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mms packet loss

Started by realdreams, January 22, 2012, 05:35:04 PM

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I just get ipv6 tunnel to work, it's fantastic :) Thanks HE

I noticed a strange problem.
I tried to play mms://bupttv.video.edu.cn/CCTV-HD  (HD streaming 45.5mbps, Payload type: DynamicRTP-Type-96 (96)). My bandwidth is around 16Mbps.
Not a surprise that I can't play it, but as soon as the streaming starts I see packet loss(both ipv4 and v6), tho the downstream bandwidth is only 10Mbps.
I have never seen this before. The only situation where packet loss occur(other than wan issues) is upstream congestion, it's certainly not the case here. DD-WRT router cpu is very low(its throughput is 100Mbps+). What can possibly cause this problem? :-\ :-\


Run MTR (or WinMTR) and see where the loss approximately is.


Quote from: broquea on January 22, 2012, 07:05:10 PM
Run MTR (or WinMTR) and see where the loss approximately is.
I think it happens on the first hop after the router.


Paste the output. "I think" doesn't help us help you.


The server appears to be down now, so I cannot test it myself.

Are you sure your downstream really support more than the 10Mbps you are receiving? Did you verify that you were able to receive 16Mbps over IPv4? Once you find a place that can successfully send you 16Mbps over IPv4, you can use that IPv4 address for your traceroute.

Another thing worth checking is if the limit of the connection is in number of bytes transferred or in number of packets. If there is a maximum number of packets per second, which can be transferred, then a difference in packet size can lead to a difference in throughput.

It is not unlikely to find situations where an IPv4 connection between a pair of hosts will use a packet size of 1500 bytes and an IPv6 connection between the same pair of hosts will use a packet size of 1280 bytes, even if the IPv6 connection was capable of packet sizes close to 1500 bytes.

But the difference between 1500 and 1280 is not enough to explain a drop from 16Mbps to 10Mbps. But maybe the mms traffic is using packet sizes even smaller than 1280 bytes. (If it is using a smaller packet size, then most likely it does so on both IPv4 and IPv6).

If you want to experiment more with the packet sizes, then try downloads from a webserver that is capable of filling your downstream over IPv4, and see what throughput you get with different MSS values. One way to change the MSS is by using iptables and --set-mss to modify the packets you send to the server.