Wednesday, December 29, 2010

How to improve home wireless network performance

If Windows ever notifies you about a weak signal, it probably means your connection isn't as fast or as reliable as it could be. Worse, you might lose your connection entirely in some parts of your home. If you're looking to improve the signal for your wireless network, try some of these tips for extending your wireless range and improving your wireless network performance.
10 tips for improving your wireless network

1. Position your wireless router (or wireless access point) in a central location

When possible, place your wireless router in a central location in your home. If your wireless router is against an outside wall of your home, the signal will be weak on the other side of your home. Don't worry if you can't move your wireless router, because there are many other ways to improve your connection.
Bad router and good router comparison

2. Move the router off the floor and away from walls and metal objects (such as metal file cabinets)

Metal, walls, and floors will interfere with your router's wireless signals. The closer your router is to these obstructions, the more severe the interference, and the weaker your connection will be.

3. Replace your router's antenna

The antennas supplied with your router are designed to be omni-directional, meaning they broadcast in all directions around the router. If your router is near an outside wall, half of the wireless signals will be sent outside your home, and much of your router's power will be wasted. Most routers don't allow you to increase the power output, but you can make better use of the power. Upgrade to a hi-gain antenna that focuses the wireless signals only one direction. You can aim the signal in the direction you need it most.
Standard antenna and hi-gain antenna examples

4. Replace your computer's wireless network adapter

Wireless network signals must be sent both to and from your computer. Sometimes, your router can broadcast strongly enough to reach your computer, but your computer can't send signals back to your router. To improve this, replace your laptop's PC card-based wireless network adapter with a USB network adapter that uses an external antenna. In particular, consider the Hawking Hi-Gain Wireless USB network adapter, which adds an external, hi-gain antenna to your computer and can significantly improve your range.
Laptops with built-in wireless typically have excellent antennas and don't need to have their network adapters upgraded.

Wireless router and wireless repeater

5. Add a wireless repeater

Wireless repeaters extend your wireless network range without requiring you to add any wiring. Just place the wireless repeater halfway between your wireless access point and your computer, and you'll get an instant boost to your wireless signal strength. Check out the wireless repeaters from ViewSonic, D-Link, Linksys, and Buffalo Technology.

Wireless channels

6. Change your wireless channel

Wireless routers can broadcast on several different channels, similar to the way radio stations use different channels. In the United States and Canada, these channels are 1, 6, and 11. Just like you'll sometimes hear interference on one radio station while another is perfectly clear, sometimes one wireless channel is clearer than others. Try changing your wireless router's channel through your router's configuration page to see if your signal strength improves. You don't need to change your computer's configuration, because it'll automatically detect the new channel.

7. Reduce wireless interference

If you have cordless phones or other wireless electronics in your home, your computer might not be able to "hear" your router over the noise from the other wireless devices. To quiet the noise, avoid wireless electronics that use the 2.4GHz frequency. Instead, look for cordless phones that use the 5.8GHz or 900MHz frequencies.

8. Update your firmware or your network adapter driver

Router manufacturers regularly make free improvements to their routers. Sometimes, these improvements increase performance. To get the latest firmware updates for your router, visit your router manufacturer's website.
Similarly, network adapter vendors occasionally update the software that Windows uses to communicate with your network adapter, known as the driver. These updates typically improve performance and reliability. To get the driver updates, do the following:

Windows 7 and Windows Vista

  • Click Start menu, click All Programs, and then click Windows Update.
  • In the left pane, click Check for updates, and then wait while Windows Vista looks for the latest updates for your computer.
  • Install any updates relating to your wireless network adapter.

Windows XP

  • Visit Microsoft Update, click Custom, and then wait while Windows XP looks for the latest updates for your computer.
  • Install any updates relating to your wireless adapter.


9. Pick equipment from a single vendor

While a Linksys router will work with a D-Link network adapter, you often get better performance if you pick a router and network adapter from the same vendor. Some vendors offer a performance boost of up to twice the performance when you choose their hardware: Linksys has the SpeedBooster technology, and D-Link has the 108G enhancement.

