May 31, 2006
IP Addresses
Every server on the internet is assigned a unique number – an IP (Internet Protocol) address. This number can be thought of as a 'telephone number' which allows other computers to find and access files no matter where they are. The IP address is 4 bytes (32 bits). Each byte is known as an octet and can have a value between 0 and 255, so IP addresses are written in the form of 123.456.78.9.
There are plans to expand the number of IP addresses with the introduction of version 6 (We currently use version 4) of the Internet Protocol. IPv6 has IP addresses which are 128 bits wide. This provides an almost unlimited number of unique addresses, but will take several years to implement because of the heavy cost of upgrading the Internet infrastructure.
Shared hosting solves the problem of limited IP addresses for web sites, but there is also a need for IP addresses for each personal computer which connects to the Internet to browse the web or send email. Rather than assign each PC a unique IP address, Internet Providers can use a system of 'dynamic addresses'. This means that each time you connect to the Internet through a dial-up or DSL modem you are assigned a different IP address.
So far we have been discussing how to use a web hosting company to host a web site, but there is no reason why you can't host a site on your home computer. The biggest technical difficulty for most people, though, is that they connect to the Internet using a dynamic IP address.
Dynamic addresses make it difficult to host a web site from home. Since the IP address is constantly changing nobody would be able to find your site unless you somehow notified them of your current IP address. There are dynamic DNS services, however, which allow you to assign a domain name to a site with a dynamic IP address. Each time you are assigned a new address your computer automatically notifies the service, which in turn updates its DNS (Domain Name Server).
Hosting a web site on your home computer, however, may not be a good idea. The computer has to operate server software and needs a high speed Internet connection. Your home Internet connection is probably a lot slower than those used by hosting companies so your web pages may load slowly – especially if they have a lot of graphics. If you have a small personal site with few visitors, though, it may be feasible to host your own site. Dynamic DNS is available as either a free or subscribed service.
Posted by WebHost at 01:33 PM | Comments (0)
May 30, 2006
Multiple Domain Web Hosting
Thanks to the low cost of domain names and hosting fees it is possible to own several websites without breaking the bank. There are several ways to manage multiple domains so it is important to know what your options are and the advantages and disadvantages of each method.
You may have an existing website and are happy with the services your host provides. If you decide to start a new website using the same host, you will have the reassurance of dealing with a company you are familiar with and trust. You may also get a discount for each additional account you open with the same host. On the other hand, using a new host for a second (or third or fourth) website can allow you to compare the quality of hosting offered by different companies. In addition, separate hosts will provide each of your web sites with a different IP address.
Having different IP addresses can be an important factor if you plan to link the sites together to aid in search engine optimization. Incoming links are an important indicator of the importance of a website, so a site with a lot of incoming links can get a higher position in search engines like Google. If all the links are coming from the same IP address, however, their value may be discounted.
Hosting your various sites with different hosting companies guarantees that each site has a different IP address. Individual IP addresses, however, are available as an extra from most web hosts. For a yearly fee each website can have its own unique IP address. This can help with search engine ranking and is also needed if you want to have a secure connection (https) on your site.
If you decide to host all your sites with the same company, there are three basic ways to go. Each site could have its own account; you could sign up for a re-seller account; or you could get a dedicated server account.
As a re-seller you are acting as an agent for the hosting company. You are allocated a certain amount of disk space and bandwidth and you are free to use them as you please. There may be a limit to the number of websites you can host with your re-seller account, but if there is space left over after using this account for your own sites you could earn some extra income by selling accounts to other people. The advantage of a re-seller account is that all the technical details are taken care of by the hosting company. Some will even provide gateways for billing your customers.
A dedicated server account gives you control of all the resources of an entire server. You are free to setup as many websites as you wish and allocate disk space and bandwidth as you see fit. The downside to this type of account is that you are responsible for maintaining the server. This can require a significant level of technical know-how so if you don't have that knowledge or don't feel like learning about it, dedicated servers are not for you. You can, of course, go with a managed dedicated server. The downside of this is the higher cost involved.
Hosting all your sites with one host can offer lots of advantages but there is one major disadvantage – if your server goes down, all your sites go down. If you are depending on your sites for income this can be a disastrous situation. For this reason, it is a good idea to have at least one of your sites with a different host. If your sites are essential for your livelihood and you can't afford any down time whatsoever, you would be advised to host everything with (at least) two hosts.
