Goodness gracious, great walls of fire

Ask most people what the default rules should look like for a network firewall and they will likely say “drop” or “stealth” – i.e. if the source address:port & destination address:port combination is not matched then the traffic is silently ignored. This is often perceived as being more secure than rejecting the connection attempts, based…

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Hyper-V Virtual Networks

The most common questions that I get on Hyper-V setups relates to the networking configuration, and it seems to be common thing to get wrong, so I’ll try to go through the 3 types of virtual network we have, and how they differ.   A private network can only be used by the child partitions,…

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Capturing network traffic in Windows 7 / Server 2008 R2

Previously a capture filter driver had to be loaded in order to intercept and record all the packets passing through network interfaces (think WinPcap & NetMon filter drivers). Now, the ability to create a network trace is in-box with Windows 7 & Server 2008, without even a reboot required! It is covered in detail over…

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Network layer tweaks in Windows Server 2008

KB article 951037 describes some of the new features in the OS related to the network layer, some similar to the “Scalable Networking Pack” released for Windows Server 2003 (included in SP2). Some environments (NICs, switches, routers) do not behave well with these new features and unpredictable symptoms can crop up with no apparent pattern…

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VM Networking Improvements in Hyper-V in Windows Server 2008 R2

On the What’s New in Windows Server 2008 R2? page you can see one of the improvements for Hyper-V has been improved virtual networking performance, and specifically “offloading” has been extended through to the child partitions for those physical NICs that offer it. I did an in-place upgrade of my home server today, from Windows…

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On Bandwidth and Latency

High bandwidth = good. Low latency = good. There is, however, no direct relationship between the two – bandwidth is measured in (multiples of) “bits per second”, whilst latency is measured in milliseconds (the time between a packet being sent and it arriving at the destination). Analogies with IT-related technologies invariably fail, and are most…

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