MEGACO Wayne Cutler Internet Draft Marconi Communications Document: July 2001 Category: Informational MGC Cookie Package for Megaco/H248 Status of this Memo 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 This documents provides a proposed definition for a supplemental package to Megaco/H.248. The proposed package addresses support of functionality to enable a MGC to store information on a MG which can subsequently be retrieved via audit. The specific purpose for storing / retrieving data in this way is regarded as being solely the concern of the MGC. This draft merely proposes the means for supporting such capability. It is worth noting that one such use of this capability would be to facilitate MGC recovery action in the event of an MGC restart. This specific capability was described in a previous draft (draft-cutler- megaco-recvpkg-01.txt) which was presented at IETF49 in San Diego. This draft supercedes the previous one. 2. 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 [1]. Cutler Expires January 2002 1 MGC Cookie Package for Megaco/H248 July 2001 3. MGC Cookie Package Package ID: mgcckie (0x????) Version : 1 Extends: None This package defines a property to enable the MGC to store a cookie on a MG. The cookie may be stored against any MG termination (i.e. both real and ephemeral). The cookie may be retrieved via the audit mechanism. The cookie is treated by the MG as an opaque digit string. 3.1 Properties MGC Cookie Property ID : cookie (0x0001) Type : 1*64 (SAFECHAR) Possible Values : Any, as defined by the MGC Defined in : Local Control Descriptor Characteristics : Read/Write 3.2 Events None. 3.3 Signals None. 3.4 Statistics None. 3.5 Procedures The MGC may store a cookie against any MG termination. The cookie may be subsequently updated at will by the MGC. In general, a cookie may be stored against any existing termination irrespective of whether that termination is in a (non-null) context or not. However, since ephemeral terminations do not exist outside of a context, it follows an ephemeral termination must be related to a context in order for a cookie to be able to be stored against it. As mentioned previously, a specific use of this capability would be to facilitate MGC recovery action in the event of an MGC restart. As an illustration of this usage, consider the following scenario :- 1) A MGC sets up a call between 2 ISUP trunk GWs. 2) The orig. MG (MG1) has a circuit termination(C1) and an ephemeral termination (E1) in context CX1. Cutler Expires January 2002 2 MGC Cookie Package for Megaco/H248 July 2001 3) The term. MG (MG2) has a circuit termination(C2) and an ephemeral termination (E2) in context CX2. 4) At MG1, cookies are stored against C1 and E1 to identify the billing reference and far end GW connection respectively. Similar cookies are stored at MG2 against its terminations. 5) During the speech phase, the MGC is restarted and loses knowledge of the active call. However, the RTP stream is unaffected and continues between the 2 MGs. 6) Eventually the call releases and an ISUP-REL message is received by the MGC. The CIC in the message identifies termination C1 on MG1. 7) Via audit of MG1, the MGC discovers CX1 and E1, plus associated cookies. This enables the billing reference to be re-learnt as well as identifying the far end (MG2) connection. 8) Audit can be performed at MG2 to discover all related connection information (CX2, C2 and E2), 9) MG2 can now be cleaned up and ISUP-REL message sent against the CIC corresponding to termination C2. 10)Both MGs disconnected, both trunks released normally and billing terminated correctly. End users oblivious to the fact that the MGC restarted in mid call. 4. Formal Syntax As in [4], the package described in this draft may be encoded as ASN.1 or augmented Backus-Naur Form (BNF) [2]. 5. Security Considerations MGs may be untrusted and therefore the MGC MAY choose to encrypt the stored cookie. For other security considerations, refer to [3]. 9. References 1 Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 2 Crocker.D & Overell.P (editors), "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. 3 Cuervo et al, "Megaco Protocol", RFC 2885, August 2000. 10. Acknowledgments Cutler Expires January 2002 3 MGC Cookie Package for Megaco/H248 July 2001 11. Author's Addresses Wayne Cutler Marconi Communications New Century Park Coventry CV3 1HJ England Phone: +44 24 76562417 Email: wayne.cutler@marconi.com Cutler Expires January 2002 4 MGC Cookie Package for Megaco/H248 July 2001 Full Copyright Statement "Copyright (C) The Internet Society (date). 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 implmentation 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 Cutler Expires January 2002 5