LB> Date: Mon, 30 Sep 2002 17:09:45 -0400 LB> From: Leo Bicknell LB> I'd like to ask a slightly different question. At the LB> providers who do support this feature, how many of your LB> customers actually use it? This is a bit like asking "how many of your customers use BGP?" LB> The last time I asked a couple of people this question in LB> private the answer was generally a number of customers that LB> could be counted on one hand, even at some quite large LB> providers. It seems most providers don't bother tuning routes unless there's congestion. i.e., proactive attempts to find lower-latency paths are rare. It also seems the people who use selective prepends really like them. I give stronger recommendations for providers who offer selective prepends... it appears people generally are oblivious to its existence, but become intrigued when they learn of it. Eddy -- Brotsman & Dreger, Inc. - EverQuick Internet Division Bandwidth, consulting, e-commerce, hosting, and network building Phone: +1 (785) 865-5885 Lawrence and [inter]national Phone: +1 (316) 794-8922 Wichita ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Date: Mon, 21 May 2001 11:23:58 +0000 (GMT) From: A Trap <blacklist@brics.com> To: blacklist@brics.com Subject: Please ignore this portion of my mail signature. These last few lines are a trap for address-harvesting spambots. Do NOT send mail to <blacklist@brics.com>, or you are likely to be blocked.

On Mon, 30 Sep 2002, Leo Bicknell wrote:

I'd like to ask a slightly different question. At the providers who do support this feature, how many of your customers actually use it?

I can tell you that since this weekend Telia has one more customer using a selective prepend. I'm glad they offer this feature since there wasn't really any other way to avoid a congested path.

The last time I asked a couple of people this question in private the answer was generally a number of customers that could be counted on one hand, even at some quite large providers.

I think most customers don't know how this works. Maybe someone should write a book that explains this kind of stuff... Iljitsch

On Mon, 30 Sep 2002, Leo Bicknell wrote:

In a message written on Tue, Oct 01, 2002 at 12:16:07AM +0200, Iljitsch van Beijnum wrote:

...

I think most customers don't know how this works. Maybe someone should write a book that explains this kind of stuff...

I'm not so sure I'd come to that conclusion. I think when most customers see a problem on their transit providers network they

Some NOCs, even ones that support this on their network, don't understand it...or at least have staff that don't even come close to grasping it. It wouldn't surprise me at all if it's beyond a great many customers.

Most people I see using this feature fall into two catagories. The first type doesn't believe the provider can fix the problem but is forced to use them (due to price, management, whatever) and uses this to avoid their NOC because it doesn't work. The second type of person believes they can actually do a better job of routing than their upstream. This may even be true in some cases (where the customer has several transit providers all supporting this 'feature'), however I suspect in many cases the customer is actually making their own life worse.

Consider a network with several transit providers. Each transit pipe is incapable of handling all that network's traffic. The pipes may even be of wildly different sizes. Letting BGP decide where traffic goes (or comes from) with no tuning just won't work. You'd end up with some pipes overutilized and others underutilized. In this case, selective prepends make it possible to shift traffic around or decide "we're going to try forcing all ASxyz traffic to come to us over pipe A." There's also the occasional case of medium to long term overloaded peering between large providers in which case you might want to do all you can to force traffic to/from ASxzy to not come/go via pipe A.

increased. Even if we assume all the people using it really need it, is it worth risking the performance of 500 or 1000 customers for the 5-10 who actually use the features?

I wonder if anyone from Sprint or C&W is willing/able to say what percentage of multihomed customers utilize these communities? With enough full views from enough route-servers, it might even be possible to analyze the data and see how many use this. ---------------------------------------------------------------------- Jon Lewis *jlewis@lewis.org*| I route System Administrator | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________

On Mon, 30 Sep 2002, Leo Bicknell wrote:

In general what this means is rather than having a couple of standard route-map's/route-policies that get configured once and applied to all peers you end up with a per-peer specific configuration. It would seem to me that the opportunity for mistakes is grealy increased. Even if we assume all the people using it really need it, is it worth risking the performance of 500 or 1000 customers for the 5-10 who actually use the features?

Are you talking about the customer or the provider? A provider with a well thought-out community policy shouldn't need per-customer route-maps. The customer sends the provider the appropriate communities and the standard customer route-map takes the appropriate actions. That's one of the major benefits of communities, match on the community not the customer. I see your point about questioning the cost-benefit; however any provider of reasonable size needs a community policy anyway, so most of the cost is unavoidable. If done right it only needs to be incurred once. A customer, on the other hand, will of course need separate policy per transit to take advantage of provider-specific TE communities. For the typical multi-homed customer with a few upstreams this is hardly unmanageable. Bradley