Xfinity Throttling or Peering Issue Upstream - Slow Speeds

Editing my original post to insert this visual diagram of my issue. 

RESOLVED

• 2 months and 5 tech visits later, the issue is resolved. 
• Confirmed this was an issue upstream, not anything in my home or neighborhood, it was a bad device upstream or software controlling the upstream device causing the slow speeds. 
• A week after my information was finally escalated to the network engineers it was fixed.
• Confirmed my speeds are back to normal - I returned the xfinity xb8 gateway and am using my old equipment again with no issues. 
• Traffic that was hopping through the slow device upstream now hops differently, I can only assume the engineers replaced that bad equipment or re-routed traffic because that IP no longer shows on my traceroute app. 
• I learned that Xfinity will blame equipment and wiring in almost every situation, even if you can prove that’s not the issue (I purchased 3 new modems and 2 wifi routers and they blamed my equipment every time even though the issue was consistently the same).  
• Keep calling them, keep escalating the issue.  
• I learned that if you have your own equipment and can’t get your issue resolved, just rent the xfinity equipment because then they’re on the hook for support and will stop blaming your equipment. 
• I learned that there could be many people in the area experiencing the same issue and customer service will not be aware of it or will not tell you it’s a known issue. 
• I learned that Xfinity support cannot escalate an issue upstream to network engineering, it has to be a tech that does it.  
• It took 5 tech visits before a local tech that lived in the area showed up and knew about the issue, he said they didn’t know what was causing it yet but it was a known issue causing problems for many people in the area.  Nobody on the phone and no other techs or contractors told me this was a known issue, they all just wanted to keep replacing equipment.   
• Once that local tech received my information and saw what I was experiencing, he emailed it up the chain to the network engineers, who promptly fixed the issue within a week. 
• I learned to get a local tech, that person seemed knowledgeable about the issue and things going on in the local area, and genuinely wanted to help - great guy.  

TLDR Summary

• Posting here in hopes someone can help me escalate this into some sort of network engineering or higher level trouble ticket. 
• I am on the gigabit internet plan in the Tucson Arizona area. 
• For the past four years my service and speeds have been fast, no issues.  
• My current speeds for the last two months are 5-25Mbps DL max, UL speeds always full. 
• I’ve done a number of steps to test and identify what’s going on. 
• Xfinity is throttling or slowing some of my traffic depending on geographic location of the endpoint destination.  
• This could be called a peering or interconnection issue upstream and not technically “throttling” because it only applies to certain traffic based on the geography of its destination. 
• All of my traffic routing through local (Pima) and west coast (PHX VEGAS LA SD SF) destinations is getting slowed to 5-25Mbps DL.  Confirmed on multiple speed test sites and servers as well as real world tests downloading data from various servers around the United States.
• Traffic going to central USA or midwest or east coast is full speed 600-900Mbps+ depending on the endpoint.
• Traceroute confirms the local slow traffic takes a different first hop past the Xfinity node than the out of area fast traffic.  
• To figure this out I’ve purchased and activated 4 different modems of different manufactures, 2 wifi routers, and now using Xfinity’s gateway and the issue is 100% consistent and reproducible and repeatable on all equipment, whether on wifi or wired directly to the cable modem via ethernet cable.
  • tested on multiple computers and devices - all generally consistent and repeatable results. 
  • multiple techs have been out and confirmed lines and connection are good
  • techs have confirmed “raw speeds” at coax are 1300Mbps and coming out of the modem’s ethernet cable are 980Mbps+ (I pay for Gig plan) and very clean power levels and SNR levels on the 4 modems I have as well as the Xfinity rental gateway. 
  • techs have said my modems are good, they are receiving and delivering full speeds at coax and at the ethernet cable to their testing device. 
  • Techs could not explain (didn’t understand) how some traffic is full speed and other traffic is slow based on its geographic destination.  One tech recommended I get geek squad out here.  Another tech could not explain it, said he’s never seen anything like it before, and left saying he’s not able to escalate it because all signal and equipment here is good. 
• Current theory, supported by everything below, is that my Xfinity traffic hits a local node/server and takes a different hop based on the destination of that traffic.  
  • if the destination is something close (local edge node in AZ or west coast USA like LA, SD, SF etc (majority of my internet traffic) my traffic takes a different first hop past the node and speeds are throttled to 5-25Mbps DL max by whatever server or device that traffic is going through.  UL speeds always full. 
  • if the destination is central USA or midwest or east coast, or even canada mexico or europe, my traffic gets routed through different first hop past the node which provide full or nearly full speeds.  
• To “solve” this problem I’ve set up my router to use a vpn that routes all traffic through Denver.  Doing this I get full speeds network wide.  If I turn off the vpn, nearly everything slows to a crawl.  Turn vpn back on, blazing fast. 
• 2/3/23 - latest tech visit confirmed this is a known issue, impacting many customers in my area.  Issue still unresolved but the last tech took all of my findings and escalated the issue to the local engineering team. 

