RE: Xfinity on Campus

[Bryan Ward via NANOG <nanog () lists nanog org>]

Hey Jason and Tony, thanks for chiming in.

After following up with my team, we ended up getting all sorted out.  Originally, nobody my colleague spoke with could 
find the circuit or figure out how to route the support request.  After contacting our account manager, everything 
ended up OK.  He provided us with the circuit IDs and support contact info we needed.

Aside from the campus TV service,  we have about 2 dozen locations with Comcast CBCI service where we provide SDWAN 
support.  We also have hundreds of work-from-home users with Xfinity home internet.  Having their traffic reach the 
main campus network via this circuit is great.  It’s better than having the traffic go out to another provider and then 
back to our network.  Based on Stephen’s original question about sending the no-export community, I don’t know if 
having customer reachability was originally intended for these circuits, but it does work and I hope it can continue to 
work that way.  It seems like an all-around good thing for your customers.


--
Bryan Ward
Lead Network Engineer
Dartmouth College Network Services
bryan.ward () dartmouth edu<mailto:bryan.ward () dartmouth edu>

Scheduling a meeting?  I prefer Zoom.

From: Livingood, Jason <Jason_Livingood () comcast com>
Sent: Friday, May 16, 2025 1:56 PM
To: North American Network Operators Group <nanog () lists nanog org>
Cc: Stephen Griffin <pktslngr () gmail com>; Bryan Ward <Bryan.Ward () dartmouth edu>; Tauber, Tony <Tony_Tauber () 
comcast com>
Subject: Re: Xfinity on Campus

Jason from Comcast here… If there are other things you think are valuable to do with these connections or would like 
them configured in a different way – we’re all ears. Just email Tony (cc’d) and I off-list – and others reading on 
NANOG using this service are welcome to do the same.

Have a nice weekend,
Jason

From: Bryan Ward via NANOG <nanog () lists nanog org<mailto:nanog () lists nanog org>>
Date: Thursday, May 15, 2025 at 15:20
To: North American Network Operators Group <nanog () lists nanog org<mailto:nanog () lists nanog org>>
Cc: Stephen Griffin <pktslngr () gmail com<mailto:pktslngr () gmail com>>, Bryan Ward <Bryan.Ward () dartmouth 
edu<mailto:Bryan.Ward () dartmouth edu>>
Subject: RE: Xfinity on Campus
I've got one of these circuits too, and it's very strange how they handle them internally.
From Comcast's point of view, these circuits don't even exist!  They're not configured the same way as their 
"customers" circuits are.
That means, calling for support for them is next to impossible...
The goal of the circuit is to just provide IPTV traffic and nothing else.
But, as you've been suggesting, you can adjust the BGP communities to use it for other purposes, such as advertising to 
their customers within their AS or even using the circuit for transit...
I'd caution against this, as the commit rate is fairly low from what I've experienced, but it does work.




--
Bryan Ward
Lead Network Engineer
Dartmouth College Network Services

-----Original Message-----
From: Eric C. Miller via NANOG <nanog () lists nanog org<mailto:nanog () lists nanog org>>
Sent: Wednesday, May 14, 2025 4:00 PM
To: North American Network Operators Group <nanog () lists nanog org<mailto:nanog () lists nanog org>>
Cc: Stephen Griffin <pktslngr () gmail com<mailto:pktslngr () gmail com>>; Eric C. Miller <eric () ericheather 
com<mailto:eric () ericheather com>>
Subject: Re: Xfinity on Campus

I think Brian may have touched on this earlier in the thread, but a dirty way to accomplish would be sending to AS7922 
your de-aggregated /24s with the noexport community. Send your aggregates(> /24) to your transit provider(s). If a 
AS7922 customer is default-free, they'd find you through your transit, if they default through AS7922, they reach you 
there. Path asymmetry is still a concern on both sides though.

I concur with the earlier statement about resolving through your customer rep. AS7922+Customers feels more natural 
while still maintaining their ability to later sell you transit.

Eric
________________________________
From: John van Oppen via NANOG <nanog () lists nanog org<mailto:nanog () lists nanog org>>
Sent: Wednesday, May 14, 2025 2:24 PM
To: North American Network Operators Group <nanog () lists nanog org<mailto:nanog () lists nanog org>>
Cc: Stephen Griffin <pktslngr () gmail com<mailto:pktslngr () gmail com>>; John van Oppen <john () vanoppen 
com<mailto:john () vanoppen com>>
Subject: RE: Xfinity on Campus

No export is pretty obviously the wrong choice here, what you want is announce to customers only.

-----Original Message-----
From: Christopher Morrow via NANOG <nanog () lists nanog org<mailto:nanog () lists nanog org>>
Sent: Wednesday, May 14, 2025 9:41 AM
To: North American Network Operators Group <nanog () lists nanog org<mailto:nanog () lists nanog org>>
Cc: Stephen Griffin <pktslngr () gmail com<mailto:pktslngr () gmail com>>; Christopher Morrow <morrowc.lists () gmail 
com<mailto:morrowc.lists () gmail com>>
Subject: Re: Xfinity on Campus

I'd guess that Stephen already checked the looking-glass at:
  ssh rviewsxr () route-server newyork ny ibone comcast net<mailto:rviewsxr () route-server newyork ny ibone comcast 
net>

and validated that the prefix(s) in question are marked no-export...
I suspect that a university also brings their own IP and ASN to the party, so seeing which prefixes have which 
communities is also something Stephen's done before asking the original question.

yea... we can't (unless we are also comcast-campus-customers) know the contract particulars, but the question at the 
end seems reasonable.

I'd suspect the overall assumption in the relationship is that the prefixes seen on
7922 from the neighbors are equality visible to all folks that default to comcast's network?
perhaps this is a situation where: "access to the comcast eyeball set"
is the goal of the relationship
not 'access to ALL comcast customers' ?

-chris

On Wed, May 14, 2025 at 11:3 AM Brian Turnbow via NANOG <nanog () lists nanog org<mailto:nanog () lists nanog org>> 
wrote:
> Hi Stephen
>
> It really depends on the network you are advertising.
> Say for example you are advertising a /24 or /48 that is  part of a
> block being advertised directly  by 7922, or maybe the university's AS.
> In this case even without announcing your netblock outside of 7922
> they will still be receiving the traffic via their announcement. so no
> blackholing and traffic would still be coming in from the customers to you.
> You can check this via looking glasses /route servers etc Your logic
> would apply only to a unique netblock that is covered by another
> announcement.
>
> HTH
> Brian
>
>
>
> Brian Turnbow
> +39 02 6706800
> [image: CDLAN SPA]
> [image: CDLAN SPA] 
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>
> Il giorno mer 14 mag 2025 alle ore 17:09 Stephen Griffin via NANOG <
> nanog () lists nanog org<mailto:nanog () lists nanog org>> ha scritto:
>
> > 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
> > _______________________________________________
> > NANOG mailing list
> >
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