March 01, 2000
Uptime Update - March 1, 2000
The Resource for Network and Protocol Analysis Professionals
A Newsletter of http://www.NetworkUptime.com
Issue 02 00 00 00 00 03 00 01
Welcome to Uptime-Update, the newsletter from the folks that bring you <http://www.NetworkUptime.com>. Thanks for joining us! As always, you can subscribe to Uptime Update or view this issue on the web at <http://www.NetworkUptime.com/newsletter>.
The Uptime Update newsletter is a place to exchange network analysis information, share networking tips, and discuss some of the finer points of keeping a network running in good condition. Please feel free to contact us with feedback, suggestions, or ideas for future newsletters!
- James Messer, Team Uptime
Editor, Uptime Update
James@NetworkUptime.com
I was working with my network analyzer last week in an attempt to learn more about the intricate menu options and output capabilities, when I saw some unfamiliar traffic wandering around my network. Our network doesn't normally broadcast AppleTalk traffic, but the analyzer clearly showed a tiny percentage of AppleTalk packets traversing the network. I tracked down the problem to a print server that was misconfigured, and I updated the print server's configuration settings to use TCP/IP only.
This brought up an interesting point when using a network analysis tool; there's always SOMETHING that can be made more efficient by using a network analyzer. I've had very few instances where using a analyzer on a network didn't provide me with at least _one_ opportunity for improving the throughput of the network!
When visiting other companies, I sometimes find that many of the network managers are only using their network analyzer in times of trouble or chaos. The rest of the time, these tools are unplugged or under someone's desk!
A quick weave of a network trace can lead to many tangled webs. Here are some issues to check on your network:
* Broadcasts - With the proliferation of switched networks, many network managers have moved from a routed configuration to a flatter network design. Unfortunately, this also means that more broadcasts are finding their way around the network! Try to keep broadcasts under 40 per second, and don't let them exceed 120 per second!
* Unwanted Protocols - In with the good, out with the bad! Almost every network has a protocol that shouldn't be there - my network was a perfect example!. Most analyzers can display a protocol distribution table which would identify any protocol that communicates on the network.
Here's an example: One very common protocol on many switched networks is the Bridge Protocol Data Unit (BPDU). BPDUs are multicasts that allow switches to communicate with each other for spanning tree configuration and keep-alive messages. The default configuration of many switches is to have spanning tree enabled, even if the network has no redundant switched links. Since most BPDU keep-alive messages are sent every two seconds, disabling spanning tree on a switch can save a packet or two of bandwidth!
* Bad Applications - They don't mean to be bad, they're just written that way. A good example of a 'bad' application is the code that was written into a popular printer brand. When used with a NetWare server, the printer would poll the file server every two seconds to query for a print job. One minute of packet capture would show 60 frames traversing the network (one for the request, and one for the answer). If 10 printers were placed on the network, the number of frames would increase to 600 per minute, and that's without ever printing anything!
In this case, the timeout for the printer was adjustable. Setting the default value to 30 seconds decreased network traffic without causing much of a delay to the waiting print jobs.
Do you have other 'quick-draw' problems that you can suggest? Send your comments to us at James@NetworkUptime.com!
One of our favorite network utilities is a Belgium import from Luc Neijens called CyberKit. This nearly free program provides a ping, traceroute, whois, finger, quote of the day, name server lookup, time synchronizer, network scanner, winsock database scanner, check for new mail, and keep alive function in one handy network utility!
One nice feature is the price. Luc has released his program as 'postcardware', allowing you to use CyberKit for the exchange of a postcard. Pick a colorful postcard of your area, and send it to Luc. It's a small price to pay for such a fantastic network utility!
You can download CyberKit from the Network Uptime Tool library at:http://www.NetworkUptime.com/tools/winnt/desktop/ping
We're interested in the programs you use for day-to-day operations, or the specialized tool that you've found for those hard-to-fix problems. Send us the name of the program and the web-page, and we'll feature it in a future edition of Uptime Update! E-mail your program suggestion to James@NetworkUptime.com
This month's web site in the spotlight is the Information Technology Professional's Resource Center (ITPRC). The ITPRC contains hundreds of links for technology professionals, including network operations, network technologies, book guides, and career management links. View the ITPRC web site at:http://www.itprc.com
Do you have a web site that helps you with your job? Send the link to us at James@NetworkUptime.com, and we'll include it in a future Surf Report!
Every protocol analyzer has a statistics function, and there's an amazing amount of information contained within those dials and displays. Packets per second, number of broadcasts, protocol distributions, packet size distributions, and other values help to form a baseline of a network's inner workings.
When I analyze a network segment for the first time, I like to take a 60-second 'snapshot' of a network to help build a baseline view. A series of one-minute captures taken at different times of the day can provide an interesting study of traffic patterns over time.
These slices of network traffic also contain a manageable subset of packets that make it easy to quickly understand the 'heartbeat' of a network. Many network problems can be identified in the first minute of a trace!
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Posted by james_messer at March 1, 2000 07:48 AM