Detailed Description of Issues - WARNING - VERY LONG DETAILED POST

12/5/22 - Approximate Date

One day in early December 2022 my internet speeds suddenly dropped drastically.  There were no equipment or other changes here on my end, I just noticed the huge drop in speeds one day.  I’m now getting max 30mbps - usually between 5-25mbps.  My upload speed is typically the full 19-20mpbs that I pay for - no issues with upload speeds. 

Prior to this, for the last 4 years, I’ve never had a speed or connection issue, they’ve always been as advertised and this past year i’ve been getting 400-600mbps all the time.  I’m a software developer and I routinely test my internet speeds for app testing and web testing for my work, so I’m keenly aware of my connection speed most of the time as I regularly document it for work. 

Troubleshooting steps I’ve taken:

The usual restart all equipment, try new cable/ethernet cord. Did not resolve. 

I connected my computer directly to the modem via ethernet cable to see if it was the modem or something in my wireless network causing the issue, and the speeds and behavior was the same when directly wired into the modem.  I tried multiple laptops directly wired to the modem and all results stayed the same.  This indicated that the issue was not with my network or wifi but was with the modem or xfinity connection. 

I checked my modem signal strength and power levels and all were well within spec and showing very ideal levels. Indicating no problem on my line or with my equipment. 

After a week or so I switched out my cable modem to a spare one that I had to see if the issue was a problem with my modem.  The problem persisted with the new modem, the same behavior, same slow speeds remained.  I checked my modem signal strength and power levels and all were well within spec and showing very ideal levels. 

Cable modem I’ve had no issues for years - Arris Surfboard SB6183 - it’s older and only Docsis 3.0. 

After a few weeks of this issue, I decided to upgrade my modem again.  I had been using older Docsis 3.0 modems and knew I should probably upgrade to a new Docsis 3.1 modem because I have been wanting gigabit speeds and I knew the DOCSIS 3.0 was holding me back at the 400-600mbps range, so on 1/5/23 I purchased and activated a new Motorola Docsis 3.1 modem.  The problem still persists, the same slow speeds and same behavior as before.  I checked my modem signal strength and power levels and all were well within spec and showing very ideal levels.  

New Docsis 3.1 modem - Motorola MB8611

After all of my testing and my equipment changes I am very certain this problem is not a problem on my end or with my equipment or my line or signal.  I believe this is some kind of peering or interconnection problem further upstream at xfinity.  Or somewhere at the local node or something has my service set to the base level or about the same speed that xfinitywifi hotspots get 25Mbps.  I am not knowledgeable as to why I can get full speeds directly connecting to some servers vs others, but it seems like whatever device upstream that negotiates my traffic to/from certain sources is stuck at this low speed, while whatever device that negotiates traffic to/from other sources gives me full speeds. Is this possibly a net neutrality issue? 

My real world speeds are very slow 5-30mpbs max, but on some speed tests and services I’m getting full 400-800Mbps speeds, while on most local and west coast speed tests I’m getting the 5-30mbps.  The xfinity speed test site routinely shows I’m getting the full bandwidth connection to xfinity, but nearly all other speed tests outside of the direct connection to xfinity are getting these slow speeds. This behavior indicates the issue is not with my line getting to xfinity, but further up the chain where xfinity interconnects to other networks.  The fact that this issue persisted with 3 modem changes and with multiple computers directly wired to the modems tells me it’s not an issue with my wifi or networking at home. 

