Features of DeleGate

DeleGate is not merely a caching proxy server dedicated to HTTP protocol but a general purpose application protocol gateway for various protocols with many notable original features. Various users in various situations can use DeleGate to cope with their own requirement.

• UNBOUND PROXY: A user can select target servers arbitrarily in ad hoc way showing destination in user level data specific to the protocol of the client.
  • HTTP ( by protocol://host:port/ )
  • FTP ( by USER user@host:port )
  • POP ( by USER user@host:port )
  • Telnet ( by Host: host port )
  • Gopher ( by /-_-gopher://host:port/original-selector )
  • LDAP ( by directory-name@host:port )
  • Socks ( by SocksV4 protocol )

• BOUND PROXY: An administrator of DeleGate can specify which destination server is used depending on accessing client.
  • NNTP
  • SMTP
  • Wais
  • X Window
  • LPR (Line Printer Daemon Protocol)
  • CU-SeeMe
  • ICP
  • Tcprelay (which transparently relay arbitrary TCP based protocols)
  • Udprelay (which transparently relay arbitrary UDP based protocols)

• CACHE: A message data transferred on a protocol is cached in its inherent format and shared among DeleGate as gateway servers of different protocols.
  • HTTP (GET) with ICPv2
  • FTP (LIST and RETR)
  • NNTP (HELP, LIST, ARTICLE(reused for HEAD,BODY,XHDR,XOVER) )
  • Gopher

• CONNECTION SHARING: An established connection to a server in anonymous user can be reused and shared among multiple clients.
  • NNTP
  • FTP
  • POP (via POP/HTTP gateway)

• DATA CONVERSION: DeleGate has several built-in data conversion filters which can be applied to a specific part of data in a message on each protocol.
  • Japanese character codes (JIS,SJIS,EUC) conversion for text data
  • MIME encoding/decoding (NNTP,SMTP,POP)
  • MIME/PGP encoding, decoding and verification (NNTP,SMTP,POP)
  • use user developed conversion as External Filter or CFI

• PROTOCOL CONVERSION: A client of a protocol can talk with servers of other protocols via DeleGate.
  • HTTP client to FTP,NNTP,POP,WAIS,Gopher server
  • NNTP client to POP server
  • POP client to NNTP server
  • SMTP client to SMTP,NNTP server with filtering by content
  • FTP client to LPR server
  • DNS client to NIS server or local hosts file

• AUTHENTICATION / SECURE PROTOCOL CONVERSION: DeleGate can relay between a non-SSL client and a SSL server, or between a SSL-client and a non-SSL server.
  • SSLway -- SSL wrapper for arbitrary protocol
  • non-HTTPS client to HTTPS server, HTTPS client to non-HTTPS server
  • Tunneling for HTTPS/SSL (CONNECT/HTTP) between SSL-client and SSL-server
  • USER+PASS client to APOP server of POP protocol
  • conversion of PASV / PORT command for data connection of FTP protocol

• ACCESS CONTROL: Accesses to be permitted to pass DeleGate are described by a set of triples of destination protocol, destination server and source client.
  • protocol name and port numbers of servers
  • hostname or IP address of servers
  • hostname or IP address of clients
  • DNS cross checking of client's hostname to be used for authorization
  • username of clients (Ident protocol)
  • username / password (ex. HTTP Proxy-Authorization)
  • username on target servers (ex. anonymous ftp only)
  • validity of e-mail address (ex. FTP password)
  • read-only access (FTP and NNTP)
  • methods on application protocols (HTTP)

• LOGGING: Detailed logging of DeleGate actions and protocol dependent logging in standard formats.
  • HTTP: common logfile format of CERN httpd
  • FTP: xferlog format of wu-ftpd

• AUTOMATIC INVOCATION: DeleGate can be invoked automatically on demand or at the startup time of the host system.
  • as a service on Unix (invoked from inetd in wait or nowait)
  • as a service on WindowsNT (it registers itself as a service automatically)
  • parameters are loadable from remote resources at specified URLs
  • restarted by SIGHUP, reloading parameters on remote resources

• RESOLVER CONTROL: You can control the combination and sequence of multiple resolution mechanisms, independently of platforms.
  • DNS (UDP only, DNS outside of firewall can be used with UDP/SocksV5)
  • NIS
  • local file (in /etc/hosts format)
  • standard resolver on each platform (gethostbyname/gethostbyaddr)
  • cache (result of above resolvers can be cached for reuse)

• ROUTING CONTROL: A route toward the server can be selected from alternatives depending on protocol, server and client (host and user).
  • direct connection
  • via DeleGate
  • via HTTP proxy (HTTP, or any-protocol on SSL tunnel)
  • via Socks(V4,V5) server
  • via VSAP server

• MOUNTING SERVERS: Multiple target servers of multiple protocols can be merged into a single server of a protocol, with resource name filtering and aliasing.
  • HTTP client to HTTP,FTP,NNTP,POP,Gopher,WAIS servers
  • FTP client to FTP servers
  • NNTP client to NNTP,POP servers
  • POP client to POP,NNTP servers

• PROXY ON DEMAND: Automatically invoked proxy just for the current session.
  • X window proxy from Telnet proxy
  • X window proxy from HTTP proxy (display in POSTed form)

• ORIGIN SERVER: You can use DeleGate as simple origin servers for several protocols.
  • HTTP
  • FTP (read only)
  • NNTP
  • DNS

• EXTENSION BY USERS: You can attach your own graphic images, messages, and programs to DeleGate without modifiying the DeleGate program.
  • Builtin icons and messages can be replaced and customizable by mounting
  • External filter program can be inserted on the way of communication
  • CFI: Common Filter Interface

• TCP WRAPPER: You can use DeleGate like inetd + TCPwrapper which make your own filter program work as a server with access control.
  • usable by non-privileged users
  • runnable on any platform

• SCHEDULER: You can use DeleGate like crond which invokes specified commands at specified timing.
  • usable by non-privileged users
  • runnable on any platform

• MULTI-PLATFORM: DeleGate runs on multiple platforms and can be compiled from a common source program without any platform dependent configuration.
  • Unix (AIX, EWS4800, HP-UX, HI-UX, IRIX, NeXT, NEWS-OS, Digital-UNIX, Solaris, BSD/OS, FreeBSD, Linux, NetBSD, OpenBSD, etc.)
  • Windows (Win32: Windows95 and WindowsNT, BOW)
  • OS/2 (EMX)

• FREE AND OPEN:
  • usable without fee (see COPYRIGHT)
  • source program is available
  • open discussion on the mailing-list