Posted by WebHost at 11:31 PM | Comments (0)
May 29, 2006
Website Monitoring Services
If you have gone through the trouble of building a web site and hosting it with a reliable company you obviously want your website to be available 24 hours a day 7 days a week. Downtime can result in lost sales and customer frustration.
There are hundreds of companies that provide monitoring services. Some are free while others charge anywhere from $5 to $60 per month. The paid services usually offer more features and allow you to use the same service with several different web sites. Web monitoring is not done continuously – time intervals range from every 3 minutes to every hour. The paid services usually offer the most comprehensive monitoring.
Monitoring works by sending an automatic request to your website and checking the response. These requests are the same as a web browser makes and the response to the request determines whether the site is up or down. Requests are usually sent from several different geographical locations to ensure that the site is available from various parts of the world.
If the response code is OK (200, 301, 302, 401, 403) nothing happens and the monitoring software waits for the next scheduled check. If the response code indicates that the web site is unreachable, there will be a second check a few seconds later from another location. There may be 3 or more of these checks before an alert is issued.
An alert can be sent to one or several email addresses or to a mobile device such as a pager or cell phone. This allows you to get in touch with your hosting company as soon as possible to ensure they are aware of the problem and are working to resolve it. As well as HTTP traffic, some website monitors can also check HTTPS, FTP, SMPT and POP3 so that all the functions of your website are covered.
Besides alerting you to downtime, these services can also provide useful statistics in the form of log files that indicate how often a site goes down. This third-party information can be used to demand better service from your web host or a refund in the case of severe amounts of downtime.
If you find that your site has an unacceptable amount of downtime, you should look for a more reliable hosting company. The best way to find a good host is to ask for recommendations from other web site owners. If they are happy with their service they will usually be glad to direct more business to their host.
Posted by WebHost at 10:28 PM | Comments (0)
May 28, 2006
Server to Web Browser – What Happens?
Each time you click on a link in a web page or type an address into your web browser you are making a 'request' for a certain document. That request is handled with the Hyper Text Transfer Protocol (HTTP) and sent over the Internet to the server which holds the document in question. If all goes well the server responds by sending the document -- usually a web page of text and graphics.
Transmission Control Protocol (TCP) is used to create connections between two computers on the Internet so they can exchange data. TCP has provisions for identifying the requesting computer and for transmitting data with time stamps so that it can be reassembled in the correct order once it arrives at its destination.
There are several TCP ports which have standardized uses. TCP port 21, for example, is usually reserved for FTP (File Transfer Protocol) for uploading and downloading files. Port 80 is usually used for HTTP.
If the server receives a request string on TCP port 80 in the form of GET / HTTP/1.1 it will send a response code depending on whether the requested web page is available or not. A typical request goes like this:
GET /faq.html HTTP/1.1
Host: http://www.mywebsite.com
This is a request for http://www.mywebsite.com/faq.html. The 'Host' needs to be specified to distinguish websites which are hosted on shared servers. If faq.html is available the server will respond:
HTTP/1.1 200 OK
Date: Mon, 12 October 2005 22:38:34 GMT
Server: Apache/1.3.27 (Unix) (Red-Hat/Linux)
Last-Modified: Wed, 08 Jan 2003 23:11:55 GMT
...followed by the actual web page.
HTTP/1.1 200 OK means that the requested web page is available. Other codes can also be returned. The code 404, for example, means that the server cannot find the requested page. The web page is sent via TCP as a series of data packets each with a header that specifies its destination and order in the data stream. The various packets can all take different paths to reach their destination. Each is sent through a router which polls other routers which are close by. If a connection with the first router is unavailable the data will be sent through another one.
As the data is received the client (the web browser) sends back an acknowledgement. This ensures that all the packets are received within a certain time. If not, they will be re-transmitted by the server. TCP also checks that the data is undamaged. The data is reassembled in the correct order thanks to the sequence number of each data packet. Voila! The web page appears on your computer screen.
The TCP connection can be kept alive for additional requests from the client. This allows several pages to be requested within a short time period without causing the overhead of opening and closing TCP ports. Either client or server can close the connection at any time.
