Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Tue, Mar 29, 2005 at 04:50:10PM -0500, Richard A Steenbergen wrote: [ snip ] I'd really hate to picture the size of the boom that would happen if people WERE to exchange transit paths with each other on anything other than a rare and isolated basis. Yup... Already happening a lot in IPv6 today, mostly from legacy 6bone operators who still refuse to clean up. Worse, such mutual full swapping / settlement-free transit exchange on large part is done over tunnels... (oh snap...) I can already go on and name at least five ASNs already that are doing this on large scale but I think I'll refrain from doing so on a public mailing list :D -J -- Richard A Steenbergen [EMAIL PROTECTED] http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC) -- James JunTowardEX Technologies, Inc. Technical Lead Boston IPv4/IPv6 Web Hosting, Colocation and [EMAIL PROTECTED]Network design/consulting configuration services cell: 1(978)-394-2867 web: http://www.towardex.com , noc: www.twdx.net
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
In a message written on Tue, Mar 29, 2005 at 02:27:56PM -0600, John Dupuy wrote:
I was looking at it from a route announcement point of view. Transit is
where AS A advertises full routes to AS B. Thus, AS B is getting transit
from A. Peering is where A B only advertise their network and, possibly,
the networks that stub or purchase transit from them.
This is oversimplistic. Transit does not have to be full routes.
Don't confuse the business case with the technical configuration.
That is, all combinations of:
{paid,settlement free}-{customer routes only, full routes, no routes,
you leak mine, I leak yours}
exist. Some are more common than others. Sometimes multiple
combinations exist between the same two parties.
It is my understanding that the top ISPs trade transit. They provide full
routes to each other without payment, regardless of how or where the route
was learned from. They are willing to pass some traffic without
compensation because it makes for better connectivity. From an announcement
POV they are not peering.
The top of the food chain is a full mesh of customer routes only.
I have never seen anyone at the top of the food chain trade full
routing tables, something that would likely be obvious from time
to time in various outage scenarios. There is no business case to
provide free transit on that level. It would be too easily abused.
That's not limited to top ISP's either. Full tables are not done
on a peering level, ever. If anything wonky is being done it's
done with selective leaking of routes in one or both directions,
never ever ever with a full table.
--
Leo Bicknell - [EMAIL PROTECTED] - CCIE 3440
PGP keys at http://www.ufp.org/~bicknell/
Read TMBG List - [EMAIL PROTECTED], www.tmbg.org
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Re: Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
[EMAIL PROTECTED] writes: Again, I'd be interested in hearing from one of the bigger ones on this: UUNet, ATT, Sprint, Level3, QWest If you can't say anything, I understand. You don't need them to say anything - just look at what they are advertising. Are they advertising each other's routes? If not, then they aren't given each other transit.
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
And how, pray tell, does one actually measure T1 vs. T2 networks? That's easy. You define a set of criteria by which you can measure the networks on some scale, and then set two thresholds. Networks which exceed the higher threshold are Tier 1, those which only exceed the lower threshold are Tier 2. I have seen people do this by counting the number of ASes that a network connects to. And I have seen this done with nodes by summing up the bandwidth of all circuits connected to a node. Even though the network is a dynamic partial mesh, researchers can learn a lot about the behavior by imposing various types measurement hierachy on the network. Thus, Tier 1 and Tier 2 are not inherent characteristics of the Internet; rather they are characteristics of a particular view of the network at a particular point in time. There are probably people who are trying to measure a hierarchy of latency or a hierarchy of jitter. The more views, the merrier. --Michael Dillon
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Mar 29, 2005, at 1:24 AM, Richard A Steenbergen wrote: On Tue, Mar 29, 2005 at 02:23:06AM +0100, Stephen J. Wilcox wrote: 701 is not the most connected, it has only customers and a restrictive set of peers? Ok, I'm just bored enough to bite. If we're talking about a contest to see who has the most number of directly connected ASNs, I think UU might still win, even with a restrictive set of peers. Taking a look at a count of customer ASNs behind some specific networks of note, I come up with the following (some data a couple weeks out of date, but the gist is the same): Network ASN Count --- - 701 2298 70181889 12391700 33561184 209 1086 174 736 3549584 3561566 2914532 2828427 6461301 1299243 Which begs the question, what is the largest number of ASNs that someone peers with? Patrick? :) Somehow I suspect that 701's customer base (702 and 703 aren't included in the above count BTW) overpower even the most aggressively open of peering policies, in this particular random pointless and arbitrary contest at any rate. Of course. There is a difference between most peers and most adjacent ASes. But it is non-trivial to see which of those adjacencies are transit and which are peering. (Nearly impossible if you define such things on Layer 8, but not impossible if you only include which ASes are propagated to which other ASes.) At the end of the day, an AS with a LOT of downstream ASes can always beat a well peered AS - there just aren't that many ASes which peer. -- TTFN, patrick
