Network Working Group F. Le Faucheur Internet-Draft Cisco Intended status: Standards Track J. Manner Expires: April 16, 2007 University of Helsinki D. Wing Cisco October 13, 2006 RSVP Proxy Approaches draft-lefaucheur-tsvwg-rsvp-proxy-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 Internet-Draft will expire on April 16, 2007. Copyright Notice Copyright (C) The Internet Society (2006). Le Faucheur, et al. Expires April 16, 2007 [Page 1] Internet-Draft RSVP Proxy October 2006 Abstract RSVP signaling can be used to make end-to-end resource reservations in an IP network in order to guarantee the QoS required by certain flows. With RSVP, both the data sender and receiver of a given flow take part in RSVP signaling. Yet, there are many use cases where resource reservation is required, but the receiver, the sender, or both, is not RSVP-capable. This document defines RSVP Proxy behaviors allowing RSVP routers to perform RSVP signaling on behalf of a receiver or a sender that is not RSVP-capable. This allows resource reservations to be established on parts of the end-to-end path. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. RSVP Proxy Behaviors . . . . . . . . . . . . . . . . . . . . . 5 2.1. RSVP Receiver Proxy . . . . . . . . . . . . . . . . . . . 5 2.2. RSVP Sender Proxy . . . . . . . . . . . . . . . . . . . . 6 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. RSVP Proxy Approaches . . . . . . . . . . . . . . . . . . . . 9 4.1. Path-Triggered Receiver Proxy . . . . . . . . . . . . . . 9 4.2. Path-Triggered Sender Proxy for Reverse Direction . . . . 11 4.3. Inspection-Triggered Proxy . . . . . . . . . . . . . . . . 14 4.4. STUN-Triggered Proxy . . . . . . . . . . . . . . . . . . . 16 4.4.1. STUN BANDWIDTH Attribute . . . . . . . . . . . . . . . 18 4.4.2. STUN APPLICATION-IDENTIFIER Attribute . . . . . . . . 18 4.5. Application-Signaling-Triggered On-Path Proxy . . . . . . 19 4.6. Application-Signaling-Triggered Off-Path Source Proxy . . 22 4.7. RSVP-Signaling-Triggered Proxy . . . . . . . . . . . . . . 24 4.8. Other Approaches . . . . . . . . . . . . . . . . . . . . . 25 5. Security Considerations . . . . . . . . . . . . . . . . . . . 26 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29 8.1. Normative References . . . . . . . . . . . . . . . . . . . 29 8.2. Informative References . . . . . . . . . . . . . . . . . . 29 Appendix A. Use Cases for RSVP Proxies . . . . . . . . . . . . . 31 A.1. RSVP-based VoD CAC in Broadband Aggregation Networks . . . 31 A.2. RSVP-based Voice/Video CAC in Enterprise WAN . . . . . . . 34 A.3. RSVP-based Voice CAC in TSP Domain . . . . . . . . . . . . 35 A.4. RSVP Proxies for Mobile Access Networks . . . . . . . . . 36 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 39 Intellectual Property and Copyright Statements . . . . . . . . . . 40 Le Faucheur, et al. Expires April 16, 2007 [Page 2] Internet-Draft RSVP Proxy October 2006 1. Introduction Guaranteed QoS for some applications with tight Qos requirements may be achieved by reserving resources in each node on the end-to-end path. The main IETF protocol for these resource reservations is RSVP specified in [RFC2205]. RSVP does not require that all intermediate nodes support RSVP, however it assumes that both the sender and the receiver of the data flow support RSVP. There are environments where it would be useful to be able to reserve resources for a flow on at least a subset of the flow path even when the sender or the receiver (or both) is not RSVP capable. Since either the data sender or receiver may be unaware of RSVP, there are two distinct use cases. In the first case, an entity in the network must operate on behalf of the data sender, generate an RSVP Path message, and eventually receive, process and sink a Resv message. We refer to this entity as the RSVP Sender Proxy. In the latter case, an entity in the network must receive a Path message sent by a data sender (or by an RSVP Sender Proxy), and reply to it with a Resv message on behalf of the data receiver(s). We refer to this entity as the RSVP Receiver Proxy. The flow sender and receiver generally have at least some (if not full) awareness of the application producing or consuming that flow. Hence, the sender and receiver are in a natural position to synchronize the establishment, maintenance and tear down of the RSVP reservation with the application requirements and to determine the characteristics of the reservation (bandwidth, QoS service,...) which best match the application requirements. For example, before completing the establishment of a multimedia session, the endpoints may decide to establish RSVP reservations for the corresponding flows. Similarly, when the multimedia session is torn down, the endpoints may decide to tear down the corresponding RSVP reservations. For example, [RFC3312] discusses how RSVP reservations can be very tightly synchronised by SIP endpoints with SIP session control and SIP signaling. When RSVP reservation establishment, maintenance and tear down is to be handled by RSVP Proxy devices on behalf of an RSVP sender or receiver, a key challenge for the RSVP proxy is to determine when the RSVP reservations need to be established, maintained and torn down and to determine what are the characteristics (bandwidth, QoS Service,...) of the required RSVP reservations matching the application requirements. We refer to this problem as the synchronization of RSVP reservations with application level requirements. The IETF Next Steps in Signaling (NSIS) working group is designing, Le Faucheur, et al. Expires April 16, 2007 [Page 3] Internet-Draft RSVP Proxy October 2006 as one their many charter items, a new QoS signaling protocol. This scheme already includes the notion of proxy operation, and terminating QoS signaling on nodes that are not the actual data senders or receivers. This is the same concept as the proxy operation for RSVP discussed in this document. One difference though is that the NSIS framework does not consider multicast resource reservations, which RSVP provides today. The next two sections introduce the notion of RSVP Sender Proxy and RSVP receiver Proxy. The following section defines useful terminology. The subsequent section then presents several fundamental RSVP Proxy approaches insisting on how they achieve the synchronization of RSVP reservations with application level requirements. Appendix A includes more detailed use cases for the proxies in various deployment environments. Le Faucheur, et al. Expires April 16, 2007 [Page 4] Internet-Draft RSVP Proxy October 2006 2. RSVP Proxy Behaviors This section discusses the two types of proxies; the RSVP Sender Proxy operating on behalf of data senders, and the RSVP Receiver Proxy operating for data receivers. The concepts presented in this document are not meant to replace the standard RSVP and end-to-end RSVP reservations are still expected to be used whenever possible. However, RSVP Proxies are intended to facilitate RSVP deployment where end-to-end RSVP signaling is not possible. 