Traffic per Prefix Length
does anyone collect stats that would facilitate the derivation of the number of packets forwarded per prefix length (per unit time) in the routing table or per prefix length range? percentages would work too.
On Thu, May 03, 2001 at 07:09:24PM -0600, Paul G. Donner wrote:
does anyone collect stats that would facilitate the derivation of the number of packets forwarded per prefix length (per unit time) in the routing table or per prefix length range? percentages would work too.
Interesting ... Do you think that this will give you any useful information? I would be more interested in how far packets go. Not in networks terms but in real distance. Next would be to go further up the stack and see if there is a difference in protocols (i.e www compared to dns). -- Arnold
There are many interesting pieces of data and there is plenty of data in the Internet to collect. ;-) might show how much work routers have to do in particular areas of the table (which, granted, varies from location to location) when doing longest-prefix match. what areas of the table are hit more than others. "sh ip cef traffic prefix" At 01:55 AM 5/4/2001 +0200, Arnold Nipper wrote:
On Thu, May 03, 2001 at 07:09:24PM -0600, Paul G. Donner wrote:
does anyone collect stats that would facilitate the derivation of the number of packets forwarded per prefix length (per unit time) in the routing table or per prefix length range? percentages would work too.
Interesting ... Do you think that this will give you any useful information? I would be more interested in how far packets go. Not in networks terms but in real distance. Next would be to go further up the stack and see if there is a difference in protocols (i.e www compared to dns).
-- Arnold
Interesting ... Do you think that this will give you any useful information? I would be more interested in how far packets go. Not in networks terms but in real distance. Next would be to go further up the stack and see if there is a difference in protocols (i.e www compared to dns).
-- Arnold
Actually, I had some interest in this same information. One thing I was thinking about is some routers that don't have the memory to hold a full BGP table. They need a default route for traffic to blocks not in their tables, but it would be interesting to work out an optimized filter to decide which routes to send them. One theory is to send them the routes to the largest blocks in the hopes that these will tend to get you the most packets for the routing table byte. DS
> does anyone collect stats that would facilitate the derivation of > the number of packets forwarded per prefix length (per unit time) > in the routing table or per prefix length range? Anybody who's doing both Netflow and BGP table dumps can do that. Of course, the corellation between the two isn't perfect, since you may have prefix-length changes between snapshots. -Bill
"bw" == Bill Woodcock <woody@zocalo.net> writes: does anyone collect stats that would facilitate the derivation of the number of packets forwarded per prefix length (per unit time) in the routing table or per prefix length range?
Anybody who's doing both Netflow and BGP table dumps can do that. Of course, the corellation between the two isn't perfect, since you may have prefix-length changes between snapshots.
Another possibility would be to use one of the bucket-based accounting mechanisms (BGP Policy Accounting on Cisco and Riverstone, Destination Class Usage on Juniper): * define a route-map which maps announcements with different prefix lengths into different buckets * have the interfaces count traffic towards prefixes in each bucket automagically. The current Cisco implementation only has 8 buckets, which is a bit low because there are more than 8 prefix lengths in the real world. Juniper has 16 buckets which looks much better, and Riverstone has 25 which would cover even the absurd cases. Randy: You could also use this mechanism to count traffic that would potentially be affected by various kinds of route filters (by assigning a bucket instead of actually dropping the announcements). Some pointers to these features can be found on http://www.switch.ch/misc/leinen/snmp/monitoring/bucket-accounting.html -- Simon.
participants (5)
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Arnold Nipper -
Bill Woodcock -
David Schwartz -
Paul G. Donner -
Simon Leinen