Pings Can Be Dangerous
I recently was asked to do some analysis of a trace file, it was only 161 seconds in duration and contained a little more than 2.6 million frames. I was amazed to discover that approximately 75% of...
View Articlepacket_monitor, mirror ports and taps, Oh My!
Many times when working an issue I ask people to send me a network trace. A network trace often points to the root cause of the problem. At a minimum, it reduces the problem space to something that...
View ArticleAre You Forwarding Packets?
I recently ran into a site with several modules, each of which was forwarding packets. The worst case was at a rate of 1 every 2 seconds or so. Not very fast you say, but, there are 86,400 seconds in a...
View ArticleDealing With Daylight Savings Time
It is coming up on the end of daylight savings time and that means questions; specifically how to change the time zone, does ntpd need to be stopped and restarted when the time zone changes and if ntpd...
View ArticleApplication Performance Problems and Latency
The impact of communication layer latency is typically under estimated when trying to fix application performance problems but correct understanding is critical if you are to direct your efforts toward...
View ArticleDo You Know Where Your TCP Connections Really End?
TCP was designed to support end to end connections, that is, one host communicating directly with another host. Sure, there were bridges and routers in between, but those devices didn’t touch the TCP...
View ArticleUsing SNMP To Monitor Your Connection To Your Switch
When trying to diagnose network problems one of the questions I always ask is “What is the status of the switch port that is connected to the module’s interface?” The typical answer is “I need to ask...
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Five tips to help speed problem resolution
When you contact customer support with a problem, the typical goal is to get it resolved FAST. I have observed that in many instances the initial contact with support coordination makes a fast...
View ArticleAutomating File Transfers With FTP Macros
Lots of people have created automated processes to transfer files using FTP. There are several different ways to do this, some better than others. This blog will discuss the different approaches and...
View ArticleAutomating File Transfers With SFTP
In my last blog I talked about automating file transfers using FTP. There are three issues with using FTP. First, your password is sent across the network in clear text making it available to anyone...
View ArticleExplaining the Traceroute Command
Traceroute can be an invaluable tool when trying to diagnose connection problems to hosts on other networks. However to be used effectively you have to understand how it works and what the output...
View ArticleWhy Didn’t My Bandwidth Upgrade Speed Up My File Copies?
“We just upgraded from a T1 (1.544 mbps) to a T3 (44.736 mbps) so why is it still taking 90 minutes to copy that file?” The simple answer is that more capacity is not the same as faster bytes. If you...
View ArticleUnblocking Calls to the recv Function Without Using Non-blocking Mode
When writing a network application you can use non-blocking mode or blocking mode. Non blocking mode is more flexible and required when the application has to do multiple things, like servicing...
View ArticleInterop report – April 27th 2010 Las Vegas NV
Show Floor: 20% faster but 20% smaller too: In 1998 it took me three days to walk the show room floor and I was pretty sure I didn’t see everything. The last few years I’ve been doing it in 1 day and...
View ArticleThank Goodness For Regression Tests
Thank goodness for regression tests. There I was, earlier this week, feeling really good about some new code that I had written and (I thought) debugged. I’m in the process of enhancing the OpenVOS...
View ArticleWhy We Renamed VOS to OpenVOS
For over 25 years, the name VOS has referred to an operating system that is reliable, continuously available, and easy to use. We did not take the decision to rename VOS lightly. The new name...
View ArticleTip: Use a Dot to Access the Current Directory
Over the years we have added a number of UNIX® features to VOS. One of the simplest and most useful of these is the ability to use dot (“.”) and dot-dot (“..”) as pathnames. A single dot accesses the...
View ArticleGet the Big Picture
Are you still working on VOS using a 80 column by 24 line view? Get with the flow and see the big picture. VOS supports many terminals and terminal emulators. Stratus supplies terminal-type files...
View ArticlePorting Open-Source code to VOS and OpenVOS
I recently revised our notes on how to port open-source code to VOS and OpenVOS. This new revision is about 30% longer and contains much more detailed information. Working with my colleague Richard...
View ArticleReorganization of the Open-Source Files on the VOS Anonymous FTP Site
Stratus has offered ports of open-source, POSIX-based software to its VOS customers for many years. When we first started offering these ports, most VOS customers were using Continuum (HP PA-RISC)...
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