INTERNET DRAFT S Arun Prasad Motorola India Private Ltd Expiration Date: March 2007 September 2006 MLDv1 and MVDv2 Optimization draft-arun-ipv6-mld-00.txt Status of this Memo 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 becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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 entire section has been prepended to this document automatically during formatting without any direct involvement by the author(s) of this draft. Abstract This document describes an optimization for MLDv1 (RFC 2710) and MLDv2 (RFC 3810). As per this optimization, a new router on coming up will not send periodic "General Query" messages to get the list of multicast listeners. Instead, it will try to get the same from the Querier on the link. Only if no Querier are present on the link, will the new router move to Querier state and send "General Query" messages. This approach provides an advantage in eliminating possibly large number of "Multicast Listener Report" messages every time a new router comes up on a link. More the number of listeners on a link, more the advantage. S Arun Prasad [Expires March 2007] [Page 1] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 Table of Contents Abstract ................................................ 1 1 Introduction ............................................ 3 1.1 Present Behavior ...................................... 3 1.2 Proposed Optimization ................................. 3 2 Message Format .......................................... 4 2.1 Type .................................................. 5 2.2 Nr of Mcast Addresses (M) ............................. 5 2.3 Multicast Address ..................................... 5 3 Protocol Description .................................... 5 4 Router State Transition Diagram ......................... 7 5 Timers, Counters and Default values ..................... 9 6 Use case scenarios ...................................... 10 7 Support for MLDv2 ....................................... 11 7.1 Message Format ........................................ 11 7.11 Type ................................................ 12 7.12 Nr of Mcast Records (M) ............................. 13 7.13 Multicast Address Record ............................ 13 7.2 Protocol Description .................................. 13 7.3 Inter operability with MLDv1 .......................... 14 7.31 New Router is MLDv1 and Querier is MLDv2 ............ 14 7.32 New Router is MLDv2 and Querier is MLDv1 ............ 14 8 Normative References .................................... 14 Acknowledgement ............................................... 15 Author's Address .............................................. 15 Intellectual Property Statement ............................... 15 Copyright Statement ........................................... 15 S Arun Prasad [Expires March 2007] [Page 2] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 1. Introduction The Multicast Listener Discovery Protocol (MLD) is used by IPv6 routers to discover the presence of multicast listeners (i.e., nodes that wish to receive multicast packets) on their directly attached links, and to discover specifically which multicast addresses are of interest to those neighboring nodes. The MLDv2 protocol, when compared to MLDv1, adds support for "source filtering", i.e., the ability for a node to report interest in listening to packets *only* from specific source addresses, as required to support Source-Specific Multicast [RFC3569], or from *all but* specific source addresses, sent to a particular multicast address. MLDv2 is designed to be interoperable with MLDv1. This draft tries to optimize the MLDv1 & MLDv2 protocol by providing new routers coming up on a link with the ability to discover the presence of multicast listeners on the link from the Querier. Every time a new router comes up on a link, a multiple "Report" messages is sent for every multicast address having a listener. In the proposed optimization, the Querier will send one single "Querier Report" message to the new router containing a list of all the multicast addresses having listeners on the link. Also, the Querier at any given point of time will have up-to-date and accurate information about the listeners and thus the same will be communicated to the new router. Only if there is no Querier on the link, will the new router move to Querier state and start sending "General Query" messages. 1.1 Present Behavior When a new router comes up on a link, in order to quickly and reliably discover the presence of multicast listeners, it will move to the Querier state and send periodic "General Query" messages [Startup Query Count] with very small intervals [Startup Query Interval]. This process will result in all the multicast listeners responding with "Report" message for every multicast address they are interested in. 1.2 Proposed Optimization When a new router comes up on a link, it will discover the presence of multicast listeners on a link from the current Querier on the link. It will then - move to Non-Querier state if the Querier IP address is lower than its own - move to Querier state if the Querier IP address is higher than its own. The Querier will move to Non-Querier state. S Arun Prasad [Expires March 2007] [Page 3] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 If there is no Querier on the link, the new router will move to Querier state and discover the presence of multicast listeners by sending "General Query" messages. This process will result in only the Querier responding with a "Querier Report" message for all multicast address having listeners on the link. 2. Message Format Two new MLD messages are introduced in this proposal. They have the following format, Multicast Listener Querier Query - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 154 | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | Multicast Address | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Multicast Listener Querier Report - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 155 | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Nr of Mcast Addresses (M) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | Multicast Address [1] | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | Multicast Address [2] | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . | | . | | . | | . