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Media Gateway Control Protocol (MGCP) Lockstep State Reporting Mechanism

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 3992.
Authors Bill Foster , Flemming Andreasen
Last updated 2013-03-02 (Latest revision 2003-07-25)
RFC stream Independent Submission
Intended RFC status Informational
Stream ISE state (None)
Consensus boilerplate Unknown
Document shepherd (None)
IESG IESG state Became RFC 3992 (Informational)
Action Holders
Telechat date (None)
Responsible AD Jon Peterson
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Internet Engineering Task Force                             B. Foster 
Internet Draft                                           F. Andreasen 
Document: <draft-foster-mgcp-lockstep-01.txt>           Cisco Systems 
Category: Informational                                     July 2003 
     Media Gateway Control Protocol (MGCP) Lockstep State Reporting 
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 
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  A Media Gateway Control Protocol (MGCP) endpoint that has encountered 
  an 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 
  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. 
Conventions used in this document 
  The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
  document are to be interpreted as described in RFC-2119 [1]. 

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1. Introduction 
  In the Media Gateway Control Protocol (MGCP) [2], 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.  
  Furthermore, 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 it 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 time, 
  however in case of 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 an endpoint to inform 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 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. 
2.1. 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: 
     LSTIME = 1*(4DIGIT) 
  where LSTIME is expressed in seconds, with a value ranging from 0 to 
  999. A value greater than 2*T-HIST (refer to [2]) is RECOMMENDED. 
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  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.  The value zero is used to turn off 
  This parameter can be audited using the AuditEndpoint command. 
2.2. 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 non-zero value for LSTIME and 
  that timer has expired.  The syntax of the restart method is as per 
     "RM" ":" 0*(WSP) "LCK/lockstep" 
  RestartDelay (see [2]) is not used with the "lockstep" RestartMethod.  
  Also, 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" and version 
  number zero should be registered with IANA as indicated in Appendix 
  C.1 in [2]. 
4.0. Security Considerations 
  Section 5 of the base MGCP specification [2] discusses security 
  requirements for the base MGCP protocol, which apply equally to the 
  package defined in this document.  Use of a security Protocol such as 
  IPsec (RFC 2401, RFC 2406) that provides per message authentication 
  and integrity services is required in order to ensure that requests 
  and responses are obtained from authenticated sources and that 
  messages have not been modified.  Without such services, gateways and 
  Call Agents are open to attacks. 
5.0. Normative References 
 [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement 
      Levels", BCP 14, RFC 2119, March 1997. 
 [2]  F. Andreasen, B. Foster "Media Gateway Control Protocol (MGCP) 
      Version 1.0", RFC 3435, January 2003. 
Authors' Addresses 
  Bill Foster 
  Phone: +1 250 758 9418 
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             MGCP Lockstep State Reporting Mechanism          July 2003 

  Flemming Andreasen 
  Cisco Systems 
  499 Thornall Street, 8th Floor 
  Edison, NJ 08837 
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