1、 CEA Standard IP-Based Digital Telephony for the Versatile Home Network CEA-851.1-A R-2014 February 2009 NOTICE Consumer Electronics Association (CEA) Standards, Bulletins and other technical publications are designed to serve the public interest through eliminating misunderstandings between manufac
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5、ner, nor does it assume any obligation whatever to parties adopting the Standard, Bulletin or other technical publication. This document does not purport to address all safety problems associated with its use or all applicable regulatory requirements. It is the responsibility of the user of this doc
6、ument to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before its use. This document is copyrighted by the Consumer Electronics Association (CEA) and may not be reproduced, in whole or part, without written permission. Federal copyrigh
7、t law prohibits unauthorized reproduction of this document by any means. Organizations may obtain permission to reproduce a limited number of copies by entering into a license agreement. Requests to reproduce text, data, charts, figures or other material should be made to CEA. (Formulated under the
8、cognizance of the CEA R3 Audio Systems Committee.) Published by CONSUMER ELECTRONICS ASSOCIATION 2014 Technology however, we leave discussion of implementing non-IP telephony on the VHN to a later version of this Standard. We note first that, as the VHN is an IP-based internet, it is capable of tran
9、sporting any IP traffic, regardless of the interpretation of the packet contents. Thus, IP-based telephony transport is “native” to the VHN, and the VHN is transparent to the transport of “telephony” packets. However, as with other services that may be provided using the VHN, control signals for IP
10、telephony require some attention. In addition, as telephony usually implies connectivity to a public telephone network outside the home, it will be necessary for the IP telephony end device (which may not be a traditional telephone set) to have a logical interface with software that will probably re
11、side on an access-backbone interface or an access-component interface, such as a Residential Gateway or a cable modem. While it is beyond the scope of this Standard to specify the architecture or operation of these devices, we feel it is important to require the presence of certain software on the a
12、ccess interfaces. CEA-851.1-A 32. GENERAL 2.1 Scope This standard addresses IP-based digital telephony (sometimes referred to as “Voice over IP”) on the VHN. As the VHN is inherently digital it does not address analog telephony; nor does it address non-packet digital telephony, such as the streaming
13、 service provided by ISDN. However, future versions of this standard may address non-IP telephony. Although this Standard has been issued as a separate document, it is an integral part of CEA-851, “VHN Home Network Specification.” Requirements and specifications in CEA-851 also implicitly apply to t
14、he functions and devices described in this Standard, unless there specifically stated otherwise. Also, note that this Standard defines the requirements for implementing a telephony function on a VHN. As such, it is not a device description. Any VHN device that implements telephony is also expected t
15、o implement all other parts of CEA-851 that are applicable and appropriate for such a device. For example, CEA-851 requires that a VHN device support a web server; thus, any device implementing the telephony function, as described in this Standard, would be expected to include a web server that woul
16、d conform to the requirements in CEA-851. 2.2 Normative References The following standards contain provisions that, through reference in this text, constitute normative provisions of this standard. At the time of publication, the editions indicated were valid. All standards are subject to revision,
17、and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the standards listed in Sec. 2.2.1. If the referenced standard is dated, the reader is advised to use the version specified. 2.2.1 Normative Reference List: 1. CEA-8
18、51, “VHN Home Network Specification,” October 2000. 2. IETF RFC 2543, “SIP: Session Initiation Protocol,” March 1999. 2.2.2 Normative Reference Acquisition: CEA standards can be ordered from Global Engineering Documents, http:/ IETF RFCs may be downloaded from http:/www.rfc-editor.org/. 2.3 Informat
19、ive References The following documents contain information that is useful in understanding this standard. Some of these documents are drafts of standards that may become normative references in a future release of this standard. CEA-851.1-A 42.3.1 Informative Document List: 3. ITU-T Recommendation H
