1. Introduction

1.1 About

OpenH323 Gatekeeper - The GNU Gatekeeper is an open-source project that implements an H.323 gatekeeper. A gatekeeper provides call control services to the H.323 endpoints. It is an integral part of most usefull internet telephony installations that are based on the H.323 standard.

According to Recommendation H.323, a gatekeeper shall provide the following services:

• Address Translation
• Admissions Control
• Bandwidth Control
• Zone Management
• Call Control Signaling
• Call Authorization
• Bandwidth Management
• Call Management

The GNU Gatekeeper implements most of these functions based on the OpenH323 protocol stack.

Recommendation H.323 is an international standard published by the ITU. It is a communications standard for audio, video, and data over the Internet. See also Paul Jones' A Primer on the H.323 Series Standard.

For a detailed description of what a gatekeeper does, see here.

1.2 Copyright

It is covered by the GNU General Public License (GNU GPL). In addition to that, we explicitely grant the right to link this code to the OpenH323 and OpenSSL library.

Generally speaking, the GNU GPL allows you to copy, distribute, resell or modify the softwares, but it requires that all derived works must be published under GNU GPL also. That means that you must publish full source for all extensions to the gatekeeper and for all programs you include the gatekeeper into. See the file COPYING for details.

If that's not what you want, you must interface to the gatekeeper through the status port and communicate via TCP with it. That way you only have to integrate the basic funtionality into the gatekeeper (and provide source for that) and can keep other parts of your application private.

1.3 Name

The formal name of this project is OpenH323 Gatekeeper - The GNU Gatekeeper, short GnuGk. Please don't confuse it with other gatekeeper projects.

There are several open-source gatekeeper projects based on the OpenH323 protocol stack.

• OpenGatekeeper

  A gatekeeper available under MPL. The project has been inactive for a period of time now.

• OpenGK

  Only in a very primary grades.

• OpenH323 Gatekeeper - The GNU Gatekeeper

  This one, also called GnuGk.

To have different gatekeepers with very similar names is really confusing for most users. Since our "OpenH323 Gatekeeper" was the first on the scene, it is not our fault that others have chosen similar names. But to make the destinction a little more clear without confusing people even more, we have decided to give the project a subtitle "OpenH323 Gatekeeper - The GNU Gatekeeper" and start using gnugk as name for executables.

1.4 Features

The version 2.2.3 contains the following new features and bugfixes:

• New [RewriteCLI] options to control CLIR features precisely.
• New CLIR/CLIP (Calling Line Identification Restriction/Presentation) features in the [RewriteCLI] module. Ability to hide CLI (enable CLIR/CLIP) per endpoint.
• New [RoutedMode] SocketCleanupTimeout config variable. More reliable socket management and better network error reporting.
• The RewriteCLI module rewrites outbound rules correctly for random numbers separated by commans.
• Broadcast request are handled correctly in the LARGE_FDSET mode.
• New ENUM routing policy from Simon Horne.
• NetMeeting compatibility problems fixed.
• A new [RasSrv::RRQFeatures] IRQPollCount config variable. Default number of "poll" IRQ messages changed from 2 to 1 to allow faster endpoint unregistration.
• Tunnelled H.245 messages were not processed correctly (were ignored).
• [FileIPAuth] module moved from the contrib section into the main branch.

The version 2.2.2 contains the following new features and bugfixes:

