I have couple of questions on Route Flaps at NAP's. 1)How often do they happen? (per hour, per day etc) 2)When route flaps occur, on an average how many routes are flapped? Any pointers indicating the above statistics will be helpful. Thanks, -Ramesh
Hi Ramesh! Check out: http://www.merit.edu/ipma/ and more specifically, http://www.merit.edu/ipma/realtime I believe that these pages will have some of the information that you are looking for. Let me know if you have any questions. -abha ;) On Wed, 17 Sep 1997, Ramesh Kalathur wrote:
I have couple of questions on Route Flaps at NAP's. 1)How often do they happen? (per hour, per day etc) 2)When route flaps occur, on an average how many routes are flapped?
Any pointers indicating the above statistics will be helpful. Thanks, -Ramesh
__________________________________________________________________________ -------------------------------------------------------------------------- abha ahuja ahuja@merit.edu Merit Network, Inc. 313.764.0294
It's my sincere hope that this code actually takes into account actual transitions in a network prefix, as opposed to just counting the number of updates received that contain said prefix. If that's not the case, the statistics gathered would be quite misleading. Paul
It's my sincere hope that this code actually takes into account actual transitions in a network prefix, as opposed to just counting the number of updates received that contain said prefix.
If that's not the case, the statistics gathered would be quite misleading.
Paul
Er Paul, How is one to tell the "actual transitions" if not by counting updates? -- --bill
From: bmanning@ISI.EDU (Bill Manning) Subject: Re: Route Flaps at NAP's How is one to tell the "actual transitions" if not by counting updates? Let me turn that back on you, Bill, how is counting updates relevant to the question being asked: "What magnitude of routing instability is there at a particular place and time?" Flap is mis-used as short-hand for a transition, but in fact you want to measure transitions, of which flaps are the most common. What's a transition: 1) a prefix was advertised, now it's withdrawn 2) a prefix wasn't advertised, now it is 3) an attribute of the prefix has changed (next hop, as path, community, etc.) (1) and (2) combined are the most common events, we call them flaps. All 3 events actually contribute to routing infrastructure stability, as all 3 typically cause messages to propogate through the network. In order to answer: "What's the routing stability at (put in your favorite pint in the network)?" you actually want to count (read this twice) the number of transitions that each prefix advertised from a neighbor has made during your sample period. Say I need to withdraw 10 prefixes I am advertising to you. I can send you 1 update message with 10 prefixes in it, or I can send you 10 updates with one prefix in it. No difference in routing stability, the change should be measured the same way either way. Say I send you an update withdrawing 10 prefixes, but the withdrawal is a no-op because you don't have them installed, possibly due to a previous withdrawal. The update is a no-op and does not affect routing stability, nor does it cause a message that needs to be propagated past the receiving router. I hope this makes it clearer why I think counting the messages themselves is not particularly relevant. It should be easy to instrument the more useful number in your RS code: Increment a counter every time a rt_entry's info is actually changed. Heck, the Merit guys shouldn't even need to change their cute little Java app's (which by the way don't work under Netscape 4.0.2b8 under FreeBSD...so much for Java uber alles), just report the right number: "the sum of the transitions of all prefixes from a neighbor since the start of the sample period"
Ramesh, Merit has done studies on this in the past. Their data is on at http://www.merit.edu/ipma/reports/ That said, why are route flaps important? In the past, its been said that certain length prefixes were the cause of lots of routing instability on the Internet, and much effort was spent on developing elaborate dampening algorithms and policy efforts were spent on determining how to set the parameters on such a system. As it turns out, these aren't important ... prefixes flap pretty much independent of length. And while dampening will help prevent lots of up/down cyclic behavior and resulting churn, the whole issue, I think, got a lot more intellectual curiosity that it deserved, not to dissuade you ;) Other than it being something that one can count, I'm not sure why route flaps, in general, are interesting. -scott At 11:38 AM 9/17/97 -0400, Ramesh Kalathur wrote:
I have couple of questions on Route Flaps at NAP's. 1)How often do they happen? (per hour, per day etc) 2)When route flaps occur, on an average how many routes are flapped?
Any pointers indicating the above statistics will be helpful. Thanks, -Ramesh
On Wed, 17 Sep 1997, Ramesh Kalathur wrote: |} I have couple of questions on Route Flaps at NAP's. |} 1)How often do they happen? (per hour, per day etc) |} 2)When route flaps occur, on an average how many routes are flapped? Check out: http://www.merit.edu/~ipma/instability/ Merit has done a good job putting together a collection of tools to analyze stuff on the network using the RS's or otherwise. http://www.merit.edu/~ipma/routing_table/ Might also prove interesting to look at routing table growth, routes being exchanged, etc. -jh-
### On Wed, 17 Sep 1997 09:30:26 -0700 (PDT), Jonathan Heiliger ### <loco@isi.net> wrote to Ramesh Kalathur <ramesh@cs.ucf.edu> concerning ### "Re: Route Flaps at NAP's": JH> Might also prove interesting to look at routing table growth, routes being JH> exchanged, etc. Routing exchange both in policy and in realtime through the RSes can be viewed at: http://www.rsng.net/rs-views -- /*===================[ Jake Khuon <khuon@Merit.Net> ]======================+ | Systems Research Programmer, IE Group /| /|[~|)|~|~ N E T W O R K | | VOX: (313) 763-4907 FAX: (313) 747-3185 / |/ |[_|\| | Incorporated | +==[ Suite C2122, Bldg. 1 4251 Plymouth Rd. Ann Arbor, MI 48105-2785 ]==*/
participants (7)
-
Abha Ahuja -
bmanning＠ISI.EDU -
Jake Khuon -
Jonathan Heiliger -
Paul Traina -
ramesh＠cs.ucf.edu -
Scott Huddle