MMUSIC Working Group D. Yon Internet-Draft Tactical Software, LLC Expires:
March 30,May 27, 2005 G. Camarillo Ericsson September 29,November 26, 2004 Connection-OrientedTCP-Based Media Transport in the Session Description Protocol (SDP) draft-ietf-mmusic-sdp-comedia-09.txtdraft-ietf-mmusic-sdp-comedia-10.txt Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on March 30,May 27, 2005. Copyright Notice Copyright (C) The Internet Society (2004). Abstract This document describes how to express media transport over connection-oriented protocolsTCP using the Session Description Protocol (SDP). It defines the SDP TCP'TCP' protocol identifier, the SDP setup'setup' attribute, which describes the connection setup procedure, and the SDP connection'connection' attribute, which handles connection reestablishment. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Protocol Identifier . . . . . . . . . . . . . . . . . . . . . 3 4. Setup Attribute . . . . . . . . . . . . . . . . . . . . . . . 4 4.1 The Setup Attribute in the Offer/answer Model . . . . . . 4 5. The Connection Attribute . . . . . . . . . . . . . . . . . . . 5 5.1 Offerer Behaviour . . . . . . . . . . . . . . . . . . . . 6 5.2 Answerer Behaviour . . . . . . . . . . . . . . . . . . . . 7 6. Connection Management . . . . . . . . . . . . . . . . . . . . 78 6.1 Connection Establishment . . . . . . . . . . . . . . . . . 78 6.2 Connection Reestablishment . . . . . . . . . . . . . . . . 8 6.3 Connection Termination . . . . . . . . . . . . . . . . . . 8 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.1 Passive/Active . . . . . . . . . . . . . . . . . . . . . . 89 7.2 Actpass/Passive . . . . . . . . . . . . . . . . . . . . . 9 7.3 Existing Connection Reuse . . . . . . . . . . . . . . . . 910 7.4 Existing Connection Refusal . . . . . . . . . . . . . . . 10 8. Other Connection-Oriented Transport Protocols . . . . . . . . 11 9. Security Considerations . . . . . . . . . . . . . . . . . . . 11 9.12 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 10.12 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 11.12. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 11.112.1 Normative References . . . . . . . . . . . . . . . . . . . . 12 11.212.2 Informative References . . . . . . . . . . . . . . . . . . . 1213 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 1314 Intellectual Property and Copyright Statements . . . . . . . . 1415 1. Introduction The Session Description Protocol  provides a general-purpose format for describing multimedia sessions in announcements or invitations. SDP uses an entirely textual data format (the US-ASCII subset of UTF-8 ) to maximize portability among transports. SDP does not define a protocol, but only the syntax to describe a multimedia session with sufficient information to participate in that session. Session descriptions may be sent using arbitrary existing application protocols for transport (e.g., SAP , SIP , RTSP , email, HTTP , etc.). SDP  defines two protocol identifiers: RTP/AVP and UDP, both of which represent unreliable connectionless protocols. While these transports are appropriate choices for multimedia streams, there are applications for which connection-oriented transports, such as TCP, areTCP is more appropriate. This document defines a new protocol identifier, TCP,'TCP', to describe TCP connetions in SDP. Connection-oriented protocols introduceTCP introduces two new factorfactors when describing a session: how and when should endpoints perform the TCP connection setup procedure. This document defines two new attributes to describe TCP connection setups: setup'setup' and connection.'connection'. 2. Terminology In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119  and indicate requirement levels for compliant implementations. 3. Protocol Identifier The following is the ABNF for an m='m' line, as specified by RFC 2327 . media-field = "m=" media space port ["/" integer] space proto 1*(space fmt) CRLF This document defines a new value for the proto field: TCP.'TCP'. The TCP'TCP' protocol identifier is similar to the UDP'UDP' protocol identifier in that it only describes the transport protocol, and not the upper-layer protocol. An m='m' line that specifies "TCP"'TCP' MUST further qualify the application-layer protocol using an fmt identifier. Media described using an m= lines'm' line containing the TCP'TCP' protocol identifier are carried using TCP . It is RECOMMENDED that documents defining new SDP protocol identifiers that involve extra protocol layers between TCP and the media itself (e.g., TLS  over TCP) start with the string "TCP/" (e.g., TCP/TLS). The following sections define the setup and the connection attributes. While both attributes are applicable to m= lines that use the TCP protocol identifier, they are not limited to them. These attributes MAY be used in conjunction with any m= line which uses a connection- oriented transport protocol, even if the protocol identifier of the m= line is not TCP.4. Setup Attribute The setup'setup' attribute indicates which of the end points should initiate the TCP connection establishment (e.g.,(i.e., send the initial TCP SYN). The setup'setup' attribute is charset-independent and can be a session-level or a media-level attribute. The following is the ABNF of the setup'setup' attribute: setup-attr = "a=setup:" role role = "active" / "passive" / "actpass" / "holdconn" Active:'active': The endpoint will initiate an outgoing connection. Passive:'passive': The endpoint will accept an incoming connection. ActPass:'actpass': The endpoint is willing to accept an incoming connection or to initiate an outgoing connection. Holdconn:'holdconn': The endpoint does not want the connection to be established for the time being. 