DNS acts in such as aside that when a request for IP address received by DNS resolver, it will then query the root hosts to find the authorized server with detailed knowledge of the specific domain name. If a valid IP address for the domain is returned by the authoritative server, the DNS resolver will cache the DNS propagation for a given time period called TTL (Time To Live) after a successful reply, in what called DNS caching in order to reduce the load on particular DNS server. DNS caching provides resolution of domain name to IP to happen locally using the cached information rather than querying the remote server for subsequent requests, till the TTL duration expires.

The Time-To-Live (TTL) timer is the trick to guarantee that the DNS cache expires promptly and all of the time stays fresh. TTL is defined by domain administrator in the authoritative DNS server for the zone wherever data originates, and its values tell DNS caching resolvers to expire and dispose the DNS records after TTL seconds. Lowering the TTL value will enable fast expiration and refreshing of DNS records, making the new records to propagate faster across the world. Still, the trick demands the name resolvers comply the RFC standards, which most do. Alongside, you must have full control to change the name server authoritative for your domains.

The tweaking of TTL in DNS records must be done a couple of days before it’s about to change (date of server moving or IP change) to assure that all DNS caching resolvers picks up the fresh TTL value and expires the old longer value. The trick will cut down the TTL in anticipation of the alteration to minimize inconsistency during the change, according to RCF 1034.

TTL is defined by Minimum field in SOA (Start of Authority) type as default TTL, or separately at each record as TTL. RCF 1912 describes the Minimum field in details as below:

Minimum: The default TTL (time-to-live) for resource records (RR) — how long data will remain in other nameservers’ cache. ([RFC 1035] defines this to be the minimum value, but servers seem to always implement this as the default value) This is by far the most important timer. Set this as large as is comfortable given how often you update your nameserver. If you plan to make major changes, it’s a good idea to turn this value down temporarily beforehand. Then wait the previous minimum value, make your changes, verify their correctness, and turn this value back up. 1-5 days are typical values. Remember this value can be overridden on individual resource records.

If you are using a web-based or GUI to manage your domain’s DNS records, and then log on to the system, and edit the SOA records. Inside you’ll see a field named Minimum, change the value to as low as possible (in seconds), such as 300 for timeout every 5 minutes. Then change the TTL for all of the A, MX, CNAME, TXT, SOA, PTR and other records, if applicable.

If you are using cPanel WebHost Manager (WHM), log-in and select Edit DNS Zone under DNS Functions section. Choose the applicable zone (domain name). You’ll be given with a list of records. Alter the minimum ttl in SOA, and TTL column of A, MX, CNAME and other records defined.

For those manually configure the authoritative nameserver for a domain zone using BIND, modification has to be done in the zone file. For example, so domain zone example.com, you will see the following resource records in the zone file:

; zone ‘example.com’
$TTL 14400

@ IN SOA ns1.example.com. host.example.com. (
2007080501 ; Serial
10800 ; Refresh 3 hours
3600 ; Retry 1 hour
604800 ; Expire 1 week
86400 ); Minimum 24 hours

@ NS ns1.example.com.
@ NS ns2.example.com.

@ A 192.168.0.1
@ MX 10 mail.example.com.

; nameservers
ns1 A 192.168.0.11
ns2 A 192.168.0.12
; mail servers
mail A 192.168.0.10
; web server
www CNAME example.com.

Now modify the $TTL 14400 with the value you wish (in seconds), such as 300 (5 minutes). This value defines the default TTL of every existing records, and by lowering this value to 300 (for example, you can choose your won value), caching server will be hold this records for more than 5 minutes before querying the authoritative name server which will be the 1st to reflect the new IP address when change later on again. Some other value that you should modify is minimum TTL, the last line of SOA type (remarked as minimum 24 hours).

Afterwards, your DNS zone file will probably looks like this:

; zone ‘example.com’
$TTL 300

@ IN SOA ns1.example.com. host.example.com. (
2007080501 ; Serial
10800 ; Refresh 3 hours
3600 ; Retry 1 hour
604800 ; Expire 1 week
300 ); Minimum 24 hours

@ NS ns1.example.com.
@ NS ns2.example.com.

