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Archive for the ‘Internet’ Category

Large-scale server systems are common in this age. A small computing grid can easily consist of a few hundred nodes. Configuring such a server network can be tedious and usually requires a centralized change management system. If the centralized change management system went down, configuration/updates on the nodes can be affected.

By establishing a standard in your DNS TXT records, we can embed information such as:

  • Remote upstream server’s hostname
  • Listening TCP ports on this hostname
  • Available services (in the form of a bitmask) on this server

For instance, we have a node with a hostname called node123.abc.com which connects to job1.abc.com to communicate information. We can embed the upstream hostname information (job1) in the DNS TXT record for node123. We will also embed the TCP listening ports and the type of services available in job1’s DNS TXT record. Now, the client software on node123 only needs to retrieve node123’s DNS TXT and learns that it needs to connect job1 as its upstream server. It will then retrieve job1’s DNS TXT record and learns of the listening TCP ports on job1 machine that will listen for incoming TCP connections.


  • Resilient distribution mechanism built on top of DNS infrastructure with DNS caching and secondary DNS servers.
  • Centralized configuration node can be “hidden” behind a firewall without being exposed on the Internet.
  • Zero-configuration on the nodes as all configuration information could potentially be learnt from the DNS TXT records, so a single installation base can be utilized for all computing nodes. In fact, in theory, you will only need to configure the node’s hostname and IP network information.


  • Delay in changes from configuration updates to actual change implementation on the server (due to DNS cache)
  • Potential leaks in configuration information as anyone can “lookup” the DNS records.
  • Often requires significant changes in client source code to use DNS TXT records to learn about its connection configuration
  • Limited by the small data size (approx 250 bytes) in the DNS TXT record specification.

I have recently upgraded my laptop from Windows Vista 32-bit to Windows 7 Home Premium. I have performed the following steps to get my Huawei E169 3G modem working in Windows 7 again.

  1. Uninstall the SingTel Broadband on Mobile software and unplug your 3G modem from your PC/laptop
  2. Download this patch from Huawei (Local Mirror), extract the setup file and run it.
  3. Reboot your PC/laptop
  4. Plug back your 3G modem. Wait for the SingTel CD drive to appear in your “My Computer”
  5. Install the SingTel Broadband on Mobile software again. Your 3G modem should be automatically be detected after the software has been installed.

PS. SingTel Broadband on Mobile web site has some firmwares and Windows 7 fixes for Huawei E169 modem. But these softwares keep giving some code 2 errors indicating that I do not have administrator permission or the data card is being used by other software on the PC/laptop. Well, in all cases, I have gotten my 3G modem working without these “upgrades”. Thank goodness.