2.1. RSVP Receiver Proxy RSVP reservations are initiated by receivers of data. When a data sender sends an RSVP Path message towards the intended recipient(s), each recipient that requires a reservation must respond with a Resv message. If, however, a data receiver is not running the RSVP protocol, the last hop RSVP router will still send the Path message to the data receiver, which will silently drop an IP packet with an unknown protocol number. In order for reservations to be made in such a scenario, one of the RSVP routers on the data path must somehow know that the data receiver will not be participating in the resource reservation signaling. This RSVP router should, thus, perform RSVP Receiver Proxy functionality on behalf of the data receiver. Various mechanisms by which the RSVP proxy router can gain the required information are discussed later in the document. Le Faucheur, et al. Expires April 16, 2007 [Page 5] Internet-Draft RSVP Proxy October 2006 |----| *** *** |----------| |----| | S |---------*r*----------*r*---------| RSVP |----------| R | |----| *** *** | Receiver | |----| | Proxy | |----------| *************************************************************> ===================RSVP======================> |----| RSVP-capable |----| non-RSVP-capable *** | S | Sender | R | Receiver *r* regular RSVP |----| |----| *** router ***> unidirectional media flow ==> segment of flow path protected by RSVP reservation 2.2. RSVP Sender Proxy If a data sender is not running the RSVP protocol, a resource reservation can not be set up; a data receiver can not alone reserve resources without Path messages first being sent. Thus, even if the data receiver is running RSVP, it still needs some node on the data path to send a Path message towards the data receiver. One example use case would be a public streaming media server, which is unaware of RSVP. In a similar manner to the RSVP Receiver Proxy, a RSVP node on the data path must somehow know that it should generate a Path message for setting up a resource reservation. This case is more complex than the Receiver Proxy, since the RSVP Sender Proxy must be able to generate all the information in the Path message (such as the Sender TSpec) without the benefit of having previously seen any RSVP messages. An RSVP Receiver Proxy, by contrast only needs to formulate an appropriate RESV message in response to an incoming Path message. Mechanisms to operate an RSVP Sender Proxy are discussed later in this document. Le Faucheur, et al. Expires April 16, 2007 [Page 6] Internet-Draft RSVP Proxy October 2006 |----| |----------| *** *** |----| | S |---------| RSVP |---------*r*----------*r*----------| R | |----| | Sender | *** *** |----| | Proxy | |----------| *************************************************************> ================RSVP======================> |----| non-RSVP-capable |----| RSVP-capable *** | S | Sender | R | Receiver *r* regular RSVP |----| |----| *** router ***> unidirectional media flow ==> segment of flow path protected by RSVP reservation Le Faucheur, et al. Expires April 16, 2007 [Page 7] Internet-Draft RSVP Proxy October 2006 3. Terminology On-Path: located on the datapath of the actual flow of data from the application (regardless of where it is located on the application level signaling path) Off-Path: not On-Path RSVP-capable (or RSVP-aware): which supports the RSVP protocol as per [RFC2205] RSVP Receiver Proxy: an RSVP capable router performing, on behalf of a receiver, the RSVP operations which would normally be performed by an RSVP-capable receiver if end-to-end RSVP signaling was used. Note that while RSVP is used upstream of the RSVP Receiver Proxy, RSVP is not used downstream of the RSVP Receiver Proxy. RSVP Sender Proxy: an RSVP capable router performing, on behalf of a sender, the RSVP operations which would normally be performed by an RSVP-capable sender if end-to-end RSVP signaling was used. Note that while RSVP is used downstream of the RSVP Sender Proxy, RSVP is not used upstream of the RSVP Sender Proxy. Regular RSVP Router: an RSVP-capable router which is not behaving as a RSVP Receiver Proxy nor as a RSVP Sender Proxy. Note that the roles of RSVP Receiver Proxy, RSVP Sender Proxy, Regular RSVP Router are all relative to one unidirectional flow. A given router may act as the RSVP Receiver Proxy for a flow, as the RSVP Sender Proxy for another flow and as a Regular RSVP router for yet another flow. Application level signaling: signaling between entities operating above the IP layer and which are aware of the QoS requirements for actual media flows. SIP and RTSP are examples of application level signaling protocol. RSVP is clearly not an application level signaling. Le Faucheur, et al. Expires April 16, 2007 [Page 8] Internet-Draft RSVP Proxy October 2006 4. RSVP Proxy Approaches This section specifies several fundamental RSVP Proxy approaches. An implementation complying to this document MUST implement the MANDATORY Path-Triggered Proxy approach and MAY implement any other approach defined in this section. When an implementation supports an OPTIONAL approach, it MUST implement all the MANDATORY aspects of that approach. 4.1. Path-Triggered Receiver Proxy In this approach, it is assumed that the sender is RSVP capable and takes full care of the synchronisation between application requirements and RSVP reservations. With this approach, the RSVP Receiver Proxy uses the RSVP Path messages generated by the sender as the cue for establishing the RSVP reservation on behalf of the receiver. The RSVP Receiver Proxy is effectively acting as a slave making reservations (on behalf of the receiver) under the sender's control. This changes somewhat the usual RSVP reservation model where reservations are normally controlled by receivers. Such a change greatly facilitates operations in the scenario of interest here, which is where the receiver is not RSVP capable. Indeed it allows the RSVP Receiver Proxy to remain application unaware by taking advantage of the application awareness and RSVP awareness of the sender. With the Path-Triggered RSVP Receiver Proxy approach, the RSVP router MUST be configurable to use receipt of a regular RSVP Path message as the trigger for RSVP Receiver Proxy behavior. On receipt of the RSVP Path message, the RSVP Receiver Proxy MUST: 1. establish the RSVP Path state as per regular RSVP processing 2. identify the downstream interface towards the receiver 3. sink the Path message 4. behave as if a Resv message (whose details are discussed below) was received on the downstream