Comcast problems?

[Steven M. Bellovin]

Anyone know what's going on with Comcast? From my house, I can reach a
few sites with TCP (fortunately, that includes my office, so I could
set up a web and email proxy). If I use traceroute, I can get more or
less anywhere. If I use a UDP-based traceroute, I can get responses
back from the first 8 hops. If I use a TCP-based traceroute, I get
nowhere.

The fact that I get different behavior for different protocols makes me
suspect they're having trouble with equipment designed to control p2p
traffic. Their help phone line simply speaks of an outage. Service
has come back occasionally, but not for long. The problem has been
going on since about 6am.

Does anyone have any data?

--Steve Bellovin, http://www.cs.columbia.edu/~smb

[Christopher Morrow]

Post by Steven M. Bellovin
The fact that I get different behavior for different protocols makes me
suspect they're having trouble with equipment designed to control p2p
traffic. Their help phone line simply speaks of an outage. Service
has come back occasionally, but not for long. The problem has been
going on since about 6am.
Does anyone have any data?

wasn't it sandvine last time? did you try calling them as well? All
joking aside, one hopes that these sorts of things show that the 'p2p
control' soutions are far from perfect and far from 'well baked' and
likely still very ill-advised.

-Chris

[Ted Fischer]

I didn't save any of my Wireshark traces, but this is what I observed
(I'm behind Charter at home but visiting my brother in NJ - Comcast territory).

All attempts to check my e-mail (neither Charter nor Comcast) showed
the syns going out but no syn acks coming back. Then, after a few
minutes (pop server time outs I guess) I started seeing fins coming
back from the pop server that matched my connection requests. Saw
that occur with various http connection attempts as well.

Of course, the only reason I can send this reply out is that they
appear to be back up. Any chance of getting a non-nonsensical RFO
from someone?

Ted

On Sat, Apr 5, 2008 at 1:44 PM, Steven M. Bellovin

Post by Steven M. Bellovin
The fact that I get different behavior for different protocols makes me
suspect they're having trouble with equipment designed to control p2p
traffic. Their help phone line simply speaks of an outage. Service
has come back occasionally, but not for long. The problem has been
going on since about 6am.
Does anyone have any data?

wasn't it sandvine last time? did you try calling them as well? All
joking aside, one hopes that these sorts of things show that the 'p2p
control' soutions are far from perfect and far from 'well baked' and
likely still very ill-advised.
-Chris

[Michael Sinatra]

Post by Ted Fischer
I didn't save any of my Wireshark traces, but this is what I observed
(I'm behind Charter at home but visiting my brother in NJ - Comcast territory).
All attempts to check my e-mail (neither Charter nor Comcast) showed the
syns going out but no syn acks coming back. Then, after a few minutes
(pop server time outs I guess) I started seeing fins coming back from
the pop server that matched my connection requests. Saw that occur with
various http connection attempts as well.
Of course, the only reason I can send this reply out is that they appear
to be back up. Any chance of getting a non-nonsensical RFO from someone?

TCP performance on my Comcast connection in the Bay Area was horrible
last night. tcpdump showed lost segments, dup acks, etc. Moreover, the
UDP traceroute I did showed high packet loss, with outbound traffic from
my connection draining to ATT (AS7012) immediately upstream. Today, the
performance is much better, with traffic draining to Level(3)(AS3356)
and no ATT in the picture.

michael