10. Upgrade 802.11b devices to 802.11g

802.11b is the most common type of wireless network, but 802.11g is about five times faster. 802.11g is backward-compatible with 802.11b, so you can still use any 802.11b equipment that you have. If you're using 802.11b and you're unhappy with the performance, consider replacing your router and network adapters with 802.11g-compatible equipment. If you're buying new equipment, definitely choose 802.11g.
Wireless networks never reach the theoretical bandwidth limits. 802.11b networks typically get 2-5Mbps. 802.11g is usually in the 13-23Mbps range. Belkin's Pre-N equipment has been measured at 37-42Mbps.

关于域名DNS解析中TTL的设置时间

网上关于域名dns解析中ttl值设置时间的文章不多,我今天遇到了这个问题,就把这个问题整理一下,希望可以给需要的朋友有所帮助。
什么是域名的TTL值?
TTL(Time-To-Live),就是一条域名解析记录在DNS服务器中的存留时间。当各地的DNS服务器接受到解析请求时,就会向域名指定的 NS服务器(权威域名服务器)发出解析请求从而获得解析记录;在获得这个记录之后,记录会在DNS服务器(各地的缓存服务器,也叫递归域名服务器)中保存 一段时间,这段时间内如果再接到这个域名的解析请求,DNS服务器将不再向NS服务器发出请求,而是直接返回刚才获得的记录;而这个记录在DNS服务器上 保留的时间,就是TTL值。
      域名DNS分两种,一种是权威域名服务器,域名注册商的服务器都为权威域名服务器,TTL值只能在权威服务器修改,还有一种域名解析服务器就是缓存DNS 服务器,比如各地ISP上网设置的DNS服务器,它的作用主要是把域名解析结果缓存到本地,方便你查询。域名DNS的TTL值实际上就是各地的DNS缓存 服务器多久去你的权威域名解析服务器(NS)获取一次你域名的解析IP。
那么域名解析的TTL只应该设置为多少合适呢,下面有两个建议,你可以结合自己参考一下:
一.增大TTL值,以节约域名解析时间,给网站访问加速。

一般情况下,域名的各种记录是极少更改的,很可能几个月、几年内都不会有什么变化。我们完全可以增大域名记录的TTL值让记录在各地DNS服务器中缓存的 时间加长,这样在更长的一段时间内,我们访问这个网站时,本地ISP的DNS服务器就不需要向域名的NS服务器发出解析请求,而直接从缓存中返回域名解析 记录。

国内和国际上很多平台的TTL值都是以秒为单位的,很多的默认值都是3600,也就是默认缓存1小时,这个值实在有点小了,难道会有人一个小时就改一次域 名记录吗?你可以根据自己的需要把这个值适当的扩大,例如要缓存一天就设置成86400。Godaddy的TTL设置比较直观,但总共只有5个值可以选 定,即时切换到高级设置模式也是如此,有点死板了。


二.减小TTL值,减少更换空间时的不可访问时间。

     更换空间99.9%会有DNS记录更改的问题,因为TTL缓存的问题,新的域名记录在有的地方可能生效了,但在有的地方可能等上一两天甚至更久才生效。结 果就是有的人可能访问到了新服务器,有的人访问到了旧服务器。如果原来的域名TTL值设置的小,各地的ISP域名缓存服务器服务器就会很快的访问你域名的 权威DNS解析服务器,尽快把你域名的DNS解析IP返回给查询者
     这就是说你如果想要解析速度,各地ISP的DNS服务器缓存你的域名,你就需要把TTL值设置大一些,如果你想域名更换空间或者IP后能尽快解析到新的 IP上,就需要把TTL值设置小一些。(我今天因为一个域名过期忘记续费被停掉了解析,结果域名被美国的根库修改了DNS,并把域名转到一个域名停放页 面,后来联系注册商才发现这个问题,由此引起了我对域名的思考,考虑到了域名DNS 解析中TTL值的问题。小插曲,和本文的技术无关)
     总结:对于IP地址相对固定,或短期内不会变更IP地址的用户来说TTL值设置的大些如几个小时或更大些为宜。调大TTL值可以显著的提 高域名的解析稳定性和速度。而对于近期有计划变更IP地址的用户需要提前把TTL值改小,以便使缓存在世界各地DNS服务器上的旧域名记录迅速过期,等 IP地址固定下来后再把TTL值改大。
    经验:百度和google的域名TTL值我看了一下,都是86400秒,也就是一天。我的一些域名我也修改成了86400秒了,你的具体多大,你自己根据需要修改吧。


source: http://www.dabaoku.com/jiaocheng/fabu/yuming/201009207014.shtml