Archive for April, 2012

27 April, 2012

Nook Simple Touch: initial impressions

by gorthx

I received a nice little bonus at work earlier this year, and instead of SAVING! IT! ALL! like my mother would have me do, I put most of it aside and decided to use the rest on a new toy. I’d been eyeing e-readers for a while; I thought they’d be great on camping trips. My main hangup about e-readers was that I’m a die-hard library user, and my local library has no support for linux users of e-readers.

Then I read this and decided I could probably figure it out.

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20 April, 2012

This is what counter rollover looks like.

by gorthx

A friend came to me about a performance monitoring tool he was using for his routers; he was concerned that his traffic in/out graphs for his 10G linkes weren’t matching up nicely with the values he found on the interface counters. The difference was fairly large and not equal across all interfaces (which would indicate a math problem). Without actually seeing his graphs & stats, my initial reaction [1] was “counter rollover!” and pointed him here for an explanation.

Basically, if you have a link that is 100Mb or faster, you want to use ifHCInOctets and ifHCOutOctets instead of ifInOctets and ifOutOctets [2]. (The caveat, of course, is that not all interface types support the ifHC counters, not even those that should.) With reasonably steady traffic, graphs depicting counter rollover have a characteristic jagged pattern. And of course, completely incorrect data.

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13 April, 2012

Monitoring Cisco IP SLAs: syslog messages

by gorthx

Now that I have an SLA in place, and have some baseline data, I want some notifications in case my SLAs drop. I’ll cover basic syslog messages here, and SNMP traps in another post.

Cisco’s docs have a neat graph that shows how the reaction-config interprets the thresholds. There’s also a handy-dandy chart that tells us which reactions are available for each type of SLA.

I configured a udp-jitter SLA, so everything in the ‘UDP Jitter’ column that’s marked with a Y is something I can configure a reaction for. I’ll check RTT [1], jitter, MOS, and timeout for starters. Initially, I tried this out on just a few routers, with some numbers very close to my collected stats (see last week’s graphs), so I could make sure it was working. Here, I have adjusted them to some more realistic numbers; YMMV.

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6 April, 2012

Ubuntu + wine + ADE + nook + library2go

by gorthx

I’m pre-empting my promised posting about Cisco SLA syslog messages (it was a bit of a disappointment, anyway) to post the steps I took to get my nook to download a book from library2go [1].

I had to try a bunch of different things (links at the bottom) to get this to work. The basic procedure is:
– Install Wine (the windows emulator).
– Install Adobe Digital Editions (ADE) under Wine.
– Configure Wine so ADE can see your nook.
– Visit the library2go website & check out your chosen reading material; it downloads as a .ascm file.
– Open the .ascm file with ADE; you can read it in ADE if you want (ew)
– Use ADE to transfer the book to your nook.

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