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Tue, 29 Mar 2005, [EMAIL PROTECTED] wrote: and if you peer with all networks in the 'transit free zone' then you too become transit free also. er.. hate to rain on your parade but if I peer with everyone these are not the words of someone hating to rain on me! i need/want to exchange traffic with, i am transit-free, even if I -NEVER- touch any other part of the commercial Internet... mmm yeah but in the context we have here of ISPs providing connectivity to other ISPs or enterprises this isnt very realistic so i dont see the point of arguing the technicality. my packets get to where they need to go and all packets I want get to me. my life is good ... even if I only appear as vestigal to the commercial Internet, if I appear at all. sounds more like an enterprise with specific requirements to connect to a limited part of the internet.. this is not the sort of ISP operation that i am working in. how would you classify such a network? T1, T2, ODDBALL-0, non-Internet-265, ??? enterprise Steve
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Tue, 29 Mar 2005, Richard A Steenbergen wrote: On Tue, Mar 29, 2005 at 02:23:06AM +0100, Stephen J. Wilcox wrote: 701 is not the most connected, it has only customers and a restrictive set of peers? Ok, I'm just bored enough to bite. but not as bored as bill, randy or patrick it would seem :) If we're talking about a contest to see who has the most number of directly connected ASNs, I think UU might still win, even with a restrictive set of peers. I didnt think we were, kinda happened.. if peering partners is a compensation for something else its pretty sad ;) Maybe I'm wrong, i checked with renesys and their data has 701 with 5200 adjacencies followed by 1239 with 3500 anyway i care enough to have snipped the data. Which begs the question, what is the largest number of ASNs that someone peers with? Patrick? :) Somehow I suspect that 701's customer base (702 and 703 aren't included in the above count BTW) overpower even the most aggressively open of peering policies, in this particular random pointless and arbitrary contest at any rate. so what are we debating again? :) Steve
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Mon, 28 Mar 2005 16:17:21 +0100, Stephen J. Wilcox said: however alex, you do highlight an excellent point - things are not as simple as 'tier1, tier2', there are complicated routing and financial arrangements in operation, which brings me back to my earlier point: does it matter what a network is paying for some connectivity providing they deliver to you the connectivity you need at the quality you desire? As long as their price point for their connectivity is set such that they can remain a viable ongoing business concern while fulfilling the requirements of my contract, it doesn't really matter, except at contract renegotiation time. At that point, if I know they're making money off selling others transit to my packets, I may try to negotiate a price concession pgpgmbrpKY1Mn.pgp Description: PGP signature
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Mar 29, 2005, at 12:24 PM, Tom Vest wrote: On Mar 29, 2005, at 12:08 PM, Stephen J. Wilcox wrote: Maybe I'm wrong, i checked with renesys and their data has 701 with 5200 adjacencies followed by 1239 with 3500 anyway i care enough to have snipped the data. Does anyone know how many of these adjacencies are with single-homed ASNs, i.e., ASNs that are out-of-spec and likely artifacts of previous MA transactions? Tom
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
My apologies to UUNet/MCI, I'm not trying to pick on you, but you are useful to the discussion. But by the technical description of a transit free zone, then 701 is not tier one, since I have encountered scenarios where many AS are transversed between 701 and other networks, not just a peer of a peer. Unless, by transit free zone you mean transit trading where large providers permit each other to transit for free. (Which gets back to my 'who hurts more' discussion.) I'm willing to be wrong. If any of the large providers on the list will say that their network does not transit beyond the customer of a peer; and they still maintain full connectivity, I will gladly be corrected. John At 07:23 PM 3/28/2005, you wrote: On Mon, 28 Mar 2005, John Dupuy wrote: I'll be brief, but I do want to perhaps word Alex's definition in a different way that might be more useful. Even tier 1 providers regularly trade transit. They must since no single network is connected to all the other ones. Not even close. Even UUNet (ASN 701), arguably the most-connected network on the planet, only connects to a fraction of the possible peerings. 701 is not the most connected, it has only customers and a restrictive set of peers? you dont need to peer with all networks tho, if all networks are buying from 701 or one of its peers then it will get those routes via peering not transit or transit trades... you seem to be forgetting what peering is. and if you peer with all networks in the 'transit free zone' then you too become transit free also. The true definition is more vague: if a peering or transit circuit between A or B is taken down, who will be hurt the most: A or B? If it predominantly B, and much less A, then A is more Tier 1 and B is of a lesser Tier. If they are equally hurt, they the are of equal status. Essentially, Tier 1 is whatever the other Tier 1 providers believe at the moment is Tier 1. It is self-referential and not distinct at all. i believe the distinction exists as shown above ie transit free.. as to why this might be considered a goal i'm not sure, its not obvious that transit free is cheaper than buying transit! this thing about 'who hurts most' is an entirely different topic and has nothing to do with who is in the transit free zone. altho destructive depeering does seem to be common practice within that zone :) This is, frustratingly, a very non-technical definition. But it seems to map with what I've actually seen the industry do. thats because non-technical definitions mean anyone can call themselves anything they like.. wiltel recently spammed me to buy their 'tier1 transit'.. presumably they are tier1 within their own definition of tier1. if you want