North American Network Operators Group

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Re: why upload with adsl is faster than 100M ethernet ?

  • From: Jay Hennigan
  • Date: Fri Oct 15 01:19:14 2004

On Fri, 15 Oct 2004, Joe Shen wrote:

> 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
> ).

There is something wrong with both scenarios.

A 5 Mbyte file is 40 megabits.  With overhead, it should
transfer in about one-half second over a 100 Mbps ethernet
connection and somewhat less than 30 seconds on a 2Mbps

Look for duplex mismatch or something similar.

> 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.

The ADSL should be substantially higher considering just
serialization delay.

> 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.

Oh!  There's another WAN link in the picture!  What are the MTU
settings?  Are the packets being fragmented?  Iis a firewall
blocking all ICMP somewhere including path MTU discovery?

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

We need more details as to the entire network.  Ethereal captures
at both ends would be a good start.  What is the connection in Japan?

Note that this isn't exactly within the realm of the NA(North American)
Network Operators Group, but the photons don't respect political
boundaries so you may get appropriate answers here.

Jay Hennigan - CCIE #7880 - Network Administration - [email protected]
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