interface. This includes admission control, establishing a Resv state (in case of successful admission control) and forward the Resv message upstream. Details on how to build the Resv message from the Path message will be provided in the next version of this document. Operation of the Path-Triggered Receiver Proxy in the case of a Le Faucheur, et al. Expires April 16, 2007 [Page 9] Internet-Draft RSVP Proxy October 2006 successful reservation is illustrated in the Figure below. |----| *** *** |----------| |----| | S |---------*r*----------*r*---------| RSVP |----------| R | |----| *** *** | Receiver | |----| | Proxy | |----------| *************************************************************> ===================RSVP======================> ---Path---> ----Path----> ---Path----> <--Resv---> <---Resv----- <--Resv---- |----| |----| *** | S | Sender | R | Receiver *r* regular RSVP |----| |----| *** router ***> media flow ==> segment of flow path protected by RSVP reservation As explained above, the synchronisation between application and RSVP reservations is handled by the sender. To ensure that the sender is notified of an admission control failure happening somewhere on the reservation path (i.e. between the RSVP Receiver Proxy and the sender), on receipt of a ResvErr message with Error Code = "01: Admission Control failure", the RSVP Receiver Proxy MUST generate a PathErr message with Error Code = "01: Admission Control failure". Operation of the Path-Triggered RSVP Receiver Proxy in the case of an admission control failure is illustrated in the Figure below. Le Faucheur, et al. Expires April 16, 2007 [Page 10] Internet-Draft RSVP Proxy October 2006 |----| *** *** |----------| |----| | S |---------*r*----------*r*---------| RSVP |----------| R | |----| *** *** | Receiver | |----| | Proxy | |----------| *************************************************************> ===================RSVP======================> ---Path---> ----Path----> ---Path----> <---Resv----- <--Resv------ ---ResvErr---> --ResvErr---> <--PathErr- <--PathErr--- <--PathErr--- |----| |----| *** | S | Sender | R | Receiver *r* regular RSVP |----| |----| *** router ***> media flow ==> segment of flow path protected by RSVP reservation We observe that this approach does not require any extensions to the existing RSVP protocol (other than the use of the Error Code = "01: Admission Control failure" in PathErr message, while it is currently only allowed in ResvErr messages). 4.2. Path-Triggered Sender Proxy for Reverse Direction In this approach, it is assumed that one endpoint is RSVP capable and takes full care of the synchronisation between application requirements and RSVP reservations. This endpoint is the sender for one flow direction (which we refer to as the "forward" direction) and is the receiver for the flow in the opposite direction (which we refer to as the "reverse" direction). With the Path-Triggered Sender Proxy for Reverse Direction approach, the RSVP Proxy uses the RSVP signaling generated by the sender as the cue for initiating RSVP signaling for the reservation in the reverse direction. Thus, the RSVP Proxy is effectively acting as a Sender Proxy for the reverse direction under the control of the sender for Le Faucheur, et al. Expires April 16, 2007 [Page 11] Internet-Draft RSVP Proxy October 2006 the forward direction. Note that this assumes a degree of symmetry for the two directions of the flow (as is currently typical for IP telephony, for example). This is illustrated in the Figure below. |----| *** *** |----------| |----| | E |---------*r*----------*r*---------| RSVP |----------| E | |----| *** *** | Receiver | |----| | Proxy | |----------| *************************************************************> <===================RSVP====================== ---Path---> ----Path----> ---Path----> <--Path---> <---Path----- <--Path---- ---Resv---> ----Resv----> ---Resv----> |----| *** | E | Endpoint *r* regular RSVP |----| *** router ***> media flow ==> segment of flow path protected by RSVP reservation in reverse direction Of course, the RSVP Proxy may simultaneously (and typically will) also act as the Path-Triggered Receiver Proxy for the forward direction, as defined in Section 4.1. Such an approach is most useful in situations involving RSVP reservations in both directions for symmetric flows. This is illustrated in the Figure below Le Faucheur, et al. Expires April 16, 2007 [Page 12] Internet-Draft RSVP Proxy October 2006 |----| *** *** |----------| |----| | E |---------*r*----------*r*---------| RSVP |----------| E | |----| *** *** | Receiver | |----| | Proxy | |----------| *************************************************************> <===================RSVP=====================> ---Path---> ----Path----> ---Path----> <--Resv---> <---Resv----- <--Resv---- <--Path---> <---Path----- <--Path---- ---Resv---> ----Resv----> ---Resv----> |----| *** | E | Endpoint *r* regular RSVP |----| *** router <***> media flow <==> segment of flow path protected by RSVP reservation in forward and in reverse direction With the Path-Triggered Sender Proxy for Reverse Direction approach, the RSVP router MUST be configurable to use receipt of a regular RSVP Path message as the trigger for Sender Proxy for Reverse Direction behavior. On receipt of the RSVP Path message for the forward direction, the RSVP Sender Receiver Proxy MUST: 1. sink the Path message 2. behave as if a Path message for reverse direction (whose details are discussed below) had been received by the Sender Proxy. This includes establishing the corresponding Path state and forward the Path message downstream. Details on how to build the Resv message from the Path message will be provided in the next version of this document Le Faucheur, et al. Expires April 16, 2007 [Page 13] Internet-Draft RSVP Proxy October 2006 We observe that this approach does not require any extensions to the existing RSVP protocol. 