to be technical tho, and aiui we are a technical forum, then tier1 means transit free. i reaffirm my earlier point - but why care, isnt it about cost and reliability, and as peering and transit are about the same cost who cares who you dont peer with Steve John At 09:17 AM 3/28/2005, Stephen J. Wilcox wrote: On Mon, 28 Mar 2005, Randy Bush wrote: Firstly, peering isn't binary. Is peering vs transit a distinction based on routes taken / accepted readvertised, or on cost? Does paid for peering count as peering or transit? If you pay by volume? If you pay for more than your fair share of the interconnect pipes? (if the latter, I am guessing there are actually no Tier 1s as everyone reckons they pay for more than their fair share...). pay? did i say pay? i discussed announcement and receipt of prefixes. this was not an accident. it is measurable. i also avoided money.. i dont think its that relevant, everyone is paying for peering or transit in one form or another, i dont think any peering is free (free != settlement free) Secondly, it doesn't cover scenarios that have have happened in the past. For instance, the route swap. EG Imagine networks X1, X2, X3, X4 are Tier 1 as Randy describes them. Network Y peers with all the above except X1. Network Z peers with all the above except X2. Y Z peer. To avoid Y or Z needing to take transit, Y sends Z X2's routes (and sends Z's routes to X2 routes marked no export to X2's peers), and Z sends Y X1's routes (and sends Y's routes to X1 marked no export to X1's peers). Perhaps they do this for free. Perhaps they charge eachother for it and settle up at the end of each month. Perhaps it's one company that's just bought another. transit (n). The act of passing over, across, or through; passage. whether it is a settlement arrangement or a mutual swap, they do NOT have peering, they ARE transitting and by our definition are not
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
--- John Dupuy [EMAIL PROTECTED] wrote: But by the technical description of a transit free zone, then 701 is not tier one, since I have encountered scenarios where many AS are transversed between 701 and other networks, not just a peer of a peer. Unless, by transit free zone you mean transit trading where large providers permit each other to transit for free. (Which gets back to my 'who hurts more' discussion.) oversimplification Transit = being someone's customer Peering = permitting your customers to go to your peer's customers or the peer's network, but not the peer's peers, without exchange of money. Any other relationship != peering for my purposes (although lots of subtly different relationships exist, the largest networks tend to take a view which is not too dissimilar to the one shown above) /oversimplification Are you implying that 701 is paying someone to carry their prefixes? While I'm not the peering coordinator for 701, I would find that improbable. I would expect that money would flow the other direction (and thus 701 would become a more valuable peer for other networks). I'm willing to be wrong. If any of the large providers on the list will say that their network does not transit beyond the customer of a peer; and they still maintain full connectivity, I will gladly be corrected. oodles and oodles of people can say this (and already have). A paying customer of mine can readvertise (with a non-munged AS_PATH) any of my prefixes which they want, and thus provide transit for other people to reach me. That does not change the fact that I'm not paying for transit. So in short, I would say that T1 vs T2 etc is a follow the money: T1 = doesn't pay anyone else to carry their prefixes, and runs a default-free network. T2 = pays one or more T1 providers to carry their prefixes, may or may not run a default-free network. T3 = leaf node, pays one or more T1/T2 providers to carry their traffic, probably uses default route. YMMV, blah blah blah David Barak Need Geek Rock? Try The Franchise: http://www.listentothefranchise.com __ Do you Yahoo!? Yahoo! Sports - Sign up for Fantasy Baseball. http://baseball.fantasysports.yahoo.com/
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
I guess I'm looking at this too much from the point of view of a BGP Admin. Yes, if you are looking at this from the point of view of payment, then the top ISPs do not pay each other. I was looking at it from a route announcement point of view. Transit is where AS A advertises full routes to AS B. Thus, AS B is getting transit from A. Peering is where A B only advertise their network and, possibly, the networks that stub or purchase transit from them. It is my understanding that the top ISPs trade transit. They provide full routes to each other without payment, regardless of how or where the route was learned from. They are willing to pass some traffic without compensation because it makes for better connectivity. From an announcement POV they are not peering. I am still curious: do any of the larger ISPs on this list want to confirm/deny the previous paragraph? I think we are getting into defining terms territory. So, I will bow out of the discussion. John At 01:56 PM 3/29/2005, David Barak wrote: --- John Dupuy [EMAIL PROTECTED] wrote: But by the technical description of a transit free zone, then 701 is not tier one, since I have encountered scenarios where many AS are transversed between 701 and other networks, not just a peer of a peer. Unless, by transit free zone you mean transit trading where large providers permit each other to transit for free. (Which gets back to my 'who hurts more' discussion.) oversimplification Transit = being someone's customer Peering = permitting your customers to go to your peer's customers or the peer's network, but not the peer's peers, without exchange of money. Any other relationship != peering for my purposes (although lots of subtly different relationships exist, the largest networks tend to take a view which is not too dissimilar to the one shown above) /oversimplification Are you implying that 701 is paying someone to carry their