Experiences with Comcast Ethernet/Transit service

We're looking at using Comcast's (business) transit and private ethernet
services at several client locations and I wanted to see what experiences
others have had regarding this. Off-list replies are preferred.


I just started looking into them as well. Mind of I has for similar info? (maybe just keep the responses on list?)


I do not know of Comcast's Ethernet services specifically, but a general problem with carrier Ethernet services that are based upon the Metro Ethernet Forum (MEF) is that PIM-snooping is not implemented for multicast traffic. The absence of PIM-snooping results in the carrier's Ethernet service operating like a 1990's style Ethernet hub in which (S,G) multicast packets are incorrectly flooded out all user ports.

If multicast traffic is to be used on the carrier Ethernet service, and there is more than one user location, then make sure that the carrier understands the implications of the lack of PIM-snooping support.

I purchased a single GigE transport link from them between a off-net building that they lit for us and a lit site. Install went without issue, including pulling in new fiber. Never underestimate the advantages of having pole and conduit rights. My only complaint would be interval - it took nearly 120 days from order to install and much of that was seemingly spent idle.

The service itself has been rock solid. Unfortunately they don't span across metros within the same logical network (yet) - this would definitely be a bonus.


Sean Head wrote:

Not implemented because it's not in the MEF specs or not implemented because of carrier operational practice?

Antonio Querubin
808-545-5282 x3003
e-mail/xmpp: tony@lava.net

PIM-snooping is not in the MEF specs, but should be if multicast is to
work properly over a carrier's Ethernet service. Regardless of the
specs, RFPs and other user requirements for Ethernet services should
include a "must have" clause requiring PIM-snooping functionality.

The Deathstar opt-e-man service says they will knee-cap you at 1Mb/s of multicast.

- Jared

This was a timely question, as we've have a GigE fiber line with them
for 6 months now.
Largely, the link performs at ~999Mbit 99% of the time :slight_smile:
However, we've had two issues with connectivity that seem to originate
from their network. The link will show up, but both sides of our fiber
will show 0 frames received, and lots of transmit errors. It takes a
call into the Comcast NOC each time for them to resolve it, but
they've been silent on what may actually be going on. These
interruptions last anywhere from 30 minutes, to the last one almost 7
hours (luckily over a weekend).

Benefits to this, being Metro Ethernet, they do support tagged VLAN's,
so cost to entry is low in terms of equipment and setup/support.

Our link goes between downtown Portland, OR, to across the river to
East Vancouver and Mill Plain.

I've found them to be quite sufficient here in the PDX metro area. They
support all L2 tunnels, in particular, QnQ which I require. We have diverse
paths, multiple strands and multi-colored. We are a bit of a special case as
we are serviced by a group that is intended for government and education
which gives us pricing breaks. The commercial shots I have out to meet-me
POPs are priced diffrently. Their CPE devices are migrating to Cisco ME3400,
etc. devices. Their tiered pricing is based on link speed which I'm not
necessarily pleased with but they're starting to become more flexible. They
aren't currently honoring our P-tags so our locations that may be
oversubscribed have difficulty with priority queueing. Their new core in our
area is a single C 7.6k. I would rather they moved from their older F Big
Iron to a J MX or C GSR, but I'm sure the group that services us is faced
with limited resources (ref pricing breaks earlier). The customer portal
provides custom/customer views on their Orion instance which I find even
more useful than my own Cacti graphs at times. The engineering staff is very
accesible (again our group is unique). I'd like to see them put gear in more
colos and hotels. Their uptime and reliability from my perspective has been
right on target.