let say i have a domain name which is hosted by web hosting company.I will have the authorities to updated my domain name zon file like add in other MX record or CNAME by myself without got thru web hosting company.This what i mean.
Also you can have your website hosted at virtually any host, and have your domain registrar, point your domain to companies like zoneedit.com or dynamic DNS. You then point it from there to your web hosting company.
This is a very good system. It's one weakness is that it adds an extra point of failure into DNS system, and also a little extra lag time for your site. However, the pluses definitely outweigh this negative.
1. These companies are very reliable, as they have multiple geographically separated servers to minimise any downtime. The only time zoneedit.com has cost me downtime was when they were being DDOS'd, but then so were many of the other big Internet sites.
2. You have full control of your DNS, independant from your host. Change hosts... no problem, adjust your pointing and its done.
3. No need to wait for 3 day propogation times. Once your initial Dom Reg -> DNS company pointing is propogated, then changes at the DNS company begin resolving within 15 - 30 minutes or less.
4. It easy to increase your site's uptime. IF you have two versions of your site on separate servers/IP's then if one is down, go to DNS Co. and switch pointing to other server, within a few minutes your site is back up, while Host 1 is still sorting out their server/network problem. This won't work too well for databases but with any other site content, then no problem.
For a site that you want to have high-availability with, but don't have the budget for a high-end solution, I would definitely recommend the above approach.
Kerry Slavin Reliable Solution Internet Services
http://www.reliablesolution.com [email protected]
then from within my normal DNS, I CNAME whatever I want over to the dyndns.org address.
so for example if my domain was "helloworld.com", and I have all my webhosting taken care of, but I wanted to have irc.helloworld.com go to a server that for some reason has a dynamic IP (DSL/Cable/etc), then I'd set up an account with dyndns.org (ie: helloworld.dyndns.org) and then I'd CNAME irc.helloworld.com to helloworld.dyndns.org. In fact that's exactly what I've done for one of my site's IRC.
It works like a charm. The trick is making sure that whatever dynamic dns client you use checks and updates the IP often enough that your availability is decent.
Best of all it's free. Unfortunately I wouldn't recommend it for IRC as I've used it simply because that's a high-usage service where a static IP really is important, however for webhosting I'd imagine that it works quite well with perhaps 10 minute gaps max between IP changes... so if your IP changes once a day, it would possibly have 10 minutes of "downtime" a day.
The other option is if you use a gateway that you can load software on, like a Unix server rather than a stock router, you can actually run some clients on your gateway to detect the IP change as soon as it happens and update it immediately, which is much better.