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Julian Anastasov wrote:
> Hello,
>
> On Thu, 25 Jan 2001, Tyrel Beede wrote:
>
> > Just a thought,
> >
> > Concerning a fastest response class scheduling algorithm which would
> > function to balance response time through out the cluster by manipulating
> > the
> > number and type of connection to each node of the cluster, is and how would
> > it
> > be possible to develop an algorithm that works by evaluating the rate of
> > change
> > for the sum of the client tcp windows? My knowledge is not exact but would
> > it
> > be possible to this? Realistically how fast does the environment between a
> > client and server on the internet change? Assuming a tcp protocol like ftp
> > which for now we assume is primarily performing bulk data transactions and
> > thus
> > over a significant period of time it would act to continuously fill up the
> > window size. Therefor this would result in a number of connections to a
> > single
>
> Only for NAT or for any forwarding method when the client uploads
> data.
True, but there is a window size and a congestion window size for each size of
a
connection. Which side of the connection data was primarily flowing doesn't
matter.
>
>
> > node having filled windows or filling windows most of the time. Now the
> > rate at
> > which the windows are/or become filled would be dependent on three factors:
> > the
> > size of the physical links over the length of the connection, the current
> > congestion over those links, and also the current congestion at the end
> > server
> > node(the node's ability to process data). Now if the sum of the rate of
> > change
> > of these links is averaged a load value may be calculated for each node and
> > as a
> > result connections maybe intelligently balanced. This should also apply to
> > data
> > exchange types which do not resemble bulk ftp. I also wonder if it would be
> > possible to create a framework within the lvs to enable balancing at a
> > packet
> > granularity rather than at a connection granularity? Would it be possible
> > for
>
> Are you trying to balance a ftp traffic?
>
> Hm, what do you mean: balancing at a packet/connection
> granularity. I don't understand. Scheduling of independent packets?
> What service needs this?
For example, within a cluster their could be two nodes. Assuming these nodes
each
had three established tcp connections it would be possible that one of the two
nodes
could have three established connections which were not transmitting data.
Therefor
when we schedual according to a connection granularity load is only shared at a
level
where the number of connections between machines are balanced. With tcp this
does
not mean that the amount of data transmitted is going to be the same per
connection
and thus, in total, would not be the same per node in the cluster. Now, what I
wonder is would such a thing be possible within the current tcp implementation.
As
you indicated I'm not sure which services would benifit from this the most but
it
wouldn't be hard to characterize a type of data transaction which would benifit
the
most. From this special case it would be possible to evaluate where or not any
real
preformance gains could be made. This, however, is getting a little bit
further away
from the topic than my original question had invisioned. I was just wondering
if it
would be possible and if possible how would it be done on paper.
>
>
> > the lvs to record the necessary state information to manipulate acks in
> > such a
> > manner that it could pass off connections between identical servers while
> > the
> > connection always appeared to be "up" to the client? Seems like all this
> > would
> > require lots of packet mugging so yeah...
>
> You have a very strange vision for the load. Be more specific.
> Explain carefully each idea you mention in this mail, I hear your
> bullets but can't see them :)
Yeah, I would agree. Most of the time I don't even see the bullets. :-)
If the lvs could keep a record of all transactions between a server and host
and if
the connection were to be closed at the server end it would have the ability to
regenerate the connection on another server providing that the two servers were
able
to serve identical content. Now the idea that the lvs could store all the
information for each transaction through it would most likely be impossible.
But
would just the control information(acks and such) be enough to regenerate the
connection? A good visualization of this would be something like a a proxy
server
designed to work at a protocol level instead of the application layer.
>
>
> IMHO, the director needs information from the real servers to
> balance the load. There are many parameters we can monitor and we can
> make different expressions based on these parameters: packet rate,
> cpu usage, free memory. In this way, we can select different expressions
> for the different services. There is a reason for this: each service
> loads differently the real host or may be other hosts too, for example
> databases, etc.
What do you mean my "the director needs information from the real servers to
balance
the load" should this information be a direct result of a platform/application
specific modification? How sould it get this information?
>
>
> I don't believe in your theory about the fastest response
> schedulng but you can surprise us with more specific details and
> may be results :) Is this scheduler for NAT only?
If I was able to figure out the details and implement something of this nature
it
would be done in NAT to prove the idea
Thanks, Tyrel
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