Re: Apology: [Re: Tier-2 reachability and multihoming]
So anyway, this internet thing.. forget this concept of tier1, 2, 3 .. they are little more than terms used by salesmen. instead assume all ISPs have connectivity to the whole internet, and that you're a new ISP wanting connectivity of your own. you can buy transit from any ISP and you will get global reachability, you could also buy from any two hence multihoming and have the same global reachability now you're up and running, consider peering.. peering with another isp will give you access to that isp and their customers (ie other isps buying global reachability as you are doing) so as per your original query, if any two nodes/asns dont have a direct connection you can assume one or both is relying on their upstream to provide the necessary global connectivity now, i see your data is from oregon.. i think theres around 50 'views' of the internet from about 25 ASNs. consider there are about 2 active ASNs currently. you would need to get all 2 routing tables in order to see exactly what relationships are active. (the reason is that from any single ASN the internet will appear to you as a tree much like your original email, showing the 'up-down' relationships but not the 'left-right' ones) also, in the context that you use 'multihoming' you're really referring to a leaf node such as an enterprise which may buy from 2 or 3 isps to have global connectivity with some redundancy. if you are looking at transit ISPs (ie tier1, 2 in your description) their connectivity is more complicated and you need to continue your reading with some of the suggested papers.. Steve On Sat, 26 Mar 2005, G Pavan Kumar wrote: This is with my deepest regrets that I apologize from the bottom of my heart to Mr.Gilmore, Mr.Woodcock, Mr.Bush and also the rest of the honourable members of the list for being ignorant of how high-profile a list this is. I couldn't be more sorry. Please, please forgive me. ps: I sure meant no harm, was just trying to be humorous,(I hope the exclamation marks might have given some hint) anyway it is too late. They say there is no natural punishment than remorse. Also, I was too embarrassed to post a quick apology. Thanking you, pavan.
Re: Apology: [Re: Tier-2 reachability and multihoming]
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. randy
Re: Tier-2 reachability and multihoming
On Fri, Mar 25, 2005 at 12:41:37PM +0530, G Pavan Kumar wrote: Okie, this has gone on long enough. If you would like some help, please stop, take a deep breath, count to ten slowly, then ask nicely and some people here might teach you something. May be you should spend more time on networking than your partime job of yoga teaching! Woody's sarcasm might have annoyed you, but your repeated flames (and not even good ones!) at the people you asked to help you annoy all of us. well guess who wouldnt think that if not being helped a minuscule amount, why not be part of the fun! If you do not want any help, you are welcome to continue in your misunderstanding of how the Internet works. I am sorry, am I not ingratiating myself with the good graces of the father of Internet?! plonk Cheers, -- jr 'someone had to do it' a -- Jay R. Ashworth[EMAIL PROTECTED] Designer Baylink RFC 2100 Ashworth AssociatesThe Things I Think'87 e24 St Petersburg FL USA http://baylink.pitas.com +1 727 647 1274 If you can read this... thank a system adminstrator. Or two. --me
Re: Tier-2 reachability and multihoming
i suspect that, rather than being a sociologist trying to catorgize operators on the surliness scale, at which you seem to have succeeded splendidly, you may be tring to understand AS relationships. you may find a useful paper trail that kinda goes from http://citeseer.ist.psu.edu/rd/22812611%2C453493%2C1%2C0.25%2CDownload/http%3AqSqqSqwww-unix.ecs.umass.eduqSq%7ElgaoqSqton.ps to the more current and more intuitively believable http://citeseer.ist.psu.edu/rd/59669334%2C702627%2C1%2C0.25%2CDownload/http%3AqSqqSqwww.ieee-infocom.orgqSq2004qSqPapersqSq34_2.PDF randy
Re: Tier-2 reachability and multihoming