4.3. Inspection-Triggered Proxy In this approach, it is assumed that the RSVP Proxy device is on the datapath of "packets of interest", that it can inspect such packets on the fly as they transit through it, and that it can infer information from these packets of interest to determine what RSVP reservations need to be established, when and with what characteristics (possibly also using some configured information). One example of "packets of interest" could be application level signaling. An RSVP Proxy device capable of inspecting SIP signaling for multimedia session or RTSP signaling for Video streaming, can obtain from such signaling information about when a multimedia session is up or when a Video is going to be streamed. It can also identify the addresses and ports of senders and receivers and can determine the bandwidth of the corresponding flows. Thus, such an RSVP Proxy device can determine all necessary information to synchronise RSVP reservations to application requirements. This is illustrated in the Figure below. Le Faucheur, et al. Expires April 16, 2007 [Page 14] Internet-Draft RSVP Proxy October 2006 |-------------| | Application | | Signaling | | Entity | |-------------| // \\ // \\ // \\ |----| |--------| *** |--------| |----| | E |--------| RSVP |------*r*--------| RSVP |----------| E | |----| | Proxy | *** | Proxy | |----| |--------| |--------| <************************************************************> <=========RSVP=============> |----| | E | End system (sender, or receiver, or both) |----| *** *r* Regular RSVP router *** application level signaling <***> media flow <==> segment of flow path protected by RSVP reservation Another example of "packets of interest" could be packets belonging to the application flow itself (e.g. media packets). An RSVP Proxy device capable of detecting the transit of packets from a particular flow, can attempt to establish a reservation corresponding to that flow. Characteristics of the reservation MAY be derived from configuration, flow measurement or a combination of those. Note however, that in case of reservation failure, the inspection- triggered RSVP Proxy does not have a direct mechanism for notifying the application (since it is not participating itself actively in application signaling) so that the application takes appropriate action (for example terminate the corresponding session). To Le Faucheur, et al. Expires April 16, 2007 [Page 15] Internet-Draft RSVP Proxy October 2006 mitigate this problem, the inspection-triggered RSVP Proxy MAY mark differently the DSCP of flows for which an RSVP reservation has been successfully proxied from the flows for which a reservation is not in place. In some situations, the Inspection-Triggered Proxy might be able to modify the "packets of interest" (e.g. application signaling messages) to convey some hint to applications that the corresponding flows cannot be guaranteed by RSVP reservations. With the inspection-triggered Proxy approach, the RSVP Receiver Proxy is effectively required to attempt to build application awareness by traffic inspection and then is somewhat limited in the actions in can take in case of reservation failure. However, this may be a useful approach in some environments. Note also that this approach does not require any change to the RSVP protocol. With the "Inspection-Triggered" RSVP Proxy approach, the RSVP router MUST be configurable to use and interpret some specific "packets of interest" as the trigger for RSVP Receiver Proxy behavior. 4.4. STUN-Triggered Proxy In this approach, the RSVP Proxy entity takes advantage of the application awareness provided by the STUN signaling to synchronise RSVP reservations with application requirements. The STUN signaling is sent from endpoint to endpoint. This is illustrated in the figure below. Le Faucheur, et al. Expires April 16, 2007 [Page 16] Internet-Draft RSVP Proxy October 2006 |---------| | SIP | | Server | |---------| // \\ // \\ // \\ // \\ // \\ |----| |--------| *** |--------| |----| | E |--------| RSVP |------*r*--------| RSVP |----------| E | |----| | Proxy | *** | Proxy | |----| |--------| |--------| <**************************************************************> <=========RSVP=============> |----| | E | End system (sender, or receiver, or both) also STUN Clients |----| *** *r* Regular RSVP router *** <***> media flow <==> segment of flow path protected by RSVP reservation // signaling In this approach, a STUN [I-D.ietf-behave-rfc3489bis] message triggers the RSVP proxy. Using a STUN message eases the RSVP proxy agent's computational burden because it need only look for STUN messages rather than maintain state of all flows. More importantly, if the STUN message also includes additional STUN attributes describing the bandwidth or the application requesting the flow, the RSVP proxy agent can authorize an appropriately-sized reservation for each flow. For unicast flows, [I-D.ietf-mmusic-ice] is an already widely-adopted emerging standard for NAT traversal. For our purposes, we are not interested in its NAT traversal capabilities. Rather, ICE's useful characteristic is its connectivity check -- the exchange of STUN Binding Request messages between hosts to verify connectivity (see Le Faucheur, et al. Expires April 16, 2007 [Page 17] Internet-Draft RSVP Proxy October 2006 Connectivity Check Usage in [I-D.ietf-behave-rfc3489bis]). By including new STUN attributes (defined below) in those messages an RSVP proxy agent can perform its functions more effectively. Additionally, the RSVP proxy agent can inform endpoints of an RSVP reservation failure by dropping the ICE connectivity check message. This provides very RSVP-like call admission control and signaling to the endpoints, without implementing RSVP on the endpoints. For multicast flows (or certain kinds of unicast flows that don't or can't use ICE), the STUN Indication message type can be used for similar purposes. Like the STUN Binding Request message, the STUN Indication message can also contain the new attributes defined below. The STUN Indication is described in [I-D.ietf-behave-rfc3489bis]. 4.4.1. STUN BANDWIDTH Attribute A new STUN attribute, BANDWIDTH, is defined for the STUN Connectivity Check and the Indication usage. This attribute would be sent by the host that wants this amount of bandwidth for its subsequent flow. The RSVP proxy agent would use this attribute's value when performing its RSVP proxy function. The BANDWIDTH attribute is a 32-bit value. The bandwidth is expressed in kilobytes per second, allowing 1kbps to 4096gbps to be expressed. 4.4.2. STUN APPLICATION-IDENTIFIER Attribute A new STUN attribute, APPLICATION-IDENTIFIER, is defined for the STUN Connectivity Check and the Indication usage. This attribute would be sent by the host to identify the application associated with this flow. Application identifier values are coordinated between applications and RSVP proxies via a mechanism outside the scope of this document. The RSVP proxy can use the application identifier to request authorization prior to issuing an RSVP reservation for a flow, to request bandwidth information for a flow (assuming the BANDWIDTH attribute was not present), or to authorize a certain application's request for bandwidth. The APPLICATION-IDENTIFIER attribute is of arbitrary length. As with other STUN attributes, its length MUST be a on a word (32-bit) boundary. Le Faucheur, et al. Expires April 16, 2007 [Page 18] Internet-Draft RSVP Proxy October 2006 4.5. Application-Signaling-Triggered On-Path Proxy In this approach, it is assumed that an entity involved in the application level signaling controls an RSVP Proxy device which is located in the