Tag Archives: internet

Network Time Protocol (And the NTP Pool)

The Network Time Protocol is, as the name implies, a standard for syncronising time across networks. This is extremely useful as it allows all computer clocks to be syncronised to a common, correct time rather than being “around” a certain time. It’s especially useful on servers, where co-ordinating events or tracing failures needs precision and accuracy.

So how can you sync your computer with a NTP time server? It’s actually quite simple;

  • Windows – Windows XP and higher already sync out of the box to time.windows.com, however time.windows.com may be very far from you and hence there is a delay in the time making it less accurate. If you want to change the server, double click the clock (XP, on Vista double click and select “Change Time and Date Settings”), then click the Internet time tab, enter the server (XP, on Vista click Change Settings) and click Update Now to sync.
  • Linux – Use the command ntpdate followed by the NTP server you want to sync with

So, how do you go about choosing a better NTP source for windows and a source for linux? Enter the NTP Pool.

There are quite a few “Stratum 1″ NTP servers, which get their time directly from cesium clocks or GPS satelits, these are the most accurate sources of time available. However, if we all synced with a stratum 1 server, they would quickly be overloaded. Most people don’t need that kind of precision, so enter “Stratum 2″ servers. Stratum 2 servers NTP sync with “Stratum 1″ servers, so while they are not as exact as they are, they are only different by a few milliseconds – hadrly a problem. Hence, you should sync with a “Stratum 2″ server. But how do you find one? The NTP pool is a pool, a collection of NTP servers intended for the masses to sync with. Either use 0.pool.ntp.org as your NTP sync source, or if you want extra accuracy select your continent, then country from the right to get a server closer to you. Now you can enjoy accurate time!

However, the demands upon the NTP pool grow daily, but not it’s supply of pooled servers. If you have a server with some spare bandwidth and a static ip address that is available 24/7, donate a server to the pool. You can adjust the amount of NTP traffic you get by setting your bandwidth in the control panel, even home users can participate as long as they meet the requirements!

Interleaving

Interleaving is part of ADSL, a protocol used to connect to the internet over phone lines. This can also be called DSL for those of you in the US.

Interleaving is a technology that increases the stability of the line, at the expensive of latency. Simply put, while it is activated your line will not disconnect as often but will have a slightly higher ping. For most people this is fine, however Gamers and users of a VOIP service or anything where latency is crucial want their ping as low as possible.

Most ISPs turn on interleaving by default, if your line is relatively stable then you can request them to turn it off. Some ISPs will not comply, but most will happily do so. My new ISP ADSL24 (who are a reseller for Entanet) allow you to control interleaving on the line. I requested that it was turned off, and my ping decreased by 10ms. Game on!

Not only this, but my line is just as stable. If you are a gamer or VOIP user, ask your ISP to turn off Interleaving to improve your latency.

Improving Mobile Broadband Speed

I recently got mobile broadband from Voadafone UK (3GB/mo for £15/mo). Now, while they advertise “upto” 7.2mbit/sec, I appreciate that you will never recieve it – the same with Wireless Networks, you never receive 54mbit/sec, even right by the WiFi point you will probably get just 30mbit/sec at most.

Anyway, you should expect to get around 2mbit/sec from your mobile broadband if your modem for it supports 3.6mbit rate or higher. However, I have heard complaints from some that they are getting extremely slow internet.

If your Mobile Broadband Access Program (e.g Vodafone Mobile Connect) is showing GPRS connection, then you are on the 2G standard of mobile internet access, giving you a speed similar to that of a dial up modem. GPRS is the “fallback connection”, when there is not enough signal for a relibable 3G or better connection.

Therefore, to get a faster speed, you need to get a better signal. The best way to do this is to relocate your modem. Many MBB modems now are based off USB, so you can buy an inexpensive USB Extension cable to move your modem to a better location. If indoors, try moving the modem to a windowsil. Do not put it outside at all, no matter what you wrap it in!

You can also look (in the UK) at SiteFinder, the UK’s database of Mobile Phone towers. You can then see where your local tower is and position the modem best.

Hopefully these steps will help you to get a faster speed – enjoy!

Secondary MX

I run my own home mailserver for two reasons, because I enjoy setting up systems and because I can. However, having just 1 mailserver introduces some problems. While according to the RFCs, sending servers are to keep sending failed mail for some time, they often dont. Consequently, if my server goes offline, loss of internet, reboot etc, I often loose a lot of email.

The solution to this is to have a Secondary MX (Mail Exchanger). This is another email server that will also accept email for your domain and keep trying to forward it to your Primary MX, forever. So, when my server comes back up, the email gets sent and not lost.

For a while, i’ve been using DNS Made Easy for my Secondary DNS and MX (don’t forget a secondary DNS, otherwise they can’t find out about your Secondary MX if your Primary DNS is down!). It worked, but not very well and recently i’ve noticed that i’ve been loosing email. DNS Made Easy have no information about their service status either, you have to trust that it’s working.

So, after searching for a while, I came across RollerNet. They provide many serivces, Primary/Secondary DNS/MX etc. I got a free account with them and was amazed at their quality of service. Most importantly, they give detailed logs of your MX status, such as mail received, mail in queue and the option to force-initiate a transfer of mail to your Primary MX. On top of that, they have all the usual spam filtering using the major blacklists, so no false-positives. Unfortunately, their free account has a limit of 50 messages a day (and many spammers target the Secondary MXes) so i’m now exceeding my message limit. No harm done though, i’m really impressed by their quality of service and going to take out a proper subscription. Good job RollerNet!