GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc4123

Network Working Group H. Schulzrinne Request for Comments: 4123 Columbia University Category: Informational C. Agboh

                                                             July 2005
 Session Initiation Protocol (SIP)-H.323 Interworking Requirements

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2005).

IESG Note

 This RFC is not a candidate for any level of Internet Standard.  The
 IETF disclaims any knowledge of the fitness of this RFC for any
 purpose, and in particular notes that the decision to publish is not
 based on IETF review for such things as security, congestion control,
 or inappropriate interaction with deployed protocols.  The RFC Editor
 has chosen to publish this document at its discretion.  Readers of
 this document should exercise caution in evaluating its value for
 implementation and deployment.  See [RFC3932] for more information.

Abstract

 This document describes the requirements for the logical entity known
 as the Session Initiation Protocol (SIP)-H.323 Interworking Function
 (SIP-H.323 IWF) that will allow the interworking between SIP and
 H.323.

Schulzrinne & Agboh Informational [Page 1] RFC 4123 SIP-H.323 Req. July 2005

Table of Contents

 1. Introduction ....................................................3
 2. Definitions .....................................................3
 3. Functionality within the SIP-H.323 IWF ..........................4
 4. Pre-Call Requirements ...........................................4
    4.1. Registration with H.323 Gatekeeper .........................5
    4.2. Registration with SIP Server ...............................5
 5. General Interworking Requirements ...............................5
    5.1. Basic Call Requirements ....................................5
         5.1.1. General Requirements ................................5
         5.1.2. Address Resolution ..................................6
         5.1.3. Call with H.323 Gatekeeper ..........................6
         5.1.4. Call with SIP Registrar .............................6
         5.1.5. Capability Negotiation ..............................6
         5.1.6. Opening of Logical Channels .........................7
    5.2. IWF H.323 Features .........................................7
    5.3. Overlapped Sending .........................................7
         5.3.1. DTMF Support ........................................7
 6. Transport .......................................................8
 7. Mapping between SIP and H.323 ...................................8
    7.1. General Requirements .......................................8
    7.2. H.225.0 and SIP Call Signaling .............................8
    7.3. Call Sequence ..............................................9
    7.4. State Machine Requirements .................................9
 8. Security Considerations ........................................10
 9. Examples and Scenarios .........................................10
    9.1. Introduction ..............................................10
    9.2. IWF Configurations ........................................11
    9.3. Call Flows ................................................11
         9.3.1. Call from H.323 Terminal to SIP UA .................11
         9.3.2. Call from SIP UA to H.323 Terminal .................12
 10. Acknowledgments ...............................................12
 11. Contributors ..................................................13
 12. References ....................................................14
     12.1. Normative References ....................................14
     12.2. Informative References ..................................15

Schulzrinne & Agboh Informational [Page 2] RFC 4123 SIP-H.323 Req. July 2005

1. Introduction

 The SIP-H.323 Interworking function (IWF) converts between SIP
 (Session Initiation Protocol) [RFC3261] and the ITU Recommendation
 H.323 protocol [H.323].  This document describes requirements for
 this protocol conversion.

2. Definitions

 H.323 gatekeeper (GK): An H.323 gatekeeper is an optional component
    in an H.323 network.  If it is present, it performs address
    translation, bandwidth control, admission control, and zone
    management.
 H.323 network: In this document, we refer to the collection of all
    H.323-speaking components as the H.323 network.
 SIP network: In this document, we refer to the collection of all SIP
    servers and user agents as the SIP network.
 Interworking Function (IWF): This function performs interworking
    between H.323 and SIP.  It belongs to both the H.323 and SIP
    networks.
 SIP server: A SIP server can be a SIP proxy, redirect server, or
    registrar server.
 Endpoint: An endpoint can call and be called.  An endpoint is an
    entity from which the media such as voice, video, or fax
    originates or terminates.  An endpoint can be H.323 terminal,
    H.323 Gateway, H.323 MCU [H.323], or SIP user agent (UA)
    [RFC3261].
 Media-Switching Fabric (MSF): This is an optional logical entity
    within the IWF.  The MSF switches media such as voice, video, or
    fax from one network association to another.

