Squid – caching proxy for the Web

Squid is a high-performance proxy caching server and web cache daemon. It supports FTP, gopher and HTTP data objects.

Squid has a wide variety of uses, from speeding up a web server by caching repeated requests, caching web, DNS and other computer network lookups for a group of people sharing network resources; to aiding security by filtering traffic.

Squid consists of a main server program squid, a Domain Name System lookup program dnsserver, some optional programs for rewriting requests and performing authentication, together with some management and client tools.

Squid offers a rich access control, authorization and logging environment to develop web proxy and content serving applications.

Features include:

  • Web proxy:
    • Caching to reduce access time and bandwidth use.
    • Keeps meta data and especially hot objects cached in RAM.
    • Caches DNS lookups.
    • Supports non-blocking DNS lookups.
    • Implements negative checking of failed requests.
  • Squid caches can be arranged in a hierarchy or mesh for additional bandwidth savings.
  • Enforce site-usage policies with extensive access controls.
  • Anonymize connections, such as disabling or changing specific header fields in a client’s HTTP request.
  • Reverse proxy.
  • Media-range limitations.
  • Supports SSL.
  • Support for IPv6.
  • Error Page Localization – error pages presented by Squid may now be localized per-request to match the visitors local preferred language.
  • Connection Pinning (for NTLM Auth Passthrough) – a workaround which permits Web servers to use Microsoft NTLM Authentication instead of HTTP standard authentication through a web proxy.
  • Quality of Service (QoS) Flow support:
    • Select a TOS/Diffserv value to mark local hits.
    • Select a TOS/Diffserv value to mark peer hits.
    • Selectively mark only sibling or parent requests.
    • Allows any HTTP response towards clients to have the TOS value of the response coming from the remote server preserved.
    • Mask certain bits in the TOS received from the remote server, before copying the value to the TOS send towards clients.
  • SSL Bump (for HTTPS Filtering and Adaptation) – Squid-in-the-middle decryption and encryption of CONNECT tunneled SSL traffic, using configurable client- and server-side certificates.
  • eCAP Adaptation Module support.
  • ICAP Bypass and Retry enhancements – ICAP is now extended with full bypass and dynamic chain routing to handle multiple adaptation services.
  • ICY streaming protocol support – commonly known as SHOUTcast multimedia streams.
  • Dynamic SSL Certificate Generation.
  • Support for the Internet Content Adaptation Protocol (ICAP).
  • Full request logging.

Support: FAQ
Developer: National Laboratory for Applied Networking Research (NLANR) and Internet volunteers
License: GNU General Public License v2.0

Squid is written in C++. Learn C++ with our recommended free books and free tutorials.

Return to Web Caches | Return to Optimize Web Delivery

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