DIME T. TSOU Internet-Draft Huawei Intended status: Informational July 28, 2008 Expires: January 29, 2009 Capabilities Update Problem Statement draft-tsou-dime-capabilities-update-statement-00 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 January 29, 2009. TSOU Expires January 29, 2009 [Page 1] Internet-Draft Capabilities Update Problem Statement July 2008 Abstract This specification clarifies "Capabilities Update" in OPEN state defined in RFC 3588bis. Capabilities update in OPEN state can reuse commands CER/CEA commands for re-negotiation between Diameter peers when one of them changes its capabilities.It is a very important function in Diameter. However, RFC 3588 has defined a mechanism of containing capabilities list both in CER and CEA commands and the peer should update its local database whenever it receives CER/CEA. This makes the process complex and redundant when they are used in OPEN state. So this draft proposes a simpler solution based on CER/CEA commands to deal with this problem. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 4 3. Problem Overview . . . . . . . . . . . . . . . . . . . . . . . 5 4. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 9 4.1. Solution Description . . . . . . . . . . . . . . . . . . . 9 4.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.3. Changes to ABNF . . . . . . . . . . . . . . . . . . . . . 12 4.4. Compatibility Consideration . . . . . . . . . . . . . . . 12 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 7.1. Normative References . . . . . . . . . . . . . . . . . . . 15 7.2. Informative References . . . . . . . . . . . . . . . . . . 15 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16 Intellectual Property and Copyright Statements . . . . . . . . . . 17 TSOU Expires January 29, 2009 [Page 2] Internet-Draft Capabilities Update Problem Statement July 2008 1. Introduction This specification clarifies "Capabilities Update" in OPEN state defined in RFC 3588bis. It specifies reusing CER/CEA commands for capabilities re-negotiation between Diameter peers when one of them changes its capabilities after establishing connection. CER/CEA mechanism is formerly used in initialization phase when two Diameter peers establish a transport connection and in this case no one ever knows the capabilities of its peers. RFC 3588 defines a mechanism of containing capabilities list both in CER and CEA commands and the peer should update its local database whenever it receives CER/CEA. However, when CER/CEA are used in OPEN state, the above CER/CEA solution will make the exchange process complex and redundant because in this case diameter peer has cached the capabilities of its peers during initialization phase. If the receiver of CER does not change its capabilities, the sender of CER can get its peer's capabilities from cache memory and it doesn't need to process CEA (e.g. update its cache memory or routing tables). On the other hand, if the receiver of CER does change its capabilities, it also doesn't need to include the capabilities list in CEA because it will initial a new CER as soon as possible. So based on current solution, redundant data is transmitted and needless reactions are implemented in diameter peers. This specification proposes the issues describing the redundancy of Capabilities Update in OPEN state defined in RFC 3588bis, and in the meantime, it proposes a simplified solution based on CER/CEA commands for Capabilities Update. This solution is fully backwards compatible with the RFC 3588 Diameter Base Protocol. TSOU Expires January 29, 2009 [Page 3] Internet-Draft Capabilities Update Problem Statement July 2008 2. Terminology and Abbreviations The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. TSOU Expires January 29, 2009 [Page 4] Internet-Draft Capabilities Update Problem Statement July 2008 3. Problem Overview RFC 3588bis section 5.6.5 defines the Capabilities Update in OPEN state in details. It specifies reusing CER/CEA for re-negotiation between diameter peers. A Diameter node must initiate peer capabilities update by sending a Capabilities-Exchange-Req (CER) to all its peers which supports peer capabilities update and is in OPEN state. The receiver of CER in OPEN state must process and reply to the CER as a described in RFC 3588bis section 5.3. The CEA which the receiver sends MUST contain its latest capabilities. Peers that successfully process the peer capabilities update SHOULD also update their routing tables to reflect the change. In order to clarify the problems, we can analyze the message exchange based on the above solution in the following key scenarios: Scenario 1: The receiver of CER doesn't change its capabilities when a CER arrives. Scenario 2: The receiver of CER does change its capabilities when a CER arrives. Figure 1 provides an example of message exchange in scenario 1. In Open State, Node A changes its capabilities and it initializes a CER for Node B. Node B does not change its capabilities when it receives the CER from node A. Node A Node B | | | | | | | | +-----------------+ +-------------------+ | Node A supports | | Node B supports | | application(a,b)| | application(a,c,d)| +-----------------+ +-------------------+ | | | | ------------------------- In Open State --------------------------- | | +-----------------------+ +----------------------------+ |Capabilities of Node A | | Capabilities of Node B | |change and it supports | | don't change and it still | |application(a,b,c) | | supports application(a,c,d)| +-----------------------+ +----------------------------+ | CER(a,b,c) | TSOU Expires January 29, 2009 [Page 5] Internet-Draft Capabilities Update Problem Statement July 2008 |------------------------------------>| | +-----------------+ | |Determine common | | |application(a,c) | | +-----------------+ | | | | | +-----------------------+ | | Cache capabilities of | | | Node A and update | | | routing tables | | +-----------------------+ | | | CEA(Result-Code=DIAMETER_SUCCESS, | | a,c,d) | |<------------------------------------| +-----------------+ | |Determine common | | |applications(a,c)| | +-----------------+ | | | | | +-----------------------+ | | Cache capabilities of | | | Node B and update | | | routing table | | +----------- -----------+ | | | | | | | Figure1: Capabilities Update in scenario 1 From Figure 1, capabilities of node B haven't been updated at that time. B will return CEA containing the same capabilities as that during initialization phase and have been cached by node A. So node A will process the CEA repeatedly. Figure 2 provides an example of message exchange in scenario 2. In Open State, node A changes its capabilities and it initializes a CER for node B. Node B also changes its capabilities at the time it receives CER. This case rarely happens but it indeed occurs sometime. Node A Node B | | TSOU Expires January 29, 2009 [Page 6] Internet-Draft Capabilities Update Problem Statement July 2008 | | +-----------------+ +-------------------+ | Node A supports | | Node B supports | | application(a,b)| | application(a,c) | +-----------------+ +-------------------+ | | | In Open State | ------------------------------------------------------------- | | +-----------------------+ +------------------------+ |Capabilities of Node A | |Capabilities of Node B | |change and it supports | |change and it supports | |application(a,b,c) | | application(a,c,d) | +-----------------------+ +------------------------+ | CER(a,b,c) | |-------------------------------------->| | +-----------------+ | |Determine common | | |application(a,c) | | +-----------------+ | | | +-----------------------+ | | Cache capabilities of | | | Node A and update | | | routing tables | | CER(a,c,d) +-----------------------+ |<--------------------------------------| +-----------------+ | |Determine common | | |applications(a,c)| | +-----------------+ | | | +-----------------------+ | | Cache capabilities of | | | Node B and update | | | routing table | | +-----------------------+ | | CEA(Result-Code=DIAMETER_SUCCESS, | | a,c,d) | |<--------------------------------------| +-----------------+ | |Determine common | | |application(a,c) | | +-----------------+ | | | +-----------------------+ | | Cache capabilities of | | | Node B and update | | TSOU Expires January 29, 2009 [Page 7] Internet-Draft Capabilities Update Problem Statement July 2008 | routing tables | | +-----------------------+ | | CEA(Result-Code=DIAMETER_SUCCESS, | | a,b,c) | |-------------------------------------->| | +-----------------+ | |Determine common | | |application(a,c) | | +-----------------+ | | | +-----------------------+ | | Cache capabilities of | | | Node A and update | | | routing tables | | +-----------------------+ | | | | Figure2: Capabilities Update in scenario 2 From Figure 2, capabilities of node B have been updated at the time it receives CER from node A. According to current solution, there will be twice capabilities updates between the same two diameter nodes with the same capabilities list exchanged. Besides, in each peer, there will be twice repetitious processes, one for receiving of CER and one for receiving of CEA. TSOU Expires January 29, 2009 [Page 8] Internet-Draft Capabilities Update Problem Statement July 2008 4. Solution Overview This specification defines a solution for Capabilities Update in OPEN State based on CER/CEA commands and it is fully backwards compatible with the RFC 3588 Diameter Base Protocol. 4.1. Solution Description A Diameter node MUST initiate peer capabilities update by sending a Capabilities-Exchange-Req (CER) to all its peers which supports peer capabilities update and is in OPEN state. The receiver of CER in OPEN state MUST process and reply to the CER. The CEA which the receiver sends SHOULD NOT contain its capabilities list. Note that the receivers of CER which successfully process the peer capabilities update SHOULD also update their routing tables to reflect the change. The receiver of the CEA, with a Result-Code AVP indicating DIAMETER_SUCCESS SHOULD not update its storage and continue using local cached capabilities of its peer until a new CER arrives. The receiver of the CEA, with a Result-Code AVP other than DIAMETER_SUCCESS, initiates the transport disconnect. The peer may periodically attempt to reconnect, as stated in RFC3588bis section 2.1. Peer capabilities update in the OPEN state SHOULD be limited to the advertisement of the new list of supported applications and MUST preclude re-negotiation of security mechanism or other capabilities. If any capabilities change happens in the node (e.g. change in security mechanisms), other than a change in the supported applications, the node SHOULD gracefully terminate (setting the Disconnect-Cause AVP value to REBOOTING) and re-establish the diameter connections to all the peers. 