1、 International Telecommunication Union ITU-T H.460.23TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2009) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMSInfrastructure of audiovisual services Supplementary services for multimedia Network address translator and firewall device determination in ITU-
2、T H.323 systems Recommendation ITU-T H.460.23 ITU-T H-SERIES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS H.100H.199 INFRASTRUCTURE OF AUDIOVISUAL SERVICES General H.200H.219 Transmission multiplexing and synchronization H.220H.229 Systems aspects H.
3、230H.239 Communication procedures H.240H.259 Coding of moving video H.260H.279 Related systems aspects H.280H.299 Systems and terminal equipment for audiovisual services H.300H.349 Directory services architecture for audiovisual and multimedia services H.350H.359 Quality of service architecture for
4、audiovisual and multimedia services H.360H.369 Supplementary services for multimedia H.450H.499MOBILITY AND COLLABORATION PROCEDURES Overview of Mobility and Collaboration, definitions, protocols and procedures H.500H.509 Mobility for H-Series multimedia systems and services H.510H.519 Mobile multim
5、edia collaboration applications and services H.520H.529 Security for mobile multimedia systems and services H.530H.539 Security for mobile multimedia collaboration applications and services H.540H.549 Mobility interworking procedures H.550H.559 Mobile multimedia collaboration inter-working procedure
6、s H.560H.569 BROADBAND, TRIPLE-PLAY AND ADVANCED MULTIMEDIA SERVICES Broadband multimedia services over VDSL H.610H.619 Advanced multimedia services and applications H.620H.629 IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV General aspects H.700H.719 IPTV terminal devices H.720H.729 IPTV middlew
7、are H.730H.739 IPTV application event handling H.740H.749 IPTV metadata H.750H.759 IPTV multimedia application frameworks H.760H.769 IPTV service discovery up to consumption H.770H.779 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T H.460.23 (12/2009) i Recommendat
8、ion ITU-T H.460.23 Network address translator and firewall device determination in ITU-T H.323 systems Summary Recommendation ITU-T H.460.23 enables an ITU-T H.323 endpoint residing behind a NAT/FW device to report NAT/FW characteristics to the gatekeeper. When used with Recommendation ITU-T H.460.2
9、4, a gatekeeper may utilize NAT/FW information in order to formulate a decision as to how to enable direct media flow between two devices. In most cases, following these procedures will allow the gatekeeper to avoid the need for a media proxy as described in Recommendation ITU-T H.460.19, as media c
10、an be successfully transmitted directly between two endpoints residing behind distinct NAT/FW devices. History Edition Recommendation Approval Study Group 1.0 ITU-T H.460.23 2009-12-14 16 ii Rec. ITU-T H.460.23 (12/2009) FOREWORD The International Telecommunication Union (ITU) is the United Nations
11、specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on t
12、hem with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU
13、-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is use
14、d for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g., interoperability or applicability) and compliance with the
15、Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of a
16、ny party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Prop
17、erty Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, im
18、plementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior wri
19、tten permission of ITU. Rec. ITU-T H.460.23 (12/2009) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation . 2 4 Abbreviations 2 5 Feature description 2 6 Capability advertisement 3 7 Remote network address translator supp
20、ort 4 8 Same NAT probe support . 4 9 Network address translator notification 4 10 RASPresentation parameter 5 11 Network address translator test . 5 12 Network address translator type reporting 6 13 General considerations 6 Rec. ITU-T H.460.23 (12/2009) 1 Recommendation ITU-T H.460.23 Network addres
21、s translator and firewall device determination in ITU-T H.323 systems 1 Scope This Recommendation defines the capability and procedures for determining whether an endpoint is located behind a network address translator (NAT) or firewall (FW) and to determine the characteristics of the NAT/Firewall d
22、evice. This feature detects the NAT/Firewall characteristics in order to allow a gatekeeper to determine whether it is possible to stream media directly between two endpoints. If used in conjunction with ITU-T H.460.24, the scalability of ITU-T H.460.18/ITU-T H.460.19 may be extended to allow media
23、to flow directly between ITU-T H.323 endpoints, thus avoiding the necessity to proxy media through an ITU-T H.460.19 server. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. A
24、t the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed
25、below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T H.225.0 Recommendation ITU-T H.225.0 (2009), Call signalling protocols and medi
26、a stream packetization for packet-based multimedia communication systems. ITU-T H.245 Recommendation ITU-T H.245 (2009), Control protocol for multimedia communication. ITU-T H.323 Recommendation ITU-T H.323 (2009), Packet-based multimedia communications systems. ITU-T H.460.1 Recommendation ITU-T H.
