Re: [9fans] A simple experiment

[Bakul Shah <bakul+plan9@bitblocks.com>]

On Thu, 29 Apr 2010 11:34:44 EDT erik quanstrom <quanstro@quanstro.net>  wrote:
> >  Wasn't IL somewhat abandoned because to make it as good as TCP you
> > basically had to implement TCP anyway?
>
> due to a failure of vision, the internet only does
> well with certain types of ip packets.

:-)

> il is still an excellent protocol for local networks.
>
> > 9P doesn't require any flow control?  That doesn't seem right :-)  But then
>
> 9p, like aoe, is a ping-pong protocol.  each message requires an ack.
> therefore, the transport layer doesn't need flow control.

Therefore, it is also not able to utilise bandwidth
effectively over longhaul links. As an example, US coast
to coast round trip time latency is about 100ms. Now consider
fcp. Each worker thread of fcp does 8K read/writes. Due to
pingponging, the *most* a thread can xfer coast to coast is
80KBps (for 16 threads, 1.28MBps).  It is actually much worse
since each thread doesn't even overlap reads with writes.

Short of a sliding window that is as large as the capacity of
the pipe, you can't expect to keep it full.  As usual one has
to trade off simplicity vs performance.

I do hope 9p evolves.