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 20000 active ASNs currently. you would need to get all 20000 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.