Schulzrinne & Agboh Informational [Page 3] RFC 4123 SIP-H.323 Req. July 2005

3. Functionality within the SIP-H.323 IWF

 This section summarizes the functional requirements of the SIP-H.323
 interworking function (IWF).
 A SIP-H.323 IWF may be integrated into an H.323 gatekeeper or SIP
 server.  Interworking should not require any optional components in
 either the SIP or H.323 network, such as H.323 gatekeepers.  IWF
 redundancy in the network is beyond the scope of this document.
 An IWF contains functions from the following list, inter alia:
 o  Mapping of the call setup and teardown sequences;
 o  Registering H.323 and SIP endpoints with SIP registrars and H.323
    gatekeepers;
 o  Resolving H.323 and SIP addresses;
 o  Maintaining the H.323 and SIP state machines;
 o  Negotiating terminal capabilities;
 o  Opening and closing media channels;
 o  Mapping media-coding algorithms for H.323 and SIP networks;
 o  Reserving and releasing call-related resources;
 o  Processing of mid-call signaling messages;
 o  Handling of services and features.
 The IWF should not process media.  We assume that the same media
 transport protocols, such as RTP, are used in both the SIP and H.323
 networks.  Thus, media packets are exchanged directly between the
 endpoints.  If a particular service requires the IWF to handle media,
 we assume that the IWF simply forwards media packets without
 modification from one network to the other, using a media-switching
 fabric (MSF).  The conversion of media from one encoding or format to
 another is out of scope for SIP-H.323 protocol translation.

4. Pre-Call Requirements

 The IWF function may use a translation table to resolve the H.323 and
 SIP addresses to IP addresses.  This translation table can be updated
 by using an H.323 gatekeeper, a SIP proxy server, or a locally-
 maintained database.

Schulzrinne & Agboh Informational [Page 4] RFC 4123 SIP-H.323 Req. July 2005

4.1. Registration with H.323 Gatekeeper

 An IWF may provide and update the H.323 gatekeeper with the addresses
 of SIP UAs.  A SIP user agent can make itself known to the H.323
 network by registering with an IWF serving as a registrar.  The IWF
 creates an H.323 alias address and registers this alias, together
 with its own network address, with the appropriate GK.
 The gatekeeper can then use this information to route calls to SIP
 UAs via the IWF, without being aware that the endpoint is not a
 "native" H.323 endpoint.
 The IWF can register SIP UAs with one or more H.323 gatekeepers.

4.2. Registration with SIP Server

 The IWF can provide information about H.323 endpoints to a SIP
 registrar.  This allows the SIP proxy using this SIP registrar to
 direct calls to the H.323 endpoints via the IWF.
 The IWF can easily obtain information about H.323 endpoints if it
 also serves as a gatekeeper.  Other architectures require further
 study.
 If the H.323 endpoints are known through E.164 (telephone number)
 addresses, the IWF can use IGREP [TGREP] or SLP [GWLOC] to inform the
 SIP proxy server of these endpoints.
 The IWF only needs to register with multiple SIP registrars if the
 H.323 terminal is to appear under multiple, different addresses-of-
 record.

5. General Interworking Requirements

 The IWF should use H.323 Version 2 or later and SIP according to RFC
 3261 [RFC3261].  The protocol translation function must not require
 modifications or additions to either H.323 or SIP.  However, it may
 not be possible to support certain features of each protocol across
 the IWF.

5.1. Basic Call Requirements

5.1.1. General Requirements

 The IWF should provide default settings for translation parameters.
 The IWF specification must identify these defaults.

Schulzrinne & Agboh Informational [Page 5] RFC 4123 SIP-H.323 Req. July 2005

 The IWF must release any call-related resource at the end of a call.
 SIP session timers [RFC4028] may be used on the SIP side.