20、.323, “Packet-based multimedia communication systems”. 4. IETF RFC 1889, “RTP: A Transport Protocol for Real-Time Applications,” January 1996. 2.3.2 Informative Document Acquisition: ITU-T International Telecommunications Union, Place des Nations, CH-1211 Geneva 20, Switzerland; Phone +41 22 730 511
21、1; Fax +41 22 733 7256; Internet http:/www.itu.ch/publications/bookstore.html; Email itumailitu.int. IETF IETF RFCs may be downloaded from http:/www.rfc-editor.org/. 2.4 Symbols and Abbreviations IETF Internet Engineering Task Force ISDN Integrated Services Digital Network ITU International Telecomm
22、unications Union POTS Plain Old Telephone Service RTP Real-time Transport Protocol SIP Service Initiation Protocol SONET Synchronous Optical Network VHN Versatile Home Network 2.5 Compliance Notation As used in this document, “shall” and “must” denote a mandatory provisions of the standard. “Should”
23、 denotes a provision that is recommended but not mandatory. “May” denotes a feature whose presence does not preclude compliance that may or may not be present at the option of the implementer. “Optional” denotes items that may or may not be present in a compliant DTV. CEA-851.1-A 53. IP-based Digita
24、l Telephony IP-based telephony in the VHN, as described in Annex A, is affected by implementation of the following requirements: 1. All telephony end devices on the VHN shall implement the SIP 2 protocol, known heretofore as a “SIP stack.” 2. All telephony control signals and all packets, including
25、signals that are inherently isochronous, such as voice or video, or other telephony user traffic shall be carried only as asynchronous packets on the IEEE 1394b backbone and on IEEE 1394a component networks of the VHN. As the SIP protocol assumes asynchronous service, use of the IEEE 1394 isochronou
26、s service for IP-based digital telephony is not supported in this Standard; if a user prefers to implement telephony on the IEEE 1394 isochronous channels, it is the responsibility of the user to define the interfaces between asynchronous services and the IEEE 1394 isochronous stream, as well to man
27、age IP telephony as an IEEE 1394 isochronous service (i.e. to define allocation of bandwidth, channel numbers, and applications that control user access to telephony services). 3. If a VHN implements IP telephony within the home, it shall host the required SIP software, including a SIP proxy server,
28、 on a networked device. 4. Connection to the public telephone network is effected through an access-backbone interface or an access-component interface. Note that the internal architecture of such devices is outside the scope of this Standard; nevertheless, we require that if such a device is connec
29、ted to the VHN to effect an IP telephony connection to the public telephone network, that device shall host a SIP proxy server, and any other SIP software necessary to realize an IP telephony connection to the public telephone network. 5. These specifications require modifications to the VHN Protoco
30、l Stack (Figure 6 in CEA-851 1). These changes are reflected in the revised Protocol Stack Figure 1 below. CEA-851.1-A 6SIP Other Other IEEE 1394 Physical Layer IEEE 1394 Link Layer 1394 Serial Bus Mgmt. (Config ROM, CSR) 1394 Transaction Layer Asynchronous IPv4 Unicast over 1394 FCP IEC61883-1 MPEG
31、-2 TS (Single Program TS) 1394 Node Discovery MPEG-2 PES MPEG-2 PSI RT MPEG A/V ES CMP IEC61883-1 AV/C AV/C App ATSC PSIP Isoch. Data Flow Mgmt IPv4 Mcast over 1394TCP UDP HTTP OMG UNORPC DSM-CC SNMPVHN Exchange (XML Messaging)VHN Object Model Layer (CAL,AV/C)MPEG-2 Section Other Data Other Isoch. f
32、ormatsDV, DSSReal Time Data Transmission Protocol (IEC 618833-1-6) OMG IDL DSM-CCPrivate SectionDSM-CCObject CarouselARP IP IPv4 Bcast over 1394BER Optional Mandatory Figure 1 Revised VHN Protocol Stack (replaces Figure 6 in CEA-851) CEA-851.1-A 7ANNEX A: IP-Based Telephony (Informative) A.1 Introdu
33、ction In this section we address the implementation of IP-based digital telephony on the VHN. Note that digital telephony does not require the use of the Internet Protocol suite1; however, we leave discussion of implementing non-IP telephony on the VHN to a later version of this Standard. We first n
34、ote that, as the VHN is an IP-based internet, it is capable of transporting any IP traffic, regardless of the interpretation of the packet contents. Thus, IP-based telephony transport is “native” to the VHN, and the VHN is transparent to the transport of “telephony” packets. However, as with many ot
