Re: [load balancing] Cascading switches off of a Foundry switch

From: Nimesh Vakharia (
Date: Thu Feb 22 2001 - 01:55:55 EST

  • Next message: tc lewis: "[load balancing] software vs appliances."

    > The full paragraph from RFC 2109 for context:
    > 4.2.1 General
    > The origin server initiates a session, if it so desires. (Note that
    > "session" here does not refer to a persistent network connection but
    > to a logical session created from HTTP requests and responses. The
    > presence or absence of a persistent connection should have no effect
    > on the use of cookie-derived sessions). To initiate a session, the
    > origin server returns an extra response header to the client, Set-
    > Cookie. (The details follow later.)
    > So, by definition, RFC 2109 has really nothing to do with using cookies to
    > make persistent network connections, but enable "logical sessions created
    > from HTTP requests and responses". So, two things. One, what if "logical"
    > persistance doesn't cut it? Two, we are really talking about making cookies
    > create the "persistent network connection" which really has nothing to do
    > with actual programatic sessions, it may make it easier to maintain
    > programatic sessions, but the two are generally handled seperately i.e. even
    > with persistent network connections, something else still has to maintain
    > session state within the application.

            The point I was trying to convey was the RFC shows you how to
    maintain state within the application using cookies without persistent
    network connections. ie you can reconstruct your session using cookies
    and not have to rely on your LB to do it. (This is an option, application
    can use a combination of "clusterin g mechanism/meta-data/cookies etc. to
    do it). The example in Section 5 (i think) gives a trivial but valid

    > And if you use a switch based LB, there simply is no way around the fact
    > that the LB will most likely carry non-LB traffic (unless you like multi
    > homed machines). Fortunately for me, I've almost always used F5 (if you
    > hadn't guessed). I've never had to route my non-lb traffic through my
    > BIG-IP. It's all routing, baby! I can go where ever I want. :-)
            Well webservers are usually seen in a multihomed architecture, but
    a LB has other applications which really do not require it and sometimes
    out of band is not feasible. Anyway DSR is not evil and can be quite
    useful and efficient in certain scenarios! :)


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