Squid Proxy Configuration

Description
This tag is used to specify the other caches in the hierarchy. The cache_peer option is split into five fields. The first field is the hostname or IP of the cache that is to be queried. The second field indicates the type of relationship. The third field sets the HTTP port of the destination server, while the fourth sets the ICP (UDP) query port. The fifth field can contain zero or more keywords. Here are the detailed explanations on each field. See cache_peer_access also.

Hostname
Hostname (FQDN) or IP address of the cache to be queried should be mentioned.

For ex,

cache_peer sib1.squidconfiguration.com sibling 3128 3130 [proxy-only]
cache_peer 172.16.1.100 sibling 3128 3130 [proxy-only]

Type
Here cache hierarchy should be specified. This option plays an important role in deciding neighbor selection.

• parent
• sibling
• multicast

Http_port
The port number where the cache listens for proxy requests. See also http_port

Icp_port
Used for querying neighbor caches about objects. To have a non-ICP neighbor specify ’7′ for the ICP port and make sure the neighbor machine has the UDP echo port enabled in its /etc/inetd.conf file. See also icp_port

OPTIONS:

proxy-only
To specify that objects fetched from this cache should not be saved locally.

Weight=n
To specify a weighted parent. The weight must be an integer. The default weight is 1, larger weights are favoured more.

ttl=n
To specify a IP multicast Time To Live (ttl) value when sending ICP queries to multicast groups. We do not accept ICP replies from random hosts. So you must configure other group members as peers with the multicast-responder option below.

no-query
This option is set for those peers, which do not support ICP queries. It is obvious to have doubt about the ICP port specified in, while using this option. Squid does not care what digit has been given in the ICP port when no-query is specified. Using any number is fine. It is recommended to use 0 to emphasis the fact that ICP is not used in any way (not even to UDP echo port 7).

This might be the typical example for this option :

cache_peer hostname sibling 8080 0 proxy-only no-query

By default, Port 3130 is typically where an ICP-aware proxy listens for ICP packets. Port 7 is the “echo” port (see /etc/services). It is typically handled by inetd as an internal process and simply “echoes” back what has been sent it. Since option “no-query” specified, port “7″ is there so that if peer is queried, Squid gets an answer and not declares peer as dead and therefore stop using it.

Port 7 is used when Squid has a non-ICP peer but still want to query it before sending requests there (no-query not specified). In such case, Squid will send the ICP queries to port 7 which is the UDP echo port.

default
If this is a parent cache which can be used as a “last-resort.” and not ICP enabled then “default” would be the appropriate option. Simply adding default to a parent does not force all requests to be sent to that parent. The term default is perhaps a poor choice of words. If the cache is able to make direct connections, direct will be preferred over default. If needed to force all requests to parent cache(s), use the never_direct option.

round-robin
To define a set of parents which should be used in a round-robin fashion in the absence of any ICP queries.

multicast-responder
Indicates that the named peer is a member of a multicast group. ICP queries will not be sent directly to the peer, but ICP replies will be accepted from it.

closest-only
Indicates that, for ICP_OP_MISS replies, we’ll only forward CLOSEST_PARENT_MISSes and never FIRST_PARENT_MISSes.

no-digest
To NOT request cache digests from this neighbor.

no-netdb-exchange
It disables requesting ICMP RTT database (NetDB) from the neighbor.

no-delay
To prevent access to this neighbor from influencing the delay pools.

login=user:password
If this is a personal/workgroup proxy and your parent requires proxy authentication.

connect-timeout=nn
To specify a peer specific connect timeout (also see the peer_connect_timeout directive).

digest-url=url
To tell Squid to fetch the cache digest (if digests are enabled) for this host from the specified URL rather than the Squid default location.

No cache peer is defined

Example
cache_peer proxy.squidconfiguration.com parent 3128 3130 default

cache_peer 172.16.1.100 sibling 3128 3130 proxy-only

cache_peer 172.16.1.123 sibling 3129 5500 weight=2

Caution
If you compiled Squid to support HTCP, your cache will automatically attempt to connect to TCP port 4827 (there is currently no option to change this port value). Cache digests are transferred via the HTTP port specified on the cache_peer line. Non-ICP neighbors must be specified as ‘parent’.