4.1 The Setup Attribute in the Offer/answer Model The offer/answer model, defined in RFC 3264 , provides endpoints with a means to obtain shared view of a session. Some session parameters are negotiated (e.g., codecs to use), while others are simply communicated from one endpoint to the other (e.g., IP addresses). The value of the setup'setup' attribute falls into the first category. That is, both endpoints negotiate its value using the offer/answer model. The negotiation of the value of the setup'setup' attribute takes places as follows. The offerer states which role or roles it is willing to perform and the answerer, taking the offerer's willingness into consideration, chooses which roles both endpoints will actually perform during connection establishment. The following are the values that the setup'setup' attribute can take in an offer/answer exchange: Offer Answer ________________ active passive / holdconn passive active / holdconn actpass active / passive / holdconn holdconn holdconn The active endpoint SHOULD initiate a connection to the port number on the m='m' line of the other endpoint. The port number on its own m='m' line is irrelevant, and the opposite endpoint MUST NOT attempt to initiate a connection to the port number specified there. Nevertheless, since the m='m' line must contain a valid port number, the endpoint specifying using the value active SHOULD specify a port number of 9 (the discard port) on its m='m' line. The endpoint MUST NOT specify a port number of zero, except to denote an m='m' line that has been or is being refused. The passive endpoint SHOULD be ready to accept a connection on the port number specified in the m='m' line. A value of actpass'actpass' indicates that the offerer can either initiate a connection to the port number on the m='m' line in the answer or accept a connection on the port number specified in the m='m' line in the offer. That is, the offerer has no preference as to whether it accepts or initiates the connection and, so, is letting the answerer choose. A value of holdconn'holdconn' indicates that the connection should not be established for the time being. The default value of the setup attribute in an offer/answer exchange is active'active' in the offer and passive'passive' in the answer. 5. The Connection Attribute The preceding description of the setup'setup' attribute has beenis placed in the context of using SDP to initiate a session. Still, SDP may be exchanged between endpoints at various stages of a session to accomplish tasks such as terminating a session, redirecting media to a new endpoint, or renegotiating the media parameters for a session. After the initial session has been established, it may be ambiguous as to whether subsequent SDP exchange represents a confirmation that the endpoint is to continue using the current mediaTCP connection unchanged, or is a request to make a new mediaTCP connection. The media-level connection'connection' attribute, which is charset-independent, is used to disambiguate these two scenarios. The following is the ABNF of the connection attribute: connection-attr = "a=connection:" conn-value conn-value = "new" / "existing" 5.1 Offerer Behaviour Offerers and answerers use the connection'connection' attribute to decide whether a new transport connection needs to be established or, on the other hand, the existing transportTCP connection should still be used. The connection value resulting from an offer/answer exchange is the connection value in the answer. If the connection value in the answer is "new", the end-points SHOULD establish a new connection. If the connection value in the answer is "existing", the end-points SHOULD continue using the exiting connection.When an offerer generates an m='m' line which uses a connection-oriented transport,TCP, it SHOULD provide a connection attribute for the m='m' line unless the application using the m='m' line has other means to deal with connection reestablishment. The connection attribute in an initial offer (i.e., no transport connection has been established yet) takes the value of "new".After the initial offer/answer exchange, any of the endpoints can generate a new offer to change some characteristics of the session (e.g., the direction attribute). If such an offerer wants to continue using the previously-established transport-layer connection for the m='m' line, the offerer MUST use usea connection value of "existing"'existing' for the m='m' line. If, on the other hand, the offerer wants to establish a new transport-layer connection for the m='m' line, it MUST use a connection value of "new".'new'. Note that, according to the rules in this section, an offer that changes the transport address (IP address or port number) of an m='m' line will have a connection value of "new".'new'. The default value ofsame way, the connection'connection' attribute in an offer/answer exchange is "new". 