On Fri, 25 Mar 2005 12:41:37 +0530 (IST), G Pavan Kumar [EMAIL PROTECTED] wrote: May be you should spend more time on networking than your partime job of yoga teaching! Pavan, what you seem to know of networking is not just outdated, its plain wrong. And you've just managed to flame some of the people who understand it well enough to be the among the best teachers of bgp, routing and DNS that I know of - and I've seen them teach at many a netops conference. And some others who have enable on huge, worldwide networks that you'd kill to get an interview call from, let alone a you're hired email. I know that passing the JEE exam to get into an IIT means that you do have more brains than the average engineering student - so try to apply them for a change. Follow that first, original suggestion of googling for partial mesh, peering, etc. Then download some of Philip Smith's elementary bgp tutorials - google will find those for you too. Finally, google for the names of the people who have replied to you in this thread. Till then, do yourself a favor. Go right back to lurking on nanog I am sorry, am I not ingratiating myself with the good graces of the father of Internet?! No. All you are doing is pissing off the people who have been giving you the right answers. If what they tell you means you have to tear up a whole paper thats based on wrong assumptions, and start from scratch, tough. It'll save you the hassle of seeing your prof fling it right back at your face with an F scrawled on it when you turn it in. -- Suresh Ramasubramanian ([EMAIL PROTECTED])
Re: Tier-2 reachability and multihoming
On Fri, 25 Mar 2005 21:15:25 +0530, Suresh Ramasubramanian [EMAIL PROTECTED] wrote: And some others who have enable on huge, worldwide networks that you'd kill to get an interview call from, let alone a you're hired email. speaking of hiring .. you'd better pray that your brief foray into nanog goes unnoticed by people who will be interviewing you for a job that lets you anywhere near a $90 linksys box let alone cisco or juniper kit :)
Re: Tier-2 reachability and multihoming
On Fri, Mar 25, 2005 at 07:43:22AM -0800, Randy Bush wrote: i suspect that, rather than being a sociologist trying to catorgize operators on the surliness scale, at which you seem to have succeeded splendidly, you may be tring to understand AS relationships. you may find a useful paper trail that kinda goes from http://citeseer.ist.psu.edu/rd/22812611%2C453493%2C1%2C0.25%2CDownload/http%3AqSqqSqwww-unix.ecs.umass.eduqSq%7ElgaoqSqton.ps to the more current and more intuitively believable http://citeseer.ist.psu.edu/rd/59669334%2C702627%2C1%2C0.25%2CDownload/http%3AqSqqSqwww.ieee-infocom.orgqSq2004qSqPapersqSq34_2.PDF randy thank you randy. and for the more energetic, who can tell me all the BGP relationships w/ AS 4555? (existing peers and operators of AS 4555 are not allowed to play :) --bill
Apology: [Re: Tier-2 reachability and multihoming]
This is with my deepest regrets that I apologize from the bottom of my heart to Mr.Gilmore, Mr.Woodcock, Mr.Bush and also the rest of the honourable members of the list for being ignorant of how high-profile a list this is. I couldn't be more sorry. Please, please forgive me. ps: I sure meant no harm, was just trying to be humorous,(I hope the exclamation marks might have given some hint) anyway it is too late. They say there is no natural punishment than remorse. Also, I was too embarrassed to post a quick apology. Thanking you, pavan.
Re: Apology: [Re: Tier-2 reachability and multihoming]
--On Saturday, March 26, 2005 11:51 AM +0530 G Pavan Kumar [EMAIL PROTECTED] wrote: This is with my deepest regrets that I apologize from the bottom of my heart to Mr.Gilmore, Mr.Woodcock, Mr.Bush and also the rest of the honourable members of the list for being ignorant of how high-profile a list this is. I couldn't be more sorry. Please, please forgive me. ps: I sure meant no harm, was just trying to be humorous,(I hope the exclamation marks might have given some hint) anyway it is too late. They say there is no natural punishment than remorse. Also, I was too embarrassed to post a quick apology. No exclamation points indicate yelling, animated, surliness, or a host of other emotions, humor is NOT one of them. If you intent was to joke or in jest then don't use !. use ;) or :) esp. since your second language is pretty clearly english where what you're typing, and what we're reading/getting can be hard to interpret. Thanking you, pavan. -- Undocumented Features quote of the moment... It's not the one bullet with your name on it that you have to worry about; it's the twenty thousand-odd rounds labeled `occupant.' --Murphy's Laws of Combat
