Understanding Squid delay pools with examples

This defines the parameters for a delay pool. Each delay pool has a number of “buckets” associated with it, as explained in the description of delay_class.

For a class 1 delay pool, the syntax is: delay_pools pool 1 delay_parameters pool aggregate

For a class 2 delay pool: delay_pools pool 2 delay_parameters pool aggregate individual

For a class 3 delay pool: delay_pools pool 3 delay_parameters pool aggregate network individual

For a class 4 delay pool: delay_pools pool 4 delay_parameters pool aggregate network individual user

For a class 5 delay pool: delay_pools pool 5 delay_parameters pool tagrate

The option variables are:

pool a pool number – ie, a number between 1 and the number specified in delay_pools as used in delay_class lines.

aggregate the speed limit parameters for the aggregate bucket (class 1, 2, 3).

individual the speed limit parameters for the individual buckets (class 2, 3).

network the speed limit parameters for the network buckets (class 3).

user the speed limit parameters for the user buckets (class 4).

tagrate the speed limit parameters for the tag buckets (class 5).

A pair of delay parameters is written restore/maximum, where restore is the number of bytes (not bits – modem and network speeds are usually quoted in bits) per second placed into the bucket, and maximum is the maximum number of bytes which can be in the bucket at any time.

There must be one delay_parameters line for each delay pool.

For example, if delay pool number 1 is a class 2 delay pool as in the above example, and is being used to strictly limit each host to 64Kbit/sec (plus overheads), with no overall limit, the line is:

delay_parameters 1 -1/-1 8000/8000

Note that 8 x 8000 KByte/sec -> 64Kbit/sec.

Note that the figure -1 is used to represent “unlimited”.

And, if delay pool number 2 is a class 3 delay pool as in the above example, and you want to limit it to a total of 256Kbit/sec (strict limit) with each 8-bit network permitted 64Kbit/sec (strict limit) and each individual host permitted 4800bit/sec with a bucket maximum size of 64Kbits to permit a decent web page to be downloaded at a decent speed (if the network is not being limited due to overuse) but slow down large downloads more significantly:

delay_parameters 2 32000/32000 8000/8000 600/8000

Note that 8 x 32000 KByte/sec -> 256Kbit/sec. 8 x 8000 KByte/sec -> 64Kbit/sec. 8 x 600 Byte/sec -> 4800bit/sec.

Finally, for a class 4 delay pool as in the example – each user will be limited to 128Kbits/sec no matter how many workstations they are logged into.:

delay_parameters 4 32000/32000 8000/8000 600/64000 16000/16000