Internet Engineering Task Force B. Foster Internet Draft F. Andreasen Document: Category: Informational Cisco Systems November 2002 MGCP Lockstep State Reporting Mechanism Status of this Document This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 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. 1. Abstract An MGCP endpoint that encountered some adverse failure condition such as being involved in a transient call when a Call Agent failover occurred could be left in a lockstep state such that events are quarantined but not notified. The MGCP LCK package described in this document provides a mechanism for reporting these situations so that the new Call Agent can take the necessary fault recovery procedures. 2.0 Conventions used in this document 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 RFC-2119. B. Foster, F. Andreasen Informational [Page 1] MGCP Lockstep State Reporting Mechanism November 2002 3. Introduction When an endpoint operating in "step" mode generates a Notify, it will enter the "notification state" where it waits for a response to the Notify. Once a response is received, the endpoint must wait for a new NotificationRequest before it can resume event processing. As long as the endpoint is waiting for this NotificationRequest, we say that is in the lockstep state. An endpoint that is in lockstep state cannot perform any event processing and hence can also not generate any new Notifys. Endpoints should only be in lockstep state for a very short period of time. In the event of a Call Agent failure, programming errors, and other adverse conditions, an endpoint could potentially end in the lockstep state without the Call Agent realizing it. Clearly, this could have very negative consequences in terms of the service provided. The Lockstep package defined in this document defines extensions to the EndpointConfiguration and RestartInProgress commands that allow a Call Agent to request that an endpoint informs it if the endpoint is in the lockstep state for a specified period of time. 2.0. Lockstep Package Package Name: LCK Version: 0 Package Description: The purpose of this package is to provide a mechanism for reporting a condition in which an endpoint has been sitting in the "lockstep state" for a specified period of time. There are two aspects of this package: * The ability for a Call Agent to request endpoints to report if they are in lockstep state. This is done with the EndpointConfiguration command as described in section 2.1. * The reporting mechanism itself, which is done with a new "lockstep" RestartMethod for the RSIP command as described in section 2.2. 2.2. Request to Report Lockstep State The new "lstime" EndpointConfiguration parameter is used by the Call Agent to request the reporting of "lockstep" state. It uses the following ABNF: "LCK/LST:" 0*WSP LSTIME LSTIME = 1*(4DIGIT) where LSTIME is expressed in seconds, with a value ranging from 1 to 999. A value of greater than 2*T-HIST (refer to [3]) is recommended. Informational [Page 2] MGCP Lockstep State Reporting Mechanism November 2002 LSTIME is the amount of time the endpoint is in the lockstep state before reporting. The timer starts when the endpoint enters the lockstep state and is cancelled if the endpoint leaves the lockstep state before the timeout occurs. This parameter can be audited using the audit endpoint command. 2.3. Lockstep restart Method A new "lockstep" restart method is defined in the "LCK" package. A RestartInProgress(RSIP) will be sent with this RestartMethod if the endpoint has been configured with a value for LSTIME and that timer has timed out. The syntax of the restart method is as per [3]: "RM" ":" 0*(WSP) "LCK/lockstep" The "lockstep" RestartMethod does not define a service-state, and hence it will never be returned when auditing the RestartMethod. 3.0. IANA Considerations The MGCP package title "Lockstep" with the name "LCK" should be registered with IANA as indicated in Appendix C.1 in [3]. 4.0. Security Considerations The MGCP packages contained in this document do not require any further security considerations beyond those indicated in the base MGCP specification [3]. 4.0. References [1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [3] F. Andreasen, B. Foster "Media Gateway Control Protocol (MGCP) Version 1.0", RFC XXXX {editors note - to be put in when RFC number is assigned to draft-andreasen-mgcp-rfc2705bis-04.txt) 5.0. Authors' Addresses Bill Foster Phone: +1 250 758 9418 EMail: bfoster@cisco.com Flemming Andreasen Cisco Systems 499 Thornall Street, 8th Floor Edison, NJ 08837 Informational [Page 3] MGCP Lockstep State Reporting Mechanism November 2002 Phone: +1 732 452 1667 EMail: fandreas@cisco.com 6.0. Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Informational [Page 4]