5.1.2. Address Resolution

 The IWF should support all the addressing schemes in H.323, including
 the H.323 URI [RFC3508], and the "sip", "sips", and "tel" URI schemes
 in SIP.  It should support the DNS-based SIP server location
 mechanisms described in [RFC3263] and H.323 Annex O, which details
 how H.323 uses DNS and, in particular, DNS SRV records.
 The IWF should register with the H.323 Gatekeeper and the SIP
 registrar when available.
 The IWF may use any means to translate between SIP and H.323
 addresses.  Examples include translation tables populated by the
 gatekeeper, SIP registrar or other database, LDAP, DNS or TRIP.

5.1.3. Call with H.323 Gatekeeper

 When an H.323 GK is present in the network, the IWF should resolve
 addresses with the help of the GK.

5.1.4. Call with SIP Registrar

 The IWF applies normal SIP call routing and does not need to be aware
 whether there is a proxy server.

5.1.5. Capability Negotiation

 The IWF should not make any assumptions about the capabilities of
 either the SIP user agent or the H.323 terminal.  However, it may
 indicate a guaranteed-to-be-supported list of codecs of the H.323
 terminal or SIP user agent before exchanging capabilities with H.323
 (using H.245) and SIP (using SDP [RFC2327]).  H.323 defines mandatory
 capabilities, whereas SIP currently does not.  For example, the G.711
 audio codec is mandatory for higher bandwidth H.323 networks.
 The IWF should attempt to map the capability descriptors of H.323 and
 SDP in the best possible fashion.  The algorithm for finding the best
 mapping between H.245 capability descriptors and the corresponding
 SDP is left for further study.
 The IWF should be able to map the common audio, video, and
 application format names supported in H.323 to and from the
 equivalent RTP/AVP [RFC3550] names.

Schulzrinne & Agboh Informational [Page 6] RFC 4123 SIP-H.323 Req. July 2005

 The IWF may use the SIP OPTIONS message to derive SIP UA
 capabilities.  It may support mid-call renegotiation of media
 capabilities.

5.1.6. Opening of Logical Channels

 The IWF should support the seamless exchange of messages for opening,
 reopening, changing, and closing of media channels during a call.
 The procedures for opening, reopening, closing, and changing the
 existing media sessions during a call are for further study.
 The IWF should open media channels between the endpoints whenever
 possible.  If this is not possible, then the channel can be opened at
 the MSF of the IWF.
 The IWF should support unidirectional, symmetric bi-directional, and
 asymmetric bi-directional opening of channels.
 The IWF may respond to the mode request and to the request for
 reopening and changing an existing logical channel and may support
 the flow control mechanism in H.323.

5.2. IWF H.323 Features

 The IWF should support Fast Connect; i.e., H.245 tunneling in H.323
 Setup messages.  If IWF and GK are the same device, pre-granted ARQ
 should be supported.  If pre-granted ARQ is supported, the IWF may
 perform the address resolution from H.323 GK using the LRQ/LCF
 exchange.

5.3. Overlapped Sending

 An IWF should follow the recommendations outlined in [RFC3578] when
 receiving overlapped digits from the H.323 side.  If the IWF receives
 overlapped dialed digits from the SIP network, it may use the Q.931
 Setup, Setup Ack, and Information Message in H.323.
 The IWF may support the transfer of digits during a call by using the
 appropriate SIP mechanism and UserInputIndication in H.245 (H.323).

5.3.1. DTMF Support

 An IWF should support the mapping between DTMF and possibly other
 telephony tones carried in signaling messages.

Schulzrinne & Agboh Informational [Page 7] RFC 4123 SIP-H.323 Req. July 2005

6. Transport

 The H.323 and SIP systems do not have to be in close proximity.  The
 IP networks hosting the H.323 and SIP systems do not need to assure
 quality of service (QoS).  In particular, the IWF should not assume
 that signaling messages have priority over packets from other
 applications.  H.323 signaling over UDP (H.323 Annex E) is optional.

