DIME Working Group M

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DIME Working Group M.LiebschInternet-DraftG. PunzIntended status: Standards Track

NECExpires: December 31, 2010 June29, 2010

Diameter General Purpose Session

draft-liebsch-dime-diameter-gps-00.txt

Abstract

The Diameter protocol has specified and relies on the use ofper-user

sessions, which are established between a Diameter client andserver

during a user's authentication and authorization procedure.

Thisdocument proposes an extension to the Diameter session

concept toestablish a general purpose Diameter session for signaling

thecontext of multiple users, such as for group handling or

applicationstate restoration.

Status of this Memo

This Internet-Draft is submitted to IETF in full conformancewith the

provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the InternetEngineering

Task Force (IETF), its areas, and its working groups. Notethat
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other groups may also distribute working documents asInternet-

Drafts.

Internet-Drafts are draft documents valid for a maximum of

six monthsand may be updated, replaced, or obsoleted by other documentsat any

time. It is inappropriate to use Internet-Drafts asreference

material or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed athttp://www.ietf.org/ietf/1id-abstracts.txt.

The list of Internet-Draft Shadow Directories can be accessedat

http://www.ietf.org/shadow.html.

This Internet-Draft will expire on December 31, 2010.

Copyright Notice

Copyright (c) 2010 IETF Trust and the persons identified asthe

document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal

Liebsch & Punz Expires December 31, 2010[Page 1]
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Internet-Draft Diameter General Purpose SessionJune 2010


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Provisions Relating to IETF Documents


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(http://trustee.ietf.org/license-info) in effect on the dateof
http://trustee.ietf.org/license-infohttp://trustee.ietf.org/license-info


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publication of this document. Please review these documents


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carefully, as they describe your rights and restrictions withrespect


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to this document. Code Components extracted from thisdocument must


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include Simplified BSD License text as described in Section4.e of
http://tools.ietf.org/html/draft-liebsch-dime-diameter-gps-00#section-4http://tools.ietf.org/html/draft-liebsch-dime-diameter-gps-00#section-4http://tools.ietf.org/html/draft-liebsch-dime-diameter-gps-00#section-4http://tools.ietf.org/html/draft-liebsch-dime-diameter-gps-00#section-4


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the Trust Legal Provisions and are provided without warrantyas


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described in the BSD License.


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Table of Contents


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1. Introduction . . . . . . . . . . . . . . . . . . . . . .. . . 3
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2. Conventions and Terminology . . . . . . . . . . . . . .. . . 4


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3. Use Cases . . . . . . . . . . . . . . . . . . . . . . .. . . 5


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3.1. PCRF Failure and Restoration . . . . . . . . . . . .. . . 5
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3.2. Optimization for Mass Handling . . . . . . . . . . .. . . 6


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3.3. Policy enforcement to subscriber groups . . . . . .. . . 7


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4. Protocol Extension . . . . . . . . . . . . . . . . . . .. . . 9


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4.1. Enhancement to the Diameter Session Concept . . . .. . . 9


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4.2. Setting up the General Purpose Session . . . . . . .. . . 10


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5. Message Extensions . . . . . . . . . . . . . . . . . . .. . . 12


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6. Security Considerations . . . . . . . . . . . . . . . .. . . 13


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7. IANA Considerations . . . . . . . . . . . . . . . . . .. . . 14


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8. References . . . . . . . . . . . . . . . . . . . . . . .. . . 15


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8.1. Normative References . . . . . . . . . . . . . . . .. . . 15


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8.2. Informative References . . . . . . . . . . . . . . .. . . 15


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Authors' Addresses . . . . . . . . . . . . . . . . . . . . .. . . 16


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1. Introduction
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Diameter [RFC3588] has received wide acceptance in largescale
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networking, e.g. in the 3rd Generation Partnership Project's(3GPP)


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Evolved Packet Core (EPC) network architecture [3GPP-EPC],based on
http://tools.ietf.org/html/draft-liebsch-dime-diameter-gps-00#ref-3GPP-EPChttp://tools.ietf.org/html/draft-liebsch-dime-diameter-gps-00#ref-3GPP-EPC


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applications like Network Access Server [RFC4005] and Credit-Control


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[RFC4006]. Such deployments also depend on application level


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defined, interoperable resilience schemes. It has beennoticed that


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these could potentially be extended beyond the originalDiameter


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session model by the concept of bulk handling. In thismanner the


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efficiency of signaling can be enhanced significantly.


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Another potential use case within 3GPP consists inoptimization for


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mass handling, (mass activation/de-activation, massregistration


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update). Similarly, there are also mobility relatedscenarios where


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Diameter clients want to communicate with servers withoutreference


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to individual user sessions. One example is the enforcementof a


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policy to all or a group of users.


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This document describes exemplary use cases of a more general


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Diameter signaling (i.e. independent from individual DiameterUser


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Sessions) in Section 3. In Section 4 the document defines an
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extension to the Diameter base protocol for such signalingusing a


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General Purpose (GP) Diameter session. The proposedextension to


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Diameter enables signaling volume reduction for variousspecific use


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cases.


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2. Conventions and Terminology


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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALLNOT",


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"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"in this


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document are to be interpreted as described in [RFC2119].


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This document uses the terminology of [RFC3588]. Thefollowing


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additional terms are used in the context of this draft:


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o GP Session: General Purpose Session -- Diameter sessionbetween a


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Diameter client and server which is not related to anindividual


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user, but can be used to signal multi-user or DiameterApplication


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specific context.


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3. Use Cases


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This section describes some use cases where Diametersignaling


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between a client and a server can benefit from a generalpurpose


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Diameter session. The use cases about Diameter noderestoration and


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mass handling are relevant in current 3GPP work and reflectthe need


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for more efficient Diameter signaling.