Re: Tier-2 reachability and multihoming
G Pavan Kumar wrote: I have been working on characterizing the internet hierarchy. I noticed that 27% of the total possible tier-2 provider node pairs are unreachable i.e., they dont have any tier-1 node connecting them nor a direct peering link between them. Multihoming can be used as a predominant reason for the reachability of tier-3 nodes which are customers of these nodes, but what about the reachability of tier-2 nodes themselves and its customers which cannot afford to multihoming? How does BGP solve this reachability problem when it gets a request to a prefix unreachable? 1tier-1 / 2 4 tier-2 / \/ \ 5 6 7 8 tier-3 here, nodes 2 and 4 have no reachability, 1 / | 2 3 4 / \ \/ \ 5 6 7 8 now, node 7 is reachable from 2 and its lower level nodes, but what about node 4 and 8, and as a typical case, suppose nodes 4 and 8 have no multihoming whatsoever, what then? I suspect there are many cases (ok, I know from experience, but couldn't tell you off the top of my head which ones) of networks that can't reach other networks, but it's probably a tiny fraction of a percent, not the 27% you came up with. It looks like the flaws in your methodology are to assume a far more rigid hierarchy than is actually there, and to ignore peering. If we assume the strict tiered hierarchy that you show in this example: 1tier-1 / 2 4 tier-2 / \/ \ 5 6 7 8 tier-3 It's unlikely that network 4 would lack a transit provider. Network 4 might not be buying transit from the same tier 1 as network 2, but they would be buying from a different tier 1, who would peer with network 1. It would look something like this: 1--9 tier-1 | | 2 4 tier-2 / \/ \ 5 6 7 8 tier-3 These do show up in the route-views data. To see some networks that are reachable from one tier 1 through another tier 1, you can use the command show ip bgp regex ^2914_701$. In the real world, the tier structure isn't nearly as clearly defined. There are also lots of interconnections (peering) in places other than the top of the hierarchy, to the point where it isn't quite clear what the hierarchy is. So, taking the above example, it could also look something like this: 1--9 tier-1 | | | 4 | / \ 27 __8 / \/ 5 6--- In this case, 2 has gotten tired of paying 1 to reach 7, and 7 has gotten tired of paying 9 and 4 to reach 2, so they've peered directly. A lot of these arrangements won't show up in route-views, since the routes learned from peers are generally only announced to customers, not to upstreams or other peers. So, if route-views had a feed from 2, 5, or 7, but not from 6 or 8, route-views would see the adjacency between 2 and 7, but not the adjacency between 6 and 8. To answer your question about what BGP does when it doesn't find any reachability data for a network, it declares the network to be unreachable and drops the packets. In the real world, you generally see this only when somebody is trying to send data to a network that doesn't exist, or when something is broken. We've got some different routing data at http://lg.pch.net/, which shows what some networks are announcing to their peers, which might be useful to you. However, our data doesn't tell you anything about our peers other peering or transit relationships, and there are a lot of networks we don't have peering data from (and it assumes they announce the same set of routes to all peers, which is a bad assumption in some cases). I don't know if that's useful to you or not. If this and the other replies you've gotten don't make sense, and you've still got a pair of networks you think don't talk to eachother, I'd be happy to look at the specific case and explain what's happening there. -Steve
Re: Tier-2 reachability and multihoming
On Thu, 24 Mar 2005, G Pavan Kumar wrote: Actually, I am not doing what you think I am. I am using the RouteViews aggregation of the BGP routing tables. RouteViews is a project at the univ. of Oregon that peers with backbones. Really? Could you tell us more about it? I thought there was just one Internet backbone. I am looking at almost full and fresh data. So what value do you assign to almost full? There's a difference between best and complete, which you may not be entirely appreciating. -Bill
Re: Tier-2 reachability and multihoming