datapath of the application flows (i.e. "on-path"). In this case, the RSVP Proxy entity does not attempt to understand the application reservation requirements, but instead is instructed by the entity participating in application level signaling to establish, maintain and tear down reservations as needed by the application flows. In other words, with this approach, the solution for synchronising RSVP signaling with application-level signaling is to rely on an application-level signaling entity which controls an RSVP Proxy function that sits in the flow datapath. In some instantiations, the application-level signaling entity may be collocated with the on-path RSVP Proxy device. The figure below illustrates such an environment in the case where the application- level signaling protocol is SIP. Le Faucheur, et al. Expires April 16, 2007 [Page 19] Internet-Draft RSVP Proxy October 2006 |--------| |--------| -----------|SIP |----------------|SIP |---------- / |Server/ | |Server/ | \ / |Proxy | |Server/ | \ |----| |--------| *** |--------| |----| | E |-----------| On |------*r*-------| Bearer |----------| E | |----| | Path | *** | Path | |----| | Entity | | Entity | | + | | + | | RSVP | | RSVP | | Proxy | | Proxy | |--------| |--------| <******************> <***********************> <***************> <=========RSVP=============> |----| | E | End system (sender, or receiver, or both) |----| *** *r* Regular RSVP router *** <***> media flow <==> segment of flow path protected by RSVP reservation / SIP signaling Consider an environment involving decomposed Session Border Controllers (SBCs). The SBC function may be broken up into a Signaling Border Element (SBE) and Datapath Border Elements (DBEs). The DBEs are remotely controled by the SBE. This may be achieved using a protocol like [RFC3525]. Where admission control and bandwidth reservation is required between the SBEs for QoS guarantees of the sessions, the SBE could implement RSVP Proxy functionality. In that case, the application-level signaling entity (the SBE) is remotely located from the on-path RSVP Proxy devices (located in the DBEs). Such an environment is illustrated in the Figure below. Le Faucheur, et al. Expires April 16, 2007 [Page 20] Internet-Draft RSVP Proxy October 2006 |---------| -----------------| SBE |------------------ / | | \ / |---------| \ / // \\ \ / // \\ \ / // \\ \ / // \\ \ / // \\ \ |----| |--------| *** |--------| |----| | E |-----------| DBE |------*r*-------| DBE |----------| E | |----| | | *** | | |----| | + | | + | | RSVP | | RSVP | | Proxy | | Proxy | |--------| |--------| <******************> <***********************> <***************> <=========RSVP=============> |----| | E | End system (sender, or receiver, or both) |----| *** *r* Regular RSVP router *** SBE Signaling Border Element DBE Datapath Border Element SBE + DBE = decomposed Session Border Controller (decomposed SBC) <***> media flow <==> segment of flow path protected by RSVP reservation / SIP signaling // control interface between the SBE and DBE This RSVP Proxy approach does not require any extension to the RSVP protocol. However, it may require extensions to the protocol (e.g. that may be based on [RFC3525]) used by the application level signaling entity to control the remote on-path RSVP Proxy entities. Le Faucheur, et al. Expires April 16, 2007 [Page 21] Internet-Draft RSVP Proxy October 2006 4.6. Application-Signaling-Triggered Off-Path Source Proxy In this approach, it is assumed that an entity involved in the application level signaling also behaves as the RSVP Source Proxy device. However, since such an application level signaling entity is generally not on the datapath of the actual application flows, the RSVP messages need to be logically "tunnelled" between the off-path RSVP Source Proxy and a router in the datapath and upstream of the segment of the path to be protected by RSVP reservations. This is to ensure that the RSVP messages follow the exact same path as the flow they protect (as required by RSVP operations) on the segment of the end-to-end path which is to be subject to RSVP reservations. With this approach, the solution for synchronising RSVP signaling with application-level signaling is to co-locale the RSVP Proxy function with a (typically) off-path application-level signaling entity and then "tunnel" the RSVP signaling towards the appropriate router in the datapath. The figure below illustrates such an environment. Le Faucheur, et al. Expires April 16, 2007 [Page 22] Internet-Draft RSVP Proxy October 2006 |-------------| --------------| Application |----------- / | Signaling | \ / | Entity + | \ / | RSVP Sender | \ / | Proxy | \ / |-------------| \ / /=/ \ / /=/ \ / /=/ \ / /=/ \ / /=/ \ |----| |--------| *** |----| | S |-----------| RSVP |-----------*r*----------------------| R | |----| | Router | *** |----| |--------| ****************************************************************> =========RSVP==============================> |----| |----| *** | S | Sender | R | Receiver *r* regular RSVP |----| |----| *** router <***> media flow ==> segment of flow path protected by RSVP reservation in forward direction / Application level signaling /*/ GRE-tunnelled RSVP (Path messages) With the "Application-Triggered Off-Path Source Proxy" approach, the RSVP Proxy MUST: o generate a Path message on behalf of the sender corresponding to the reservation needed by the application and maintain the corresponding Path state o build a Path message which is exactly the same as would be built by the actual sender (if it was RSVP capable), with one single exception which is that the RSVP Sender Proxy MUST put its own IP address as the RSVP Previous Hop Le Faucheur, et al. Expires April 16, 2007 [Page 23] Internet-Draft RSVP Proxy October 2006 o encapsulate the Path message into a GRE tunnel whose destination address is an RSVP Router sitting on the datapath for the flow (and upstream of the segment which requires QoS guarantees via RSVP reservation) o process the corresponding received RSVP messages (including Resv messages) as per regular RSVP o synchronise the RSVP reservation state with application level requirements and signaling Note that since the Off-Path Source Proxy encodes its own IP address as the RSVP PHOP in the Path message, the RSVP Router terminating the GRE tunnel naturally addresses all the RSVP messages travelling upstream hop-by-hop (such as Resv messages) to the Off-Path Source Proxy (without having to encapsulate those in a reverse-direction GRE tunnel to the Off-Path Proxy). This RSVP Proxy approach does not require any extension to the RSVP protocol (other than tunneling the Path messages in a GRE tunnel). 