@ A 192.168.0.1
@ MX 10 mail.example.com.

; nameservers
ns1 A 192.168.0.11
ns2 A 192.168.0.12
; mail servers
mail A 192.168.0.10
; web server
www CNAME example.com.

Restart the DNS service. The fresh TTL value will propagate to other DNS nameserver. This process normally takes 48 hours to 72 hours (hence the need to reduce TTL to try to make it faster when altering the critical A and MX records). After waiting for a few days, move your websites to new server or modify the IP address, then update the DNS records to point to the new server or IP.

Once done, you can now return back the TTL values to reduce the load on your DNS server.

Posted by:

Balvinder Singh Rawat

What is a bogon, and why should I filter it?

A bogon prefix is a route that should never appear in the Internet routing table. A packet routed over the public Internet (not including over VPNs or other tunnels) should never have a source address in a bogon range. These are commonly found as the source addresses of DDoS attacks.

Bogons are defined as Martians (private and reserved addresses defined by RFC 1918 and RFC 5735) and netblocks that have not been allocated to a regional internet registry (RIR) by the Internet Assigned Numbers Authority. Fullbogons are a larger set which also includes IP space that has been allocated to an RIR, but not assigned by that RIR to an actual ISP or other end-user. IANA maintains a convenient IPv4 summary page listing allocated and reserved netblocks, and each RIR maintains a list of all prefixes that they have assigned to end-users.

It is important to realize that the bogon and fullbogon lists are NOT static lists. IP ranges are regularly added to, and more importantly, removed from the bogon lists. If you filter bogons, please try to make sure that you have a plan for keeping your filters up-to-date, or within a short space of time you will be filtering legitimate traffic and creating work for network administrators everywhere. This is especially true for the fullbogons list, which has significant changes every day.

Posted by:

Balvinder Singh Rawat

The features in the service are good. The uptime is fast, the bandwidth is reasonably satisfactory and the server space is good enough for anything to fit in.

Linux as an operating system too found a lot of admirers during its launch. The operating system had the ability to support any language or software. It had the capacity to host many complex applications that its contemporaries and rivals failed miserably at doing. So, this virtue struck the common user who identified every benefit that came from Linux. Eventually, when the Linux based web hosting service was launched, people who had used the Linux operating system were the first ones to come forward and have their applications/websites hosted on this service.

The Linux web hosting service offers some exemplary comfort, something not visible in other services. Any interested party which wants its services to find a home where they can be presented as ventures and used for profitability can always come and hire this service, which ensures some sailing and operation. One does not have to struggle hard to know whether it works or not as the efficacy is evident from the moment usage starts.

 1.  Go to the DotNetNuke portal and register yourself as a new user .  If “Register” is not displayed for the portal, go to table “Portals”  in your database and enter value “2″ into column “UserRegistration”.

2. Create a new user account by registration (please remember the password this time the one you entered)

3. Go to database, and find and enter the table “ASPNet_Membership”

4. Go to new user account (usually the last one) and copy the encrypted values of columns “Password” and “PasswordSalt” into the same columns of user account “host” (usually the first entry in this table) 

5. Login as user “host” using the new password and delete the newly created other user.

 6. Complete!

Note : This solution may help you in DNN 3 and 4.

Shaukat Ali

Sr.Software Engineer
www.idslogic.com

The term ‘unlimited’ is often heard with broadband offerings. In an unlimited broadband package, you get the option to download any amount of data (limited to the space of your hard disk), but with a limited speed. If you want to increase the speed of your broadband connection, you need to pay extra.

Nothing is unlimited. Do you have unlimited Money? Do you have unlimited disk space on your computer or laptop? No.. Everything has a Limit, like 80GB, 160GB or 250GB hard disk space on your computer or laptop.

Come to the point: can a hosting provider offer ‘unlimited space’ or ‘unlimited bandwidth’ for hosting a Web site? When the provider itself is limited by the space in his hosting server, how can he boast of offering ‘unlimited’ space to his clients? The term unlimited bandwidth does not make sense since they have purchased a limited speed package from the market. The bandwidth also varies from one provider to another depending on the technologies they are using; however, the fact is that there is a limit. Despite these limitations, there are many such unlimited offers flying around us, targeting the not-so-educated customers. Beware!