35、her services that may be provided over the VHN, control signals for IP telephony require some attention. In addition, as telephony usually implies connectivity to a public telephone network outside the home, it will be necessary for the IP telephony end device (which may not be a traditional telepho
36、ne set) to have a logical interface with software that will probably reside on an access-backbone interface or an access-component interface, such as a Residential Gateway or a cable modem. While it is beyond the scope of this Standard to specify the architecture or operation of these devices, we fe
37、el it is important to require the presence of certain software on the access interfaces. A.2 Assumptions We begin by stating some assumptions underlying the telephony specifications in this Standard: A.2.1 Digital Telephony (not POTS) As the VHN is a digital network, we assume that specifications fo
38、r telephony exclude analog systems, such as “Plain Old Telephone Service” (POTS). At this time, almost all telephony is analog, but the presence of digital telephony is expected to grow over the next several years. For the transition period between analog and digital telephone systems it is suggeste
39、d that digital systems have “friendly” codec(s) for existing analog devices such as fax/modem devices. We confine our discussion to the integration of these emerging digital telephony technologies into the VHN. 1For instance, ISDN uses synchronous streams that are circuit-switched, rather than packe
40、t-switched. CEA-851.1-A 8A.2.2 Packet-based Telephony (not ISDN) Furthermore, as mentioned above, not all digital telephony is packet-based, let alone IP-based. In particular, ISDN (Integrated Services Digital Network) uses a streaming, synchronized digital signal, similar to other traditional digit
41、al telephony transport signals, such as T1 and SONET. While ISDN has had some recent popularity for implementing Internet connections to the home (and, in fact, most digital telephony at this time uses ISDN), it is expected that ISDN will give way to packet-based systems within a few years. Thus, we
42、 confine ourselves, in this version of the Standard, to packet-based telephony. If ISDN proves to be more resilient and long-lived than we have assumed, a future version of this Standard may include provisions for implementing ISDN on the VHN. A.2.3 All telephony traffic will be asynchronous on IEEE
43、 1394 busses Digital telephony may be used to carry the full range of digital signals, from traditional voice telecommunications, to asynchronous data, to video. However, because we assume digital telephony is IP-based; all telephony signals will be carried as asynchronous packets on the IEEE 1394b
44、backbone of the VHN, including signals that are inherently isochronous, such as voice or video. At present, almost all packet-based digital telephony end devices are equipped with Ethernet connections, and it is assumed that this choice of component network will continue in the future; however, ther
45、e is nothing to prevent a manufacturer from developing an IP “telephone” with an IEEE 1394 connector on the back. A homeowner could connect such an IP end device to any IEEE 1394 network in the home, and it would operate exactly the same as when connected to an Ethernet. Note, however, that in this
46、instance, the IP end device would use the asynchronous service of the IEEE 1394 bus, rather than the isochronous service, even though the contents of the signal might represent an isochronous stream. A.2.4 Telephony will be based on SIP (Service Initiation Protocol) There are currently two standards
47、 for implementing packet-based telephony: H.323 3 and SIP 2; H.323 is an ITU-T recommendation, while SIP (RFC 2543) is an IETF Proposed Standard. Each of these protocols uses RTP 4, the Real-time Transport Protocol, along with RTCP2, the Real-time Transport Control Protocol, to implement transport o
48、f IP telephony content. However, they use different techniques to affect telephone signaling, and to implement interworking of the digital telephony system with the non-IP public telephone network. 2RTCP is included in the specifications for RTP in IETF RFC 1889 4. CEA-851.1-A 9Efforts are underway
49、in the ITU and IETF to merge these standards into a common protocol for IP telephony. However, at present, it appears that the telephony industry (at least in North America) is settling on SIP for IP telephony. We therefore assume that IP Telephony on the VHN will be implemented using SIP. Should, in fact, the telephone industry turn to other telephony standards, it may be necessary to modify the telephony specifications for the VHN; therefore, future versions of this Standard may incorporate specifications for other IP Telephony standards. CEA Document Im