5.2 Answerer Behaviour The connection value for an m= line is negotiated usinginitial offer (i.e., no transport connection has been established yet) takes the offer/ answer model.value of 'new'. The resulting connection'connection' value afterresulting from an offer/answer exchange is the connection'connection' value in the answer. If the connection'connection' value in the offeranswer is "new",'new', the answerer MUST also useend-points SHOULD establish a value of "new" in the answer.new connection. If the connection value in the offeranswer is "existing",'existing', the answerer uses a value of "existing"end-points SHOULD continue using the exiting connection. Taking into consideration the rules in Section 5.2, the following are the values that the 'connetion' attribute can take in an offer/answer exchange: Offer Answer ________________ new new existing existing / new If the answer if it wishes toconnection value resulting from an offer/answer exchange is 'existing', the end-points continue using the existing connectionconnection. Consequently, the port numbers, IP addresses, and 'setup' attributes negotiated in the offer/answer exchange are ignored because there is no need to establish a new connection. The previous rule implies that an offerer generating an offer with a connection value of "new" if it wants'existing' and a new connectionsetup value of 'passive' needs to be established. In some scenarios where third party call control  is used, an endpoint mayready (i.e., needs to allocate resources) to receive an initial offer witha connection request from the answerer just in case the answerer chooses a connection value of "existing". Following'new' for the answer. However, if the previous rules, such ananswerer would useuses a connection value of "new"'existing' in the answer. Ifanswer, the offerer would need to deallocate the previously allocated resources which were never used because no connection request was received. To avoid allocating resources unnecessary, offerers using a connection value for an m= line resulting from an offer/answer exchange is "new",of 'existing' in their offers may choose to use a setup value of 'holdconn'. Nevertheless, offerers using this strategy should be aware that in the endpoints SHOULD establishcase the answerer chooses a new transport-layerconnection as indicatedvalue of 'new', a new offer/answer exchange (typically initiated by the setup attribute. If aprevious offerer) with setup value different than 'holdconn' will be needed to establish the new connection. This may, of course, cause delays in the application using the TCP connection. The default value of the connection attribute in both offers and answers is 'new'. 5.2 Answerer Behaviour The connection value for an 'm' line is negotiated using the offer/ answer model. The resulting connection value after an offer/answer exchange is the connection value in the answer. If the connection value in the offer is 'new', the answerer MUST also use a value of 'new' in the answer. If the connection value in the offer is 'existing', the answerer uses a value of 'existing' in the answer if it wishes to continue using the existing connection and a value of 'new' if it wants a new connection to be established. In some scenarios where third party call control  is used, an endpoint may receive an initial offer with a connection value of 'existing'. Following the previous rules, such an answerer would use a connection value of 'new' in the answer. If the connection value for an 'm' line resulting from an offer/ answer exchange is 'new', the endpoints SHOULD establish a new TCP connection as indicated by the 'setup' attribute. If a previous TCP connection is still up, the endpoints SHOULD close it as soon as the offer/answer exchange is completed. It is up to the application to ensure proper data synchornization between the two TCP connections. If the connection value for an m='m' line resulting from an offer/answeroffer/ answer exchange is "existing",'existing', the endpoints SHOULD continue using the existing TCP connection. 6. Connection Management This section addresses connection establishment, connection reestablishment, and connection termination. 6.1 Connection Establishment An endpoint that according to an offer/answer exchange is supposed to initiate a new TCP connection SHOULD initiate it as soon as it is able to, even if the endpoint does not intend to immediately begin sending media to the remote endpoint. This allows media to flow from the remote endpoint if needed. Note that some endpoints need to wait for some event to happen before being able to establish the connection. For example, a wireless terminal may need to set up a radio bearer before being able to initiate a TCP connection. 6.2 Connection Reestablishment If an endpoint determines that the transport-connectionTCP for an m='m' line has been closed and it should be reestablished, it SHOULD perform a new offer/answeroffer/ answer exchange using a connection value of "new"'new' for this m='m' line. Note that the SDP direction attribute (e.g., a=sendonly)'a=sendonly') deals with the media sent over the transport-connection,TCP connection, but has no impact on the transport-connectionTCP connection itself. 