tag:blogger.com,1999:blog-1978652979840829013.post4730376733125707598..comments2024-02-13T07:05:41.069-08:00Comments on sFlow: Accuracy and packet lossPeterhttp://www.blogger.com/profile/00856599914190257147noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-1978652979840829013.post-41668464710827492692009-06-06T09:06:08.886-07:002009-06-06T09:06:08.886-07:00Thank you for the link. I read the article with in...Thank you for the link. I read the article with interest and have the following comments:<br /><br />The blog entry contains a limited comparison of sFlow and NetFlow data from a single link (the topic of network-wide scalability isn't discussed). The article does demonstrate some important differences, sFlow reports on IP and non-IP traffic, NetFlow is IP only. The time smearing effect of NetFlow monitoring and its effect in delaying measurements and distorting utilization trends is also demonstrated. <br /><br />Unfortunately, problems with the experimental setup make it hard to draw any conclusions about accuracy from the results. Problems with the methodology, some of which were identified in the article, include: the lack of an accurate reference (how can you compare measurement technologies if you don't know the correct answer?), problems with the NetFlow and sFlow configuration in the switches (flow timeouts, sampling rates) and finally problems with the scaling of sampled data (see the comments at the end of the article).Peterhttps://www.blogger.com/profile/00856599914190257147noreply@blogger.comtag:blogger.com,1999:blog-1978652979840829013.post-74086203227298146662009-06-04T05:25:08.981-07:002009-06-04T05:25:08.981-07:00If you want to read about the differences between ...If you want to read about the differences between NetFlow and sFlow, I would check out this blog: http://www.networkworld.com/community/node/29117Unknownhttps://www.blogger.com/profile/03821247855819344146noreply@blogger.comtag:blogger.com,1999:blog-1978652979840829013.post-48677892946415630762009-06-03T19:45:08.799-07:002009-06-03T19:45:08.799-07:00I am familiar with NetFlow sequence numbers. NetFl...I am familiar with NetFlow sequence numbers. NetFlow sequence numbers let you detect that data has been lost, but they don't provide a way to compensate for the lost records. Understanding that NetFlow accuracy is sensitive to packet loss is an important consideration when configuring NetFlow. Care should be taken to check for lost NetFlow records and NetFlow configuration settings may need to be tuned to minimize loss.<br /><br />I agree that both NetFlow and sFlow have their merits, but they are very different technologies and have different strengths and weaknesses. Understanding the differences is important if you want to pick the best solution for a given application. If you want to monitor thousands of 10G Ethernet switch ports in a data center then sFlow is clearly the best choice. If you want to monitor routed DS3 links and collect billing data then NetFlow may well be the best choice.<br /><br />Arguing about whether sFlow or NetFlow is better makes as much sense as arguing whether switching or routing is better, or whether Ethernet or IP is better. In practice people use all of the technologies because each solves a distinct problem and plays an important role in the overall network design.Peterhttps://www.blogger.com/profile/00856599914190257147noreply@blogger.comtag:blogger.com,1999:blog-1978652979840829013.post-8508699909655276822009-06-03T18:07:45.664-07:002009-06-03T18:07:45.664-07:00Regarding your comment "NetFlow has no mechan...Regarding your comment "NetFlow has no mechanism to compensate for lost records." Are you familiar with NetFlows FlowSequence number which indicates missed flow records? <br /><br />Both technologies have their merits. Seeing how this is sflow.com it would be great if you focused on sFlow and why it is great rather than why it is better than NetFlow. I for one like both and don't believe one is better than the other or that this blog will be unbiased in its opinions when comparing the two.Jake Wilsonhttps://www.blogger.com/profile/17809477740687629419noreply@blogger.com