[e2e] Question on TCP throughput and host's access speed

[Fu Cheng Peng, Franklin]

This is interested issue. Basically, the uplink speed of ADSL is quite lower than the down link speed.  Therefore, intuitively it should be quite slower than the fiber link if all other considtions are same. You may need double check where is the actual bottleneck of actual bandwidth.  Perhaps you can check by uploading a file to your client being attached to the fiber link from ADSL client, and vice versa.

Another reason may be due to the asymmetry of data path and acks path.

-Franklin




====================================
Dr. Fu Cheng Peng, Franklin
Asst Professor 
School of Computer Engineering
Nanyang Technological University, Singapore 639798
Tel: (65) 6790-4287 Fax: (65) 6792-6559 
www.ntu.edu.sg/home/ascpfu
====================================

> -----Original Message-----
> From: end2end-interest-bounces at postel.org 
> [mailto:end2end-interest-bounces at postel.org] On Behalf Of Jing Shen
> Sent: 2004Äê10ÔÂ14ÈÕ 18:59
> To: end-to-end list
> Subject: [e2e] Question on TCP throughput and host's access speed
> 
> 
> Hi,
> 
> I met a question with upload speed and network access
> speed. 
> 
> We use two leased line from ISP. One is a 2Mbps ADSL
> the other is a 100Mbps fiber link. Usually it is
> required to upload files to a server in Japan. 
> To my understanding, upload speed should be higher if
> leased line is used. On the contrary,  upload using
> ADSL is a little faster than using Fiber link, while
> packet loss and retransmission happen more frequently
> when I use Fiber link. Analizing routing path between
> our computer and server in jappan, we found there is
> no difference between ADSL access and Fiber Link
> beside the access method.
> 
> If I do not make a mistake, TCP throughtput is
> determined by bottleneck bandwidth, RTT and its
> fluctuation. So, although ADSL's  speed is much slower
> than fibre, the upload speed should be similar when
> bottleneck is the same, or ADSL should be slower. 
> 
> Why the phenomon comes up? 
> 
> 
> regards
> 
> Jing Shen 
> 
>   
> 
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