7. Mapping between SIP and H.323

7.1. General Requirements

 o  The call message sequence of both protocols must be maintained.
 o  The IWF must not set up or tear down calls on its own.
 o  Signaling messages that do not have a match for the destination
    protocol should be terminated on the IWF, with the IWF taking the
    appropriate action for them.  For example, SIP allows a SIP UA to
    discard an ACK request silently for a non-existent call leg.
 o  If the IWF is required to generate a message on its own, IWF
    should use pre-configured default values for the message
    parameters.
 o  The information elements and header fields of the respective
    messages are to be converted as follows:
  • The contents of connection-specific information elements, such

as Call Reference Value for H.323, are converted to similar

       information required by SIP or SDP, such as the SDP session ID
       and the SIP 'Call-ID'.
  • The IWF generates protocol elements that are not available from

the other side.

7.2. H.225.0 and SIP Call Signaling

 o  The IWF must conform to the call signaling procedures recommended
    for the SIP side regardless of the behavior of the H.323 elements.
 o  The IWF must conform to the call signaling procedures recommended
    for the H.323 side regardless of the behavior of the SIP elements.

Schulzrinne & Agboh Informational [Page 8] RFC 4123 SIP-H.323 Req. July 2005

 o  The IWF serves as the endpoint for the Q.931 Call Signaling
    Channel to either an H.323 endpoint or H.323 Gatekeeper (in case
    of GK routed signaling).  The IWF also acts as a SIP user agent
    client and server.
 o  The IWF also establishes a Registration, Admission, Status (RAS)
    Channel to the H.323 GK, if available.
 o  The IWF should process messages for H.323 supplementary services
    (FACILITY, NOTIFY, and the INFORMATION messages) only if the
    service itself is supported.

7.3. Call Sequence

 The call sequence on both sides should be maintained in such a way
 that neither the H.323 terminal nor the SIP UA is aware of presence
 of the IWF.

7.4. State Machine Requirements

 The state machine for IWF will follow the following general
 guidelines:
 o  Unexpected messages in a particular state shall be treated as
    "error" messages.
 o  All messages that do not change the state shall be treated as
    "non-triggering" or informational messages.
 o  All messages that expect a change in state shall be treated as
    "triggering" messages.
 For each state, an IWF specification must classify all possible
 protocol messages into the above three categories.  It must specify
 the actions taken on the content of the message and the resulting
 state.  Below is an example of such a table:
 State: Idle
 Possible Messages   Message Category   Action         Next state
 -------------------------------------------------------------------
 All RAS msg.        Triggering         Add Reg.Info.  WaitForSetup
 All H.245 msg.      Error              Send 4xx       Idle
 SIP OPTIONS         Non Triggering     Return cap.    Idle
 SIP INVITE          Triggering         Send SETUP     WaitForConnect

Schulzrinne & Agboh Informational [Page 9] RFC 4123 SIP-H.323 Req. July 2005

8. Security Considerations

 Because the IWF whose requirements have been described in this
 document combines both SIP and H.323 functionality, security
 considerations for both of these protocols apply.
 The eventual security solution for interworking must rely on the
 standard mechanisms in RFC3261 [RFC3261] and H.323, without extending
 them for the interworking function.  Signaling security for H.323 is
 described in H.235 [H.235].
 Because all data elements in SIP or H.323 have to terminate at the
 IWF, the resulting security cannot be expected to be end-to-end.
 Thus, the IWF terminates not only the signalling protocols but also
 the security in each domain.  Therefore, users at the SIP or H.323
 endpoint have to trust the IWF, like they would any other gateway, to
 authenticate the other side correctly.  Similarly, they have to trust
 the gateway to respect the integrity of data elements and to apply
 appropriate security mechanisms on the other side of the IWF.
 The IWF must not indicate the identity of a user on one side without
 first performing authentication.  For example, if the SIP user was
 not authenticated, it would be inappropriate to use mechanisms on the
 H.323 side, such as H.323 Annex D, to indicate that the user identity
 had been authenticated.
 An IWF must not accept 'sips' requests unless it can guarantee that
 the H.323 side uses equivalent H.235 [H.235] security mechanisms.
 Similarly, the IWF must not accept H.235 sessions unless it succeeds
 in using SIP-over-TLS (sips) on the SIP side of the IWF.