4.7. RSVP-Signaling-Triggered Proxy An RSVP proxy can also be triggered and controlled through extended RSVP signaling from the remote end that is RSVP-capable (and supports these RSVP extensions for Proxy control). The challenges in these explicit signaling schemes are: o How does the proxy differentiate between reservation requests that must be proxied, from requests that should go end-to-end? o How does the node sending the explicit messages know where the proxy is located, e.g., an IP address of the proxy that should reply to the signaling? o How are sender and receiver proxy operations differentiated? An example of such a mechanism is the Localized RSVP (LRSVP) [I-D.manner-tsvwg-rsvp-proxy-sig]. This scheme is primarily targeted to local access network reservations whereby an end host can request resource reservations for both incoming and outgoing flows only over the access network. This may be useful in environments where the access network is typically the bottleneck while the core is comparatively over-provisioned, as may be the case with a number of radio access technologies. In LRSVP, messages targeted to the proxy are identified with one bit in all RSVP message. Similarly, all messages sent by the proxy back Le Faucheur, et al. Expires April 16, 2007 [Page 24] Internet-Draft RSVP Proxy October 2006 are marked. The use of one bit allows differentiating between proxied and end-to-end reservations. For triggering an RSVP receiver proxy, the sender of the data sends a PATH message which is marked with the mentioned one bit. The receiver proxy is located on the signaling and data path, eventually gets the PATH message, and replies back with a RESV. A node triggers an RSVP sender proxy with a new PATH_REQUEST message, which instructs the proxy to send a PATH messages towards the triggering node. The node then replies back with a RESV. More details can be found in [I-D.manner-tsvwg-rsvp-proxy-sig]. Such RSVP-Signaling-Triggered Proxy approaches require RSVP signaling extensions, however they can provide more flexibility in the control of the Proxy behavior (e.g. control of reverse reservation parameters). 4.8. Other Approaches In some cases, having a full RSVP implementation running on an end host can be seen to produce excessive overhead. In end-hosts that are low in processing power and functionality, having an RSVP daemon run and take care of the signaling may introduce unnecessary overhead. One article [Kars01] proposes to create a remote API so that the daemon would in fact run on the end-host's default router and the end-host application would send its requests to that daemon. Thus, we can have deployments, where an end host uses some proprietary simple protocol to communicate with its pre-defined RSVP router - a form of RSVP proxy. Le Faucheur, et al. Expires April 16, 2007 [Page 25] Internet-Draft RSVP Proxy October 2006 5. Security Considerations In the environments concerned by this document, RSVP messages are used to control resource reservations on a segment of the end-to-end path of flows. To ensure the integrity of the associated reservation and admission control mechanisms, the mechanisms defined in [RFC2747]] and [RFC3097] can be used. Those protect RSVP messages integrity hop-by-hop and provide node authentication, thereby protecting against corruption and spoofing of RSVP messages. An important issue regarding the various types of proxy functionality is authorization: which node is authorized to send messages on behalf of the data sender or receiver, and how is the authorization verified? RFC 3520 [RFC3520] presents a mechanism to include authorization information within RSVP signaling messages. Subsequent versions of this document will discuss in more details how such mechanisms can be used to address security of RSVP Proxy approaches. Le Faucheur, et al. Expires April 16, 2007 [Page 26] Internet-Draft RSVP Proxy October 2006 6. IANA Considerations This document requires IANA registration for its new STUN attributes, BANDWIDTH and APPLICATION-IDENTIFIER. The registration details of these STUN attributes will be described in a later version of this document. Le Faucheur, et al. Expires April 16, 2007 [Page 27] Internet-Draft RSVP Proxy October 2006 7. Acknowledgments This document benefited from earlier work on the concept of RSVP Proxy including the one documented by Silvano Gai, Dinesh Dutt, Nitsan Elfassy and Yoram Bernet. It also benefited from discussions with Pratik Bose, Chris Christou and Michael Davenport. Le Faucheur, et al. Expires April 16, 2007 [Page 28] Internet-Draft RSVP Proxy October 2006 8. References 8.1. Normative References [I-D.ietf-behave-rfc3489bis] Rosenberg, J., "Simple Traversal Underneath Network Address Translators (NAT) (STUN)", draft-ietf-behave-rfc3489bis-04 (work in progress), July 2006. [I-D.ietf-mmusic-ice] Rosenberg, J., "Interactive Connectivity Establishment (ICE): A Methodology for Network Address Translator (NAT) Traversal for Offer/Answer Protocols", draft-ietf-mmusic-ice-11 (work in progress), October 2006. [RFC1633] Braden, B., Clark, D., and S. Shenker, "Integrated Services in the Internet Architecture: an Overview", RFC 1633, June 1994. [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, September 1997. [RFC2210] Wroclawski, J., "The Use of RSVP with IETF Integrated Services", RFC 2210, September 1997. [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998. [RFC2747] Baker, F., Lindell, B., and M. Talwar, "RSVP Cryptographic Authentication", RFC 2747, January 2000. [RFC2961] Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F., and S. Molendini, "RSVP Refresh Overhead Reduction Extensions", RFC 2961, April 2001. [RFC3097] Braden, R. and L. Zhang, "RSVP Cryptographic Authentication -- Updated Message Type Value", RFC 3097, April 2001. 8.2. Informative References [I-D.manner-tsvwg-rsvp-proxy-sig] Manner, J., "Localized RSVP for Controlling RSVP Proxies", October 2006. Le Faucheur, et al. Expires April 16, 2007 [Page 29] Internet-Draft RSVP Proxy October 2006 [Kars01] Karsten, M., "Experimental Extensions to RSVP -- Remote Client and One-Pass Signalling", IWQoS Karlsruhe, Germany, 2006. [RFC3312] Camarillo, G., Marshall, W., and J. Rosenberg, "Integration of Resource Management and Session Initiation Protocol (SIP)", RFC 3312, October 2002. [RFC3520] Hamer, L-N., Gage, B., Kosinski, B., and H. Shieh, "Session Authorization Policy Element", RFC 3520, April 2003. [RFC3525] Groves, C., Pantaleo, M., Anderson, T., and T. Taylor, "Gateway Control Protocol Version 1", RFC 3525, June 2003. Le Faucheur, et al. Expires April 16, 2007 [Page 30] Internet-Draft RSVP Proxy October 2006 Appendix A. Use Cases for RSVP Proxies A.1. RSVP-based VoD CAC in Broadband Aggregation Networks As broadband services for residential are becoming more and more prevalent, next generation aggregation networks are being deployed in order to aggregate traffic from broadband users (whether attached via Digital Subscriber Line technology aka DSL, Fiber To The Home/Curb aka FTTx, Cable or other broadband access technology) and service providers core network or service delivery platforms. Video on Demand (VoD) services which may be offered to broadband users present significant capacity planning challenges for the aggregation network because each VoD stream requires significant dedicated sustained bandwidth (typically 2-4 Mb/s in Standard Definition TV and 8-12 Mb/s in High Definition TV), the VoD codec algorithms are very sensitive to packet loss and the load resulting from such services is very hard to predict (e.g. it can vary very suddenly with block-buster titles made available as well as with commercial offerings). As a result, transport of VoD streams on the aggregation network usually translate into a strong requirement for admission control, so that the quality of established VoD sessions can be protected at all times by rejecting the excessive session attempts during unpredictable peaks, during link or node failures, or combination of those factors. RSVP can be used in the aggregation network for admission control of the VoD sessions. However, since Customer Premises equipment such as Set Top Boxes (which behave as the receiver for VoD streams) often do not yet support RSVP, the last IP hop in the aggregation network can behave as an RSVP Receiver Proxy. This way, RSVP can be used between VoD Pumps and the Last IP hop in the Aggregation network to perform accurate admission control of VoD streams over the resources set aside for VoD in the aggregation network (typically a certain percentage of the bandwidth of any link). As VoD streams are unidirectional, a simple "Path-Triggered" RSVP Receiver Proxy (as described in Section 4.1) is all that is required in this use case. The Figure below illustrates operation of RSVP-based admission control of VoD sessions in an Aggregation network involving RSVP support on the VoD Pump (the senders) and RSVP Receiver Proxy on the last IP hop of the aggregation network. All the customer premises equipment remain RSVP unaware. Le Faucheur, et al. Expires April 16, 2007 [Page 31] Internet-Draft RSVP Proxy October 2006 |-------------| ----| VoD SRM |----------- / | | \ / | | \ / | | \ / | | \ / |-------------| \ / \ / \ / \ / \ / \ |----| |------| *** *** |--------| |-----| |---| | VoD|--|RSVP |----*r*--*r*--|RSVP |--|DSLAM|~~~~|STB|--TV |Pump| |Router| *** *** |Receiver| |-----| |---| |----| |------| |Proxy | |--------| <---Aggregation Net-------------> ******************************************************> ====================RSVP==============> SRM Systems Resource Manager *** |---| *r* regular RSVP |STB| Set Top Box *** router |---| <***> media flow ==> segment of flow path protected by RSVP reservation in forward direction / VoD Application level signaling In the case where the VoD Pumps are not RSVP-capable, an Application- Signaling-triggered Off-Path Source Proxy (as described in Section 4.6) can also be implemented on the VoD Controller or Systems Resource Manager (SRM) devices typically involved in VoD deployments. The Figure below illustrates operation of RSVP-based admission control of VoD sessions in an Aggregation network involving such Application-Signaling-triggered Off-Path Source Proxy on the SRM and RSVP Receiver Proxy on the Last IP hop of the aggregation network. Le Faucheur, et al. Expires April 16, 2007 [Page 32] Internet-Draft RSVP Proxy October 2006 All the customer premises equipment, as well as the VoD pumps, remain RSVP unaware. |-------------| ----| VoD SRM |----------- / | | \ / | + | \ / | RSVP Sender | \ / | Proxy | \ / |-------------| \ / /=/ \ / /=/ \ / /=/ \ / /=/ \ / /=/ \ |----| |------| *** *** |--------| |-----| |---| | VoD|--|RSVP |----*r*--*r*--|RSVP |--|DSLAM|~~~~|STB|--TV |Pump| |Router| *** *** |Receiver| |-----| |---| |----| |------| |Proxy | |--------| <---Aggregation Net-------------> ******************************************************> ==============RSVP==============> SRM Systems Resource Manager *** |---| *r* regular RSVP |STB| Set Top Box *** router |---| <***> media flow ==> segment of flow path protected by RSVP reservation in forward direction / VoD Application level signaling /*/ GRE-tunnelled RSVP (Path messages) The RSVP Proxy entities specified in this document play a significant role here since they allow immediate deployment of an RSVP-based admission control solution for VoD without requiring any upgrade to Le Faucheur, et al. Expires April 16, 2007 [Page 33] Internet-Draft RSVP Proxy October 2006 the huge installed base of non-RSVP-capable customer premises equipment. In one mode described above, they also avoid upgrade of non-RSVP-capable VoD pumps. In turn, this means that the benefits of on-path admission control can be offered to VoD services over broadband aggregation networks. Those include accurate bandwidth accounting regardless of topology (hub-and-spoke, ring, mesh, star, arbitrary combinations) and dynamic adjustment to any change in topology (such as failure, routing change, additional links...). A.2. RSVP-based Voice/Video CAC in Enterprise WAN More and more enterprises are migrating their telephony and videoconferencing applications onto IP. When doing so, there is a need for retaining admission control capabilities of existing TDM- based systems to ensure the QoS of these applications is maintained even when transiting through the enterprise's Wide Area Network (WAN). Since many of the endpoints already deployed (such as IP Phones or Videoconferencing terminals) are not RSVP capable, RSVP Proxy approaches are very useful by allowing deployment of an RSVP- based admission control solution over the WAN without requiring upgrade of the existing terminals. A common deployment architecture for such environments involves Application-Signaling-Triggered On-Path RSVP Proxy as defined in Section 4.5. Routers sitting at the edges of the WAN network behave as Media Relay in the datapath. For example, such a Media Relay router on the WAN Edge may terminate a call-leg from the calling IP phone and relay it to another call-leg setup on the WAN side towards another Media Relay router on the egress side of the WAN towards the called IP phone. Finally that egress Media Relay router may terminate the call leg from the ingress Media Relay router and relay it onto a call-leg setup to the called IP Phone. The Media Relay routers setup, maintain and tear down the call-legs on the WAN segment under the control of the SIP Server/Proxy. They also establish, maintain and tear-down RSVP reservations over the WAN segment for these call-legs also under the control of the SIP Server/ Proxy. The SIP Server/Proxy synchronises the RSVP reservation status with the status of end-to-end calls. For