squid限速

squid有个delay_pool，可以做限速，虽然效果不太准~（嗯，就像限制并发连接数的maxconn一样）
首先搬个老虎皮做大旗——《Squid: The DefinitiveGuide》的相关段落：
The buckets don't actually store bandwidth (e.g., 100 Kbit/s),but
rather some amount of traffic (e.g., 384 KB). Squid adds some
amount of traffic to the buckets each second. Cache clientstake
some amount of traffic out when they receive data from anupstream
source (origin server or neighbor).
The size of a bucket determines how much burst bandwidth is
available to a client. If a bucket starts out full, a clientcan
take as much traffic as it needs until the bucket becomesempty.
The client then receives traffic allotments at the fill rate.
The mapping between Squid clients and actual buckets is a bit
complicated. Squid uses three different constructs to doit: access
rules, delay pool classes, and types of buckets. First, Squid
checks a client request against the delay_access list. If the
request is a match, it points to a particular delay pool.Each
delay pool has a class: 1, 2, or 3. The classesdetermine which
types of buckets are in use. Squid has three types ofbuckets:
aggregate, individual, and network:
A class 1 pool has a single aggregate bucket.
A class 2 pool has an aggregate bucket and 256 individual
buckets.
A class 3 pool has an aggregate bucket, 256 network buckets,and
65,536 individual buckets.
As you can probably guess, the individual and network buckets
correspond to IP address octets. In a class 2 pool, theindividual
bucket is determined by the last octet of the client's IPv4
address. In a class 3 pool, the network bucket is determined bythe
third octet, and the individual bucket by the third andfourth
octets.
For the class 2 and 3 delay pools, you can disable bucketsyou
don't want to use. For example, you can define a class 2 poolwith
only individual buckets by disabling the aggregate bucket.
When a request goes through a pool with more than one buckettype,
it takes bandwidth from all buckets. For example, consider aclass
3 pool with aggregate, network, and individual buckets. Ifthe
individual bucket has 20 KB, the network bucket 30 KB, butthe
aggregate bucket only 2 KB, the client receives only a 2-KB
allotment. Even though some buckets have plenty of traffic,the
client is limited by the bucket with the smallest amount.
C.2 Configuring Squid
Before you can use delay pools, you must enable the featurewhen
compiling. Use the —enable-delay-pools option when running
./configure. You can then use the following directives to setup
the delay pools.
C.2.1 delay_pools
The delay_pools directive tells Squid how many pools you wantto
define. It should go before any other delaypool-configuration
directives in squid.conf. For example, if you want to havefive
delay pools:
delay_pools 5
The next two directives actually define each pool's class andother
characteristics.
C.2.2 delay_class
You must use this directive to define the class for each pool.For
example, if the first pool is class 3:
delay_class 1 3
Similarly, if the fourth pool is class 2:
delay_class 4 2
In theory, you should have one delay_class line for eachpool.
However, if you skip or omit a particular pool, Squid doesn't
complain.
C.2.3 delay_parameters
Finally, this is where you define the interesting delay pool
parameters. For each pool, you must tell Squid the fill rateand
maximum size for each type of bucket. The syntaxis:
delay_parameters N rate/size [rate/size [rate/size]]
The rate value is given in bytes per second, and size intotal
bytes. If you think of rate in terms of bits per second, youmust
remember to divide by 8.
Note that if you divide the size by the rate, you'll know howlong
it takes (number of seconds) the bucket to go from empty tofull
when there are no clients using it.
A class 1 pool has just one bucket and might look likethis:
delay_class 2 1
delay_parameters 2 2000/8000
For a class 2 pool, the first bucket is the aggregate, andthe
second is the group of individual buckets. Forexample:
delay_class 4 2
delay_parameters 4 7000/15000 3000/4000
Similarly, for a class 3 pool, the aggregate bucket is first,the
network buckets are second, and the individual buckets are
third:
delay_class 1 3
delay_parameters 1 7000/15000 3000/4000 1000/2000
C.2.4 delay_initial_bucket_level
This directive sets the initial level for all buckets whenSquid
first starts or is reconfigured. It also applies to individualand
network
buckets, which aren't created until first referenced. The valueis
a percentage. For example:
delay_initial_bucket_level 75%
In this case, each newly created bucket is initially filled to75%
of its maximum size.
C.2.5 delay_access
This list of access rules determines which requests gothrough
which delay pools. Requests that are allowed go through thedelay
pools, while those that are denied aren't delayed at all. Ifyou
don't have any delay_access rules, Squid doesn't delay any
requests.
The syntax for delay_access is similar to the other accessrule
lists (see Section 6.2), except that you must put a poolnumber
before the allow or deny keyword. Forexample:
delay_access 1 allow TheseUsers
delay_access 2 allow OtherUsers
Internally, Squid stores a separate access rule list for eachdelay
pool. If a request is allowed by a pool's rules, Squid usesthat
pool and stops searching. If a request is denied, however,Squid
continues examining the rules for remaining pools. In otherwords,
a deny rule causes Squid to stop searching the rules for asingle
pool but not for all pools.
C.2.6 cache_peer no-delay Option
The cache_peer directive has a no-delay option. If set, itmakes
Squid bypass the delay pools for any requests sent to that
neighbor.
然后说老实话：我也看不太懂……
只好贴一些百度出来的结果：
class类型1为单个IP地址流量
class类型2为C类网段中的每个IP地址流量
class类型3为B类网段中的每个C类网段中的每个IP地址流量
具体的说：
类型1只有一个总带宽流量实际也就是这个IP地址的流量
delay_parameters 1 64000/64000
类型2有两个带宽流量参数，第一个为整个C类型网段流量，第二个为每个IP流量
delay_parameters 1 -1/-1 64000/64000
类型3有三个带宽流量参数,第一个为整个B类网总流量，第二个为每个B类网段中的C类网段总流量,第三个为了B类网段中每个C类网段中的每个IP流量
delay_parameters 1 -1/-1 -1/-1 64000/64000
但似乎我还没百度到谁用class为2或者3的。一般大家都只用1……
举个例子：
两个域名，分别限制网民下载速度为50kb/s和100kb/s。配置如下：
#定义域名
acl LIMIT_A dstdomain a.test.com
acl LIMIT_B dstdomain b.test.com
#定义受限IP段
#acl LIMIT_IP src 192.168.1.0/24
#acl ALL src 0/0
#开启两个连接延迟池
delay_pools 2
#定义两个延迟池，class类型均为1
delay_class 1 1
delay_class 2 1
#分配域名到不同的延迟池
delay_access 1 allow LIMIT_A
delay_access 2 allow LIMIT_B
#受限网段延迟池
#delay_access 1 allow LIMIT_IP
#定义下载速率，速率定位为restore(bytes/sec)/max(bytes)，，restore是表示以bytes/sec的速度下載object到bucket裡，而max則表示buckets的bytes值
delay_parameters 1 50000/50000
delay_parameters 2 100000/100000
#squid启动时初始化的池的带宽百分比
delay_initial_bucket_level 100
据网友的测试，当限速配置为20000/20000即20000/1024=19.53kb/s的时候，实际的下载速度大概在11-15kb/s之间。