Do we consider loadbalancer configuration on topic? Though they certainly do things on layer 2/3, a lot of the things they do is on higher layers as well. At the company I work for loadbalancers are managed by NOC engineers, but I know other companies where loadbalancers are managed by systems engineers, so I'm curious what others thing about this.
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2 Answers
Short Answer: A question about a load-balancer, that is involved in balancing traffic at the network layer (layer 4 or below) is directly involved with end to end visibility of network traffic, so by that measure, I believe it to be on topic.
I think if you are asking about how to set up a stateful load-balancer, synchronising TCP state tables between them for example, that would be OK. This is a networking question. I don't think asking about setting up a HTTP load balancer would be acceptable though (that is probably more for ServerFault's realm). That example is aimed at the application layer if you like (viewing this from a typical OSI 7 layer model view). Although I do think layer 7 can be on topic, perhaps not in this case.
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2Network engineers don't stop at the TCP layer... we have to be fluent all the way to the application boundaries. HTTP-aware load-balancing is in-fact the best thing to do if you're balancing an HTTP service... I don't see a good reason to punt this question to another site if the underlying hardware (call it an F5 for sake of argument) is the same Commented May 22, 2013 at 5:53
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@MikePennington I do agree with you, but I have recently been involved in a situation where the load-balancer was under the control of both network techs and sys admins. The sys admins want to control the insertion of cookies into the HTTP sessions and/remove custom headers. This is deep into the application layer, and wasn't part of my remit. My remite was making sure load balancers had multiple vlan sub interfaces to serve all the attached networks, and where failing over IPs between each other using VRRP. This is a prime example I think, of when layer 7 becomes off-top, tuning HTTP headers.– BaldrickCommented May 22, 2013 at 9:24
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while I can understand that you don't want to be involved in cookies, that isn't sufficient justification to punt all questions about HTTP load-balancing from the site... that merely means that sometimes network engineers share service administration with system administrators Commented May 22, 2013 at 9:52
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@MikePennington again I agree, so where do we drawn the line? I suppose, it could end up simply being one of those "post and see" scenarios where some get closed, and some get answered?– BaldrickCommented May 22, 2013 at 11:07
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Ask a SysAdmin to configure a load-balancer so the server itself can reach another server via the load-balancer in the same VLAN, and you'll see this is not a job for someone who doesn't know what and where sNAT is needed. Commented May 24, 2013 at 7:31
Responsibility for load balancers often fall to the network folks and without proper consideration of the network there will be issues. Even if they are talking about a HTTP load balancer, in my mind this makes them on topic for network engineering along with other devices that operate above L4, such as traffic shaping/policing.
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1I agree, I know many a Network Engineer that spend a lot of time working on F5 or ACE load balancing setup and issues. A quick search of Stack Exchange shows questions like this spread all over. I would think over time that the questions would find their way to the best site for the specific question. Commented May 23, 2013 at 18:17