prefixes? While I'm not the peering coordinator for 701, I would find that improbable. I would expect that money would flow the other direction (and thus 701 would become a more valuable peer for other networks). I'm willing to be wrong. If any of the large providers on the list will say that their network does not transit beyond the customer of a peer; and they still maintain full connectivity, I will gladly be corrected. oodles and oodles of people can say this (and already have). A paying customer of mine can readvertise (with a non-munged AS_PATH) any of my prefixes which they want, and thus provide transit for other people to reach me. That does not change the fact that I'm not paying for transit. So in short, I would say that T1 vs T2 etc is a follow the money: T1 = doesn't pay anyone else to carry their prefixes, and runs a default-free network. T2 = pays one or more T1 providers to carry their prefixes, may or may not run a default-free network. T3 = leaf node, pays one or more T1/T2 providers to carry their traffic, probably uses default route. YMMV, blah blah blah David Barak Need Geek Rock? Try The Franchise: http://www.listentothefranchise.com __ Do you Yahoo!? Yahoo! Sports - Sign up for Fantasy Baseball. http://baseball.fantasysports.yahoo.com/
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Tue, 29 Mar 2005, John Dupuy wrote: I was looking at it from a route announcement point of view. Transit is where AS A advertises full routes to AS B. Thus, AS B is getting transit from A. Peering is where A B only advertise their network and, possibly, the networks that stub or purchase transit from them. no, they MUST send their customer nets else their customers will not have global reachability It is my understanding that the top ISPs trade transit. They provide full routes to each other without payment, regardless of how or where the route was learned from. They are willing to pass some traffic without compensation because it makes for better connectivity. From an announcement POV they are not peering. ahhh. no, they send peering only between each other (approx 5 routes for each of the biggest providers - level3, sprint, uunet, att) Steve I am still curious: do any of the larger ISPs on this list want to confirm/deny the previous paragraph? I think we are getting into defining terms territory. So, I will bow out of the discussion. John At 01:56 PM 3/29/2005, David Barak wrote: --- John Dupuy [EMAIL PROTECTED] wrote: But by the technical description of a transit free zone, then 701 is not tier one, since I have encountered scenarios where many AS are transversed between 701 and other networks, not just a peer of a peer. Unless, by transit free zone you mean transit trading where large providers permit each other to transit for free. (Which gets back to my 'who hurts more' discussion.) oversimplification Transit = being someone's customer Peering = permitting your customers to go to your peer's customers or the peer's network, but not the peer's peers, without exchange of money. Any other relationship != peering for my purposes (although lots of subtly different relationships exist, the largest networks tend to take a view which is not too dissimilar to the one shown above) /oversimplification Are you implying that 701 is paying someone to carry their prefixes? While I'm not the peering coordinator for 701, I would find that improbable. I would expect that money would flow the other direction (and thus 701 would become a more valuable peer for other networks). I'm willing to be wrong. If any of the large providers on the list will say that their network does not transit beyond the customer of a peer; and they still maintain full connectivity, I will gladly be corrected. oodles and oodles of people can say this (and already have). A paying customer of mine can readvertise (with a non-munged AS_PATH) any of my prefixes which they want, and thus provide transit for other people to reach me. That does not change the fact that I'm not paying for transit. So in short, I would say that T1 vs T2 etc is a follow the money: T1 = doesn't pay anyone else to carry their prefixes, and runs a default-free network. T2 = pays one or more T1 providers to carry their prefixes, may or may not run a default-free network. T3 = leaf node, pays one or more T1/T2 providers to carry their traffic, probably uses default route. YMMV, blah blah blah David Barak Need Geek Rock? Try The Franchise: http://www.listentothefranchise.com __ Do you Yahoo!? Yahoo! Sports - Sign up for Fantasy Baseball. http://baseball.fantasysports.yahoo.com/
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Mar 29, 2005, at 3:27 PM, John Dupuy wrote: I guess I'm looking at this too much from the point of view of a BGP Admin. Yes, if you are looking at this from the point of view of payment, then the top ISPs do not pay each other. I was looking at it from a route announcement point of view. Transit is where AS A advertises full routes to AS B. Thus, AS B is getting transit from A. Peering is where A B only advertise their network and, possibly, the networks that stub or purchase transit from them. It is my understanding that the top ISPs trade transit. They provide full routes to each other without payment, regardless of how or where the route was learned from. They are willing to pass some traffic without compensation because it makes for better connectivity. From an announcement POV they are not peering. I am still curious: do any of the larger ISPs on this list want to confirm/deny the previous paragraph? I would be AMAZINGLY interested if anyone confirms the above paragraph. AFAIK, 701/1239/209/etc. do not give full tables to _anyone_ unless they are paid. Someone care to correct me? -- TTFN, patrick
