Semi-regular web-link clearance (3) – January 2010

How to Install GPMC on Server 2008, 2008 R2, and Windows 7 (via RSAT)

Can You See Me – Open Port Check Tool

Is a free utility for remotely verifying a port is open or closed. It will be useful for users who wish to check to see if a server is running or a firewall or ISP is blocking certain ports.

Setting up a Windows 7 Media Center

Windows XP Power Management and Group Policy Preferences

Windows XP only has one active power scheme for the entire computer and that scheme is based on the current or previously logged on user—that is to say Windows XP power schemes are only user-based. This means the power scheme can change as each user logs on. Also, it means that last logged on user’s power settings are the settings that remain once the user logs off. And yes, each user has its own power configuration; however, the entire operating system only has one active power scheme.

PHP and IE8 Web Slices

Internet Explorer 8 (IE8) shipped with a new feature for web users called Web Slices. … Essentially it lets you add enhanced links to your favorite bar that allow you to preview snippets of content from websites that you frequently visit without having to open up the page. It’s really useful to do little tasks like check on your web based Inbox, check the weather in cities you live or visit, traffic status, stock tickers, headlines, sports, the list goes on and on and you can check the IE add-on gallery for more examples of useful web slices and for inspiration.

How to customize default user profiles in Windows 7 (KB973289)

To customize a default user profile or a mandatory user profile, you must first customize the default user profile. Then, the default user profile can be copied to the appropriate shared folder to make that user profile either the default user profile or a mandatory user profile.

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“We don’t do that here.”

IBM_3705_Front_Panel_Asmall 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 Netview Product.

You could use either product to detect network problems, but the (free) NetView product required more skill to interpret the information.

The type of errors we’d generally aim to spot were latency and transmission errors.

Latency is a measure of how long it takes for a packet to travel along a network.  With IBM SNA, you would get a broken network connection with a latency of more than 2 seconds.  So you start to worry about traffic taking 1.2+ seconds.

Transmission errors. Much like how static on a phone line makes it hard to talk, high transmission error rates makes it hard for computers to talk on networks.  Eventually, with growing transmission errors, the computers would stop talking.

So in a well managed network, you’d monitor both, with the aim of keeping up times, up.

“We don’t do that here.”, was the comment I heard in the first week I was there.  I was amazed the company managed to function at all.

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Latency effects everything we do … … no wait!

I’ve run into latency issues over the last 20 years, and in short, they’ve been

  • X-Modem
  • IBM SNA
  • Citrix
  • Windows Vista

X-modem

… was created in August 1977 to allow file transfers between Bulletin Board Systems.  Developed by Ward Christensen.  A simple protocol by design, which was it’s beauty and it’s downfall.  Didn’t work so well over satellite links with a latency of 300ms.  Relaxed X-modem was the workaround.

IBM SNA

… has a heartbeat of 2 seconds.  Miss the heartbeat and the link dies.  Which is what was happening in the remote community of Gove, in the Northern Territory.  Because of WAN congestion, and a tropospheric WAN link, mainframe terminals in Gove would drop out.  Reconfiguring the Gove Cisco switch to provide a local SNA heartbeat solved the problem.

Citrix

… curse of an idea I tell you.  In August 2003, Citrix sessions were dropping out at a remote site.  Citrix is very intolerant of WAN congestion (20ms).  So are the users who lose their Citrix sessions.  Given that a picture tells a thousand words, here’s what the network capture told us:

network_traffic 

The RED lines indicate traffic inbound to the client site.
The BLUE lines are outbound traffic.
Both measured at the Cisco switch, so it didn’t tell us what the local LAN was doing.

The inbound red traffic indicated that our desktop management toolset was heavily utilising the line, after hours in particular (desktop patching).  The outbound blue traffic didn’t tell us much from the graph.  Further investigation, with a network sniffer, showed that 70 Citrix clients were communicating with a (remote) Citrix Server farm.  Now each Citrix client uses about 20k/s bandwidth, so 70 clients across a 128k WAN link just didn’t fit.  The answer was for the customer to increase the size of the WAN link, which they did.

Vista

I had drafted why the Vista file copy routine was broken, due I think, to latency issues, but Mark Russinovich explains it so much better, here.