9. Examples and Scenarios

9.1. Introduction

 We present some examples of call scenarios that will show the
 signaling messages received and transmitted.  The following
 situations can occur:
 o  Some signaling messages can be translated one-to-one.
 o  In some cases, parameters on one side do not match those on the
    other side.
 o  Some signaling messages do not have an equivalent message on the
    other side.  In some cases, the IWF can gather further information
    and the signal on the other side.  In some cases, only an error
    indication can be provided.

Schulzrinne & Agboh Informational [Page 10] RFC 4123 SIP-H.323 Req. July 2005

9.2. IWF Configurations

 Below are some common architectures involving an IWF:
 Basic Configuration: H.323 EP  -- IWF -- SIP UA
 Calls using H.323 GK: H.323 EP -- H.323 GK -- IWF -- SIP UA
 Calls using SIP proxies: H.323 EP -- IWF -- SIP proxies -- SIP UA
 Calls using both H.323 GK and SIP proxy: H.323 EP -- H.323 GK -- IWF
    -- SIP proxies -- SIP UA
 SIP trunking between H.323 networks: H.323 EP -- IWF -- SIP network
    -- IWF -- H.323 EP
 H.323 trunking between SIP networks: SIP EP -- IWF -- H.323 network
    -- IWF -- SIP UA

9.3. Call Flows

 Some call flow examples for two different configurations and call
 scenarios are given below.

9.3.1. Call from H.323 Terminal to SIP UA

      H.323                        SIP
       EP    Setup   IWF           UA
        |------------>|    INVITE   |
        |             |------------>|
        |             | 180 RINGING |
        |   Alerting  |<------------|
        |<------------|   200 OK    |
        |  Connect    |<------------|
        |<------------|             |
        |   H.245     |             |
        |<----------->|    ACK      |
        |             |------------>|
        |            RTP            |
        |<.........................>|

Schulzrinne & Agboh Informational [Page 11] RFC 4123 SIP-H.323 Req. July 2005

9.3.2. Call from SIP UA to H.323 Terminal

    SIP                        H.323
     UA           IWF            EP
     |             |             |
     |   INVITE    |             |
     |------------>|   Setup     |
     |             |------------>|
     |             |  Alerting   |
     | 180 RINGING |<------------|
     |<------------|   Connect   |
     |             |<------------|
     |             |    H.245    |
     |     200 OK  |<----------->|
     |<------------|             |
     |     ACK     |             |
     |------------>|             |
     |            RTP            |
     |<.........................>|

10. Acknowledgments

 The authors would like to acknowledge the many contributors who
 discussed the SIP-H.323 interworking architecture and requirements on
 the IETF, SIP, and SG16 mailing lists.  In particular, we would like
 to thank Joon Maeng, Dave Walker, and Jean-Francois Mule.
 Contributions to this document have also been made by members of the
 H.323, aHIT!, TIPHON, and SG16 forums.

Schulzrinne & Agboh Informational [Page 12] RFC 4123 SIP-H.323 Req. July 2005

11. Contributors

 In addition to the editors, the following people provided substantial
 technical and written contributions to this document.  They are
 listed alphabetically.
 Hemant Agrawal
 Telverse Communications
 1010 Stewart Drive
 Sunnyale, CA 94085
 USA
 EMail: hagrawal@telverse.com
 Alan Johnston
 MCI WorldCom
 100 South Fourth Street
 St. Louis, MO 63102
 USA
 EMail: alan.johnston@wcom.com
 Vipin Palawat
 Cisco Systems Inc.
 900 Chelmsford Street
 Lowell, MA  01851
 USA
 EMail: vpalawat@cisco.com
 Radhika R. Roy
 AT&T
 Room C1-2B03
 200 Laurel Avenue S.
 Middletown, NJ 07748
 USA
 EMail: rrroy@att.com