Posted by WebHost at 01:25 PM | Comments (0)
May 27, 2006
Shared versus Dedicated Web Hosting
There are two basic types of web hosting packages – shared and dedicated. This article will explain what the terms mean and how to choose an appropriate type of hosting for your web site.
A web site that uses dedicated hosting has the server all to itself. This means that all the resources of the server as well as the IP address are unique to that web site. Shared hosting, on the other hand, places several websites on the same server, all of them sharing resources and the same IP address.
Shared hosting is much cheaper than dedicated hosting because the cost of operating the server is split between many different customers. Shared hosting is available for as little as $2 a month but dedicated hosting could cost up to $100 a month or more.
Shared Hosting
As we mentioned above, websites that share a single server are sharing all the resources of that computer. This includes disk space and bandwidth as well as the IP address. In order to provide adequate service to all sites on a server, your host will limit each site to a certain amount of disk space and bandwidth used per month. Sites that exceed these limits may have to pay a hefty penalty.
Since each server has a limited amount of bandwidth, the amount of traffic your neighbors receive can affect how quickly your web site is displayed. Each request coming in to the server is dealt with in the order it was received, so if there is a large queue, there will be a long wait.
The number of sites that are sharing a particular server is not as important as the amount of traffic each site receives. A server hosting 200 low traffic sites will respond much faster than one which has 50 sites that are receiving a lot of visitors.
There are some risks associated with shared hosting. If one of your neighbours runs a badly programmed script that runs amok the entire server could be affected. In extreme cases this could cause your site to be inaccessible for a time. Another risk is that if one of your neighbours is banned from search engines (for spamming tactics, for example) it could affect everyone sharing that IP address. Check with your hosting company to see their policy about third-party scripts and inappropriate activity.
Dedicated Hosting
With a dedicated server all the resources are yours to use as you please. You can use it to host a single site or multiple sites, you have access to the full bandwidth of the server, and you can use as much disk space as necessary. Companies with large complex websites that receive a lot of traffic need to have dedicated hosting. Sites that use a dedicated server are also free to run any kind of script they wish. This may be ideal for those who are developing new scripts and need to test them without affecting other websites.
How to Choose
Small websites are usually better off with shared hosting. The cost is more affordable – especially for small companies and individuals. A reputable host will be careful not to allow activities that could jeopardize your site. Large complicated sites that receive more than 1000 visitors a day are better off with dedicated hosting. It is also a good choice for developers who wish to experiment with new Internet technologies.
Posted by WebHost at 11:22 PM | Comments (0)
May 26, 2006
Starting A Web Hosting Company
Rather than use the services of a web hosting company to host your web site you could start your own web hosting company. If your business is successful this could provide secondary income and lower the hosting costs for your own site(s).
The second way is to become a re-seller for an established host. For a monthly fee you can have an allotment of disk space and bandwidth which can be used to sell to other people. Re-selling is usually anonymous – there is no visible connection to the parent host and you are free to set your own prices and develop your own 'brand'.
All that is needed to become a re-seller is the ability to pay the monthly fee. All the technical details are handled by the parent company. The re-seller package usually includes everything – even name servers under your own name. All you have to do is to sign up customers and watch the money roll in. Easy – right?
Signing up customers, though, may not be as easy as you imagine. There are literally thousands of hosting companies competing for customers, and making your web hosting business stand out from the crowd is no mean feat. Just think about the process you went through in choosing your own web host. You probably visited several hosting web sites, maybe asked for personal references from your friends or business acquaintances, and then after narrowing down your choices, perhaps did more in-depth research on each of the companies. Or perhaps you just signed up with the first host you saw.
So, in order for your own hosting company to be successful it has to build up a good reputation or be easy to find. Advertising can make your company more visible, but advertising is expensive – especially in a competitive market like web hosting.
A re-seller account, however, may be ideal for certain situations. If you already have several websites of your own, your monthly costs may be similar to a re-selling account. For the same amount of money you could switch all your accounts to your own hosting company. Sign up a few friends or associates and you are ahead of the game.
If this sounds attractive, make sure you are going with a reputable hosting company. You will be entirely dependent on them for technical support. This relieves you of many of the headaches of running a hosting company but you are still responsible to your clients if their sites go down.
There are many types of re-seller packages. Some require you to operate under the name of the hosting company while others allow you to set up a shop under your own business name. Pay attention to the billing aspect of the package. Some re-seller accounts have everything you need to get started immediately, while others require you to set up your own billing gateway.
