the root server are not made, because the local server itself knows the addresses of remote zone servers, to which it has delegated the rights to manage these zones.

There is also another option for the server to operate when it does not query the root server for the address of the remote domain name server. This happens when shortly before the server has already resolved the task of obtaining an IP address from the same domain. If you need to obtain the IP address of a remote domain name server responsible for a domain, it will simply be retrieved from the server buffer (cache), because for a certain time specified in the zone description configuration (Time To Live - TTL), this address will be stored in the server cache. And it got there as a result of executing the previous request.

In addition to the non-recursive name resolution procedure, it is also possible recursive procedure name resolution. This differs from the non-recursive procedure described above in that the remote server itself queries its zone servers, rather than reporting their addresses to the local domain name server. Let's consider this case in more detail.

Figure 4 demonstrates the non-recursive procedure for resolving an IP address from a domain name. The main load in this case falls on the local domain name server, which polls all other servers. In order to reduce the number of such exchanges, if volume allows random access memory, you can enable buffering (caching) of addresses. In this case, the number of exchanges with remote servers will be reduced.

In Figure 5, the remote domain server itself resolves the request to obtain the IP address of its domain host by recursive request, using non-recursive polling of its subdomain servers.

Figure 4. Non-recursive processing of a request by a local domain name server to obtain an IP address for a domain name.

Rice. 5. Recursive (for a local server) and non-recursive (for a remote server) procedures for resolving an address by IP name.

Wherein local server immediately receives from remote address host, not the addresses of subdomain servers. To a remote server In this case, servicing recursive requests from the corresponding IP address must be allowed; the local server must contact the remote server with a recursive request.

The options presented here for how the domain name system works are not exhaustive. For more detailed information reference should be made to RFC-1034 and RFC-1035.

1. P. Mockapetris. RFC-1034. DOMAIN NAMES - CONCEPTS AND FACILITIES. ISI, 1987. (http://www.ietf.org/rfc/rfc1034.txt?number=1034)
2. P. Mockapetris. RFC-1035. DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION. ISI, 1987. (http://www.ietf.org/rfc/rfc1035.txt?number=1035)
3. Albitz P., Lee K.. DNS and BIND. - Per. from English - St. Petersburg: Symbol-Plus, 2002. - 696 p.

1. http://www.microsoft.com/windows2000/en/server/help/sag_DNS_und_HowDnsWorks.htm?id=1945 - Microsoft Documentation for Windows 2000 Server. This section is devoted to the principles of operation of the domain name system. Describes general principles building DNS and interaction between resolver and servers.
2. http://www.microsoft.com/windows2000/en/server/help/sag_DNS_ovr_ClientFeatures.htm?id=1942 - Microsoft Documentation for Windows 2000 Server. This section is devoted to the principles of resolver operation.
3. - BIND 9 documentation. Help Guide system administrator. You need to read the section on lightweight resolver.
4. http://www.igc.ru/cgi-bin/man-cgi?traceroute - description of the traceroute command, since it was mentioned here.
5. http://www.menandmice.com/online_docs_and_faq/glossary/glossarytoc.htm - glossary of DNS terms.

Greetings, dear readers! In this article I will try in simple words tell you what a domain is and why it is needed. And also, for those who are planning to launch their website on the Internet, I will give a few additional instructions that you definitely need to know.

Domain(more precisely called “ fully qualified domain name") is the address of the Internet space (site) on which it is located and at which global network You can find it on the internet.

If you now go to blog home page and look at the browser line, you will see the following.

This address is called the full domain name of the site. In the browser you are using, given address may look different.

• . Many modern browsers it is hidden.

Prefixes http, https And www do not relate to domains in any way.

A domain name can be compared to the address of any house in the world. Knowing the address, you can find the right house.

Basically, ordinary user You don't need to know more. I hope I answered your question.

Now let's take it to a more advanced technical level.

The definition is not for dummies

I'll start with an analogy. Every seat on ours globe there are coordinates at which it is located. For example, a couple of days ago we passed through Volgograd and visited the famous place Mamayev Kurgan with the highest monument in Russia and Europe “The Motherland Calls!”, which is located at coordinates 48°44′32″N, 44°32′14″E48 .742286, 44.537112.

Naturally, we did not look for this place by its coordinates, but by its name.

The same thing happens on the global Internet, each place (space) where site data is stored has its own IP address (unique network address). Thus, you can get to the site not only by domain, but also by its IP address.

For example, if you enter the following IP address 93.158.134.3 in the address bar of your browser, it will open home page Yandex. But sometimes several sites can be stored at one such address, and so that the user can get to the resource he needs, unique domain names are used in a convenient human form.

It's like apartments in a building at the same address.

Domain name structure

All domain names consist of areas - domains (from English domain is translated as region, territory).

Each name includes a top (first) level domain; it is customary to define a zone by it. In my case it is “ru”. Next comes mine unique domain second level “iklife”..site.

It turns out that no one except me can locate their website in this domain zone; it belongs only to me.

Again, by analogy, they have a similar structure: country, region, city, street, etc.