ISA Server 2006 TCP Retransmits

Health Checks

I perform ISA Server Health Checks for Premier Support (via Premier Field Engineering) as part of my role.

I’ve seen something a few times recently that I thought it might be helpful to call out, while poking around in the Performance Monitor TCPv4 counter area.

The Problem

In short: Lots of TCP retransmissions per second.

Like, lots. More than 1% is annoying; any more than 5% and you pretty surely have a problem.

Recently, I’ve been seeing 20%.

That’s right, kids, according to Perfmon’s statistics, one in five TCP packets requires retransmission. But! That doesn’t necessarily jive with what’s seen on the wire, suggesting it might be an internal driver or hardware problem.

If your ISA Server seems like it might be a bit slow, and you haven’t looked yet, go look. I’ll wait. You’re interested in the TCPv4 object, specifically the Segments/sec and Segments Retransmitted/sec counters.

What I’ve seen looks like this:


The green area is TCPv4\Segments/sec. The red area is TCPv4\Segments Retransmitted/sec. They’re using the same scale.

Notice that the retransmission figures track with the overall volume.

This 20% figure has been seen across HP and Broadcom (and possibly Intel) server NICs, so I don’t think it’s specific to either vendor.

Fixing It

In at least one of the places I found this, a simple driver upgrade to the latest version available looked like it fixed the problem.

Otherwise, it could indicate a NIC issue, or a hardware issue with the switch.

If you find yourself in this situation, and do resolve it, please do post details in the comments section below.

My new roadmouse

They wanted me to post about Windows phones.

Well, I’m going to fight the power. Buck the trend. Talk about my new favourite travelling companion.

It is the surprisingly-catchily-titled Microsoft Mobile Memory Mouse 8000.


First cool feature: Magnets everywhere!

The wireless transceiver doubles as a 1GB USB stick, and has a magnetic doohickie on the end that the charge cable happily snuggles up to.

The same cable has another magnetic dock on the underside of the mouse.

Next cool feature: Use it like a wired one!

With the mouse power switch in the “off” position, I’m still happily mousing away with the cable connected.

Next cool almost-hidden feature: It does Bluetooth too!

You can select between the 2.4Ghz Wireless thingy supplied by the dongle, or regular Bluetooth connectivity with a switch under the battery cover. And since I got bluetooth fixed on my laptop, that actually makes some sense, and means that – as long as it’s charged already – I can use the mouse for a fair while without having to find the memory stick slash dongle slash cord thing.

I have no idea how I came into possession of this one, but it’s quickly replaced the (fleet of) Notebook Optical Mouse (s) that I’ve loved – yes, loved – over the years for its size, lightness and plucky go-anywhere courage.

It is, however, heavier: there’s a nice metal finish, and obviously a rechargeable battery in there, but I don’t find myself minding that much.

From the wish-it-didn’t department: 4-way scroll wheel that I’d have happily substituted for a fatter non-side-scrolling regular wheel (middle clicks are a bit sharp and rolly), and thumb buttons discreetly out of thumb’s reach on the left. I hate thumb buttons (unlike Jeff), but these are unobtrusive enough that you’re unlikely to hit them accidentally.

So perhaps I’m just getting old – and I certainly don’t play as many first person shooters as I used to, especially not on this 1.2Ghz-and-PATA-toting Dell XT – but this mouse seems to do just fine for the moment. Recommended!

Brought to you by the number 8000, and the word “shill”. 🙂