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 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
--- John Dupuy <jdupuy-list@socket.net> 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/
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 <jdupuy-list@socket.net> 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
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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 50000 routes for each of the biggest providers - level3, sprint, uunet, at&t) 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 <jdupuy-list@socket.net> 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/
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
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
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 <ras@e-gerbil.net> http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)
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, AT&T, Sprint, Level3, QWest.... If you can't say anything, I understand. John
jdupuy-list@socket.net writes:
Again, I'd be interested in hearing from one of the bigger ones on this: UUNet, AT&T, 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.
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 <ras@e-gerbil.net> http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)
-- James Jun TowardEX Technologies, Inc. Technical Lead Boston IPv4/IPv6 Web Hosting, Colocation and james@towardex.com Network design/consulting & configuration services cell: 1(978)-394-2867 web: http://www.towardex.com , noc: www.twdx.net
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 - bicknell@ufp.org - CCIE 3440 PGP keys at http://www.ufp.org/~bicknell/ Read TMBG List - tmbg-list-request@tmbg.org, www.tmbg.org
participants (10)
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David Barak -
Dorian Kim -
James -
jdupuy-list＠socket.net -
jmalcolm＠uraeus.com -
John Dupuy
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Leo Bicknell -
Patrick W Gilmore -
Richard A Steenbergen -
Stephen J. Wilcox