Problem with high latency/ping

@dreaminggates  I don’t have an answer for you but this has been my internet experience:

I have been with T-Mobile since last October, about 3-½ months. 5G isn't available in my area to everyone so they gave me a 4G gateway. My ping was in the 30's and 40's ms. I had the gateway in the upstairs window facing the tower it's connected to less than a mile away. I only had 3 bars at best. My speed was between .25mbps and 10mbs. Averaged about 7mbs. These are not the advertised speeds and there was nothing customer service could do to get me better speeds. 

Last week T-Mobile sent me a 5G gateway that allows me to get better speeds. My average speed is around 15-20 mbs. Still not the advertised speed of 5G. Customer service says that I won't always get 5G speeds and that I would mostly be on the 4G speeds until the 5G network expands. With the new 5G gateway my ping is worse. It's around 50-60 ms ping at times. Certain online games are unplayable because the in-game ping is well over 100 ms bouncing to 400-600 ms at times. I also used TCPOptimizer, to no avail.

Even though it's sub-par service I'm thankful that I have SOME internet as it's my only choice besides satellite where I live. I think the nature of sending data over the airways lends itself to high ping. I don't have any proof but just seems to be the common complaint of T-Mobile home internet users.

Multiple things in play that contribute... the upper layers are a mess because of their XLAT464/CGNAT crud.  Can't really do anything about that.

Their peering is pretty bad sometimes as well... can break 100mbps with decent ping to something like cloudflare, then turn around and hit others in the same city and it struggles to hit 60 with jitter all over the map.

One thing you could try is manually setting the MTU.  May eliminate at least one  potential hiccup if you are throwing 1500 bytes out and it is having to break them down into two packets. May want to test it to confirm what yours is actually running with.  1420 should be safe, but you MIGHT be able to pass 1440... so may want to check it with no defrag bit set on some pings to be sure.

@djb14336 Thank you for your ideas! Is there any place you can link me to, that would detail how to test and limit the MTU?

Finding the max value is pretty straightforward.  Here is a link to a netgear article about using the ping command from a Windoze DOS prompt:

https://kb.netgear.com/19863/Ping-Test-to-determine-Optimal-MTU-Size-on-Router

How you would put that in effect can vary though.  Some routers have a way to set it on the router itself so your auto config clients pick it up right away.  Otherwise you can manually set it per machine from an Administrative cmd prompt (search for cmd and right click to launch as Administrator):

http://networking.nitecruzr.net/2007/11/setting-mtu-in-windows-vista.html?m=1

Would note this is somethimg that can trip up some VPN's.  Some may default to assuming they have the headroom typically available to insert their headers (somewhere around 1450-1460), but TMO is eating up additional space with their header information.  If that VPN cannot have it's MSS or MTU adjusted to something below 1400 (like 1380... 1420 MTU - 40 for the VPN), it can cause a lot of problems.

@djb14336 Thanks! I’ll check it out.

We  had a severe problem with most pings being lost, even though we had 100+Mbps download speed. The problem was the T-Mobile gateway. Some of their gateways  have problems with some of their towers. They replaced the round silver one with a square black one and the problem went away. No lost ping packets now and 400+ Mbps download speeds. (We are only a block away from the tower. :) )