6.3 Connection Termination Typically, endpoints do not close the TCP connection until the session has expired, been explicitly terminated, or a new connection value has been provided for the m='m' line. Additionaly, specific applications can describe further scenarios where an end-point may close a given connection.TCP connection (e.g., whenever a connection is in the half-close state). As soon as an end-point notices that it needs to terminate a TCP connection, it SHOULD do so. While in TCP both end-points need to close a connection, other connection-oriented transport protocols may not have the concept of half-close connections.In thisany case, individual applications may provide further considerations on how to achieve a connection would be terminated as soon as one of the end-points closed it, making it unnecessary for the other end-point to perform any further action to terminate the connection. In any case, individual applications may provide further considerations on how to achieve a gracefulgraceful connection termination. For example, a file application using TCP receiving a FIN from the remote endpoint may need to finish the ongoing transmission of a file before sending its own FIN. 7. Examples The following examples show the most common usage of the setup'setup' attribute combined with TCP-based media descriptions. For the purpose of brevity, the main portion of the session description is omitted in the examples, which only show m='m' lines and their attributes (including c='c' lines). 7.1 Passive/Active An offerer at 192.0.2.2 signals its availability for a T.38 fax session at port 54111: m=image 54111 TCP t38 c=IN IP4 192.0.2.2 a=setup:passive a=connection:new An answerer at 192.0.2.1 receiving this offer responds with the following answer: m=image 9 TCP t38 c=IN IP4 192.0.2.1 a=setup:active a=connection:new The endpoint at 192.0.2.1 then initiates the TCP connection to port 54111 at 192.0.2.2. 7.2 Actpass/Passive In another example, an offerer at 192.0.2.2 signals its availability for a T.38 fax session at TCP port 54111. Additionally, this offerer is also willing to set up the media stream by initiating the TCP connection: m=image 54111 TCP t38 c=IN IP4 192.0.2.2 a=setup:actpass a=connection:new The endpoint at 192.0.2.1 responds with the following description: m=image 54321 TCP t38 c=IN IP4 192.0.2.1 a=setup:passive a=connection:new This will cause the offerer (at 192.0.2.2) to initiate a connection to port 54321 at 192.0.2.1. 7.3 Existing Connection Reuse Subsequent to the exchange in Section 7.2, another offer/answer exchange is initiated in the opposite direction. The endpoint at 192.0.2.1 wishes to continue using the existing connection: m=image 54321 TCP t38 c=IN IP4 192.0.2.1 a=setup:passive a=connection:existing The endpoint at 192.0.2.2 also wishes to use the existing connection and responds with the following description: m=image 9 TCP t38 c=IN IP4 192.0.2.2 a=setup:active a=connection:existing The existing connection from 192.0.2.2 to 192.0.2.1 will be reused. Note that the endpoint at 192.0.2.2 uses setup:active'setup:active' in response to the offer of setup:passive,offer of 'setup:passive', and uses port 9 because it is active. 7.4 Existing Connection Refusal Subsequent to the exchange in Section 7.3, another offer/answer exchange is initiated by the endpoint at 192.0.2.2, again wishing to reuse the existing connection: m=image 54111 TCP t38 c=IN IP4 192.0.2.2 a=setup:passive a=connection:existing However, this time the answerer is unaware of the old connection and so wishes to establish a new one. (This could be the result of a transfer via third-party call control.) It is unable to act in the 'passive' mode so responds as 'active': m=image 9 TCP t38 c=IN IP4 192.0.2.3 a=setup:active a=connection:new The endpoint at 192.0.2.3 then initiates the TCP connection to port 54111 at 192.0.2.2, and the endpoint at 192.0.2.2 closes the old connection. Note that the endpoint at 192.0.2.2, while using a connection value of 'existing' has used a setup value of 'passive'. Had it not done this and used a setup value of 'holdconn' instead (probably to avoid allocating resources as described in Section 5.1), a new offer/answer exchange would have been needed in order to establish the new connection. 8. Other Connection-Oriented Transport Protocols This document specifies how to describe TCP-based media streams using SDP. Still, some of the attributes defined here could possibly be used to describe media streams based on other connection-oriented transport protocols as well. This section provides advice to authors of specifications of SDP extensions which deal with connetion-oriented transport protocols other than TCP. It is recommended that documents defining new SDP protocol identifiers that involve extra protocol layers between TCP and the media itself (e.g., TLS  over TCP) start with the string 'TCP/' (e.g., 'TCP/TLS'). The 'setup' and the 'connection' attributes are specified in Section 4 and Section 5 respectively. While both attributes are applicable to 'm' lines that use the 'TCP' protocol identifier, they are general enough to be reused in 'm' lines with other connection-oriented transport protocols. Therefore, it is recommended that the 'setup' and uses port 9 because'connection' attributes are reused, as long as it is active. 