Visitor

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3 Messages

Saturday, August 29th, 2026 8:31 AM

Intermittent multi-second latency spikes

I'm seeing intermittent multi-second latency spikes and failed connection attempts to external services, specifically on a hop inside Comcast's own
network — not at my modem/router, and not at the destination server. This is NOT a general "my internet feels slow" complaint: I have traceroute/mtr data
pinpointing the exact hop, and it happens while every other hop (including the destination) stays under 15ms.


The spikes are large enough (2-3 seconds of added latency) to break new outbound HTTPS connections from a service I run at home, even though basic
ping tests to the same destination often look completely clean — the problem is specific to new TCP connection setup, not general reachability,
so it's easy to miss with a quick ping check. Could you check for node congestion or a problem on the segment my account's node connects through?
The hop in question is a few hops past my gateway, still within Comcast's network, around the Seattle area (IPs 24.124.128.249, 96.110.44.86, 96.110.34.x below).

EVIDENCE: TCP (port 443) traceroute to a Cloudflare-hosted destination
--------------------------------
Captured 2026-08-29T08:23:14Z, 20 probes per hop, TCP SYN to port 443
(more representative of real application traffic than plain ICMP ping).

Hop  1  192.168.0.1 (my own gateway)
        loss 0%, avg 1.1ms, worst 1.3ms

Hop  2  10.27.176.114
        loss 0%, avg 11.8ms, worst 15.3ms

Hop  3  68.86.98.253
        loss 0%, avg 11.0ms, worst 15.2ms

Hop  4  96.216.61.81
        loss 0%, avg 12.5ms, worst 25.9ms

Hop  5  24.124.128.249
        loss 0%, avg 11.8ms, worst 20.1ms

Hop  6  24.124.128.249
        loss 0%, avg 11.7ms, worst 15.4ms

Hop  7  96.110.44.86 (and several sibling IPs on the same hop: 96.110.34.134,
        68.86.93.x, 96.110.44.90/82, 96.110.34.142/130 — normal load-balancing
        across parallel links, not a separate problem)
        loss 0%, avg 166.8ms, WORST 2089ms, stddev 506ms
        >>> THIS IS THE PROBLEM HOP — over 2 full seconds of latency on some
            probes, while hops 6 and 8 on either side of it stay under 15ms.

Hop  8  96.110.34.138 (+ sibling IPs, same load-balancing as hop 7)
        loss 50%, avg 12.2ms, worst 15.2ms

Hop  9  108.162.243.61 (+ sibling IPs — Comcast/Cloudflare peering boundary)
        loss 50%, avg 15.6ms, worst 23.6ms

Hop 10  108.162.243.45 (+ sibling IPs)
        loss 0%, avg 12.5ms, worst 21.6ms

Hop 11  162.159.137.232 (Cloudflare/Discord's edge — the destination)
        loss 20%, avg 11.5ms, worst 14.3ms


Notes on hops 8-10: these show partial "loss," but each probe returned a different IP (visible as multiple addresses per hop) — that's normal
load-balancing (ECMP) across parallel links at the Comcast/Cloudflare peering boundary, and routers there commonly deprioritize generating the
ICMP replies traceroute relies on without actually dropping real traffic. The meaningful finding is hop 7: a single, consistent latency spike deep
inside Comcast's own network, well before reaching Cloudflare.


ADDITIONAL EVIDENCE: repeated short bursts on a separate occasion
--------------------------------
Earlier capture (same hop, different time window) showed the same pattern:

Hop 6  24.124.128.249
       Run 1: avg 269ms, worst 3083ms
       Run 2 (minutes later): avg 123ms, worst 2064ms

Every other hop in both runs stayed under 25ms. This is not a one-off blip;
it recurs at this same point in the path across multiple independent
captures, at different times.

--------------------------------
A service I self-host at this address (discord bot) makes routine outbound HTTPS connections to Cloudflare-hosted infrastructure (discord.com). Around the
timestamps of these spikes, new outbound connections fail outright with a connect timeout, while already-established connections and basic ping
checks remain unaffected. This has been observed recurring at various points across multiple days (not a single isolated incident), including one
episode where the affected service was unable to establish an outbound connection at all for roughly 75 seconds straight.


