08-06-2024 04:13 AM
Is it fair to compare performance of IPSLA with BFD?
In traditional network setup we can not find out BrownOut condition using BFD. Therefore we have to use IPSLA for the same. But in SD-WAN we can poll the BFD parameters and use it to identify the link latency or other parameters. Lately i have been considering comparing the performance of Application Aware Routing (SD-WAN) which relies on BFD and the similar solution we can achieve in traditional WAN which is using IPSLA with PBR.
Looking for insightful suggestion.
08-07-2024 05:51 AM
Hi,
there is no direct yes and no answer.
In SD-WAN BFD can be used in two different forms. One is as in traditional network, you use it for faster routing convergence.
Another form is native SD-WAN usage which checks tunnel health and gathers statistics for AAR. Also, you still have IP SLA support for different checks.
Actually, both do checks and gathering statistical information. So, they look similar.
However, their usage are different and can't be used for the same purpose.
BFD is used for tunnel health (tunnel goes down if BFD is down) and statistical info for AAR (AAR changes path based on BFD statistics).
IP SLA can be used to check path validity (remote node validity etc.) and do action. Also, can be used to gather statistics for monitoring purposes.
08-09-2024 06:54 AM
From my understanding, both AAR and PBR can be used to perform the same task. If we focus on traffic at layers 3 or 4 and disregard DPI, what AAR does can similarly be achieved with PBR using IPSLA. AAR relies on BFD to gather statistics and steer traffic according to policy, while PBR can use IPSLA (in Jitter mode) for similar data collection and make decisions based on route-maps.
08-07-2024 06:15 AM
Assuming SD-WAN's BFD is built on traditional BFD, I suspect it will not be much superior to IPSLA for brown outs, black outs, possibly to likely.
08-09-2024 07:17 AM
I appreciate your reply and was wondering if you could elaborate further on your thoughts. I understand that while both BFD and IPSLA may collect similar statistics, the way they do so is different. I think that in making final decision by a router to steer traffic based on BFD could be faster than deciding to steer based on PBR relying on IPSLA.
08-09-2024 11:20 AM
@Deependra Yadav wrote:
I appreciate your reply and was wondering if you could elaborate further on your thoughts. I understand that while both BFD and IPSLA may collect similar statistics, the way they do so is different. I think that in making final decision by a router to steer traffic based on BFD could be faster than deciding to steer based on PBR relying on IPSLA.
Yes, I agree BFD could be faster. The reason "could", much depends on the frequency of either the SLA or BFD exchange. BFD, should be able to do it faster, as it was designed for lightweight exchanging "liveliness" with a peer.
However, my prior reply's point is there's a difference between detecting "brown outs" vs. "black outs". "Brown outs" are looking for a spike in latency and/or packet loss, something IP SLA was designed to do. "Black outs" are looking for a total lost of a path, something BFD was designed to do (quickly, and with minimal overhead).
I don't know what enhancements were made to basic BFD for AAR (if any). I'm also mostly unknowledgeable about SD-WAN.
I can say, years ago, I worked with OER/PfRv1, which managed performance of flows to all outbound destinations. Under the covers, it used both NetFlow and IP SLA for its analysis. It worked well enough, that our concurrent performance monitoring stopped seeing WAN performance issues, because OER/PfR would route around issues. I suspect AAR's development linage might be based on the early OER/PfR technology.
My guess, either will likely satisfy the basic need, but one of them might be better than the other for specific situations and/or resource consumption on the network devices.
Hopefully, the above provides the additional information you're looking for about my thoughts. If not, and if you can specify a specific concern, let me know and I'll try to clarify my thinking even further.
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