October 2012
Intermediate to advanced
419 pages
10h 47m
English
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Chapter 21. sFlow
sFlow is an open source sampling tool that provides constant traffic flow information on all enabled interfaces simultaneously. sFlow data is sent from the switch by a process called an agent in sFlow parlance. The sFlow data is sent to a collector that usually formats the data into cool-looking charts and graphs while recording and reporting trends for use in diagnostics, troubleshooting, and analysis. sFlow is defined in RFC 3176, and because it’s an open source tool, there are many agents and collectors out there, some of which are free, and some of which cost tens of thousands of dollars. If you’re thinking that this all sounds like Cisco’s NetFlow, you’re right, but sFlow is open source, while NetFlow is Cisco proprietary.
The agent within the switch samples packets from the data flows, and then forwards the headers of those sampled packets to the collector at regular intervals. The sampling is just that, a sample packet from the data flows and not a copy of every packet. The number of packets sampled from the total packets seen is called the sample rate, which can be configured with the default being about 1 in every 65,000 packets. These packets are stored and then sent to the collector at a configurable interval called the polling interval. The default polling interval is two seconds.
Not all packets or flow types are sampled. Packets that are sampled include frames sent to the interfaces or CPU of the switch, routed packets (with certain exceptions), flooded ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.