7.4 Existing Connection Refusal Subsequent to the exchange inpossible, for new proto values associated with connection-oriented transport protocols. Section 7.3, another offer/answer exchange is initiated by the endpoint at 192.0.2.2, again wishing to reuse the existing connection: m=image 541116 deals with TCP t38 c=IN IP4 192.0.2.2 a=setup:actpass a=connection:existing However, this time the answerer is unaware of the oldconnection and so wishesmanagement. It should be noted that while in TCP both end-points need to establishclose a new one. (This could beconnection, other connection-oriented transport protocols may not have the resultconcept of half-close connections. In such a transfer via 3pcc.) It is unable to act in the passive mode so respondscase, a connection would be terminated as active: m=image 9 TCP t38 c=IN IP4 192.0.2.3 a=setup:active a=connection:new The endpoint at 192.0.2.3 then initiatessoon as one of the TCP connection to port 54111 at 192.0.2.2, andend-points closed it, making it unnecessary for the endpoint at 192.0.2.2 closesother end-point to perform any further action to terminate the oldconnection. Note that the endpoint at 192.0.2.2, while specifying connection: existing has revertedSo, specifications dealing with such transport protocols may need to setup:actpass and its real port number, rather than repeating setup:active and port 9 from the previous cycle. Had it not done this, this negotiation would have failed. 8.specify slightly different procedures regarding connection termination. 9. Security Considerations See RFC 2327  for security and other considerations specific to the Session Description Protocol in general. An attacker may attempt to modify the values of the connection and setup attributes to have endpoints reestablish connections unnecesaryly or to keep them from establishing a connection. So, it is STRONGLYstrongly RECOMMENDED that integrity protection be applied to the SDP session descriptions. For session descriptions carried in SIP , S/MIME is the natural choice to provide such end-to-end integrity protection, as described in RFC 3261 . Other applications MAY use a different form of integrity protection. 9.10. IANA Considerations This document defines two session and media level SDP attributes: setup and connection. Their formats are defined in Section 4 and Section 5 respectively. These two attributes should be registered by the IANA on http://www.iana.org/assignments/sdp-parametersunder "Session Description Protocol (SDP) Parameters" under "att-field (both session and media level)". This document defines a proto value: TCP. Its format is defined in Section 3. This proto value should be registered by the IANA on http://www.iana.org/assignments/sdp-parametersunder "Session Description Protocol (SDP) Parameters" under "proto". SpecificationsThe SDP specification, RFC2327, states that specifications defining new proto values, like the TCP proto value defined in this one,RFC, must define the rules by which their media format (fmt) namespace is managed. For the TCP protocol, new formats SHOULD have an associated MIME registration. Use of an existing MIME subtype for the format is encouraged. If no MIME subtype exists, it is RECOMMENDED that a suitable one is registered through the IETF process  by production of, or reference to, a standards-track RFC that defines the transport protocol for the format. 10.11. Acknowledgements Jonathan Rosenberg, Rohan Mahy, Anders Kristensen, Joerg Ott, Paul Kyzivat, Robert Fairlie-Cuninghame, Colin Perkins, and Christer Holmberg provided valuable insights and contributions. 11.12. References 11.112.1 Normative References  Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981.  Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", BCP 13, RFC 2048, November 1996.  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  Handley, M. and V. Jacobson, "SDP: Session Description Protocol", RFC 2327, April 1998.  Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, June 2002. 11.212.2 Informative References  Schulzrinne, H., Rao, A. and R. Lanphier, "Real Time Streaming Protocol (RTSP)", RFC 2326, April 1998.  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, January 1999.  Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.  Handley, M., Perkins, C. and E. Whelan, "Session Announcement Protocol", RFC 2974, October 2000.  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.  Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003.  Rosenberg, J., Peterson, J., Schulzrinne, H. and G. Camarillo, "Best Current Practices for Third Party Call Control (3pcc) in the Session Initiation Protocol (SIP)", BCP 85, RFC 3725, April 2004. Authors' Addresses David Yon Tactical Software, LLC 670 N Commercial St Manchester, NH 03101 USA EMail: firstname.lastname@example.org Gonzalo Camarillo Ericsson Hirsalantie 11 Jorvas 02420 Finland EMail: Gonzalo.Camarillo@ericsson.com Intellectual Property Statement 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 email@example.com. Disclaimer of Validity 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. Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society.