Elephants on the network – LFNs (Long Fat Networks), Bandwidth Versus Latency

I can’t tell you how many times I have had to explain to someone who has just updated their connection to 10, 45, 100 Mb so they can quickly transfer there critical files to the other side of the planet only to find they aren’t getting any better throughput than they had before. This is a common misunderstanding about the relationship between bandwidth and throughput. The bottleneck is not the bandwidth, it’s the latency, and it is tough to argue with the speed of light.

TextMate Blogging Bundle workaround

I like to use the blogging bundle from the great text editor TextMate to do my posting here. The other day I encountered an error that gave me some problems, and I just want to point out a workaround. After posting to this blog, I received and error that went something like this…

Received exception:Wrong size. Was 1275, should be <unknown>

On Mistakes and Errors

There was an interesting quote I read today in Michael Shermer’s Skeptic column in Scientific American this month.

This administration intends to be candid about its errors. For a wise man once said, “An error does not become a mistake until you refuse to correct it.” We intend to accept full responsibility for our errors… We’re not going to have any search for scapegoats… the final responsibilities of any failure are mine, and mine alone.

Setting Your MTU

So to follow up with the previous post about MTU and MSS, I wanted to show you how to set the MTU value on your computer. On most Unix-like boxes it is a fairly straight forward process to change your MTU. On Windows it gets a little trickier with registry changes and such things that can brick your computer.

How big is your packet, MTU / MSS and other TCP headaches

There are a lot of misperceptions about packet size and the various mechanisms that allow a packet to flow smoothly along a network path. In order to avoid fragmentation, which will hurt performance and potentially overwhelm some network devices, it is important for both ends to send the appropriate sized packet.

That Pesky Close Door Button

I work in a building with an elevator. Just about every day I am in the elevator with someone who is furiously pushing the door close button. Some days I just laugh to myself, others I need to restrain myself from throttling the individual. When I feel generous, I tell the person the truth, pushing that button won’t make the doors close faster.

Busy This Week, Here’s A tcpdump example

I have been behind in my posts, and I have quite a few items to get posted. Today I wanted to walk through an example of tcpdump can be useful when tracking down malicious traffic on your network. I am going to use the example of IrnBot to demonstrate a handy technique. IrnBot (named after the Scottish drink IrnBru), also popularly known as Rinbot, produces a lot of traffic on port 1433, 2967 and 139. It also opens up a connection to irc servers on the outside over port 8080.

Getting stats with awk, sort and uniq

I find myself sorting through logs all the time, and I have developed a couple of tricks for pulling the information I need out. With a little awk, sort and uniq magic you can get a great deal of info out of your logs.

More Fun With tcpdump and Resets

Here is another handy little trick for tcpdump that will help you identify some potential network issues. Often times when there is some trouble along the line you will see reset connections. This happens for many reasons and can be an indication of everything form a network program to a crashed application that suddenly stops responding.

Quicksilver Setup

When I was getting started using Quicksilver I was always hearing about all the great things it would do, but it was a struggle to get it set up the right way to get at that functionality. In order to prevent that struggle for others I am including my basic set up.