Tag: Name server

DNS Terminology

In this post, I am going to give few basic DNS components before going to discuss the DNS functionality in depth in technical terms.

Who invented the DNS?

Paul V. Mockapetris (born 1948 in Boston, Massachusetts, US) is an American computer scientist and Internet pioneer, who, together with Jonathan Bruce Postel (August 6, 1943 – October 16, 1998) invented the Internet Domain Name System (DNS)

DNS Inventors

Paul has dual B.S. degrees in Physics and Electrical Engineering from MIT, and a Ph.D. in Information and Computer Science from the University of California, Irvine.

Postel has done his B.S. degree, M.A in Engineering and Ph.D. in Computer Science from UCLA.

Domain Terminology:

There are many terms used when talking about domain names and DNS that aren’t used too often in other areas of computing.

Domain Name System

The domain name system, more commonly known as “DNS” is the networking system in place that allows us to resolve human-friendly names to unique addresses.

Domain Name

A domain name is a human-friendly name that we are used to associating with an internet resource. For instance, “google.com” is a domain name. Some people will say that the “google” portion is the domain, but we can generally refer to the combined form as the domain name.

The URL “google.com” is associated with the servers owned by Google Inc. The domain name system allows us to reach the Google servers when we type “google.com” into our browsers.

IP Address

An IP address is what we call a network addressable location. Each IP address must be unique within its network. When we are talking about websites, this network is the entire internet.

IPv4, the most common form of addresses, are written as four sets of numbers, each set having up to three digits, with each set separated by a dot. For example, “111.222.111.222” could be a valid IPv4 IP address. With DNS, we map a name to that address so that you do not have to remember a complicated set of numbers for each place you wish to visit on a network.

Top-Level Domain

A top-level domain, or TLD, is the most general part of the domain. The top-level domain is the furthest portion to the right (as separated by a dot). Common top-level domains are “com”, “net”, “org”, “gov”, “edu”, and “io”.

Top-level domains are at the top of the hierarchy in terms of domain names. Certain parties are given management control over top-level domains by ICANN (Internet Corporation for Assigned Names and Numbers). These parties can then distribute domain names under the TLD, usually through a domain registrar.

Hosts

Within a domain, the domain owner can define individual hosts, which refer to separate computers or services accessible through a domain. For instance, most domain owners make their web servers accessible through the bare domain (example.com) and also through the “host” definition “www” (www.example.com).

You can have other host definitions under the general domain. You could have API access through an “api” host (api.example.com) or you could have ftp access by defining a host called “ftp” or “files” (ftp.example.com or files.example.com). The hostnames can be arbitrary as long as they are unique for the domain.

SubDomain

A subject related to hosts are subdomains.

DNS works in a hierarchy. TLDs can have many domains under them. For instance, the “com” TLD has both “google.com” and “ubuntu.com” underneath it. A “subdomain” refers to any domain that is part of a larger domain. In this case, “ubuntu.com” can be said to be a subdomain of “com”. This is typically just called the domain or the “ubuntu” portion is called an SLD, which means second level domain.

Likewise, each domain can control “subdomains” that are located under it. This is usually what we mean by subdomains. For instance, you could have a subdomain for the history department of your school at “www.history.school.edu“. The “history” portion is a subdomain.

The difference between a hostname and a subdomain is that a host defines a computer or resource, while a subdomain extends the parent domain. It is a method of subdividing the domain itself.

Whether talking about subdomains or hosts, you can begin to see that the left-most portions of a domain are the most specific. This is how DNS works: from most to least specific as you read from left-to-right.

Fully Qualified Domain Name

A fully qualified domain name, often called FQDN, is what we call an absolute domain name. Domains in the DNS system can be given relative to one another, and as such, can be somewhat ambiguous. An FQDN is an absolute name that specifies its location in relation to the absolute root of the domain name system.

This means that it specifies each parent domain including the TLD. A proper FQDN ends with a dot, indicating the root of the DNS hierarchy. An example of an FQDN is “mail.google.com.”. Sometimes software that calls for FQDN does not require the ending dot, but the trailing dot is required to conform to ICANN standards.

Name Server

A name server is a computer designated to translate domain names into IP addresses. These servers do most of the work in the DNS system. Since the total number of domain translations is too much for any one server, each server may redirect the request to other name servers or delegate responsibility for a subset of subdomains they are responsible for.

Name servers can be “authoritative”, meaning that they give answers to queries about domains under their control. Otherwise, they may point to other servers, or serve cached copies of other name servers’ data.