Posted by WebHost at 11:20 PM | Comments (0)
May 25, 2006
UNIX versus Windows Web Hosting
When browsing through the offerings of various web hosting companies you are sure to notice that some offer UNIX hosting and others offer Windows. Some hosts even offer a choice of the two operating systems. What are the differences and which one is better?
In terms of reliability UNIX systems have a slight advantage. They are known to extremely stable and able to run for years without rebooting. Windows is also very reliable – slightly less so than UNIX but still able to handle the demands of modern web sites.
The majority of web hosts use various flavours of UNIX like Linux and FreeBSD. These operating systems are free and reduce the costs of a hosting operation. Windows costs thousands of dollars so some hosts charge extra for Windows accounts if they offer both types.
As well as being free, Linux and the other UNIX varieties are open-source software. Anyone can alter the source code and make improvements, updates, and additions. There is a large pool of dedicated enthusiasts who use their free time to work on this software. Windows, on the other hand, is Microsoft proprietary software so users are dependent on Microsoft to release updates. There is no way for an individual user to modify the code.
The main difference between the two types of operating systems is the type of software each can run. Windows is suitable for Microsoft products such as MS Access databases, ASP for delivering dynamic content, and VBScript for site enhancements. UNIX cannot accommodate these technologies so if you absolutely need ASP or VBScript you should pick a Windows host. UNIX hosts deliver dynamic content by using software such as PHP, CGI, and MySQL – technologies which are also available on Windows hosts.
Windows is necessary for hosting Windows media files such as videos and audio. Other types of media such as MP3, Flash, Shockwave and Real can be handled by either UNIX or Windows. Websites created in Microsoft FrontPage (a graphical HTML development package) can also be hosted on either type as long as MS databases or dynamic content are not included for use on a UNIX host.
Which is Best?
Before deciding which type of hosting to use for your website, consider carefully what kind of technologies you will need. Do you need a dynamic site? Will you have multimedia content such as streaming video or audio?
Both UNIX and Windows can provide dynamic content with PHP, MySQL, as well as CGI, and there are thousands of dynamic scripts readily available. Multimedia can also be hosted by either type of server, although Windows media (WMA and WMV) need to be hosted on a Windows server.
If you absolutely need Microsoft databases, ASP, and Windows media you have to go with a Windows host. Otherwise most websites are probably better off with a UNIX host. The advantages of UNIX over Windows include greater choices in web hosts, slightly better reliability, and (sometimes) cheaper hosting costs.
Posted by WebHost at 01:17 PM | Comments (0)
May 24, 2006
Web Hosting and Databases
Most web hosting packages include one or more databases. What can you use them for? How will they help your website? Read on for the answers to these questions. A database stores data, but more importantly, allows that data can easily be accessed. Data can be product information, customer names and addresses, sales records, or even the information that appears on web pages. Using a database to retrieve that information can allow you to better serve your visitors and provide them with a more interactive experience.
Dynamic pages use a template for the static content of the site such as headers, menus and footers. The contents of the database are inserted into the template by the server software before the page is sent to be viewed in a browser. Any content from the database can be placed anywhere on a dynamic page. This allows you to set up visually appealing pages which include text and pictures and also add shopping suggestions like: 'Customers who bought this also bought...'
Databases can also be used for storing and accessing customer records. This allows you to tailor your pages according to your customer's previous purchases. Each page could have a personalized greeting (Welcome back Peter) and when they make another purchase all their personal data including address and credit card number could be pulled from the database so they don't have to fill in the same form again.
Another use of a database is mailinglists. Many websites send out information to their visitors to remind them about the site and encourage them to visit again. Email addresses can be stored in a database for the purpose of sending out announcements and newsletters. Also the newsletters can be archived in a database so that visitors can browse or search through previous mailings.
Each database can be divided into tables which are a complete set of data, so one database could be used for most of your website information by setting up a number of tables.The number of databases that your site needs depends on how many applications you are going to run.
It's one thing to have a database, it's another to access that data. There are several ways to retrieve information from a database so that it can be usefully applied to your website. One of the most popular combinations is PHP along with MySQL. PHP can be used to create dynamic web pages that pull data from a MySQL database. The programming language is quite straightforward and can be used to set up complex interactive forms. Other database applications include MySQL with ASP, MSSQL with ASP, and PostgreSQL with PHP.