Everyday we listen to stories of innocent users falling victims to such things. If you ever happen to see such offer, take a deep look at their Terms of Service, especially for clauses that reads like “PROVIDER will not restrict the bandwidth used by the CLIENT as long as the use is in compliance with the policies set by the PROVIDER.” Following this, there will be a huge list of clauses, which a normal user will find difficult to gulp down.

By claiming unlimited bandwidth or unlimited space, the provider is limiting the service on other criteria. Experienced customers say they have been victims to such offers. One of the common traps in these offers is the restriction to number of files. Though the provider does not limit the user by disk space, there is restriction on the number of files uploaded! All of us know that it is impossible to create ‘limited’ number of files with ‘unlimited’ memory.

To make situations worse, some providers do not mention these limitations openly anywhere. The customer comes to know about it only when they activate their account – the restriction on file numbers will be mentioned in their file manager control panel. Some hosting provider claims that they offer unlimited space to its users, provided at least 90 percent of the Web pages are linked with files (images, flash, video, etc.). Web sites that have several unlinked files will face penalty or they may be deleted from the hosting server.

Similarly, in the unlimited bandwidth offer, the service provider limits the speed of the service. For example, one of these ‘unlimited bandwidth’ providers in the market say they offer 512 Kbps (connect speed) which is actually 64KBps (transfer speed). In some cases, the speed will be so slow that the Web page does not open in less than 20 sec. A normal user won’t wait for more than 20 sec for a Web page to open. Ultimately, this will affect the page ranking of the Web site.

Marissa Mayer of Google states “Speed Wins” you will gain an better understand of how important Google believe speed to be.

Google Vice President Marissa Mayer (Vice President, Search Products & User Experience) last spoke at the Web 2.0 Conference and offered tidbits on what Google has learned about speed, the user experience, and user satisfaction. Marissa started with a story about a user test they did. They asked a group of Google searchers how many search results they wanted to see.

Users asked for more, more than the ten results Google normally shows. More is more, they said.

So, Marissa ran an experiment where Google increased the number of search results to thirty. Traffic and revenue from Google searchers in the experimental group dropped by 20%. Ouch. Why? Why, when users had asked for this, did they seem to hate it?

After investigation Marissa explained that they found an uncontrolled variable. The page with 10 results took .4 seconds to generate. The page with 30 results took .9 seconds.

Half a second delay caused a 20% drop in traffic. Half a second delay killed user satisfaction.

This conclusion may be surprising — people notice a half second delay? — but Amazon.com had a similar experience. In A/B tests, they tried delaying the page in increments of 100 milliseconds and found that even very small delays would result in substantial and costly drops in revenue.

Being fast really matters. As Marissa said in her talk, “Users really respond to speed.”

Marissa went on to explain how the same effect was tested and observed on Google Maps. When Google trimmed their page load time down by about 30 percent, they experienced a 30 percent increase in requests. “It was almost proportional,” said Marissa. “If you make your site faster, you get back that in terms of increased usage almost immediately”.

It’s a situation between the devil and deep blue sea. The only option left for the distressed customer in this situation is to upgrade the service to a costlier plan or withdraw from their service – the last thing they would opt for, owing to the complexity of the process and the expenses involved in hiring a new provider.

It’s business after all. Customers have to be aware of such deals. The very fact that a concept like ‘unlimited bandwidth’ or ‘unlimited disk space’ does not exist reveals the extent of trickery spreading in today’s highly prospective hosting market. This is simply the fight for survival, but it’s clearly the violation of the minimum ethics that should be followed by a responsible provider.

To find out, we asked our 25,000 registered users to take a 30-second anti-spam comparison survey. Over 1,200 people responded and rated their filters with a letter grade from A-F. The results for all filters with 3 or more responses (slightly over 1,000 responses for the top 50 systems) are summarized below and sorted with the highest rated on top. Dates of the responses are 6/29/06 – 7/20/06.