--------------------------------
Please check for congestion, oversubscription, or a hardware issue on the node/segment serving my account (24.19.49.68), particularly around the
segment reached via 24.124.128.249 / 96.110.44.86 / 96.110.34.x. Happy to provide additional traceroute captures, modem signal-level stats, or run
tests at a specific time if that helps your team investigate.

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Official Employee

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3.1K Messages

2 days ago

Greetings, @user_a1999e! I hope your week has been treating you well. Thanks so much for taking a moment out of your busy day to leave a post on our community forum about these latency spikes. You have definitely come to the right place for assistance.

 

Can you tell me a little more about what's been happening? Is this an ongoing issue with hop 7, or did it just develop recently? Have you noticed the congestion occurring consistently throughout the day, or does it increase/decrease, depending on when the traceroute is run? Have you noticed any changes since this was originally discovered?

Visitor

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3 Messages

1. Ongoing, not new — same two routers (hop 6/7, Comcast's Seattle backbone) showed the issue on all 22 checks today, matching what was first seen on 2026-08-29.

2. Varies in magnitude, never resolves — severity swung from near-clean (avg ~12ms, twice) to avg 627ms/worst 7.18s, but some degree of spiking showed up at nearly every check across 11 hours. Worst spikes were actually in the afternoon, not the typical evening peak, so it doesn't track a simple demand/congestion pattern.

3. No change since discovery — same routers, same magnitude range, same 0% packet loss two days later.

I have some full logs that I took after doing the 22 checks over the course of 12 hours, but here is the synopsis:

DATA - HOP 6/7, PACIFIC TIME, 0% LOSS THROUGHOUT

  Time        Hop 6 avg/worst (ms)   Hop 7 avg/worst (ms)
  ----------  ---------------------  ---------------------
  12:54 PM    251 / 2078             628 / 3103
  1:10 PM     458 / 3068             391 / 5150
  1:41 PM     457 / 5158             390 / 3123
  2:12 PM     218 / 3062             595 / 7179
  2:43 PM     357 / 4112             288 / 2092
  3:14 PM     256 / 3075             287 / 5176
  3:45 PM     356 / 2094             456 / 5125
  4:16 PM     287 / 4138             218 / 2086
  4:47 PM     531 / 4122             526 / 5109
  5:18 PM     288 / 3116             82 / 2084
  5:49 PM     219 / 3118             219 / 3094
  6:20 PM     93 / 1063              12 / 15
  6:51 PM     153 / 1059             117 / 3118
  7:22 PM     220 / 2062             13 / 16
  7:53 PM     85 / 1022              46 / 1029
  8:24 PM     186 / 2101             114 / 1057
  8:55 PM     151 / 2067             216 / 2060
  9:26 PM     80 / 1029              47 / 1058
  9:58 PM     288 / 2075             48 / 1072
  10:29 PM    183 / 2061             83 / 1057
  11:00 PM    113 / 1034             48 / 1049
  11:31 PM    149 / 2070             185 / 3103

Edit: For what it's worth it seems like this is a queuing/congestion delay, not a drop, consistent with an oversubscribed or faulty link/interface on that segment.

(edited)

Official Employee

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3K Messages

 

user_a1999e Thanks again for reaching out via our Xfinity Community Forums. Based on the information you've provided, the consistent pattern across multiple days and the fact that packet loss remains at 0% makes this worth a closer look. I'd like to review the account and gather a few more details to determine whether there's an issue affecting that network segment or if the behavior is related to how those intermediate routers are responding to traceroute requests. I appreciate your patience and the thorough documentation you've shared. The data you've collected is very helpful. When you have a moment, please send me a direct message with your full name and service address, so I can take a deeper look and see what additional troubleshooting or escalation options may be available.
 

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Expert

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120.4K Messages

6 hours ago

@user_a1999e @XfinityChristy 

Please circle back here and post any possible solutions for the issue here in these open public forums so that all readers here may benefit from the exchange / info. This is in keeping with the spirit for which these public help forums were originally intended. Thank you.

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