What's up with GTT's super limited bandwidth for anything originating from the GPON IPs?

General discussions and other topics.
5 posts Page 1 of 1
by bubba198 » Sun Nov 25, 2018 9:34 am
Hi guys,

What's up with GTT's super limited bandwidth for anything originating from the GPON IPs? The issue is that any traffic initiated from the GPON range 198.27.207.* to an AT&T ABN range 12.220.104.* goes via GTT and the best speed I get is 25M or so (up or down, it doesn't matter).

However any traffic initiated from the ABN side to my 198.27.207.* IP goes via Cogent and then it's a "wire speed" so to speak, very lose to the expected Gig which is exactly what I expect.

So now I have to initiate my transfer from the opposite end just so I can get the true speed. To be clear this does not relate to the direction of the transfer (both upload and download directions are affected equally), it relates to where it is initiated so that it is routed via different peering vendors and today, at least GTT sucks and Cogent is awesome? Anyone facing something like this?

by tomoc » Mon Nov 26, 2018 2:54 pm
Thank you for bringing your concerns to our attention.

Reading over your problem, you mentioned that both upload and download can achieve line rate. Because of this, we can rule out congestion between AT&T and ourselves over both Cogent and GTT. Your difference in traceroute is a symptom of asymmetric routing, which is very common over the internet. The thing to keep in mind here, is regardless of which side you source your traffic from, packets going from AT&T to Sonic will take Cogent, and packets from Sonic to AT&T will take GTT.

The most likely reason for slow throughput from connections initiated on one end but not the other, is a difference in TCP window size.

First, what is your round trip time between the two sites?

In order to verify or rule out window sizing issues, please tcpdump the traffic on one of you transfers sourced from one end, then the other.
Sonic NOC
by bubba198 » Tue Nov 27, 2018 8:39 am
Hi Tomoc,

Thank you for your reply. I forgot to add, ftp to ftp.sonic.net from AT&T gets the expected wire speed so I wonder if this has to do with the GPON side of things?

by tomoc » Tue Nov 27, 2018 11:17 am
It is more likely to be an issue with the application or OS on one side of your connection or the other. A packet capture should clear that up!
Sonic NOC
by bubba198 » Mon Dec 24, 2018 8:17 am
@tomoc Well whether you did something explicitly as a result of this post or things just "got changed magically" I do not care - I am super happy either way. The routing to AT&T ABN POP in SF is now via Telia and at near wire speed!

Thank you

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