I'm currently taking care of a WAN which includes a link between the US
and Japan. The link currently has 256K bandwidth with approx. 128ms
round trip delay. However, recently, our carrier had a undersea fiber
repeater failure and our link was routed over satellite. Our 128ms
round trip delay became 600ms after the re-route.
Using rcp to copy files between the US and Japan nodes, our average
thruput on that 256kbps link w/128ms delay was about 120kbps.
That's about 50% utilization! Not very impressive at all.
Now, when that link was routed over satellite, the thruput dropped to
33kbps (13% utilization).
FYI, here's our test setup:
USA node Japan node
PC: 386/33 SCO Unix machines
ROUTER: Cisco MGS
BWM: Network Express NE3000 Bandwidth Managers (additional bandwidth
=====: 256kpbs link
1- What can be done to improve thruput under normal circumstances?
(that is, over fiber with 128ms round-trip delays)
2- Is 'rcp' just not very good at handling long delay paths?
(as far as I know, rcp is UDP based, so all flow control/error
checking handled in rcp...)
3- What can be done to handle the really large delay situations?
4- Can anyone point out some other WAN test results/papers?