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Tue, Mar 29, 2005 at 02:27:56PM -0600, John Dupuy wrote: I was looking at it from a route announcement point of view. Transit is where AS A advertises full routes to AS B. Thus, AS B is getting transit from A. Peering is where A B only advertise their network and, possibly, the networks that stub or purchase transit from them. It is my understanding that the top ISPs trade transit. They provide full routes to each other without payment, regardless of how or where the route was learned from. They are willing to pass some traffic without compensation because it makes for better connectivity. From an announcement POV they are not peering. I am still curious: do any of the larger ISPs on this list want to confirm/deny the previous paragraph? ISPs formerly known as tier1s in general peer with each other, not trade transit. If one of the peers started sending us full routes, that would quickly result in a NOC to NOC chat about route leaks. If they exchanged full routes, wouldn't that be mutual transit, not peering? This isn't meant to imply that networks don't play kinky games with each other at various times that can confuse outside observers, but peering is peering and transit is transit, most of the time. -dorian
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Tue, Mar 29, 2005 at 03:57:51PM -0500, Dorian Kim wrote: If they exchanged full routes, wouldn't that be mutual transit, not peering? Settlement free transit? Sounds like the wave of the future to me. Oh wait it's only March 29th, we're still 3 days away. :) Alas, as anyone who has ever watched Internap when they go flappy flappy can attest, BGP does not handle an excessive number of transit paths very well. I'd really hate to picture the size of the boom that would happen if people WERE to exchange transit paths with each other on anything other than a rare and isolated basis. -- Richard A Steenbergen [EMAIL PROTECTED] http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)
Re: Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
Alas, as anyone who has ever watched Internap when they go flappy flappy can attest, BGP does not handle an excessive number of transit paths very well. I'd really hate to picture the size of the boom that would happen if people WERE to exchange transit paths with each other on anything other than a rare and isolated basis. True. And I fully support the common practice of heavy filtering on both ends of most BGP sessions to prevent route leakage. Nothing upsets an upstream more than announcing a major network via a smaller connection. Perhaps things have changed a lot in the last six years, which is the last time I got much face-to-face time with other BGP admins. Back then it seemed that the larger networks horse-traded transit pretty regularly. I do not know if was partly automated or case-by-case for each route. (And I suspect it was not always with corporate knowledge.) Especially since some networks (foreign government networks, etc.) were not as flexible as one would hope about peering. Again, I'd be interested in hearing from one of the bigger ones on this: UUNet, ATT, Sprint, Level3, QWest If you can't say anything, I understand. John
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
--On 27 March 2005 12:59 -0800 Randy Bush [EMAIL PROTECTED] wrote: better? i did not say better. a simple way to look at it, which we have repeated here every year since com-priv migrated here is a tier-1 network does not get transit prefixes from any other network and peers with, among others, other tier-1 networks. a tier-2 gets transit of some form from another network, usually but not necessarily a tier-1, and may peer with other networks. this does not please everyone, especially folk who buy transit and don't like discussing it. and there are kinky corners Even this is debatable ( I know you know this Randy). Firstly, peering isn't binary. Is peering vs transit a distinction based on routes taken / accepted readvertised, or on cost? Does paid for peering count as peering or transit? If you pay by volume? If you pay for more than your fair share of the interconnect pipes? (if the latter, I am guessing there are actually no Tier 1s as everyone reckons they pay for more than their fair share...). Secondly, it doesn't cover scenarios that have have happened in the past. For instance, the route swap. EG Imagine networks X1, X2, X3, X4 are Tier 1 as Randy describes them. Network Y peers with all the above except X1. Network Z peers with all the above except X2. Y Z peer. To avoid Y or Z needing to take transit, Y sends Z X2's routes (and sends Z's routes to X2 routes marked no export to X2's peers), and Z sends Y X1's routes (and sends Y's routes to X1 marked no export to X1's peers). Perhaps they do this for free. Perhaps they charge eachother for it and settle up at the end of each month. Perhaps it's one company that's just bought another. All this come down to the fact that Tier n is not a useful taxonomy because there is no clear ordering of networks. If I was really pushed for a definition, I'd say it was this: you are a Tier-1 network, when, if you tell all third parties not to advertise your routes to anyone but their customers, and you get a phone call from one of your customers complaining about a resultant connectivity problem, you can be confident before you've analyzed it, that the customer will accept it's that networks problem, not yours. This boils down to does the customer believe you. Alex
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
