I think the question is for what purpose/reason Comcast offers you this
connection, it sounds like it may have downsides or side effects in
practice, but I have a suspicion Comcast offers this in order to help
with performance and routing from the students connections to the
university systems, and as residential type users they are covered by
the routing policy they require you to use, so it accomplishes the goal
they set out to do, make connections between Xfinity on Campus users at
your university and the university's own systems fast and cheap for them
to handle.
I'm not sure why you say this is configured like a normal customer, I
assume that's in regards to other aspects of the setup, as normal
customer would propagate routes in more directions than peering, not
less, but it may also tie back into the why, the team wanting to sell
Xfinity on Campus wants connections from students to the university to
be fast and cheap to handle and so adds this to that offering to help
with that, but they are the customer facing team, they can only set up
versions of customer side links, not peering or other types of links.
Again, all pure speculation, but I suspect it is driven by the goal and
reason why they bundle this extra connection for you, and given it's not
as transit for you as an incentive to sign up (given the no-export), I
suspect it's something like what I'm guessing here.
On 5/14/2025 11:08 AM, Stephen Griffin via NANOG wrote:
So, I currently work for a university that offers Xfinity on Campus for our
students. As part of that, we receive essentially peering.. with a twist...
it is actually configured more like a normal customer.
We're required to send 7922:999, which is essentially 7922's no-export.
However, 7922:888 (7922+customers), seems like the better choice, while
still respecting the goal of not providing transit.
The former makes it such that 7922 doesn't advertise our prefixes to their
BGP customers, which can lead to blackholes if their customer is
default-free and their other provider(s) have an outage, or if the customer
is doing link (but not provider) redundancy with BGP. It also means that
billable traffic from xfinity customers to us is actually driven away from
7922, which would seem to not be in 7922's best interest (maybe folks no
longer bill on usage?).
no-export and its ilk just seems like the wrong choice in nearly every
case, but I thought I would check myself with the assembled.
Cheers,
Stephen Griffin
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