• New CLI rewrite types - prefix replacement (*=) and identity match ( =).
• A new TranslateFacility config variable to enable Facility message conversion between H.323v4 and previous versions of the protocol.
• SignalTimeout, AlertingTimeout and %t, %p, %{ring-time}, %{alerting-time} accounting variables ported from 2.0 branch. ConnectTimeout config variable replaced with SignalTimeout and AlertingTimeout.
• A new %r accounting variable to provide infomation about who was the one that disconnected a call.
• A new, generic SQLAuth module for RRQ, ARQ, LRQ and Setup authentication and authorization.
• New --core command line argument to enable core dump generation for Unix.
• A new Vendor config variable for [Endpoint] section to provide vendor specific extensions when registering with a parent gatekeeper.
• LRQ nonStandardData field was not included for CiscoGK neighbors.
• New [RewriteCLI] config section that allows arbitrary rewritting of ANI/CLI numbers.
• New numberanalysis routing policy.
• New FileIPAuth module in the contrib/ipauth directory.
• Call accounting updates/call disconnect handling is now more robust and does not lock the whole call table and (effectively) the gatekeeper for long time periods.
• Do not support mutiple rewrite targets, as this feature does not work well if rewrite is performed more than once.
• The gatekeeper could crash if the connection was closed before the welcome message has been sent to the client.
• Different Username was reported during Setup auth and acct step, if no sourceAddress has been present for an unregistered call.
• More missing config reload locks added to allow seamless config reload.
• A default value for the config variable ForwardOnFacility changed to 0.
• Ability to encrypt all passwords in the config. A new EncryptAllPasswords config variable, KeyFilled config variable usage extended.
• Ability to read config settings from an SQL database ported from 2.0 branch. Read [SQLConfig] for more details.
• Framed-IP-Address could not be determined for unregistered calls with no Setup-UUIE.sourceCallSignalAddress field, causing authentication to fail.
• Provide proper handling of aliases of type partyNumber (e164Number or privateNumber).
• A fix for RTP/Q931/H245/T120PortRange to correct a bug with port range wraparound if the last port is 65535. This caused a next port to be set to 0 and any subsequent port allocation to fail.
• Dynamic allocation of RTP ports did not work, use a fixed port range 1024-65535 as a default for the RTPPortRange config variable.
• Obsolete auth modules MySQLAliasAuth and MySQLPasswordAuth are now removed.
• SQL modules accept only one database host in the Host parameter.

The version 2.2.1 contains the following new features and bugfixes:

• Enchanced prefix matching for routing policies. A dot (.) matches any digit.
• Enchanced prefix matching for neighbors. A dot (.) matches any digit, ! at the beginning disables the prefix.
• A missing lock during config reload caused the gatekeeper to crash.
• More reliable port number selection for Q.931, H.245, T.120 and RTP port ranges (earlier, a config reload could cause many calls to fail because of unability to allocate a new socket).
• Default value for RTPPortRange is now to let the OS select a port number.
• More flexible rewrite rules (both global and per-gw) with new '.' and '%' wildcard characters.
• Enchanced prefix matching for gateways. A dot (.) matches any digit, ! at the beginning disables the prefix.
• Insert missing Calling-Party-Number-IE/Display-IE if corresponing Screen... options are enabled.
• Shutdown the gatekeeper if there are errors in SQL auth/acct modules configuration.
• Called-Station-Id number type can be selected between the original one (dialed number) and the rewritten one. New UseDialedNumber config option for RadAuth/ RadAliasAuth / RadAcct modules, new %{Dialed-Number} variable for SQLAcct and FileAcct modules.
• Ability to customize timestamp formats. New TimestampFormat config variables for main, [SqlAcct], [RadAcct], [FileAcct] and [CallTable] sections.
• RadAuth/RadAliasAuth modules can now add/remove endpoint aliases during endpoint registration (using h323-ivr-in=terminal-alias: Cisco AV-Pair).
• New TcpKeepAlive option to solve the problem with network errors and calls hanging in the call table. See docs/keepalive.txt for more details.
• New status port RouteToGateway command.

The version 2.2.0 contains the following new features and bugfixes:

• New RoundRobinGateways config option.
• Call capacity limits and priority routing for gateways. New EP:: config sections for per-endpoint configuration settings (see Per-Endpoint Configuration Settings).
• RTP proxy handling moved to a separate RTP proxy threads, so processing of signaling messages does not block RTP packets. New RtpHandlerNumber config option.
• REUSE_ADDRESS option enabled on listening sockets in non-LARGE_FDSET mode to fix a bug with the gatekeeper being unable to open listening ports after restart.
• Ability to set call destination in auth modules. RADIUS based call routing.
• Support for SqlBill tariff table import from an OpenOffice.org Calc spreadsheet.
• Fixed sourceInfo LRQ field handling - now it contains an H.323 identifier of the gatekeeper. Nonstandard data and gatekeeperIdentifier fields are set only when the neighbor is defined as GnuGk.
• Ability to set shared secrets for each radius server separatelly.
• New, much faster, Radius client implementation.
• Called-Party-Number-IE rewrite occured too late, causing auth/acct modules to receive the original number instead of the rewritten one.
• Fixed proxying of RTP packets, so RTP sockets are not closed on temporary errors (like remote socket not yet ready). This bug affected especially NAT traversal and situation, when audio was sent very early, when reverse proxy path has not been yet established.
• Fixed handling of RRJ from an alternate GnuGk.
• New direct SQL accounting module ( [SQLAcct]).
• Handling multiple reply messages (RIP/LCF/LRJ) from neighbors fixed.
• Support for CallCreditServiceControl in RCF and ACF messages, which allows reporting call duration limit and user's account balance to endpoints. Currently RadAuth and RadAliasAuth modules support this feature.
• Log file rotation, new LogFile config section, new setlog and rotatelog status interface commands.
• Do not include an invalid access token (with null object identifier) in LCF to prevent interoperability problems.
• Better handling of multiple calls over a single signalling channel by setting multipleCalls and maintainConnection H.225.0 fields to FALSE in all messages passing through the gatekeeper.
• Better User-Name, Calling-Station-Id and Called-Station-Id handling.
• IncludeEndpointIP flag for RadAuth, RadAliasAuth and RadAcct is obsolete, these modules will always send Framed-IP-Address.
• New Gatekeeper::Auth flag SetupUnreg to toggle Q.931 Setup authentication for unregistered endpoints only.
• New RADIUS h323-ivr-out=h323-call-id parameter that contains an H.323 Call Identifier.
• The SQL billing from the contrib section can now authenticate users only by their IP (ignoring User-Name) and has a new, more flexible tariff/rating engine.
• RadAliasAuth can authenticate now Setup messages without sourceAddress field present (it will use Calling-Party-Number instead).
• Better signal handling to prevent accidental gatekeeper crashes (due to SIGPIPE, for example).
• CDR rotation per number of lines works correctly.

