Severe Latency and Routing Instability Across Comcast California Backbone (ccal.comcast.net / ibone.comcast.net)

Hello,

I’m observing persistent high latency and routing instability within Comcast’s California backbone when reaching external destinations such as Akamai (example.com).
This issue appears to start within your Sacramento and Sunnyvale regional routers, well before traffic leaves the Comcast network.

This has been going on for a couple days now

Summary of Findings

• Symptoms:
  High latency (500–1100 ms) and route oscillation between Northern and Southern California Comcast core routers.

• Example target:
  example.com (23.192.228.80) — hosted on Akamai.

• Test details:
  Reproduced from Elk Grove, CA on a wifi.
  Issue persists across multiple runs and different times of day and on different machines

• Traceroute output:

  3  po-104-rur101.florin.ca.ccal.comcast.net (96.110.223.233)  28.340 ms
      po-104-rur102.florin.ca.ccal.comcast.net (96.216.234.121)  64.244 ms
      po-104-rur101.florin.ca.ccal.comcast.net (96.110.223.233)  115.682 ms
   4  po-100-xar02.florin.ca.ccal.comcast.net (96.217.68.165)  49.976 ms
      po-100-xar01.florin.ca.ccal.comcast.net (96.217.68.157)  72.488 ms
      po-100-xar02.florin.ca.ccal.comcast.net (96.217.68.165)  67.752 ms
   5  be-31-arsc1.sacramento.ca.ccal.comcast.net (96.217.68.133)  607.153 ms  603.330 ms
      be-31-arsc1.fresno.ca.ccal.comcast.net (96.217.68.137)  625.112 ms
   6  be-36431-cs03.sunnyvale.ca.ibone.comcast.net (96.110.41.105)  610.012 ms
      be-36441-cs04.losangeles.ca.ibone.comcast.net (96.110.45.237)  552.097 ms
      be-36411-cs01.sunnyvale.ca.ibone.comcast.net (96.110.41.97)  775.356 ms
   7  be-3111-pe11.600wseventh.ca.ibone.comcast.net (96.110.33.50)  522.445 ms
      be-2211-pe11.9greatoaks.ca.ibone.comcast.net (96.110.32.246)  332.523 ms
      be-3112-pe12.600wseventh.ca.ibone.comcast.net (96.110.33.66)  385.501 ms

• Pattern observed:
  Traffic alternates between Sacramento, Sunnyvale, and Los Angeles backbone routers.
  Latency spikes begin at the Sacramento core (arsc1.sacramento.ca.ccal.comcast.net) and persist across subsequent ibone hops.
  This strongly suggests congestion or dynamic routing instability inside Comcast’s regional backbone.

• Local network status:
  LAN and modem levels are normal (no packet loss).
  Latency increase starts only after hop 4, inside Comcast’s internal network.