• xfinity speed test website - usually get fast full speeds, indicating my connection directly to xfinity is great. 
• google speed test (M—Lab) usually always getting 200Mbps DOWN and 20Mbps UP. 
• Cloudflare speed test - typically 50-75Mbps DOWN and 23Mbps UP. 
• speedtest.net - I’ve tested on dozens of servers here, using the website and their app on multiple devices, and most show the 5-30mbps speeds, usually hovering around the 25Mbps.  
  • • My real world speeds, tested and reconfirmed many times, using a 2021 MacBook Pro laptop on wifi and then tested directly wired to the modem through a usb gigabit ethernet adapter (I have two adapters and confirmed speeds with both as well as swapping ethernet cables to check for inconsistencies), also checked and confirmed these at the same time on an iPhone 14 pro via wifi, all speeds over wifi or directly wired to the modem were the same or very similar, any inconsistencies noted. 
    • comcast Pima - 25Mbps DOWN max - 23Mbps UP
      • this is my closest speed test site that speedtest.net  defaults to.  
      • varies between 5-25Mbps DOWN, UP is always good. Speeds during the workday are typically slower in the 5-12Mbps range, sometimes as low as 1.5-2Mbps, evenings and weekends 25-30Mbps range. 
      • I notice the speed test usually starts out fast over 100, but then throttles down quickly to the 25Mbps. 
    • comcast San Francisco - 6.87Mpbs DOWN - 23Mbps UP
    • comcast Sacramento - 3.47Mbps DOWN - 23Mpbs UP
    • most other servers or speed test sites that I test show similar 25Mbps max speeds. 
  • some other speed test servers get me full speeds, but I don’t think most of my internet traffic goes through these by default:
    • comcast Salt Lake City - 634Mpbs DOWN - 23Mbps UP
    • comcast Denver - 679Mbps DOWN - 23Mbps UP
    • comcast Albuquerque - 692Mbps DOWN - 23Mbps UP
    • Comcast Houston - 719Mpbs DOWN - 23Mbps UP
    • some others that I’ve tested also get me full speeds
    • testmy.net usually gives full speeds. - Texas endpoint I believe
• apple tv service streaming - seems fast and full speed HD quality no buffering
• Netflix steaming - seems fast and full speed HD quality no buffering
• Disney plus streaming - slow pixelated and buffering SD or worse quality - unwatchable
• amazon prime video streaming - slow pixelated and buffering SD or worse quality - unwatchable

1/8/23 - Tech visit - contractor from out of state not employee

• confirmed signal and power levels good at the coax connection
• confirmed speeds to modem 1300
• confirmed on his device ethernet cable delivering 1 gig
• no issues at my line or with equipment
• testing directly at the modem confirmed the speeds are not an issue with my router or network because the same behavior occurs when directly wired to the modem. 
• tech agreed very strange that real world speeds are 6-30Mbps, most speed tests are showing 25Mbps DOWN, but I can connect to other speed test servers at full 600+speeds.  Said he has never seen anything like it.  
• Said if it was an issue with my modem or router, I wouldn’t be able to get these full speeds at all, so the fact that I get them at some speed tests or on some services, but very slow on most others is something he’s never seen and has no idea how to fix or even to put in a ticket about it. 
• Tech reactivated my modem, checked boot file and said that was correct. Everything on the account side looked good. 
• Tech activated my old modem to compare, same issues no changes. 
• Suggested I could try an xfinity owned modem but thought that would have the same result and having their modem doesn’t guarantee any faster speeds or better service, said my equipment should be fully capable of these speeds. 
• Tech said the fact that I swapped three modems indicates it’s not an equipment problem but something upstream.  Also because I can get full speeds to xfinity speed test and others doesn’t indicate it’s a speed issue here with my equipment. 
• Said he could not put in a service ticket because everything is passing here at my house, all the signal and levels and speeds are perfect here, it’s not an issue with anything here as far as he can tell, he was at a loss unable to further do anything. 
• Apologized profusely, left without any other resolution, I’m basically stuck with this. 