Posted by WebHost at 11:13 PM | Comments (0)
May 23, 2006
Web Statistics
Now that your web site is up and running you want to know how many people are visiting your site and how they are finding it. Most web hosts give you access to this information (and a lot more) in the form of web statistics.
The trouble is, raw log files are scary to look at and impossible to make any sense of. They are long lists of numbers and cryptic words that can only reveal their secrets with the aid of a statistics program. There are a few stats programs to choose from. They take the raw server logs and parse them into readable (and sometimes colourful) charts that are fairly easy to interpret.
Most web hosts will include a stats program as part of their hosting package. You should be able to access it through the control panel which is used to make various settings on your account. Some of the popular web stat programs are AWStats, Analog, and WebAlizer. All three of these programs are free.
Stats programs divide the information of the log files into useful categories. A summary of the data may be included at the top of the readout and tell you information such as 'unique visitors', 'number of hits', and 'number of pages'.
Not all this information is important. The number of hits, for example, simply counts the total number of requests for any individual part of your site including graphics, script files and any other files that are part of a page. If your home page has 4 pictures and 2 other files the hit count is increased by 7 each time someone views that page.
The number of page views is important because it tells you which pages are popular. This allows you to fine-tune your site by dropping or modifying unpopular pages and making sure that popular pages link to areas that you want to promote.
Popular entry and exit pages are also worth tweaking. Visitors will not always arrive at your site through the home page, especially if they've found your site through a search engine. Make sure that popular entry pages contain relevant information and adjust exit pages to be more appealing. Exit pages should provide one last chance for them to buy or bookmark your site for future reference.
Referring sites show you where people are coming from. If they have found you from a search engine you will also see what keywords they used to find your site. This information tells you which keywords are important for optimizing your site. You can then design new content based on these keywords to attract even more visitors in the future.
Rather than rely on the stats produced by your server, you can hire a third party service to monitor your web site. These services range from basic 'counter' that usually offer less information than your server does, to comprehensive client-side stats collection.
Stats services can be useful if you need more precise information about your visitors. For example, visitors from a large organization may all appear to be the same because they all have the same IP address. Stat services can break down IP addresses into individual users.
These services can be useful for more precise monitoring of your website and for targeting specific niches. Most site owners, however, will find enough useful information in their server's statistics.
Posted by WebHost at 09:50 PM | Comments (0)
May 22, 2006
Virtual Private Server (VPS) Web Hosting
Shared hosting allows thousands of people to host their own sites at a very reasonable cost. It has some drawbacks, however. Since hundreds of sites can be hosted on a single server resources such as CPU, disk space, and bandwidth have to be shared with your virtual neighbors.
Many people would say 'So what? I don't want to do that stuff anyway!' It's true that the majority of website owners have no interest or ability to handle this kind of work and are happy to leave it to the hosting company. Those who desire more control over their server environment or wish to experiment with new software, however, can get access to this level of management with a Virtual Private Server.
A virtual private server (VPS) is a physical server that has been divided (using software) into several virtual machines, each acting as an independent dedicated server. The physical resources such as RAM, CPU and disk space are still shared, but each VPS acts independently of the others. Each VPS can have a different operating system and can be configured in any way possible.
The key advantage of VPS is allowing each VPS administrator access to the root level of his virtual server. This kind of access allows the administrator to install and delete software, set permissions, create accounts – in short, do everything that the administrator of a 'real' sever can.
As well as providing more control over your hosting environment, a VPS is more secure than shared hosting. Websites on a shared server all have the same operating system, so if a hacker were to find access to the root of the server he could damage any or all of the websites on that server. A VPS, on the other hand, is divided in such a way that even if a hacker were to gain entry through one account, there is no way to access the others. Each VPS is invisible to the others and there is no way to set up root level access from one VPS to another.
Virtual Private Servers can be set up in various ways so be sure to understand how the hosting company has allocated resources. The most common configuration is to divide all the physical resources evenly by the number of accounts. Thus, if there are 10 virtual servers, each would receive 10% of the total bandwidth, CPU, memory and disk space.