4.2. Examples Figure 3 provides an example of message exchange in scenario 1 with node A and node B using the new solution: TSOU Expires January 29, 2009 [Page 9] Internet-Draft Capabilities Update Problem Statement July 2008 Node A Node B | | | | +-----------------+ +-------------------+ | Node A supports | | Node B supports | | application(a,b)| | application(a,c,d)| +-----------------+ +-------------------+ | | ------------------------- In Open State ------------------------- | | +-----------------------+ +----------------------------+ |Capabilities of Node A | | Capabilities of Node B | |change and it supports | | don't change and it still | |application(a,b,c) | | supports application(a,c,d)| +-----------------------+ +----------------------------+ | CER(a,b,c) | |------------------------------------>| | +-----------------+ | |Determine common | | |application(a,c) | | +-----------------+ | | | | | +-----------------------+ | | Cache capabilities of | | | Node A and update | | | routing tables | | +-----------------------+ | | | CEA(Result-Code=DIAMETER_SUCCESS) | |<------------------------------------| | | +-----------------+ | | Contiune using | | | local cached B's| | | capabilities | | +-----------------+ | | | Figure3: Capabilities Update in scenario 1 From Figure 3, capabilities of node B haven't been updated at that time. Node B returns CEA with a result-Code AVP indicating "DIAMETER_SUCCESS" not containing any capabilities list. In this way, node A will continue using local cached node B's capabilities. TSOU Expires January 29, 2009 [Page 10] Internet-Draft Capabilities Update Problem Statement July 2008 Figure 4 provides an example of message exchange in scenario 2 with node A and node B using the new solution: Node A Node B | | | | +-----------------+ +-----------------+ | Node A supports | | Node B supports | | application(a,b)| | application(a,c)| +-----------------+ +-----------------+ | | | | -------------------- In Open State --------------------------- | | +-----------------------+ +------------------------+ |Capabilities of Node A | |Capabilities of Node B | |change and it supports | |change and it supports | |application(a,b,c) | | application(a,c,d) | +-----------------------+ +------------------------+ | CER(a,b,c) | |------------------------------------->| | +-----------------+ | |Determine common | | |application(a,c) | | +-----------------+ | | | +-----------------------+ | | Cache capabilities of | | | Node A and update | | | routing tables | | CER(a,c,d) +-----------------------+ |<-------------------------------------| +-----------------+ | |Determine common | | |applications(a,c)| | +-----------------+ | | | +-----------------------+ | | Cache capabilities of | | | Node B and update | | | routing table | | +-----------------------+ | | CEA(Result-Code=DIAMETER_SUCCESS) | |<-------------------------------------| +-----------------+ | | Continue using | | |local cached B's | | | capabalities | | TSOU Expires January 29, 2009 [Page 11] Internet-Draft Capabilities Update Problem Statement July 2008 +-----------------+ | | | | CEA(Result-Code=DIAMETER_SUCCESS) | |-------------------------------------->| | +-----------------+ | | Continue using | | |local cached A's | | | capabalities | | +-----------------+ | | | | Figure4: Capabilities Update in scenario 2 From Figure 4, capabilities of node B have been updated at that time. According to the new solution, node B will initiate a CER containing its capabilities list as soon as possible. Node B processes CER sent from node A and node A also processes CER from node B. Each peer will continue using local cache capabilities when it receives CEA. 4.3. Changes to ABNF In order to implement the new solution, a simplified CEA should be defined in Open State. This simplified CEA should not contains any capabilities-related AVPs. The receiver of CEA should continue using local cached capabilities of its peer identified by Origin-Host and Origin-Realm. Message format ::= < Diameter Header: 257 > { Result-Code } { Origin-Host } { Origin-Realm } 1* { Host-IP-Address } { Vendor-Id } { Product-Name } [ Origin-State-Id ] [ Error-Message ] [ Failed-AVP ] * [ AVP ] 4.4. Compatibility Consideration In the new solution, CER/CEA in Open State is a little different from that in initialization phase. Considering the need for compatibility, the states defined in RFC3588bis Section 5.6 "Peer State Machine" can be used to differentiate the current phase in order to adopt proper CER/CEA process. For example, if the state indicates "Open", simplified CEA should be used. TSOU Expires January 29, 2009 [Page 12] Internet-Draft Capabilities Update Problem Statement July 2008 5. IANA Considerations TBD TSOU Expires January 29, 2009 [Page 13] Internet-Draft Capabilities Update Problem Statement July 2008 6. Security Considerations TBD TSOU Expires January 29, 2009 [Page 14] Internet-Draft Capabilities Update Problem Statement July 2008 7. References 7.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 7.2. Informative References [1] V. Fajardo,Ed.,J. Arkko, J. Loughney, G. Zorn, "Diameter Base Protocol draft-ietf-dime-rfc3588bis-10", January 22, 2008. TSOU Expires January 29, 2009 [Page 15] Internet-Draft Capabilities Update Problem Statement July 2008 Author's Address Tina TSOU Huawei Technologies Huawei Base, Bantian, Longgang District Shenzhen, Guangdong 518129 P. R. China Phone: +86(755)28972352 Email: Tena@huawei.com TSOU Expires January 29, 2009 [Page 16] Internet-Draft Capabilities Update Problem Statement July 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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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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. TSOU Expires January 29, 2009 [Page 17]