1/9/23 - Thoughts and moving forward

• tested and reconfirmed all of my speed test stuff above, no change in behavior. 
• I have a hunch that something upstream in the local area that handles traffic to/from some sources does not have my correct speed set, and defaults me to the speed of their basic plan, which I think is xfinity base speed by default, 25Mbps. 
• I am going to switch my internet speed tier to the lowest speed, 75Mbps DOWN, and see if that change in the system propagates through to whatever upstream device has my speeds throttled to the base speeds. 

1/9/23 - Changed Plan

• went to website and downgraded plan to the lowest, 75Mbps DOWN 10Mbps UP. 
• Figured this might trigger some kind of change through Xfinity’s system and possibly reset whatever is limiting my speed. 
• Will test and report back 
• Tested all the speed test sites above -
  • all of the slow speed tests listed above, including my local traffic, are unaffected and are behaving just as they were before the plan change, still getting the 5-30Mbps DOWN, now getting 10Mbps UP due to the plan change. 
  • all of the fast/normal speed tests listed above I’m getting the full 75+ (many 80-88Mpbs) DOWN and 11Mpbs UP consistently whether on wifi or wired directly to modem.  
• My hypothesis that changing my plan speed would propagate through to whatever upstream device is limiting my bandwidth was incorrect.  
• Revising my hypothesis now I think whatever device is limiting bandwidth is broken or defective, needs to be fixed or swapped out, seems to be totally ignoring my subscription plan speeds. 
• Going to leave this for a day and then upgrade back to a higher speed. 
• During work today I noticed my DL speeds have been between 1-3Mbps most of the day, UL 12Mbps. 
• At end of work day around 5pm speeds jumped back up to 25-30Mbps. 

1/9/23 - Upgrading Plan to gigabit

• changing plan on website to see if I get higher speeds after making a change, don’t think it’s likely but going to try. 
• Tested all sites as listed above, no change in behavior.  5-30Mbps DL 23Mbps UL. 

1/10/23 - Purchased Netgear Docsis 3.1 modem

• Figured it’s possible some error is in common with the old arris modems and the new Motorola modems and the new Motorola modems firmware has reported issues on xfinity forum, or something in Xfinity service that might not be happening to a Netgear.  Will trying a completely different modem manufacturer fix the problem? 
• Bought a netgear cm1100 to see if the issue still happens on other hardware - this will be my 4th modem in a month. 
• If this doesn’t work, I plan to capitulate and rent the xfinity Xfi equipment and see if that resolves it. 
• Activated Netgear modem, however behavior is unchanged. speed tests confirm the same as above with little difference. 
• Deactivated netgear and reactivated the Motorola mb8611. Ran speed tests again as above and confirmed very similar results again. 

1/11/23 - 

• at this point I’m not sure how to move forward. 
• I firmly believe this is an upstream issue, but I can’t get Xfinity to put in a ticket or do anything since the signal passes at my house, even though speed tests are as above typically 6-25Mbps DL 20Mbps UL. 

1/11/23 - Called and asked for Tech to bring Xfinity gateway and wifi 

• Tech confirmed my speeds are perfect at the coax 1300Mbps DL. 
• Tech said my modem is good, speeds coming out of modem are 980Mbps at the ethernet cable. - according to his device which measures raw data - not actual real world traffic. 
• Tech observed the multiple slow speed tests, but insisted my wifi router was bad.   Even though I showed him over wifi I can get 800Mbps+ on certain servers speed tests but not the local or west coast ones. 
• To placate the tech, we plugged directly into the modem via ethernet cable, same slow speeds of 12Mbps DL and 19Mbps UL were observed by the tech. 
• Tech’s explanation was that this speed test site must be bad.  even though we connected to 10+ servers on the speed test that all showed the same results, tech insisted it was just the speed test website causing problems because “those websites don’t make a lot of money”.  Speed test.net was the site and app, tried with numerous servers and I could show the tech how most local and west coast ones were very slow but the servers outside of these areas were running quite fast 300-800+Mbps range. 
• Tech said my hypothesis that a local hub or node has an error or bad cable or wrong setting was not possible - said their signal is like a faucet and it’s turned on, nothing gets blocked.
• Tech could not explain my theory or the results when we performed speed tests through google, many other speed test sites that the tech suggested, all of my speed test behavior was shown to the tech and was consistent where local and western usa traffic was 5-25Mbps DL but connecting to Salt Lake City, Denver, Albuquerque, etc were all super fast. 
• I showed the tech how my neighbor has Xfinity and uses their Xfinity gateway and wifi hardware, and when I hop on my neighbor’s connection I am able to get full speeds to that local pima server and all others.  But when we hop back on my wifi or hard wire to my newly rented xfinity xb7, my speeds show 12Mbps DL.  Hop back on my neighbor’s xfinity equipment wifi and we get full speeds.  This still did not seem to alert the tech that the issue is upstream and not here with my equipment. 
• Very clear that my neighbors Wi-Fi and devices can ping and speed test these local and west coast servers at full speed, but at my house with the same Xfinity equipment I get 6-25mbps max. 
• Tech left saying he would look into it and noted my account but to give the new Xfinity equipment an hour to download the latest updates which would make it much faster he said

