on 3/15/09 4:53 PM, Robert Hajime Lanning said: > So? And how many people work in that environment? Yes, it is there, > and a lot of people use the system. But, it is invisible to the users.
How many people use the root nameservers? That's the size of the potentially affected community. Even a tiny fraction of one percent of the daily traffic could easily be millions or billions of queries, and the potentially affected user community could easily number in the thousands, tens of thousands, hundreds of thousands, or millions. > Usually when you do use anycast, it is on-top of a standard > NAT/next-hop/proxy based cluster. (And to be clear, I said "Usually" > not "Every".) I'm sure that is your experience in this area. However, others may well have other experience regarding the nature or frequency of the implementation of the technique. When you and they both collapse the mental tag down to just "anycast", you're throwing away a great deal of information that could clearly demonstrate that your situation completely different from theirs. I can tell you that there are at least three or four different root nameserver operators who all say that they use anycast as part of their mechanism for distributing the load, but I can also tell you that each of those groups use a different implementation method. When they talk to each other, they know enough about the situation to ask the other side to remind them of their implementation details (if they've forgotten), so that they can more accurately share notes. This is a technique that is complex enough, and can be implemented in enough different ways, that you need to be more specific when you discuss the use of this method with respect to certain types of protocols -- especially protocols that use UDP because it's much lighter in weight, but where a great deal of state information is maintained over very long periods of time using complex statistical methods, despite the fact that no particular given packet may be delivered reliably. > No, but if someone wants to do it, I would say "go ahead, but here are > the caveats..." It might work enough for there needs. So what are the caveats? Do you know all of them? Have you shared any of that information with anyone when discussing this subject? Joe Abley is a very talented network engineer, and my recollection is that he has been one of the most experienced persons at ISC with regards to their use of anycast for f.root-servers.net. However, this expertise does not actually translate to use with NTP, regardless of whatever you think he says in his article "Fear and Loathing in the Routing System" published in the February 2008 issue of _;login:_ magazine, which you can read at <http://www.usenix.org/publications/login/2008-02/openpdfs/abley.pdf>. In fact, it was his article with all of its serious mistakes, that lead me to write my article for _;login:_ magazine. I don't know nearly so much about anycast, but I do know more about NTP, and I know enough about anycast to have a pretty good idea of some of the serious risks with regards to NTP. > Ok, so what is the purpose of the LOPSA "Tech" mailing list? Since it > seems that all Tech topics have their own lists. <sarcasm>I guess we > should disband this list. And, everyone should go a subscribe to the > 150 lists pertaining to all the topics of interest.</sarcasm> There are plenty of areas where lots of people have wide and useful experience with a given program or protocol, and most any of those areas should be perfectly suitable for discussion on this list. However, NTP is an area where it seems like ~99% of the people who talk about it understand precisely zero of how it actually works and how it should be architected, and they tend to have a lot of myths that they continue to propagate about it to everyone they talk to. Part of why I'm here is to stop these myths from being re-propagated yet once again, and to redirect people to a resource where there is a wide collection of knowledgeable individuals who are happy to share their experience with others, and where they are relatively likely to share the correct information in the correct way. > These topics are not outside the list's stated topic. Just because > there is a "better" place to discuss a specific topic, does not make > this an inappropriate place to also discuss it. It is inappropriate > when it becomes off-topic for the list. It's not just a matter of whether it's on-topic or not. It's also a matter of whether the information to be given is likely to be correct, and whether people casually toss around concepts like NTP via anycast, without properly covering the caveats. Note that this is not the multicast or manycast techniques, this is the use of plain anycast. -- Brad Knowles <[email protected]> If you like Jazz/R&B guitar, check out LinkedIn Profile: my friend bigsbytracks on YouTube at <http://tinyurl.com/y8kpxu> http://preview.tinyurl.com/bigsbytracks _______________________________________________ Tech mailing list [email protected] http://lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