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | Multicast Address [M] | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ S Arun Prasad [Expires March 2007] [Page 4] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 2.1 Type Multicast Listener Querier Query : ICMP type = 154 (decimal) Multicast Listener Querier Report : ICMP type = 155 (decimal) In the rest of this document, the above message types are referred to simply as "Querier Query" and "Querier Report". 2.2 Nr of Mcast Addresses (M) Number of multicast addresses field is valid only in "Querier Report" message and it signifies the number of multicast addresses being reported in this message. 2.3 Multicast Address In the "Querier Query" message, the multicast address field will be set to zero. In the "Querier Report" message, the multicast address fields are set to the multicast addresses being reported. Thus a "Querier Report" message COULD be more than 24 octets long. If there are no multicast addresses to report, then "Nr of Mcast Addresses" is set to zero and the first multicast address field is also set to zero. Thus a "Querier Report" message will NEVER be less than 24 octets long. 3. Protocol Description A new router on startup, will move to the "Initial Non-Querier state". It will immediately send "Querier Query" message to link-scope all-routers multicast address FF02::2. The routers in the Non-Querier state on the link MUST ignore this "Querier Query" message. The router in the Querier state on the link will check if the source address in the "Query Querier" message is less than its own source address. - If YES, then it will immediately make a transition to the Non-Querier state. - If NO, then it will continue to be in Querier state. and respond (without any delay) with a unicast "Querier Report" message to the new router. This "Querier Report" message will contain the list of multicast addresses for which there are listeners on the link. It will then respond (without any delay) with a unicast "Querier Report" message to the new router. This "Querier Report" message will contain the list of multicast addresses for which there are listeners on the link. S Arun Prasad [Expires March 2007] [Page 5] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 When the new router receives the "Querier Report" message from the Querier, it will check if the source address in the "Querier Report" message is less than its own source address. - If YES, then it will immediately make a transition to the Non-Querier state and start the "Other Querier present" timer. - If NO, then it will immediately make a transition to the Querier state and start the "General Query Timer" (not the "Initial General Query timer" as it will be getting the list of multicast listeners on the link from this "Querier Report" message). It will then update (without any delay) its "multicast listeners" list with the multicast addresses present in the "Querier Report" message. If the new router does not receive any "Querier Report" message, this indicates that there is no Querier on the link. The new router will immediately make a transition to the Querier state, send the "General Query Message" and start the "Initial General Query timer" (as it needs to quickly and reliably discover the presence of multicast listeners on the link). NOTE: The new router in the "Initial Non-Querier state" will start a timer [Querier Query Response Interval] when sending the "Querier Query" message. If the "Querier Report" message is not received by this time, then it will re-send the "Querier Query" message "Querier Present Count" times before concluding that there is no Querier on the link. The router in Querier state will respond to the "Querier Query" message with the "Querier Report" message. If all multicast addresses having listeners on the link cannot be fitted into a single "Querier Report" message, then it will send additional "Querier Report" messages (without any delay) with the remaining multicast addresses. Each set of "Querier Report" messages will be sent [Robustness variable] times with a delay of [Querier Report Interval]. S Arun Prasad [Expires March 2007] [Page 6] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 4. Router State Transition Diagram --------------------- | Querier query | | resp. tmr expires | | (dec Querier | | pres. cnt., | | [if Querier pres. | Querier query | cnt. > 0] | resp. tmr expires | send Querier query, | (dec Querier | start Querier q. | pres. cnt., | resp. tmr) | [if Querier pres. | -------------- cnt. = 0] -------------->| | send gen. query, | | start i. gen. --------- | Initial | query. tmr) ------------- | Initial |------>| Non-Querier |------------------- | | --------- | | | | gen. q. tmr | (send Querier. q.| | | | expired | start Querier -------------- | |(send gen. q,| q. resp tmr, | | | |start gen. q.| dec Querier | |Querier report recd | | tmr) | present cnt.) | |with higher IP address \/ | | | |(update MLD record, -------------- | | |start gen. q. tmr) | |<--- Querier report| ------------------------>| | recd| | | with lower IP| | Querier | addr| | | (update MLD| ------------------------>| | record, start other| |other Querier present | |<--- Querier present| |timer expired | | | tmr)| |(send gen. query, -------------- | | |start gen. q. tmr) | | | \/ | | |Querier query| -------------- | | recd with | | | | | higher IP | | | | | address | | | | |(send Querier| | Non-Querier |<------------------ | report) | | | Querier query | | | | recd with ------------- -------------->| | lower IP address | -------------- (send Querier | general query | report, start | received | other Querier | with a lower | present tmr) | IP address | / | (start other | gen. query recd | Querier | with lower IP address | present tmr) | (start other Querier | | present tmr) --------------------- S Arun Prasad [Expires March 2007] [Page 7] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 A router may be in one of three possible states with respect