Zone File

A zone file is a simple text file that contains the mappings between domain names and IP addresses. This is how the DNS system finally finds out which IP address should be contacted when a user requests a certain domain name.

Zone files reside in name servers and generally define the resources available under a specific domain, or the place that one can go to get that information.

Records

Within a zone file, records are kept. In its simplest form, a record is basically a single mapping between a resource and a name. These can map a domain name to an IP address, define the name servers for the domain, define the mail servers for the domain, etc.

 

Source: internet hall of fame, digitaloceanwikipedia

 

Tips for speeding up a slow PC

Tips for speeding up a slow PC:

Over the time, the speed of computers can decrease. This appears as the system taking more time to respond to a user’s actions like opening files, folders, surfing the Internet and other tasks. Here are a few steps which are helpful to make your machine (especially Windows machines) run faster.

Clean up the Desktop: 

Each time Windows starts; operating memory is used to open your profile. The total amount of memory used will be small. If however, there are several or dozens of files on the Desktop lot of operating memory is used by these files, essentially for no purpose or gain. With less memory available, the computer runs slower because it has to swap out information from operating memory to the hard drive. It does this process (called memory paging) to keep everything the user wants to do running at the same time.

The simple action of cleaning the Desktop will make your computer run faster.

Clean up the disk and registry:

One of the first things to check on a machine that’s running slowly is how much of the hard disk has been used. If there isn’t roughly 10% of the hard disk free, it’s time to clean the HDD. One of the tools I like is CCleaner. It quickly clears out all temp files for you. 

Remove Spyware/Malware:

One of the most common causes of the “my PC used to be fast, and now it isn’t!” complaint is actually the presence of malware. Malware can sneak onto a computer in a zillion different ways and quite often it sits in the background slowing your machine as it sends out spam emails, searches for other computers to infect, works on cracking cryptography, or performs any number of the other nefarious tasks that hackers like to use their botnet slaves for.

Try a different browser:

Different browsers perform differently, and most people spend a lot of time on their Web browser. Some browsers perform well on some but poorly on others, even when they are supposed to test the same thing. The problem with the benchmarks is that what they usually test is not real work performance! While JavaScript is an important part of the modern Web, few Web applications beat on the JavaScript engine hard enough to produce a noticeable impact on performance. If you want to have your Web browser feel more responsive and lively, consider a switch to Chrome.

Add a faster DNS lookup Server:

Most ISPs love to brag about how much bandwidth they are giving you. But they don’t mind letting the rest of their infrastructure slowly get overwhelmed or deteriorate. Among the biggest offenders are the DNS servers our ISPs use. If you want to know why things seem to take forever to start loading, slow DNS servers are often the cause. Consider adding a fast DNS server as your primary DNS server in your TCP/IP settings. Google’s Public DNS server is a great option.

Defragmentation:

Defragmentation is the process of physically organizing the contents of the mass storage device used to store files in to the smallest number of contiguous regions.

Visualization of fragmentation and then of defragmentation

Defragmentation places all parts of a file together in the same place on the drive. It organizes all directories and files according to how you use your computer. After this process is complete, your computer will most likely run faster.

Following precautions should be taken before doing defragmentation:

 Make sure your data is backed up to another medium like pen drive, DVD or external HDD.

 Close all the running programs including virus scanner.

 Assure your computer has a constant source of power.  If you have frequent power outages, you should not use a defragmentation program without a battery backup. Note: If your computer does shut off while defragmenting, it may crash the hard drive or corrupt the operating system, or both.

Steps for Defragmentation:    
  1. Open My Computer.
  2. Right-click the local disk volume that you want to defragment, and then click Properties.
  3. On the Tools tab, click Defragment Now.
  4. Click Defragment.

Improve Your Hardware:

If your computer is slow, it may be because your hardware isn’t getting the job done. How will you find that out? By using the Windows Experience Index, found in Windows Vista and Windows 7. This will show you where your computer is weak, and what you would need to beef up to turn your PC into a screamer.

Go to Start –> Control Panel — > System and Security –> under System click on Check the Windows Experience Index

Use ReadyBoost:

You can speed up the computer with a flash drive. Through the magic of a Windows technology called ReadyBoost, your PC can see a real speed increase. It’s a little-known Windows secret that can help you zip on down the Information Superhighway, or make whatever you’re doing faster.

Note:  ReadyBoost is available in Windows Vista, and Windows 7 Operating Systems.

source: about.com, Wikipedia, Techrepublic,