You can not limit a single HTTP request’s connection speed. You can limit individual hosts to some bandwidth rate. To limit a group of hosts, then you must use a delay pool . For example:
acl only128kusers src 192.168.1.0/255.255.255.0
acl all src 0.0.0.0/0.0.0.0
delay_pools 1
delay_class 1 3
delay_access 1 allow only128kusers
delay_access 1 deny all
delay_parameters 1 64000/64000 -1/-1 16000/64000
For an explanation of these tags please see the configuration file.
The above gives a solution where a cache is given a total of 512kbits to operate in, and each IP address gets only 128kbits out of that pool.