The disadvantages of VPS are almost the same as the advantages. The control that a VPS account provides can be dangerous if you don't know what you are doing. You have the ability to delete files, set permissions improperly, allow virus-laden software on the system and, in general, really screw things up. If you don't have the knowledge to administer a server, or are not willing to learn, VPS is not for you.
If your website has outgrown shared hosting, however, VPS offers an affordable alternative to dedicated hosting. When shopping for a VPS host, be sure to find out how system resources are divided up, the number of VPS accounts on each physical server, the method for upgrading, and the choices of operating systems.
Posted by WebHost at 10:32 PM | Comments (0)
May 21, 2006
Disk Space
Every hosting account has a certain allotment of disk space. The disk space is used to hold all the files which make up your web site – HTML files, graphics, scripts, and multi-media content. Usually the more expensive the hosting package the more disk space and the more bandwidth you receive.
What will happen if you use too much disk space? Each web host has their own policy about this but it's safe to say that you will be charged for the extra space. Often this penalty is much higher than regular rates for disk space so it's important to keep an eye on how much space you are using and if you are approaching the limit, either purchase more space or delete some files.
How can you tell how much space you are using? Most hosting packages have a control panel for making adjustments to almost every aspect of your account. These control panels usually tell you how much disk space is being used and may also rate it against your allotment so you can see at a glance if you are approaching your limit. If your hosting account does not have this feature you can judge the amount of space by downloading your entire site to a folder on your personal computer in order to check how much space it takes.
As a rough guide, consider that an average web page (3 graphics and 2 screen lengths of text) takes about 20 kb (to be generous). At this rate, a hosting package with 10 MB can have about 500 pages. Since most small sites are less than 50 pages 10 MB should be plenty to get started. But what about databases? They are usually calculated separately from your disk allotment but check with your web host to see what their policy is.
If you place music or video files on your website your need for disk space (and bandwidth) starts to take off. A typical 3 minute MP3 file takes about 2.5 to 3 MB of disk space. A short video (very poor quality) can take 1 MB. A good rule of thumb for those wishing to host multimedia is to estimate the total size of the files and get an account with double that space. This will allow for future expansion. Always check with your web host, though, before placing sound or video files on your website. Some have policies against this type of content because it places a strain on the bandwidth allotment – a serious consideration with a shared hosting package.
Posted by WebHost at 01:26 AM | Comments (0)
May 20, 2006
Bandwidth
Bandwidth is a term that has several different meanings depending on the context. When talking about bandwidth in terms of Web Hosting it refers to the amount of data that transfers into and out of your web hosting account. Incoming data can include requests for web pages, email, FTP requests, and FTP uploads, while outgoing data includes file transfers, web pages, and email. Each hosting account is allocated a certain amount of bandwidth per month. Common figures for bandwidth range from 3 GB for small personal sites up to 200 GB for large business systems.
The best way to calculate the amount of bandwidth you need is to calculate the size of your downloadable content and multiply by the number of visitors you receive each month. Add to that the number of emails sent and received and other content such as FTP uploads. The figure you come up with should be pretty accurate because it is unlikely that every visitor to your site is going to download every file or view every page. This will give you a bit of margin to play with.
As your web site grows and as you receive more traffic you may have to increase your bandwidth allotment accordingly. It is better to plan ahead and arrange with your web host for a larger hosting package rather than wait until you go over your limit. Check with your host to see what their policy is in regards to exceeding your bandwidth. Some will allow you to go over by a certain amount while others will shut down your site and demand that you upgrade your account before resuming service. It is always best to keep track of how much bandwidth you are using and anticipate when you need to upgrade.
If you feel that you have sufficient bandwidth and would prefer not to upgrade you may be able to 'throttle' traffic if you are approaching your monthly limit. Some hosts offer this service as a way to limit incoming requests or to exclude requests once a certain number has been reached.
There are several throttling options. You can limit the number of incoming requests by specifying an idle time between requests. This causes incoming requests to be delayed by a specified amount of time if too many are arriving at once. Other options are to impose a limit on data transfer within a certain time period or to limit the number of requests for a certain file. The speed of transfers can also be capped at a certain level.
Throttling may not be a good idea if you depend on web traffic for your business. If your pages are slow to load or if users can't access files they are looking for they may give up and move on to another site. If you have a lot of free content, though, throttling can be useful for keeping your hosting budget within a certain amount.
Posted by WebHost at 08:59 PM | Comments (0)