27、460.1 (2002), Guidelines for the use of the generic extensible framework. ITU-T H.460.17 Recommendation ITU-T H.460.17 (2005), Using H.225.0 call signalling connection as transport for H.323 RAS messages. ITU-T H.460.18 Recommendation ITU-T H.460.18 (2005), Traversal of H.323 signalling across netwo
28、rk address translators and firewalls. ITU-T H.460.19 Recommendation ITU-T H.460.19 (2005), Traversal of H.323 media across network address translators and firewalls. ITU-T H.460.24 Recommendation ITU-T H.460.24 (2009), Point-to-point media through network address translators and firewalls within ITU
29、-T H.323 systems. 2 Rec. ITU-T H.460.23 (12/2009) IETF RFC 3489 IETF RFC 3489 (2003), STUN Simple Traversal of User Datagram Protocol (UDP) Through Network Address Translators (NATs). NOTE The IETF published a new RFC that obsoletes IETF RFC 3489, changing the name of the standard and the procedures
30、 defined therein. This Recommendation relies on the protocol and procedures specified in IETF RFC 3489, and the protocol and procedures defined in the new RFC are neither suitable nor compatible. As such, this Recommendation does not reference the new RFC and deliberately makes reference to the orig
31、inal specification, which is now referred to as “classical STUN“. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following term defined elsewhere: 3.1.1 transport address ITU-T H.323: The transport layer address of an addressable H.323 entity as defined by the (inter)network
32、protocol suite in use. The Transport Address of an H.323 entity is composed of the Network Address plus the TSAP identifier of the addressable H.323 entity. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 P2Pnat media: Indicates that media flows direct
33、ly (peer-to-peer) between two communicating endpoints through NAT devices without the assistance of a media proxy. 3.2.2 pinhole: A temporary binding of an internal and an external transport address in the NAT/FW, which allows the bidirectional passage of packets between those addresses. 3.2.3 STUN
34、server: Server to assist in NAT type detection (as defined in IETF RFC 3489). 3.2.4 well-behaved NAT: A NAT that exhibits consistent behaviour over time of a given NAT type as categorized in clause 5 of IETF RFC 3489. 4 Abbreviations This Recommendation uses the following abbreviations: FW Firewall
35、GCF Gatekeeper Confirmation GRQ Gatekeeper Request NAT Network Address Translator RCF Registration Confirm RRQ Registration Request STUN Simple Traversal of User datagram protocol (UDP) through Network address translators 5 Feature description This Recommendation defines a procedure wherein a gateke
36、eper may detect whether a registering endpoint is behind a NAT/FW. This Recommendation provides instructions for a gatekeeper to instruct an endpoint to detect if it is behind a NAT/FW and to collect characteristics of the intervening NAT/FW device. These findings are then reported back to the gatek
37、eeper, which can then be used as input into ITU-T H.460.24 point-to-point media (P2Pnat media) traversal calculations. Rec. ITU-T H.460.23 (12/2009) 3 This Recommendation is designed for use in networks that employ NAT/FW devices with well-behaved NAT characteristics. Networks that do not employ wel
38、l-behaved NAT devices should continue to utilize ITU-T H.460.18 and ITU-T H.460.19 to ensure proper end-to-end media flows. 6 Capability advertisement Endpoints capable of supporting NAT/FW determination shall advertise this capability via the generic extensibility framework (GEF) defined in ITU-T H
39、.323 and ITU-T H.460.1. This feature is to be used in conjunction with ITU-T H.460.18 or optionally ITU-T H.460.17. ITU-T H.323 devices wishing to use this feature shall also support either ITU-T H.460.18 or ITU-T H.460.17, respectively. In supporting the various NAT/FW conditions and configurations
40、 covered in ITU-T H.460.18, a client gatekeeper (refer to Figure 3 of ITU-T H.460.18) or a client proxy (refer to Figure 2 of ITU-T H.460.18) residing behind a NAT/FW providing direct NAT traversal support through the NAT/FW shall be considered as an endpoint for the purpose of this Recommendation.
41、An endpoint, which performs gatekeeper, discovery, shall set the supportedFeatures field of its GRQ to include NAT/FW determination as defined in Table 1. If the gatekeeper responds with a GCF, it shall include NAT/FW determination in the supportedFeatures field. Endpoints shall send an RRQ to the g
42、atekeeper, including NAT/FW determination in the supportedFeatures field. Endpoints shall omit NAT/FW determination from the supportedFeatures field of lightweight RRQs. Table 1 defines the NAT/FW determination feature in this Recommendation. Table 1 Indication of the NAT/FW determination feature Fe
43、ature name: NAT/FW determination (dD) Feature description: This feature allows for the gatekeeper to determine the characteristics of the network address translator or firewall behind which an ITU-T H.323 device may reside when it registers to the gatekeeper. Feature identifier type: Standard Featur
44、e identifier value: 23 Parameters associated with the advertisement of this capability are specified in the following clauses. In consideration of backward compatibility with further revisions to this Recommendation, the recipient shall simply ignore any parameters received other than those specifie
45、d in this Recommendation. For the purpose of this Recommendation, where an optional parameter of type bool is to be omitted then it shall automatically be deemed to have a default value of FALSE. 4 Rec. ITU-T H.460.23 (12/2009) 7 Remote network address translator support An endpoint supporting this
46、feature shall notify the gatekeeper via the capability advertisement whether the endpoint supports remote NAT clients (i.e., the endpoint supports Master mode as described in clause 9.6 of ITU-T H.460.24). Table 2 RemoteNAT parameter Parameter name: RemoteNAT Parameter description: Indicates whether
47、 the endpoint can support calls from remote NAT clients (Local Master). Parameter identifier type: Standard Parameter identifier value: 1 Parameter type: bool Parameter cardinality: One and only one 8 Same NAT probe support If the endpoint supports probing for a direct route when behind the same NAT
48、/FW device (supports ITU-T H.460.24 Annex A), then this shall be indicated by the SameNATProbe parameter. Table 3 Same NATProbe parameter Parameter name: SameNATProbe Parameter description: Indicates whether the endpoint supports probing for Same NAT (ITU-T H.460.24 Annex A). Parameter identifier ty
49、pe: Standard Parameter identifier value: 2 Parameter type: bool Parameter cardinality: One and only one 9 Network address translator notification On receipt of the RRQ from an endpoint supporting this feature, the gatekeeper shall include in the responding RCF the NATPresent parameter to notify the endpoint that it has been detected as being behind a NAT/FW. If ITU-T H.460.19 traversal support is disabled or the device has been determined as not being behind a NAT/FW, this paramet
