[streaming] Streaming problems through a 100M interface

[Marshall Eubanks]

I don't regard your tests as conclusive regarding switches, etc.  
(I.e., I don't think you can necessarily jump to conclusions A,B,C).

Run tcpdump or ethereal on both laptops and see what happens when the  
stream stops. Does it really stop, or just drastically slow down, are  
errors being generated, etc.

It sounds to me like you might be using tcp streaming. Verify from  
packet inspection whether or not you are streaming UDP or TCP.

If you transfer a large file (several GB) using tcp from Lenova -> HP,  
what sort of performance do you get ? (I would use tcp or ftp for  
this.) Does this stop after 1 second, or drastically slow down or ... ?

Check to make sure that you do not have Ethernet duplex mismatching  
issues (for example, that the Lenova doesn't autoconfigure the  
connection to 10 base T). That would give you about 8 Mbps throughput,  
by the way.

Regards
Marshall


On Aug 16, 2009, at 11:53 AM, Shmuel Vagner wrote:

> HI All,
> I have the following strange problem when I try to stream a video  
> file between 2 laptops:
> The Setup:
> Streaming laptop: LenovoX60 with windows XP SP3 running VLC 0.8.6c.
> Receiving laptop: HP Compaq nc6320 with windows XP SP3 running VLC  
> 0.8.6c.
> Firelwalls on both LPTs are off.
> The laptops are connected through a 10M/100M Ethernet switch.
> When I start streaming a single 15M unicast stream, it streams for  
> about 1 second and then stops.
> Now I will describe several scenarios where the streaming works fine  
> between these 2 laptos:
> 1 – When I reverse the roles of the laptops then the streaming works.
> 2 – When I connect the laptops directly using a cross cable then the  
> streaming works. (Both laptops have a 1GB Ethernet NICs).
> 3 – Using the same connection settings (Lenovo à Ethernet Switch à  
> HP) I run IPERF with 1370B packets (The same packet sizes that VLC  
> generates) and I get 95Mbps throughput without problems.
> So.. .
> A - It cannot be a problem with the switch – Ruled out by scenarios  
> 1 and 3
> B – It cannot be a problem with the NICs – Ruled out by all scenarios.
> C – It cannot be because of weak laptops – ruled out by scenario 2.
>
> Another interesting observation is that when I check the network  
> utilization on the transmitter LPT (Lenovo), it never goes above 8%  
> (which is 8Mbps in a fast Ethernet network) when streaming through  
> the VLC, while it gets up to 95% when stream using IPERF.
>
> I am out of ideas!!!
> If anybody has a clue about what is happening, please let me know.
> Thanks,
> Shmuel
>
>
>
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