Of course, the major functions in version 2.0 are also included:

• The registration table and call record table are redesigned, thread-safe, and very efficient. Support ten thousands of registrations and thousands of concurrent calls.
• A new routed mode architecture that support H.225.0/Q.931 routed and H.245 routed without forking additional threads. Thus the thread number limit will not restrict the number of concurrent calls.
• Support H.323 proxy by routing all logical channels, including RTP/RTCP media channels and T.120 data channels. Logical channels opened by H.245 tunnelling and fast-connect procedure are also supported. In proxy mode, there is no traffic between the calling and called parties directly. Thus it is very useful if you have some endpoints using private IP behind an NAT box and some endpoints using public IP outside the box.
• Support gatekeepers cluster by exchanging LRQ/LCF/LRJ (neighboring function). If the destination of a received LRQ is unknown, the GnuGk can forward it to next hop. Therefore the GnuGk can work as a directory gatekeeper.
• Support various authentication methods for selectable RAS requests, including H.235 password (MD5, SHA-1 and CAT), IP pattern and prefixes matching.
• Support alternate gatekeepers for redundancy and load balancing. If the GnuGk is overloaded, the endpoints can be redirected to other gatekeepers.
• Can work as an endpoint (gateway or terminal) by resigtering with a parent gatekeeper. With this feature, building gatekeeper hierarchies is easily.
• Monitor and control the GnuGk via TCP status port, including registration and call statistics.
• Output CDR(call detail record) to status port for backend billing system. The CDR contains call identifier, calling and called IP, start and end time and call duration.
• Most configurations are changeable at runtime. The GnuGk rereads the configurations on receiving reload command via status port, or on receiving HUP signal (Unix platform).

1.5 Download

The newest stable and a development version are available at the download page.

The very latest source code is in the CVS at Sourceforge ( Web-GUI). Beware - that's the bleeding edge.

You can also download some executables from the download page.

1.6 Mailing Lists

There are two mailing list for the project, one for the developers and one for the users.

General user questions should be send to the users mailing list. You can find the list archive here. To join this mailing list, click here.

To report problems or submit bugs/patches, send mails to the developers mailing list. The list archive is here. Please send user questions to the users mailinglist and keep this list to development! If you want to contribute to the project, please join the mailing list.

Note: Please don't send your questions as private emails to individual developer. We are usually busy. We would not like to be your private consultant, unless you'd like to pay us. Send your problems to the appropriate public mailing list so everybody can help you.

Also please don't send the GnuGk specific problems to the OpenH323 mailing list, or vice versa. They are different projects, though closely related.

Before you sending an email, make sure you have read the related documents carefully. Describe your problems clearly and precisely. Show us the error messages or logs if there is any.

1.7 Contributors

The current project coordinator is Jan Willamowius <jan@willamowius.de>

The main features and functions of version 2.0 are contributed by Chih-Wei Huang <cwhuang@linux.org.tw> and Citron Network Inc., including thread-safe registration and call tables, new routed mode architecture, H.323 proxy, H.235 authentication and MySQL backend.

Michal Zygmuntowicz <m.zygmuntowicz@onet.pl> has done some great work on Radius support and other improvements.

The initial version of the gatekeeper has been developed by Xiang Ping Chen, Joe Metzger and Rajat Todi.