Schulzrinne & Agboh Informational [Page 13] RFC 4123 SIP-H.323 Req. July 2005

 Kundan Singh
 Dept. of Computer Science
 Columbia University
 1214 Amsterdam Avenue, MC 0401
 New York, NY 10027
 USA
 EMail: kns10@cs.columbia.edu
 David Wang
 Nuera Communications Inc.
 10445 Pacific Center Court
 San Diego, CA 92121
 USA
 EMail: dwang@nuera.com

12. References

12.1. Normative References

 [H.235]    International Telecommunication Union, "Security and
            encryption for H-Series (H.323 and other H.245-based)
            multimedia terminals", Recommendation H.235,
            February 1998.
 [H.323]    International Telecommunication Union, "Packet based
            multimedia communication systems", Recommendation H.323,
            July 2003.
 [RFC2327]  Handley, M. and V. Jacobson, "SDP: Session Description
            Protocol", RFC 2327, April 1998.
 [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
            A., Peterson, J., Sparks, R., Handley, M., and E.
            Schooler, "SIP: Session Initiation Protocol", RFC 3261,
            June 2002.
 [RFC3263]  Rosenberg, J. and H. Schulzrinne, "Session Initiation
            Protocol (SIP): Locating SIP Servers", RFC 3263,
            June 2002.
 [RFC3508]  Levin, O., "H.323 Uniform Resource Locator (URL) Scheme
            Registration", RFC 3508, April 2003.

Schulzrinne & Agboh Informational [Page 14] RFC 4123 SIP-H.323 Req. July 2005

 [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
            Jacobson, "RTP: A Transport Protocol for Real-Time
            Applications", STD 64, RFC 3550, July 2003.

12.2. Informative References

 [GWLOC]    Zhao, W. and H. Schulzrinne, "Locating IP-to-Public
            Switched Telephone Network (PSTN) Telephony Gateways via
            SLP", work in progress, February 2004.
 [RFC3578]  Camarillo, G., Roach, A., Peterson, J., and L. Ong,
            "Mapping of Integrated Services Digital Network (ISDN)
            User Part (ISUP) Overlap Signalling to the Session
            Initiation Protocol (SIP)", RFC 3578, August 2003.
 [RFC3932]  Alvestrand, H., "The IESG and RFC Editor Documents:
            Procedures", BCP 92, RFC 3932, October 2004.
 [RFC4028]  Donovan, S. and J. Rosenberg, "Session Timers in the
            Session Initiation Protocol (SIP)", RFC 4028, April 2005.
 [TGREP]    Bangalore, M., "A Telephony Gateway REgistration Protocol
            (TGREP)", work in progress, March 2004.

Authors' Addresses

 Henning Schulzrinne
 Columbia University
 Department of Computer Science
 450 Computer Science Building
 New York, NY  10027
 US
 Phone: +1 212 939 7042
 EMail: hgs@cs.columbia.edu
 URI:   http://www.cs.columbia.edu
 Charles Agboh
 61 Bos Straat
 3540 Herk-de-Stad
 Belgium
 Phone: +32479736250
 EMail: charles.agboh@packetizer.com

Schulzrinne & Agboh Informational [Page 15] RFC 4123 SIP-H.323 Req. July 2005

Full Copyright Statement

 Copyright (C) The Internet Society (2005).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78 and at www.rfc-editor.org/copyright.html, and
 except as set forth therein, the authors retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at ietf-
 ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Schulzrinne & Agboh Informational [Page 16]

/data/webs/external/dokuwiki/data/pages/rfc/rfc4123.txt · Last modified: 2005/07/05 23:02 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki