From: Michael Snyder (msnyder@xxxxxxx)
Date: Sun Aug 11 2002 - 15:23:48 GMT-3
Part of the thread I started was if could you use GTS "Traffic-shape
group" vs. "rate-limit output access-group" to police these
requirements? Which I believe we answered as we could do so.
If you substitute the traffic-shape group where you have rate-limit
output access-group, keeping the same access lists and bit values, I
believe it will also work.
In other words, going by it's parameters, the GTS command, seems to be
the grandfather of the rate-limit command.
I have a question about your bit values.
You have:
Bit Rate = x
Burst Size = 3x/16 ; 1.5/8=3/16=.1875
Maximum Burst Size = 3x/8 ; 2(1.5/8)=3/8=.375
Where Burst size is 1.5 times bit rate over 8 and Maximum Burst Size is
twice that value. I understand that 8 comes from the timer interval.
Here's my question. Why (3/16)x for the burst and (3/8)x for the max
burst?
Doesn't that undermine the limiting you are trying to do?
Is it the convention to use 3/16's and 3/8's? If so I'll start using
3/16's and 3/8's, they are easily to remember.
Personally, if I was trying to limit a bit rate, I would use:
Bit rate = x
Burst Size= x/8 (time interval)
Max Burst = 0 (no extra bits on my watch)
Could someone enlighten me, if we are trying to limit something, why
would we inflate the burst and max burst sizes?
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Glenn Johnson
Sent: Sunday, August 11, 2002 11:44 AM
To: ccielab@groupstudy.com
Subject: RE: QOS Question from Routopia LAB 3
Quoting original problem --
; Configure the serial interface on R6 so that Ping
; traffic can only
; utilize 10% of available bandwidth. Allow BGP to
; utilize no more
; than 20% of available bandwidth. Allow all other
; traffic to utilize up
; to 70% of available link capacity.
I'm _far_ from a QoS expert, but wouldn't three separate rate-limit
statements work? (you could add three more if 'input' control was an
issue as well -- something you can't do with CBWFQ, which seems limited
to output control [at least on my equip])
Assuming a 256k link for purposes of calc.
10% is 25600
20% is 51200
70% is 179200
The burst values below were calculated using the target limit/8 and then
multiplying by 1.5, and finally multiplying that number by 2.
Originally entered as:
(Conf-if)
101 25600 4800 9600 conform-action
transmit exceed-action drop
rate-limit output access-group 102 51200 9600 19200 conform-action
transmit exceed-action drop
rate-limit output access-group 103 179200 33600 67200 conform-action
transmit exceed-action drop
Then from sh run int fa0/0 (things get rounded)
Interface FastEthernet0/0
ip address 10.1.1.1 255.255.255.0
rate-limit output access-group 101 24000 4800 9600 conform-action
transmit exceed-action drop
rate-limit output access-group 102 48000 9600 19200 conform-action
transmit exceed-action drop
rate-limit output access-group 103 176000 33600 67200 conform-action
transmit exceed-action drop
access-list 101 permit icmp any any
access-list 102 permit tcp any any eq bgp
Access-list 103 permit ip any any
(following some intense icmp traffic)
Router#sh int fa0/0 rate-limit
FastEthernet0/0
Output
matches: access-group 101
params: 24000 bps, 4800 limit, 9600 extended limit
conformed 31 packets, 27334 bytes; action: transmit
exceeded 3 packets, 4542 bytes; action: drop
last packet: 14692ms ago, current burst: 6068 bytes
last cleared 00:01:10 ago, conformed 3000 bps, exceeded 0 bps
matches: access-group 102
params: 48000 bps, 9600 limit, 19200 extended limit
conformed 0 packets, 0 bytes; action: transmit
exceeded 0 packets, 0 bytes; action: drop
last packet: 3233872ms ago, current burst: 0 bytes
last cleared 00:01:10 ago, conformed 0 bps, exceeded 0 bps
matches: access-group 103
params: 176000 bps, 33600 limit, 67200 extended limit
conformed 0 packets, 0 bytes; action: transmit
exceeded 0 packets, 0 bytes; action: drop
last packet: 3233876ms ago, current burst: 0 bytes
last cleared 00:01:10 ago, conformed 0 bps, exceeded 0 bps
This seems to work. My question is should we go back and adjust the
burst values based on the IOS rounding of our initial numbers?
Thanks
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