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> I think you could have it work that way, but you could also avoid doing
> so. I believe what Alteon does when doing L7 balancing is to look at
> the relevant info (e.g. cookie) and then decide which real server to
> send the traffic to. Once that decision is done, they are just
> forwarding packets like any router would, and thus aren't actually
> subject to any concurrent open port limits. Once the decision of which
> real server to send it is made, it doesn't get changed until the TCP
> connection closes.
>
> Now if the L7 load balancer does something like aggregate connections
> (e.g. clients send in connections to LB, then LB keeps an HTTP/1.1
> persistent connection open and multiplexes those client requests over
> that persistent connection), then you would have to worry about port
> limitations.
>
> The tricky word here I think is 'persistent'. You can get 'stickiness'
> without having a persistent connection.
True.
Expensive boxes made by Redline Networks and Netscaler aggregate HTTP1.0
connections from a large number a clients into a small number of persistent
HTTP1.1 connections to the real servers. I remember reading marketing
collateral describing how this isolates web servers from slow modem-based
clients that hog up webserver resources. And if you read the Zeus docs,
you'll also see them refer to this aggregation functionality as a selling
point.
I guess this feature is something they use to differentiate themselves from
traditional L7 balancers. I think they name it something like "traffic
management" in their collateral.
Ed
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