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why upload with adsl is faster than 100M ethernet ?

  • From: Joe Shen
  • Date: Thu Oct 14 22:44:01 2004

Hi,

I met a question with upload speed and network access
speed. 

One of our customer lease two lines from us. One is 
2Mbps ADSL line the other is  100Mbps fiber ethernet
link. The customer needs to upload files to  server in
Japan usually. Now, the customer complaint that the
upload speed of ADSL is much slower than fiber link.
For a 5MB file, it takes 420 seconds with fiber link
to finish uploading while the time for ADSL is 170
seconds.  There is no difference in routing path
between ADSL far end and fiber ethernet far end other
than the access method. ( from the first acess router
). 

We measured the latency between our core router and
customer's computer, and find there is no packet loss
between with both line while latency on ADSL is 0.3ms
higher than fiber ethernet. And, no link along the
path inside our network is over burdened. That is,
bottleneck locates somewhere outside our network. And
there is asymetric route between our network and Japan
server. 

But, why TCP throughput experience so much difference
between ADSL acess and fiber link access? 

Thanks.

Joe






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