Comcast / Level3 Peering Issues?

Hey guys,

VoIP provider here with primary connectivity through Level3 in LAX.

For the past week+ we have seen dropped RTP packets between our Level3
connection and Comcast fiber customers located in Denver and Detroit

Initially we worked under the assumption that something was occuring at the
customer locations (such as localized packet loss), however we now suspect
dropped packets between L3 and Comcast. Forcing traffic over to other
carriers through community strings resulted in no packet loss.

The issue appears to be in the evening and I was hoping either someone from
L3 network ops or a list member in the know might have some useful


I’m no expert in the way Comcast run their network, so the following advice needs to be taken with a giant grain of salt.

Historically, Comcast have a tendency to run their peering hot.

It sounds like you’re trying to reach a Comcast wholesale customer. In which case, steering your traffic around the Level3<->Comcast Interconnect by filtering Comcast’s prefixes from your Level3 connection and manipulating your community strings is the right move.

If you’re trying to reach Comcast broadband customers, steering the traffic away from their Level3 interconnect is still probably the correct thing to do but with the caveat that broadband cable access is and always has been a best-effort service.