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It’s amazing how some companies manage to function, or even survive. I worked with a company who operated a large IBM Mainframe network. Now back in the day (late 1980’s), essentially there were two products that could be used to monitor an IBM SNA Network. The NetMaster product, and the somewhat inferior IBM [...] When we talk about networking, sometimes we’ll talk about Maximum Transmission Unit (MTU) packet sizing. I briefly referred to MTUs in the SSL errors, and how to diagnose them post. Why should you care? Well if you want a fast internet connection, you should. Think of the MTU as a 4 pint jug. Your 4 pint jug can ever only hold 4 pints. But say you are trying to fill it from an 8 pint (gallon) bucket. You need two jugs. This, in networking, we call packet fragmentation. Packet fragmentation was the root cause of the issue in the SSL errors post. Packet fragmentation is bad. To stretch the bucket example, you’d need to make two trips as your 4 pint is too small. It’s faster to make one trip. So how do you set the maximum MTU for your network connection? Well there are two ways to adjust your MTU. The hard way – MTU Ping Test We do a series of ping tests using the ping command like this: Reading a Microsoft blog post recently, I was reminded of a customer request from late 2002. The emailed request was something like this: Had to use the generic Win NT4 install on a Toshiba laptop yesterday. There were some issues. No network adapter is installed at the time of the Win NT4 installation.* This [...] Frankly, I don’t know, but here’s what I learnt. It started with a customer reporting a problem When we press the publish button on the website, we get a 403 error. A co-worker of mine picked up the call. After trying many different things, he asks our Network team for help. If it works [...] Non routable IP addresses are IP addresses which are not usable on the internet, but can be used on your home/corporate network. 10.0.0.0 – 10.255.255.255 172.16.0.0 – 172.31.255.255 192.168.0.0 – 192.168.255.255 … as defined by RFC1597 – http://www.faqs.org/rfcs/rfc1597.html [...] A senior project manager reminded me of the power of Freedom of Information requests to stop things. Yes, we can do that for the Minister, but the Minister should be aware that his request will be FOI discoverable. Back in the day, let’s say 1998, a request came though to the IT group. ”Configure [...] IF you wanted to analyse some network traffic, to see where things were going wrong, you would use a network hub. A network hub is one of the devices you can use to listen to network traffic, as it’s happening. In other words, you can listen in on a conversation between two or [...] I, of course, researched everything beforehand and had it all planned out so that the implementation of the new policy went without incident. Well, maybe there was a little trial and error. Now that I think about it, I guess there could have been a few issues on the back-end. OK, so I really [...] … then it’s unmanaged and open to exploit. As happened with a customer in mid-2004. The “batphone” rings and it’s one of our desktop support guys. “We’re detected a wireless router plugged into the customers network, what do you want me to do?” Wait 5 while I see if it’s authorised… (it’s not) [...] |
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