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Experts |
Maps |
Network Mgmt |
OS |
Packets |
Philosophy |
SAN
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How Packets Work BlueHeat WinCati IP VTC How Packets Work Warriors of the Net Sniffing Primer Chassis vs Stackable MS NLB Catalyst Configuration Forwarding Delay |
How Packets WorkThroughput, latency, and frame loss. 2005 BlueHeat Project starts with the ~1500 users employing a particular NAS box as their home and group directory server who were experiencing intermittent performance problems, accompanied by crashing applications. We spent several evenings gathering data around the issue, comparing normal behavior with pathological behavior. We developed an NVRAM exhaustion model which explained the experience, realizing that a few of our users were overwhelming NVRAM by writing hundreds of gigabytes of small files to the slowest volume on the box. Kudos to Robert McDermott for gathering the data from the NAS box, for developing the tools to massage it, and for teasing out the relationship between Ethernet traffic, Fibre Channel traffic, and NVRAM utilization. During this effort, we also benched throughput, comparing various protocol / application combinations. 2004 WinCati Event describes how we analyzed and resolved an interaction between an EFI Fiery Server ZX (print server) and a vertical market application called WinCati. 2003 IP VTC Event describes how we analyzed and resolved an intermittent disconnect issue affecting our Polycom video-conferencing units. How Packets Work is a document I wrote to support in-house seminars which I've orchestrated. It has evolved substantially over the last decade, as my understanding of this subject has increased. The actual seminar wants props and a lively audience, in addition to this document. Cisco offers a flash page which illustrates many of these functions, as part of a larger page describing layer 2 functions in general. Warriors of the Net presents a high-level visualization of how packets traverse networks. The movie showcased within this site comes in various flavors -- at the high-end, it consists of a 140Mb MPG file. Ericson, the global communications manufacturer, produced and published this movie. From a technical point of view, this production contains numerous errors. On the other hand, it offers a four dimensional visualization of how packets move, the only such visualization I've ever seen, so until I find something better, I keep pointing people to it. In Sniffing Primer, I outline options for our department as we consider how to enhance our packet capture and analysis capabilities. More interesting for the general reader, I think, is the 'Sniffing Primer' section, in which I describe the various ways to insert a packet sniffer into a switched/routed infrastructure. Chassis versus Stackable illustrates one aspect of the debate between these two approaches to populating IDFs. Naturally, the prices illustrated here are dated -- but conceptually, the graph illustrates that at some level of density, chassis' become more cost-effective than stackables, as far as up front cost goes. The more subtle aspects to this decision come from less quantifiable sources: hardware reliability, maintenance costs, functionality. Microsoft Network Load Balancing and Cisco Catalyst Configuration describes how to configure Cisco Catalyst switches to support this Microsoft product. Measuring Forwarding Delay Across A Campus Network records measurements of forwarding delay across typical electronics (Catalyst 4000/4500, Catalyst 6500) deployed on our network. A Teaser for OmniPeek illustrates some of this analyzer's features. TutorialsIn this section, I stash links to educational material at other sites.
Cool ToolsHere I stash links to software I find useful in analyzing client/server issues. |
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Prepared by: Stuart Kendrick Last modified: 2008-July-15 |