a tier-1 network does not get transit prefixes from any other network and peers with, among others, other tier-1 networks. a tier-2 gets transit of some form from another network, usually but not necessarily a tier-1, and may peer with other networks. this does not please everyone, especially folk who buy transit and don't like discussing it. and there are kinky corners Even this is debatable ( I know you know this Randy). in this forum, everything is debatable. some portion of the debate makes sense. ymmv. Firstly, peering isn't binary. Is peering vs transit a distinction based on routes taken / accepted readvertised, or on cost? Does paid for peering count as peering or transit? If you pay by volume? If you pay for more than your fair share of the interconnect pipes? (if the latter, I am guessing there are actually no Tier 1s as everyone reckons they pay for more than their fair share...). pay? did i say pay? i discussed announcement and receipt of prefixes. this was not an accident. it is measurable. Secondly, it doesn't cover scenarios that have have happened in the past. For instance, the route swap. EG Imagine networks X1, X2, X3, X4 are Tier 1 as Randy describes them. Network Y peers with all the above except X1. Network Z peers with all the above except X2. Y Z peer. To avoid Y or Z needing to take transit, Y sends Z X2's routes (and sends Z's routes to X2 routes marked no export to X2's peers), and Z sends Y X1's routes (and sends Y's routes to X1 marked no export to X1's peers). Perhaps they do this for free. Perhaps they charge eachother for it and settle up at the end of each month. Perhaps it's one company that's just bought another. seems to me that, if you look at the prefixes, it's pretty clear. randy
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
I'll be brief, but I do want to perhaps word Alex's definition in a different way that might be more useful. Even tier 1 providers regularly trade transit. They must since no single network is connected to all the other ones. Not even close. Even UUNet (ASN 701), arguably the most-connected network on the planet, only connects to a fraction of the possible peerings. The true definition is more vague: if a peering or transit circuit between A or B is taken down, who will be hurt the most: A or B? If it predominantly B, and much less A, then A is more Tier 1 and B is of a lesser Tier. If they are equally hurt, they the are of equal status. Essentially, Tier 1 is whatever the other Tier 1 providers believe at the moment is Tier 1. It is self-referential and not distinct at all. This is, frustratingly, a very non-technical definition. But it seems to map with what I've actually seen the industry do. John At 09:17 AM 3/28/2005, Stephen J. Wilcox wrote: On Mon, 28 Mar 2005, Randy Bush wrote: Firstly, peering isn't binary. Is peering vs transit a distinction based on routes taken / accepted readvertised, or on cost? Does paid for peering count as peering or transit? If you pay by volume? If you pay for more than your fair share of the interconnect pipes? (if the latter, I am guessing there are actually no Tier 1s as everyone reckons they pay for more than their fair share...). pay? did i say pay? i discussed announcement and receipt of prefixes. this was not an accident. it is measurable. i also avoided money.. i dont think its that relevant, everyone is paying for peering or transit in one form or another, i dont think any peering is free (free != settlement free) Secondly, it doesn't cover scenarios that have have happened in the past. For instance, the route swap. EG Imagine networks X1, X2, X3, X4 are Tier 1 as Randy describes them. Network Y peers with all the above except X1. Network Z peers with all the above except X2. Y Z peer. To avoid Y or Z needing to take transit, Y sends Z X2's routes (and sends Z's routes to X2 routes marked no export to X2's peers), and Z sends Y X1's routes (and sends Y's routes to X1 marked no export to X1's peers). Perhaps they do this for free. Perhaps they charge eachother for it and settle up at the end of each month. Perhaps it's one company that's just bought another. transit (n). The act of passing over, across, or through; passage. whether it is a settlement arrangement or a mutual swap, they do NOT have peering, they ARE transitting and by our definition are not transit-free (and hence not tier1) however alex, you do highlight an excellent point - things are not as simple as 'tier1, tier2', there are complicated routing and financial arrangements in operation, which brings me back to my earlier point: does it matter what a network is paying for some connectivity providing they deliver to you the connectivity you need at the quality you desire? Steve
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Mon, 28 Mar 2005, John Dupuy wrote: I'll be brief, but I do want to perhaps word Alex's definition in a different way that might be more useful. Even tier 1 providers regularly trade transit. They must since no single network is connected to all the other ones. Not even close. Even UUNet (ASN 701), arguably the most-connected network on the planet, only connects to a fraction of the possible peerings. 701 is not the most connected, it has only customers and a restrictive set of peers? you dont need to peer with all networks tho, if all networks are buying from 701 or one of its peers then it will get those routes via peering not transit or transit trades... you seem to be forgetting what peering is. and if you peer with all networks in the 'transit free zone' then you too become transit free also. The true definition is more vague: if a peering or transit circuit between A or B is taken down, who will be hurt the most: A or B? If it predominantly B, and much less A, then A is more Tier 1 and B is of a lesser Tier. If they are equally hurt, they the are of equal status. Essentially, Tier 1 is whatever the other Tier 1 providers believe at the moment is Tier 1. It is self-referential and not distinct at all. i believe the distinction exists as shown above ie transit free.. as to why this might be considered a goal i'm not sure, its not obvious that transit free is cheaper than buying transit! this thing about 'who hurts most' is an entirely different topic and has nothing to do with who is in the transit free zone. altho destructive depeering does seem to be common practice within that zone :) This is, frustratingly, a very non-technical definition. But it seems to map with what I've actually seen the industry do. thats because non-technical definitions mean anyone can call themselves anything they like.. wiltel recently spammed me to buy their 'tier1 transit'.. presumably they are tier1 within their own definition of tier1. if you want to be technical tho, and aiui we are a technical forum, then tier1 means transit free. i