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Speed weirdness.


fizzyade

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fizzyade

This is related to Emby, but it’s not a problem in Emby, I’m just posting to see if anybody can explain the behaviour I’m seeing!

 

I recently switched from dynamic ip on my connection to a 13 static ip configuration. My ISP (UK Virginmedia Business) is a cable provider, the way they implement static IP’s is that the modem connects normally and then creates a GRE tunnel to virgin media’s business data Center where the static IP’s route to my modem, in this special mode I don’t have access to the dynamic IP as the modem blocks it and only allows the GRE based connections through, I then have untangle running as my gateway with the WAN interfaces configured for one of my static IP’s, all good.

 

however since switching to the GRE assigned IP’s single connections have plummeted in download and upload speed, apparently this used to be a problem but VM fixed it this year.

 

the upside is that I have to set the remote quality on my phone to 1Mbps otherwise Emby stutters every couple of seconds while it buffers (well; I’m assuming it’s buffering, some sort of diagnostic build into the server and clients would be very helpful in diagnosing what is going on).

 

What’s odd is that in the early hours of the morning I enabled the Cloudflare proxy as a test, and bang straight away I was able to direct stream 14Mbps files no problem, they started quickly and there was no buffering.

 

Disable the Cloudflare proxy and it goes back to buffering on low bitrates. (I have an nvidia card transcoding and it doesn’t flinch transcoding loads of streams).

 

Can anybody explain this behaviour, because I’m absolutely baffled by it, seriously don’t understand how enabling the Cloudflare proxy suddenly makes Emby not buffer.

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fizzyade

Have you tried running a traceroute? Maybe there is a peering issue that Cloudflare is solving.

 

 

Yeah, I did that after and spotted why.

 

the gre endpoint is supposed to be in manchester, if you do a traceroute to pretty much anywhere it goes via Manchester.

 

what's weird is that I did a traceroute externally to the cloudflare proxy and then did a traceroute from my network to the cloudflare proxy ip and it didn't go via manchester, very odd, all traffic is supposed to go via there,

 

It does explain why it's working perfectly, but I don't know why it isnt hitting Manchester.

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fizzyade

i got to the bottom of this, it was an MTU issue, the MTU on my gateway was set to 1500, however, my static IP service is delivered over a GRE tunnel, so a packet of 1500 was being fragmented, well, pretty much every packet going out from emby was being fragmented.

 

Once i realised this earlier today i reduced my MTU to allow for the overhead and instantly the speed returned!

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