to any single attached link: - "Initial Non-Querier", when the router comes up for the first time. - "Querier", when this router is designated to transmit MLD Queries on this link. - "Non-Querier", when there is another router designated to transmit MLD Queries on this link. The following six events can cause the router to change states: - "Querier report received from a router with lower IP address" occurs when a valid MLD Querier Report is received from a router on the same link with a lower IPv6 Source Address. To be valid, the Querier Report message MUST come from a link-local IPv6 Source Address, be at least 24 octets long, and have a correct MLD checksum. This event is significant only when in the "Initial Non-Querier" state. - "Querier report received from a router with higher IP address" occurs when a valid MLD Querier Report is received from a router on the same link with a higher IPv6 Source Address. To be valid, the Querier Report message MUST come from a link-local IPv6 Source Address, be at least 24 octets long, and have a correct MLD checksum. This event is significant only when in the "Initial Non-Querier" state. - "Querier query response timer expired" occurs when the timer set to receive the Querier Response from the current Querier on the link expires. This event is valid only when in "Initial Non-Querier" state. - "other Querier present timer expired" occurs when the timer set to note the presence of another Querier with a lower IP address on the link expires. This event is significant only when in the "Non-Querier" state. - "Querier query received from a router with a lower IP address" occurs when a valid MLD Querier Query is received from a router on the same link with a lower IPv6 Source Address. To be valid, the message MUST come from a link-local IPv6 Source Address, be at least 24 octets long, and have a correct MLD checksum. This event is significant only when in the "Querier" state. S Arun Prasad [Expires March 2007] [Page 8] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 - "General Querier received from a router with a lower IP address" occurs when a valid MLD General Query is received from a router on the same link with a lower IPv6 Source Address. To be valid, the message MUST come from a link-local IPv6 Source Address, be at least 24 octets long, and have a correct MLD checksum. This event is significant only when in the "Querier" state. There are seven actions that may be taken in response to the above events: - "start other Querier present timer" for the attached link to [Other Querier Present Interval]. - "send General Query" on the attached link. The General Query is sent to the link-scope all-nodes address (FF02::1), and has a Maximum Response Delay of [Query Response Interval]. - "start General Query timer" for the attached link to [Query Interval]. - "send Querier Query" on the attached link. The Querier query is sent to the link-scope all-router address (FF02::2). - "start Querier Query response timer" for the attached link to [Query Response Interval]. - "send Querier Report" on the attached link. The Querier Report is sent to the ipv6 unicast address from which the "Querier Query" message was received. - "decrement Querier present count" variable by one. The variable is decreased whenever "Querier Query response timer" expires. 5. Timers, Counters and Default values 5.1 Querier Query Response Interval The Querier Query Response Interval is the time interval between "Querier Query" messages sent by a router in the "Initial Non-Querier" state. Default: 1/16 the Query Interval. 5.2 Querier Present Count The Querier Present Count is the number of "Querier Query" messages sent by the router in "Initial Non-Querier" state. Default: Robustness variable. S Arun Prasad [Expires March 2007] [Page 9] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 5.3 Querier Report Interval Querier Report Interval is the time interval between re-transmission of the "Querier Report" message by the Querier to the new router. Default: 10 seconds. 6 Use case scenarios 6.1 New router comes up on a link. No other router present on the link. - New router will move to Querier state. 6.2 New router comes up on a link. Querier with a higher IP address present on the link. - New router will get the multicast listeners list from the Querier. Querier will move to Non-Querier state. New router will move to Querier state. 6.3 New router comes up on a link. Querier with a lower IP address present on the link. - New router will get the multicast listeners list from the Querier. New router will move to Non-Querier state. 6.4 New router comes up on a link. Querier with a higher IP address present on the link. "Querier Query" message gets lost on the link. - New router (after "Querier Present Count" retries) will move to Querier state and send periodic General Query messages. Querier on receiving this will move to Non-Querier state. 6.5 New router comes up on a link. Querier with a lower IP address present on the link. "Querier Query" message gets lost on the link. - New router will move to Querier state and send periodic General Query messages. Querier will also send periodic General Query messages. New router on receiving this message will move to Non-Querier state. 6.6 New router comes up on a link. Querier with a higher IP address present on the link. "Querier Report" message gets lost on the link. - New router (after "Querier Present Count" retries) will move to Querier state and send periodic General Query messages. Querier will have already moved to Non-Querier state. S Arun Prasad [Expires March 2007] [Page 10] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 6.7 New router comes up on a link. Querier with a lower IP address present on the link. "Querier Report" message gets lost on the link. - New router will move to Querier state and send periodic General Query messages. Querier will also send periodic General Query messages. New router on receiving this message will move to Non-Querier state. 7. Support for MLDv2 7.1 Message Format A 32 bit reserved field is appended at the end of MLDv1 "Querier Query" message in MLDv2. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 154 | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | Multicast Address | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ A new MLDv2 "Querier Response" message is introduced. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 156 | Reserved | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Nr of Mcast Records (M) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Multicast Address Record [1] . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . | . . . . . . | . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Multicast Address Record [M] . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ S Arun Prasad [Expires March 2007] [Page 11] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 Each Multicast Address Record has the following format, +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Record Type | Aux Data Len | Number of Sources (N) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Multicast Address | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | Source Address [1] | | | +- -+ | | | | | Source Address [2] | | | +- -+ . . . . . . . . . +- -+ | | | | | Source Address [N] | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Auxiliary Data . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 7.11 Type Multicast Listener Querier Query version 2: ICMP message type = 154 (decimal) Multicast Listener Querier Report version 2 : ICMP message type = 156 (decimal) In the rest of this document, the above message types are referred to simply as "Querier Query v2" and "Querier Report v2". The "Querier Query v2" message is identical to "Querier Query" message with only a 32 bit reserved field added at the end. S Arun Prasad [Expires March 2007] [Page 12] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 7.12 Nr of Mcast Records (M) Number of multicast records specifies how many Multicast Address Records are present in this Querier Report. 7.13 Multicast Address Record Each Multicast Address Record is a block of fields that contain information about a single multicast address having listeners on a link and the sources they are interested in. It is valid only in the "Querier Report v2" message. - Record Type Record Type specifies the filter type of this Multicast Address Record. There are two types, - INCLUDE (value = 1) indicates the listeners of the corresponding multicast address are interested only in the source addresses listed in this Multicast Address Record. - EXCLUDE (value = 2) indicates the listeners of the corresponding multicast address are not interested in the source addresses listed in the Multicast Address Record. - Multicast Address The Multicast Address field contains the multicast address to which this Multicast Address Record pertains. - Number of Sources (N) The Number of Sources (N) field specifies how many source addresses are present in this Multicast Address Record. - Source Address The Source Address fields contains the source addresses associated with this Multicast Address Record. 7.2 Protocol Description Continuation from section 3 described in this draft. When a new router comes up on a link, it will go to the "Initial Non-Querier" state and send a "Querier Query v2" message. The Querier on the link will respond with the "Querier Report v2" message. If all multicast address records cannot be fitted into a single "Querier Report v2" message, then it will send additional "Querier Report v2" messages with the remaining multicast address records. A single multicast address record may be spread across multiple "Querier Report v2" messages. S Arun Prasad [Expires March 2007] [Page 13] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 7.3 Inter operability with MLDv1 7.31 New router is MLDv2 capable and the Querier on the link is operating in MLDv1 mode. When a new router (MLDv2 capable) comes up on a link, it will send the "Querier Query v2" message (28 octets). The Querier (in MLDv1 mode) will read only the first 24 octets of the "Querier Query v2" message and respond with the "Querier Report v1 (type = 155)" message. The new router on receiving this message will come to know that the Querier is in MLDv1 mode. The new router will transit to Querier / Non-Querier state as described in section (3) of this draft. It will then update its multicast listeners list with the multicast addresses reported in "Querier Report v1" message, with filter type EXCLUDE and empty source address. After this the behavior of the new router is as described in RFC-3810. 7.32 New router is MLDv1 capable and the Querier on the link is operating in MLDv2 mode. When a new router (MLDv1 capable) comes up on a link, it will send a "Querier Query v1" message (24 octets). The Querier (in MLDv2 mode) will read the 24 octet "Querier Query v1" message and recognize the new router to be in MLDv1 mode. The Querier will transit to Querier / Non-Querier state as described in section (3) of this draft. It will respond with the "Querier Report v1 (type = 155)" message listing all the multicast address having listeners on the link. The new router will update its multicast listener list with the multicast addresses reported in the "Querier Report v1" message. After this the behavior of the old Querier (now may be in Querier or Non-Querier state) on the link is as described in RFC-3810. Inter operation with listeners in MLDv1 and MLDv2 modes are as described in RFC-3810. It is not impacted by this proposed enhancement. 8. Normative References [RFC2710] Deering, S., Fenner, W. and B. Haberman, "Multicast Listener Discovery (MLD) for IPv6", RFC 2710, October 1999. [RFC3810] R. Vida and L. Costa, "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, June 2004 S Arun Prasad [Expires March 2007] [Page 14] Internet Draft draft-arun-ipv6-mld-00.txt September 2006 Acknowledgment I would like to thank my "Motorola India Pvt Ltd" colleagues for their Guidelines and Support in helping me complete this draft. Author's Address S Arun Prasad arun@motorola.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 ietf-ipr@ietf.org. 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 (2006). 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. S Arun Prasad [Expires March 2007] [Page 15]