reaffirm my earlier point - but why care, isnt it about cost and reliability, and as peering and transit are about the same cost who cares who you dont peer with Steve John At 09:17 AM 3/28/2005, Stephen J. Wilcox wrote: On Mon, 28 Mar 2005, Randy Bush wrote: Firstly, peering isn't binary. Is peering vs transit a distinction based on routes taken / accepted readvertised, or on cost? Does paid for peering count as peering or transit? If you pay by volume? If you pay for more than your fair share of the interconnect pipes? (if the latter, I am guessing there are actually no Tier 1s as everyone reckons they pay for more than their fair share...). pay? did i say pay? i discussed announcement and receipt of prefixes. this was not an accident. it is measurable. i also avoided money.. i dont think its that relevant, everyone is paying for peering or transit in one form or another, i dont think any peering is free (free != settlement free) Secondly, it doesn't cover scenarios that have have happened in the past. For instance, the route swap. EG Imagine networks X1, X2, X3, X4 are Tier 1 as Randy describes them. Network Y peers with all the above except X1. Network Z peers with all the above except X2. Y Z peer. To avoid Y or Z needing to take transit, Y sends Z X2's routes (and sends Z's routes to X2 routes marked no export to X2's peers), and Z sends Y X1's routes (and sends Y's routes to X1 marked no export to X1's peers). Perhaps they do this for free. Perhaps they charge eachother for it and settle up at the end of each month. Perhaps it's one company that's just bought another. transit (n). The act of passing over, across, or through; passage. whether it is a settlement arrangement or a mutual swap, they do NOT have peering, they ARE transitting and by our definition are not transit-free (and hence not tier1) however alex, you do highlight an excellent point - things are not as simple as 'tier1, tier2', there are complicated routing and financial arrangements in operation, which brings me back to my earlier point: does it matter what a network is paying for some connectivity providing they deliver to you the connectivity you need at the quality you desire? Steve
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Mar 28, 2005, at 8:29 PM, [EMAIL PROTECTED] wrote: and if you peer with all networks in the 'transit free zone' then you too become transit free also. er.. hate to rain on your parade but if I peer with everyone i need/want to exchange traffic with, i am transit-free, even if I -NEVER- touch any other part of the commercial Internet... my packets get to where they need to go and all packets I want get to me. my life is good ... even if I only appear as vestigal to the commercial Internet, if I appear at all. Absolutely correct. how would you classify such a network? T1, T2, ODDBALL-0, non-Internet-265, ??? I doubt it is a tier. I am certain it is not an Internet network if it does not have connectivity to substantially all other Internet networks. -- TTFN, patrick
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Mon, Mar 28, 2005 at 09:15:53PM -0500, Patrick W Gilmore wrote: On Mar 28, 2005, at 8:29 PM, [EMAIL PROTECTED] wrote: and if you peer with all networks in the 'transit free zone' then you too become transit free also. er.. hate to rain on your parade but if I peer with everyone i need/want to exchange traffic with, i am transit-free, even if I -NEVER- touch any other part of the commercial Internet... my packets get to where they need to go and all packets I want get to me. my life is good ... even if I only appear as vestigal to the commercial Internet, if I appear at all. Absolutely correct. how would you classify such a network? T1, T2, ODDBALL-0, non-Internet-265, ??? I doubt it is a tier. I am certain it is not an Internet network if it does not have connectivity to substantially all other Internet networks. begs the definition of internet networks ... It has IP connectivity to the other IP networks of interest. For networks that are not of interest, there is no expressly defined connectivity. The term Internet has devolved into a series of interconnected -COMMERCIAL- networks and from that viewpoint, anyone on a non-commercial network, that has no desire to be connected to a commercial network, is relegated, BY THE COMMERCIAL OPERATORS, to intranet status. The historical term - INTERNET - reflected a catanet of networks that used IP for packet delivery. with the inclusion of robust policy expression on network edges - full, global, end2end reachability truely became a myth ... and the term Internet became based on a shifting foundation. So from a commercial networking perspective, yes, my network is vestigal. But it is transit-free and has full connectivity to all of the parties it wants/needs to talk to. So by that definition (e.g. transit-free) its a Tier-1. Sort of points out some of the weaknesses in terminology and the biases in a single viewpoint. as usual, YMMV. --bill TTFN, patrick
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
er.. hate to rain on your parade but if I peer with everyone i need/want to exchange traffic with, i am transit-free, even if I -NEVER- touch any other part of the commercial Internet... my packets get to where they need to go and all packets I want get to me. my life is good ... even if I only appear as vestigal to the commercial Internet, if I appear at all. how would you classify such a network? billnet. we're used to it. randy
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Mon, Mar 28, 2005 at 06:47:30PM -0800, Randy Bush wrote: er.. hate to rain on your parade but if I peer with everyone i need/want to exchange traffic with, i am transit-free, even if I -NEVER- touch any other part of the commercial Internet... my packets get to where they need to go and all packets I want get to me. my life is good ... even if I only appear as vestigal to the commercial Internet, if I appear at all. how would you classify such a network? billnet. we're used to it. randy and you have even used it on occasion. :) --bill