On Thu, Mar 24, 2005 at 12:18:34PM -0800, Bill Woodcock wrote: On Thu, 24 Mar 2005, G Pavan Kumar wrote: Actually, I am not doing what you think I am. I am using the RouteViews aggregation of the BGP routing tables. RouteViews is a project at the univ. of Oregon that peers with backbones. Really? Could you tell us more about it? I thought there was just one Internet backbone. Bill... Stop it!!! shooting fish in a barrel is no sport at all. I am looking at almost full and fresh data. So what value do you assign to almost full? There's a difference between best and complete, which you may not be entirely appreciating. -Bill almost full == just after dessert and as you (and almost every one else on this list) know, there is zero chance of complete ... and best is always in the eye/routing-table of the beholder. --bill
Re: Tier-2 reachability and multihoming
On Thu, 24 Mar 2005, Bill Woodcock wrote: On Thu, 24 Mar 2005, G Pavan Kumar wrote: Actually, I am not doing what you think I am. I am using the RouteViews aggregation of the BGP routing tables. RouteViews is a project at the univ. of Oregon that peers with backbones. Really? Could you tell us more about it? I thought there was just one Internet backbone. Would you excuse me if I didnt predict that you couldnt improvize and make out of the context? I am looking at almost full and fresh data. So what value do you assign to almost full? There's a difference between best and complete, which you may not be entirely appreciating. -Bill
Re: Tier-2 reachability and multihoming
On Mar 25, 2005, at 12:25 AM, G Pavan Kumar wrote: On Thu, 24 Mar 2005, Bill Woodcock wrote: On Thu, 24 Mar 2005, G Pavan Kumar wrote: Actually, I am not doing what you think I am. I am using the RouteViews aggregation of the BGP routing tables. RouteViews is a project at the univ. of Oregon that peers with backbones. Really? Could you tell us more about it? I thought there was just one Internet backbone. Would you excuse me if I didnt predict that you couldnt improvize and make out of the context? Okie, this has gone on long enough. If you would like some help, please stop, take a deep breath, count to ten slowly, then ask nicely and some people here might teach you something. Woody's sarcasm might have annoyed you, but your repeated flames (and not even good ones!) at the people you asked to help you annoy all of us. If you do not want any help, you are welcome to continue in your misunderstanding of how the Internet works. -- TTFN, patrick
Re: Tier-2 reachability and multihoming
On Fri, 25 Mar 2005 [EMAIL PROTECTED] wrote: On Thu, Mar 24, 2005 at 12:18:34PM -0800, Bill Woodcock wrote: On Thu, 24 Mar 2005, G Pavan Kumar wrote: Actually, I am not doing what you think I am. I am using the RouteViews aggregation of the BGP routing tables. RouteViews is a project at the univ. of Oregon that peers with backbones. Really? Could you tell us more about it? I thought there was just one Internet backbone. Bill... Stop it!!! shooting fish in a barrel is no sport at all. You think I am a fish in a barrel? Well, guess what, I didnt think it through while entering your mouth that you're dumb enough to prefer it rather in a barrel!! I am looking at almost full and fresh data. So what value do you assign to almost full? There's a difference between best and complete, which you may not be entirely appreciating. -Bill almost full == just after dessert and as you (and almost every one else on this list) know, there is zero chance of complete ... and best is always in the eye/routing-table of the beholder. --bill
Re: Tier-2 reachability and multihoming
On Fri, 25 Mar 2005, Patrick W Gilmore wrote: Okie, this has gone on long enough. If you would like some help, please stop, take a deep breath, count to ten slowly, then ask nicely and some people here might teach you something. May be you should spend more time on networking than your partime job of yoga teaching! Woody's sarcasm might have annoyed you, but your repeated flames (and not even good ones!) at the people you asked to help you annoy all of us. well guess who wouldnt think that if not being helped a minuscule amount, why not be part of the fun! If you do not want any help, you are welcome to continue in your misunderstanding of how the Internet works. I am sorry, am I not ingratiating myself with the good graces of the father of Internet?!
