Hi Andy, On Wed, 2011-12-28 at 17:59 -0500, Andy Susag wrote:

If you add or remove an upstream provider to your network, do you provide notification to your downstream customers? Likely, it would cause a shift in their traffic. If they are peering with multiple ISPs themselves, they may see a traffic flux.

We raised this question recently. The answer (from those with seniority) was that we sell "IP transit". We do not specify where it comes from or how it's made; beyond what a sales person may say to clinch a sale, the contract does not mention our upstreams, only that we agree to transit traffic to/from their ASN at an agreed rate per mbit. The point came that if anyone whom requires BGP transit also *requires* the fastest possible connectivity to a particular ASN (3356, 20940, etc.) then they can always buy transit/peer with that ASN separately. In most cases, this would also be preferable to taking blended tier-1 transit from a tier-2 (or however you describe that.)

I know for a fact that our upstreams do not notify us of events so we tend to not send out these sort of notifications. Just wonder what everyone else does or if anyone happens to know "best practice"

*cough* Cogent. Perfect example. Automagic de-peer^H^H^H^H^H^H^Hblack-holing happens without prior warning, notification OR explanation. And it's the same answer. We buy transit, we don't specify whom they must be connected to. Morally I agree that it would be nice to tell your customers. Practically, I don't believe you can win. I mean, would you tell your downstreams every time you bring-up a new peer? That's not _always_ going to be positive for them. The answer, speaking as a downstream and a transit provider, is to just peer where you need guaranteed connectivity. If change is a problem to your customers, they don't understand how BGP works and they need to cut out the middle-man. Tom

Most transit networks have some sort of blanket notification that they can send to customers. Something like between 12AM and 6AM sometime next week you may or may not have a moderate or severe impact, but we're not going to give you details. It also depends on the peering that is being added or removed. The larger providers are mostly static. I can't imagine Level 3 permanently depeering from Verizon for example. Also, if paths change but latency and hop count are still acceptable most customers will not notice the change. The same goes for outages. Also, where do you draw the line. For example if someone severs a peering with a content network like google some of their downstreams will care others will not. If ISP's notified everyone of every change it would more or less become spam so I can see an argument for both. In large transit networks it probably comes down to the predicted impact of the a particular change versus visibility and contractual liabilities. 2011/12/28 Andy Susag <asusag@ifncom.net>

Hi All,

Just a quick question for those of you running ISPs with BGP downstreams.

If you add or remove an upstream provider to your network, do you provide notification to your downstream customers? Likely, it would cause a shift in their traffic. If they are peering with multiple ISPs themselves, they may see a traffic flux.

I know for a fact that our upstreams do not notify us of events so we tend to not send out these sort of notifications. Just wonder what everyone else does or if anyone happens to know "best practice"

Thanks,

Andy