How to Understand the Domain Name System

Posted on June 09, 2011 by Dave W

How to understand the Domain Name System

By Clare Lawrence 13th August 2004

Ever wonder why DNS systems came into existence? Efficiency. Every computer has a distinct IP address, and the Internet needed an elite method for obtaining these addresses and for managing the system as a whole. Enter ICANN.

The Internet Corporation for Assigned Names and Number manages the DNS root of the Internet domain namespace. ICANN’s role is to manage the assignment of identifiers, ensuring that all users have unique names.

The DNS system is run by a series of servers called DNS servers. ICANN manages the root DNS domains, under which are the top-level domains.

It also manages:

Organizational domains

Geographical domains

Reverse domains

Beneath the top-level domains are other naming authorities such as Nominet, the UK’s naming authority.

How does a DNS Query work?

The process occurs in two parts. Firstly, a name query begins at a client computer and is passed to DNS client service for resolution. When the query cannot be resolved locally, DNS servers are queried.

For example, when a web browser calls the fully qualified <a href="http://www.discountdomainsuk.com>domain name</a> www.discountdomainsuk.com, the request is passed on to the DNS client service to resolve the name by using locally cached information. If the query is held in the cache, then the process is complete.

If, however, the query cannot be answered locally, the DNS client service uses a server list (ordered in sequence) to query external DNS servers. When a DNS server receives a query, it first checks to see if it is authoritive for that domain name. If it is authoritive, it resolves the name, and the process is complete.

If the DNS server is unable to resolve the query, it in turns queries other DNS servers, using a process known as recursion. DNS servers make use of root hints to assist in locating DNS servers, which are able to provide the required result. In this way, DNS queries are minimised and the Internet is able to operate quickly and effectively.

A typical query may run as follows:

Client contacts Nameserver A looking for www.discountdomainsuk.com

Nameserver A checks its cache, but can’t answer, so it queries a server authoritive for the Internet root.

The root server responds with a referral to a server authoritive for the .com domains.

NameserverA queries the the .com server and gets referred to the server authoritive for www.discountdomainsuk.com

Nameserver A queries this server and gets the IP address for www.discountdomainsuk.com.

Nameserver A replies to the client with the IP address.

Queries can return answers that are authoritive, positive, negative or referral in nature. In the event of a negative answer, another DNS server is queried.

Article Source: http://www.articlealley.com/how-to-understand-the-domain-name-system-1.html

Cycle Training?

Hi All,
In three months I am entering my first significant time trial event. My training at the moment is
a daily commute of 20miles a day and doing basic leg excercises in the gym three times a week.
I was hoping some of you yahooers may have some tips on gym/outdoor activities to help improve my fitness.
The time trial will be over 118 miles.
ok
a lot of you are questioning the length of the ride. It’s simply a fact and I am asking only for your responses on ways to approach the training. The answers I have received are good but 118 miles is the distance and I want to do it in araound 6-7 hours.

Answer
A 118 mile time trial?? That seems really, really far for a time trial. You are definitely going to have to bump up your daily miles. A 20 mile commute is fine, but you need quality saddle time. The best way to compete in cycling is to train on the bike. The only time I am ever hit the gym is during “off season”.

This plan helped me race my first 100+ miles race. I’ve adapted it a little to suit your 3 month goal, but you can adjust it accordingly.

Every Monday: Easy Pace
Tuesday: Brisk (your Time Trial pace)
Wednesday: Rest Day
Thursday: Hills / Intervals
Friday Easy Pace
Saturday: Long Distance
Sunday: Rest / Easy Recovery Ride (5-15 miles easy pace)

Week 1: 22 miles daily / 65 weekend ride
Week 2: 24 miles daily / 70 weekend ride
Week 3: 26 / 75
Week 4: 28 / 80
Week 5: 30/60
Week 6: 35/65
Week 7: 40/70
Week 8: 45/75
Week 9: 50/80
Week 10: 40/85
Week 11: 30/90
Week 12: 20 miles during the first half of the week, and only 10 the two days leading up to the race

If you flip Sat/Sun for your long distance ride, make sure you always have your Rest Day or your easy Recovery Ride on the day immediately following! Recovery is so, so important when training for endurance events.

Good luck!

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