Re: Tier-2 reachability and multihoming
I have been working on characterizing the internet hierarchy. I noticed that 27% of the total possible tier-2 provider node pairs are not connected i.e., they dont have any tier-1 node connecting them nor a direct peering link between them. It's quite simple. The Internet is not a tree hierachy; it is a partial mesh. Partial meshes can often be characterised as having some sort of hierarchy of connectedness, however the Internet does change continuously which means that an analysis of hierarchy done today will come up with different results from last year's analysis. The terminology of tier 1 and tier 2 only refers to a brief time in the evolution of the Internet in North America during the 1990s when the topology was much more treelike. That is all changed. Go to google and search the following line exactly as written. internet topology partial mesh --Michael Dillon
Re: Tier-2 reachability and multihoming
[cisco-nsp-request@ snipped, since it does not seem to belong] Le 23 mars 2005, à 23:15, G Pavan Kumar a écrit : here, nodes 2 and 4 have no reachability, 1 / | 2 3 4 / \ \/ \ 5 6 7 8 now, node 7 is reachable from 2 and its lower level nodes, but what about node 4 and 8, and as a typical case, suppose nodes 4 and 8 have no multihoming whatsoever, what then? If the verticial position on the page indicates some kind of hierarchy (e.g. 2 and 3 are transit customers of 1, 7 is a transit customer of 3 and 4) then 4 has transit customers but no peering or transit. I would suggest this is not indicative of a realistic business plan in the real network. Joe
Re: Tier-2 reachability and multihoming
--On Wednesday, March 23, 2005 4:54 PM +0530 G Pavan Kumar [EMAIL PROTECTED] wrote: Hi there, I have been working on characterizing the internet hierarchy. I noticed that 27% of the total possible tier-2 provider node pairs are not connected i.e., they dont have any tier-1 node connecting them nor a direct peering link between them. Multihoming can be used as a predominant reason for the reachability of tier-3 nodes which are customers of these nodes, but what about the reachability of tier-2 nodes themselves and its customers which cannot afford to multihoming? How does BGP solve this reachability problem when it gets a request to a prefix unreachable? I think that likely you're looking at partial data (well i am sure you are, since i'm part of the internet and you didn't' get routing data from me...) and not seeing paths because of that. The BGP tables of a single node list all outward paths to other places. Thus from a single sample point it is totally impossible to 'map' the internet. Not to mention the *constant* change in routing.
Re: Tier-2 reachability and multihoming
On Wed, 23 Mar 2005, Michael Loftis wrote: I think that likely you're looking at partial data (well i am sure you are, since i'm part of the internet and you didn't' get routing data from me...) Duh ! and not seeing paths because of that. The BGP tables of a single node list all outward paths to other places. Thus from a single sample point it is totally impossible to 'map' the internet. Not to mention the *constant* change in routing. Actually, I am not doing what you think I am. I am using the RouteViews aggregation of the BGP routing tables. RouteViews is a project at the univ. of Oregon that peers with backbones and other ASes at interesting locations so as to make it as comprehensive as possible. Also, it updates the data every 2 hours of everyday. So, I am looking at almost full and fresh data :
Re: Tier-2 reachability and multihoming
i don't thing an operator or seasoned researcher would characterize route-views or ripe ris as almost full data. they provide such a small and narrow peek as to require great caution when dealing with them. considering the topologies you suggest, folk may legitimately wonder if perhaps you have not exercised sufficient caution. randy
Re: Tier-2 reachability and multihoming
On Mar 24, 2005, at 12:06 AM, G Pavan Kumar wrote: On Wed, 23 Mar 2005, Michael Loftis wrote: I think that likely you're looking at partial data (well i am sure you are, since i'm part of the internet and you didn't' get routing data from me...) Duh ! Not nice to make fun of people who are trying to help you. and not seeing paths because of that. The BGP tables of a single node list all outward paths to other places. Thus from a single sample point it is totally impossible to 'map' the internet. Not to mention the *constant* change in routing. Actually, I am not doing what you think I am. I am using the RouteViews aggregation of the BGP routing tables. RouteViews is a project at the univ. of Oregon that peers with backbones and other ASes at interesting locations so as to make it as comprehensive as possible. Also, it updates the data every 2 hours of everyday. So, I am looking at almost full and fresh data : Unfortunately, the paragraph above shows me that there are errors in your base assumptions about how the Internet works. A couple of people have tried to point this out to you, you should listen instead of telling them why they are wrong. It is bad to base conclusions on incorrect assumptions. It is even worse to assume those of whom you ask for help know less than you do about the topic at hand. I am very sorry that you spent a lot of time probably doing good work digging through the route-views archives but have seem to come to false conclusions. It can be difficult to admit hard work has come to a bad end. However, it might not have been a waste. You seem to have the motivation, time, and energy to research the topic, perhaps your research can be quickly applied to different data, or in a different way? Might I suggest a Google search for past research on Internet topology? I believe the University of Oregon has done some. :) And CAIDA. And many others. Many are still doing research and happy to collaborate. Good luck in your research. -- TTFN, patrick
