[nsp] Rate - limiting

[Bruce Robertson]

> Rate limiting at lower speeds severelt impacts TCP performance, a single 
> TCP session hitting a rate limit will start, hit the ratelimit, lose 
> several packets, pretty much go into slow-start, go logarithmically up 
> again to the rate limit, hit the hard ceiling and then go into slow-start 
> again, cutting the used bandwidth to approx 40% of the ratelimit.

This behavior is avoided if you use random-detect along with rate limiting.
Here's an example that works perfectly at limiting a user to 500 Kb/s:


interface FastEthernet0/0
 no ip address
 random-detect 

interface FastEthernet0/0.22
 encapsulation isl 22
 ip address x.x.x.x y.y.y.y
 ip verify unicast reverse-path
 no ip redirects
 no ip proxy-arp
 rate-limit input 496000 93750 187500 conform-action transmit exceed-action drop
 rate-limit output 496000 93750 187500 conform-action transmit exceed-action drop


--
Bruce Robertson, President/CEO				     +1-775-348-7299
Great Basin Internet Services, Inc.			fax: +1-775-348-9412
http://www.greatbasin.net