1/13/23 - Two days using the xfinity gateway and wifi.  

• speeds are exactly the same as with any of my previous equipment. 
• Max speeds I get are 30Mbps DL and 23Mbps UL whether hardwired ethernet or on wifi.  I can still hit servers outside of AZ and west coast and get full speeds but most of my internet traffic is super slow - currently getting 2Mbps DL I can barely browse websites let alone work.  
• I have had to hop over onto my neighbor’s xfinity wifi (she uses the same exact xfinity owned equipment) and I get full speeds on her wifi.  
• Nobody can explain to me how it’s possible that on my connection, whether hardwired to the xfinity (or any of my own 4 modems) I can only get 5-25Mbps DL, but when I connect to my next door neighbor’s xfinity equipment I can get full speeds.  I’m not sure why this doesn’t alert any of the workers or techs there that this seems to be an upstream issue, whether it’s routing or peering or interconnection or maybe a wrong setting or bad cable or something.  
• The neighbor on the other side of my house also has xfinity and uses their equipment.  I knocked on their door and told them I was having issues with xfinity and asked if I could hop on their wifi to run some speed tests.  I hopped on their xfinity equipment xb7 same as mine, ran speed tests on their wifi to the same Pima server (and 8 other of the closest local servers), and got full speeds UL and DL.  I hopped back on my wifi, tested the same server, and getting 12Mbps DL.  
• So both of my neighbors, using the same xfinity equipment, can hit those local speed test servers and get full speeds.  But when I hop back onto my connection, whether hard wired or wifi, I get a max of 5-30Mbps DL.  I tested this multiple times, using multiple laptops, phones, iPads, at the same time some devices connected to neighbors wifi some connected to my wifi and the neighbors are able to get full speeds and mine never go above 30Mbps DL. 
• Turned on xfinitywifi hotspot setting on the gateway to “be part of xfinity hotspot network”.  When I connect to this public wifi on the router (not my actual home wifi) I get much faster speeds, full hotspot speeds sometimes hitting 50+Mbps.  So one solution is to use the xfinity equipment but hop on the xfinitywifi public hotspot it puts out because that connection is much faster than my actual home connection.  Tried this wired to ethernet on multiple laptops and swapped cables, same result, the xfinity gateway wired connection is a slow crawl compared to the same device’s public wifi hotspot.  

1/14/23

• VPN Testing 
• When I connect through my VPN service to certain locations, I am able to get full or nearly full internet speeds 
• Connecting to VPN locations in AZ, Vegas and Southern California I get the same slow DL speeds. 
• Connecting to Denver or many other VPN locations further away geographically seems to bypass whatever local traffic server and routes through a different connection giving me full internet speeds 
• My latest hypothesis is that Xfinity routes my traffic through one server if it’s local or western USA, and traffic goes through another server or device if the destination is central or eastern USA or foreign country. 
• Routing all of my traffic through Denver or Kansas City or Texas I can get nearly full speeds on all speed tests, and when I ping the local pima or AZ servers from Denver etc I get very fast 300+ speeds. As soon as I turn off the vpn and connect to pima or AZ servers directly I am back to 5-25Mbps. 
• Press button for vpn, super fast, turn off vpn and back to super slow. 100% reproducible and repeatable on any device in my home whether hard wired or Wi-Fi and using Xfinity equipment or the 3 of my own routers. 