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Tue, Mar 29, 2005 at 02:23:06AM +0100, Stephen J. Wilcox wrote: 701 is not the most connected, it has only customers and a restrictive set of peers? Ok, I'm just bored enough to bite. If we're talking about a contest to see who has the most number of directly connected ASNs, I think UU might still win, even with a restrictive set of peers. Taking a look at a count of customer ASNs behind some specific networks of note, I come up with the following (some data a couple weeks out of date, but the gist is the same): Network ASN Count --- - 701 2298 70181889 12391700 33561184 209 1086 174 736 3549584 3561566 2914532 2828427 6461301 1299243 Which begs the question, what is the largest number of ASNs that someone peers with? Patrick? :) Somehow I suspect that 701's customer base (702 and 703 aren't included in the above count BTW) overpower even the most aggressively open of peering policies, in this particular random pointless and arbitrary contest at any rate. -- Richard A Steenbergen [EMAIL PROTECTED] http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)
T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Mar 26, 2005, at 11:21 PM, Randy Bush wrote: forget this concept of tier1, 2, 3 .. they are little more than terms used by salesmen. at least t1 and t2, also permeate academic papers where the real topology is actually measured. but we should not let demonstrable measurements get in the way of our defense of the position of our smaller networks by marketing people. And how, pray tell, does one actually measure T1 vs. T2 networks? (Assuming you are not talking about two of the Terminator movies. ;-) If someone is paying Network A, but sends communities to be treated as a peer, are they T1 or T2? If someone buys from Network B, but peers with all of Network B's peers, and therefore does not appear in a path through Network B in those peers' BGP tables (except at the actual peering router), are they T1 or T2? If someone peers with Network C, but is out-of-balance and pays a settlement fee every month, are they T1 or T2? Assume someone else is out-of-balance with Network C, but in the other direction, does that make Network C a T2? Even if the network in question still pays Network C? Etc., etc., etc. There might be a way to define Tier 1 and Tier 2 sufficiently well as to disambiguate all the variations, but I do not think you could do it without seeing (NDA'ed) contracts and/or actual router configurations - neither of which are likely without the help of the network in question. And if you have their help, you can just ask. :-) Back on a more operational topic, it really doesn't matter what tier you are, it just matters how good your connectivity is. There is no need to 'defend' the 'smaller networks'. Some of the tier 1 networks have totally suck ass connectivity. (Yes, 'suck ass' is a technical term. =) -- TTFN, patrick
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
On Sun, 27 Mar 2005, Patrick W Gilmore wrote: On Mar 26, 2005, at 11:21 PM, Randy Bush wrote: forget this concept of tier1, 2, 3 .. they are little more than terms used by salesmen. at least t1 and t2, also permeate academic papers where the real topology is actually measured. but we should not let demonstrable measurements get in the way of our defense of the position of our smaller networks by marketing people. And how, pray tell, does one actually measure T1 vs. T2 networks? (Assuming you are not talking about two of the Terminator movies. ;-) i would agree it is possible to mark some networks as transit free - tier1 - and therefore any network using a tier1 to access another tier1 is tier2. arguably a tier3 would be a network not connected to a tier1. If someone is paying Network A, but sends communities to be treated as a peer, are they T1 or T2? imho: T1, forget the money other points snipped, i largely agree :) Back on a more operational topic, it really doesn't matter what tier you are, it just matters how good your connectivity is. There is no need to 'defend' the 'smaller networks'. Some of the tier 1 networks have totally suck ass connectivity. (Yes, 'suck ass' is a technical term. =) absolutely!! it amazes me how much value is placed in this 'tier' system, why not just buy connectivity that (a) is compatible with your size as an ISP (b) reliably delivers bits from A to B Steve
Re: T1 vs. T2 [WAS: Apology: [Tier-2 reachability and multihoming]]
here is what i answered a private message on the subject, with a typo corrected. [un]fortunately, i seem not to have saved the follow-on mess age where i suggested how one could get a good first cut at this from route-views data. randy --- From: Randy Bush [EMAIL PROTECTED] Date: Sat, 26 Mar 2005 22:17:03 -0800 To: a nanogian Subject: Re: Apology: [Re: Tier-2 reachability and multihoming] ...which I read to mean you believe there is a measurement or a demonstration (performance-wise or topology-wise) to support at least two classes of networks. I'm not arguing, but I am curious since you are indicating you believe its demonstrable. read, for example, the paper trail i cited earlier in this thread. What measures do you believe are most indicative of a better network? better? i did not say better. a simple way to look at it, which we have repeated here every year since com-priv migrated here is a tier-1 network does not get transit prefixes from any other network and peers with, among others, other tier-1 networks. a tier-2 gets transit of some form from another network, usually but not necessarily a tier-1, and may peer with other networks. this does not please everyone, especially folk who buy transit and don't like discussing it. and there are kinky corners (if i have the bad taste to tunnel through someone, that is not transit). but it does not make one network 'better' than another. for our biwa office (where my employer has no presence), the best network is one where i know the ceo, so can get something fixed if i need to panic and the csr does not cut it. randy