example, the called IP phone will only be instructed to play a ring tone if the RSVP reservations for the corresponding WAN call leg has been successfully established. This architecture allowing RSVP-based admission control of voice and video on the Enterprise WAN is illustrated in the Figure below. Le Faucheur, et al. Expires April 16, 2007 [Page 34] Internet-Draft RSVP Proxy October 2006 |---------| --------------| SIP |------------ / | Server/ | \ / | Proxy | \ / |---------| \ / // \\ \ / // \\ \ / // \\ \ / // \\ \ / // \\ \ |-----| |--------| *** *** |--------| |-----| | IP |------| Media |---*r*---*r*---| Media |-------|IP | |Phone| | Relay | *** *** | Relay | |Phone| |-----| | + | | + | |-----| | RSVP | | RSVP | | Proxy | | Proxy | |--------| |--------| <--campus--> <--campus--> network network <---------WAN-----------> <*************> <***********************> <**************> <=========RSVP===========> *** *r* Regular RSVP router *** <***> media flow <==> segment of flow path protected by RSVP reservation / SIP signaling // control interface between the SIP Server/Proxy and Media Relay/RSVP Proxy A.3. RSVP-based Voice CAC in TSP Domain Let us consider an environment involving multiple Telephony Service Providers (TSPs). Those may be interconnected through Session Border Controllers (SBC) which are on-path i.e. on the datapath of the voice Le Faucheur, et al. Expires April 16, 2007 [Page 35] Internet-Draft RSVP Proxy October 2006 media streams. The SBCs may be remotely controlled by a SIP Server/ Proxy. Support of RSVP Proxy on one side of the SBC may be used to perform RSVP-based admission control through one of the TSP Domain, even if it is not used end-to-end (and in particular when another TSP domain remains entirely non-RSVP-aware). This relies on the Application-Signaling-Triggered On-Path RSVP Proxy presented in Section 4.5. This is illustrated in the Figure below. |---------| --------------| SIP |------------ / | Server/ | \ / | Proxy | \ / |---------| \ / || \ / || \ / || \ / || \ / || \ |-----| |---------| |--------| |---------| |-----| | IP |------| TSP |-----| SBC |-----| TSP |--|IP | |Phone| | Domain1 | | + | | Domain2 | |Phone| |-----| | | | RSVP | | | |-----| | | | Proxy | | | | | |--------| | | |---------| |---------| <******************************> <*************************> <=========RSVP===========> <***> media flow <==> segment of flow path protected by RSVP reservation / SIP signaling || control interface between the SIP Server/Proxy and SBC/RSVP Proxy A.4. RSVP Proxies for Mobile Access Networks Mobile access networks are increasingly based on IP technology. This implies that, on the network layer, all traffic, both traditional data and streamed data like audio or video, is transmitted as packets. Increasingly popular multimedia applications would benefit Le Faucheur, et al. Expires April 16, 2007 [Page 36] Internet-Draft RSVP Proxy October 2006 from better than best-effort service from the network, a forwarding service with strict Quality of Service (QoS) with guaranteed minimum bandwidth and bounded delay. Other applications, such as electronic commerce, network control and management, and remote login applications, would also benefit from a differentiated treatment. The IETF has two main models for providing differentiated treatment of packets in routers. The Integrated Services (IntServ) model [RFC1633] together with the Resource Reservation Protocol (RSVP) [RFC2205] [RFC2210] [RFC2961] provides per-flow guaranteed end-to-end transmission service. The Differentiated Services (DiffServ) framework [RFC2475] provides non- signaled flow differentiation that usually provides, but does not guarantee, proper transmission service. However, these architectures have weaknesses, for example, RSVP requires support from both communication end points, and the protocol may have potential performance issues in mobile environments. DiffServ can only provide statistical guarantees and is not well suited for dynamic environments. Let us consider a scenario, where a fixed network correspondent node (CN) would be sending a multimedia stream to an end host behind a wireless link. If the correspondent node does not support RSVP it cannot signal its traffic characteristics to the network and request specific forwarding services. Likewise, if the correspondent node is not able to mark its traffic with a proper DiffServ Code Point (DSCP) to trigger service differentiation, the multimedia stream will get only best-effort service which may result in poor visual and audio quality in the receiving application. Even if the connecting wired network is over-provisioned, an end host would still benefit from local resource reservations, especially in wireless access networks, where the bottleneck resource is most probably the wireless link. RSVP proxies would be a very beneficial solution to this problem. It would allow distinguishing local network reservations from the end- to-end reservations. The end host does not need to know the access network topology or the nodes that will reserve the local resources. The access network would do resource reservations for both incoming and outgoing flows based on certain criterion, e.g., filters based on application protocols. Another option is that the mobile end host makes an explicit reservation that identifies the intention and the access network will find the correct local access network node(s) to respond to the reservation. RSVP proxies would, thus, allow resource reservation over the segment which is the most likely bottleneck, the wireless connectivity. If the wireless access network uses a local mobility management mechanism, where the IP address of the mobile node does not change during handover, RSVP reservations would follow Le Faucheur, et al. Expires April 16, 2007 [Page 37] Internet-Draft RSVP Proxy October 2006 the mobile node movement. Le Faucheur, et al. Expires April 16, 2007 [Page 38] Internet-Draft RSVP Proxy October 2006 Authors' Addresses Francois Le Faucheur Cisco Systems Greenside, 400 Avenue de Roumanille Sophia Antipolis 06410 France Phone: +33 4 97 23 26 19 Email: flefauch@cisco.com Jukka Manner University of Helsinki P.O. Box 68 University of Helsinki FIN-00014 University of Helsinki Finland Phone: +358 9 191 51298 Email: jmanner@cs.helsinki.fi URI: http://www.cs.helsinki.fi/u/jmanner/ Dan Wing 771 Alder Drive Milpitas, CA 95035 United States Email: dwing@cisco.com Le Faucheur, et al. Expires April 16, 2007 [Page 39] Internet-Draft RSVP Proxy October 2006 Full 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. 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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. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Le Faucheur, et al. Expires April 16, 2007 [Page 40]