Saw another post online about a Spectrum customer and Steam gaming that sort of explained the issue I think I’m having is similar: 

The VPN is causing your connection to route differently. The shortest point from you to the steam server most likely hops through a network that is throttling data. The hops from your VPN are not hitting the same throttled network. Spectrum isn't throttling you. If they were it wouldn't matter whether you were on a VPN or not.

Because they don't. A VPN's purpose is to encrypt, and route your traffic. What you're experiencing is peering congestion, which means the default route your traffic is going is hitting a server that is overloaded; the VPN is re-routing your connection to a different server which is resulting in the speed "increase". Instead of taking your car up the main interstate, you're now driving on a back road to by-pass it thanks to your GPS.

A throttle would result in ALL websites seeing reduced performance - and since Spectrum doesn't participate in throttling, that's not the case here.

1/16/23 - updates

• figuring out a way to summarize all this for the Xfinity support web forum. The only hope I have someone might push this issue up the chain past a cs agent or tech to someone in network engineering. 
• Had a speed test 6am of 60Mvps DL fastest I’ve had in two months. Something might be changing or it’s just this peering or interconnection issue isn’t as bad at 6am on a holiday. 
• Turn on vpn to Denver, Salt Lake, or anywhere in Midwest and east coast and get nearly full speeds  turn vpn off and check same servers (including local Pima) and back to the slow crawl. 
• 8:30am - back to the 25Mbps DL speeds. As reported above, using my VPN to other areas resolves issue and gives me full speeds. 

1/19/23 - Updates

• Same behavior persists, no changes.  
• No matter if using xfinity equipment or my own, the behavior is the same. 
• Went back to my own wifi router and had to configure it to use my vpn service to route all my traffic through Denver or a Midwest endpoint to keep my traffic fast.  
• When/if I disable the router-wide vpn (same behavior with my individual devices) the speeds all go back down to the slow crawl of 5-25Mbps DL.  

1/27/23 - Third tech visit

• Xfinity customer service said three tech visits are required before any issues can be escalated further to any type of engineering trouble ticket. 
• Tech is from Denver - says working down here in AZ due to outages and issues 
• Tech wanted to install new modem right away before seeing any of my speed test results or anything else.
• Tech installed new modem xb8. - this is the 5th modem I’ve had since December, all give the same results. 
• Same results as described above.  I showed tech everything I’ve described above and he observed the speed issues. 
• Tech took photos of my speed tests and traceroute results showing only local traffic getting throttled and full 980Mbps DL speeds when connecting to servers in Albuquerque Salt Lake Denver Boston NYC or when on vpn to anywhere else outside of AZ/ Western USA as described above.
• Tech said he can put in an escalated ticket with engineering but didn't specify further. 
• Scheduled to come back next week. 
• Tech said will likely have to replace cabling outside the home out to the neighborhood but doesn’t think that’s the issue because he saw my speed test results. It appears that Xfinity requires jumping through many hoops before they will escalate an issue up further.  
• I will report back with any updates. 
   

2/2/23 - Fourth tech visit

• Tech was supposed to have put in a ticket to network engineering but I'm not sure that has happened yet.
• Tech did not show up for the appointment, no text no call.  
• I messaged Xfinity support again asking how to move forward.  
• There is no change in my internet connection as reported above. 

2/3/23 - Fifth tech visit

• Tech was a employee from the local area and immediately said this is a known issue, many people in the area are having it, not sure why customer service makes it seem like I’m the only one having an issue or why they assume this is equipment related, it’s not. 
• Tech said they do not know the cause yet, they are trying to figure it out
• Demonstrated my findings for the tech, showed him trace route and how local slow traffic takes different first hop than other traffic, how I can bypass this slowdown with my VPN, etc. 
• Tech said he’s sending this up to their engineering team in the area so they can diagnose this, their techs and networking people have been trying to figure this out for a long time now.  All of their techs see fast speeds at customers addresses, but customers are still getting very slow speeds. 
• Still unresolved at this point.