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Smarter Compression Technology
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June 13, 2003
By Mike DeMaria
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If you were going to send a large data file across the Internet, you'd compress it first. Peribit's Sequence Reducer, or SR, series, takes compression a step further. It can compress similar and repeating traffic patterns to increase network performance. In fact, Peribit claims up to a tenfold increase in bandwidth optimization--and my tests back this claim, but only with repetitive traffic.
Peribit sent me its new SR-20 (maximum 2 Mbps), an older model SR-55 (max 45 Mbps) and a copy of its new Central Management System (CMS) software for evaluation in our Syracuse University Real-World Labs®. To use the SR devices, you must have a unit at the end of each link. Because of its proprietary compression algorithm, you can only compress data flowing between the SRs. The device is customarily installed behind the Internet gateway, but if you have a site-to-site VPN, the SR should be installed behind the VPN servers. If you don't install it this way, the product will try to compress encrypted traffic, which does not compress very well, if it all, and you won't be able to take advantage of the product's application QoS (Quality of Service) and monitoring capabilities.
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Compression Tests
I set up my test environment to simulate a central office with two remote offices connected via T1 (1.5 Mbps) lines. First I installed the SR-55 and designated it as the registration server, which keeps track of the other SRs on the network.
For my baseline test I transferred a 1-MB text file via FTP. It transferred in 5.61 seconds at 187 KB per second (approximately 1,496 Kbps). I then transferred the same file five times consecutively with the SRs on. The transmission time progressively decreased from 2.94 seconds to 0.18 seconds at 5,799.64 KB per second. I repeated the test with a 1.1-MB PDF file; its transfer speed went from 206.23 KB per second to 387 KB per second. Finally, I transferred a 50-MB Windows Cabinet File. The initial test ran at 182.14 KB per second and subsequent runs took just as long. That's because there is very little repetition in a Cab File. Overall, I saw an average 25 percent to 50 percent reduction in file size.
Customizing
Peribit's device lets you create application classifications so you can instruct the SR to ignore encrypted or previously compressed data.
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Good
• Reduces bandwidth usage dramatically
• Simple configuration and management interface
• Centralized management
Bad
• Not all traffic reduces well
• Only compresses traffic between SR units
• Centralized monitoring could be better
SR-20 Sequence Reducer, starts at $2,900. Central Management System (CMS), starts at $5,000. Peribit Networks, (866) Peribit, (408) 330-5600. peribit.com/products/cms.htm
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The SR also has some limited reporting capabilities. It can generate graphs for throughput, data-reduction rates and total data transferred, and display them by application.
Peribit's CMS is primarily for large deployments. I installed a copy of CMS on my LAN segment, and after specifying the registration server's IP, I was given a list of the SRs on the LAN. I could extract from or load software images and configuration files to all my SRs. To test this capability, I extracted the configuration from SR-2 and specified it be loaded on SR-3. The unit rebooted, and a minute later the config was there.
The CMS lets you view traffic reduction stats, though it offers only a graphical representation of how much data is reduced for each tunnel; it doesn't provide hard numbers for the entire network.
Michael J. DeMaria is an associate technology editor at Network Computing's Syracuse University's Real-World Labs®. Write to him at mdemaria@nwc.com.
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