From: my-ccie-test@libero.it
Date: Sat Dec 17 2005 - 14:06:03 GMT-3
Hi all,
I have a doubt about the use of multiple rate-limit for a single interface.
at the url
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cg/hqos_c/part20/qchpolsh.htm
the doc cd says:
Cascading of rate policies allows a series of rate limits to be applied to packets to specify more granular policies (for example, you could rate limit total traffic on an access link to a specified subrate bandwidth and then rate limit World Wide Web traffic on the same link to a given proportion of the subrate limit) or to match packets against an ordered sequence of policies until an applicable rate limit is encountered (for example, rate limiting several MAC addresses with different bandwidth allocations at an exchange point). You can configure up to a 100 rate policies on a subinterface.
my doubt is on the words:
you could rate limit total traffic on an access link to a specified subrate bandwidth and then rate limit World Wide Web traffic on the same link to a given proportion of the subrate limit
suppose you want to limit dns traffic to a rate of 5k/s of a total rate assigned to udp traffic of 100K/s.
you will configure a rate-limit for dns traffic and a second rate-limit for generic udp traffic, the udp dns packet will match the first sentence of rate-limit and it will be transmit according with the configured rule, a generic udp packet will not match the first rate-limit configured,so it will go to the second rate-limit and it will be transmitted or dropped according to the configured rate-limit.
I think the total amount of traffic permitted on this link will be 5K/s for dns traffic and 100K/s for generic udp traffic, for a total of 105K/s of traffic permitted and not a total of 100K/s,so the udp traffic will not be a proportion of the entire udp traffic.
infact generic udp packet not matching the first rate-limit will be limited to 100K/s while dns packet will be limited to 5K/s for a total of available bandwith of 105 K/s because the dns packet will never match both the first and the second rate-limit, resulting in two different portions of bandwith dedicated for dns packets and udp packets.
Wath is the right configuration for subrate limit bandwith?
TIA
Max
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