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3.1. PCRF Failure and Restoration
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A use case encountered in 3GPP's network architecture is thePolicy


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and Charging Rules Function (PCRF) failure and restoration


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[3GPP-PCRFFR]. The PCRF is a control function interactingvia
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Diameter with BBERF (Bearer Binding and Event ReportingFunction) and


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PCEF (Policy Enforcement Function) in the bearer plane, aswell as AF


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(Application Function) in the application plane; a simplified


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functional view is given in Figure 1. The PCRF appears as acentral


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entity, keeping and coordinating states per mobile terminal;it is a


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Diameter server, whereas BBERF, PCEF and AF are Diameterclients.


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Note that in real network deployments all functions would bepresent


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in multiple instances (e.g. geographically distributed andincluding


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load balancing).


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+----+


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| AF |Application


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+----+Plane


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|


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|....Diameter


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+=======+ |


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| PCRF |-----+Control


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+=======+Plane


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Diameter.../ \....Diameter


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/ \


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Mobile / \


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Terminal/ +-------+ +-------+


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User PacketData NW


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+-------+ +-------+


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(Gateway) (Gateway)Bearer Plane


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Figure 1: Usage scenario of Diameter bulk signaling forPCRF


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restoration


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User sessions in the bearer plane are controlled by PCRFsessions,


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e.g. regarding Quality of Service, packet filters andcharging


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parameters.


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Although a PCRF can certainly be implemented as a highlyresilient


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node in itself, there is also the desire to provideresilience by


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network based means. In case of failure of one particularPCRF node


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this could mean that PCRF session state has to be restored oneither


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the same PCRF node (after recovery), or on other, alternativePCRF


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nodes (during the downtime of the failed PCRF). Preferablythis


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restoration procedure is performed in a bulk mode, e.g. forhundreds


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or thousands of user sessions. After detecting the failureof a


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PCRF, clients will have to send PCRF session stateinformation of


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affected sessions to the alternative PCRF (the target for


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restoration). Obviously this signaling must be independentof any


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user sessions being currently handled on a target PCRF.Details


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about the restoration procedure are out of scope of thisdocument,


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but are currently under study in 3GPP [3GPP-PCRFFR].
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3.2. Optimization for Mass Handling


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One typical case (again for the EPC architecture [3GPP-EPC])is


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depicted in Figure 2; the Mobility Management Entity (MME)


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communicates with Home Subscription Server (HSS) via Diameterfor the


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purpose of performing location registration anddownload/update of


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subscription information.


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+=========+


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| HSS | UpdateLocation


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+=========+ Request


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| ^


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|...Diameter | |


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+-------+ | (S6a interface) | |


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Mobile / radio \ +------+ | |


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Terminal/ --| access |---- | MME | v


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User \ network / +------+ UpdateLocation


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+-------+Response


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Figure 2: Usage scenario of Diameter bulk signaling for masshandling


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optimizations in EPC


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Especially for machine-type applications, external triggersmay lead


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to a massive amount of attachments, or recurring applicationsmay


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exhibit (almost) synchronized behavior, leading to massiveamount of


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registration updates. Both may (and most likely do, see[3GPP-EPC])


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require Diameter signaling exchanges between MME and HSS(Update


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Location Request/Response pairs, as part of the S6aapplication


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realized on top of Diameter). HSS is here in the role of aDiameter


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server, and MME acts as Diameter client. More details can befound


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in [3GPP-DIAM].
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3.3. Policy enforcement to subscriber groups


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A further use case for the GP Session is the signaling ofgroup


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related context. As example, a Policy Control entity maycomprise a


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Diameter server function, whereas a Diameter client is co-located


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with the entity implementing the Policy Enforcement engine.The


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Diameter client and server may have individual user sessionsset up,


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but could consider grouping of multiple users andidentification of


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groups according to a group key. Instead of applying thesame policy


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to individual users one after the other by means ofsequential


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handshakes, the Diameter server may use the GP Session and aRAR/RAA


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handshake to enforce the policy to a group of users. Figure3


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depicts policy enforcement to a group of users by means of aGP


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Session.


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The Diameter server identifies the group of users with thegroup key.


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Alternatively, the Diameter server could use the GP Sessionto


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enforce the policy to a sub-set of users by means ofidentifying the


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addressed users with user keys. The user key may be anyuser-


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individual AVP according to [RFC3588] or [RFC4005], such asthe user
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name AVP, or a new AVP which serves as user identification.In case


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the Diameter client and server have individual Diameter UserSession


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IDs set up for the users, the GP Session related signalingmay


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identify individual users also by means of appending multipleUser


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Session ID AVPs as user keys. However, in such case theDiameter


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signaling context is identified by means of the GP SessionID,


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whereas a set of User Session IDs is used solely to identify


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individual users and apply an accompanying value to theirpolicy


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settings. Details about group identification and individualuser


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identification in the context of GP Session signaling are outof


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scope of this version of the document.


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+----------------+


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| |


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| Policy Control |


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| |


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+----------------+


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^


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|


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\___RAR/RAA(GPSessionID, groupkey,value)


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| RAR/RAA(GPSessionID, user1key,value1,


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| user2key,value2,


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| user3key,value3)


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|


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V


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+--------------------+


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User1 | |


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User2 -------- | Policy Enforcement | ----------datatraffic


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: | |


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UserN +--------------------+


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Figure 3: Multi-User policy enforcement


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4. Protocol Extension


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4.1. Enhancement to the Diameter Session Concept


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The Diameter base protocol [RFC3588] explicitly distinguishesa


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Connection between a Diameter client and a Diameter serverfrom


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Diameter Sessions. Whereas a connection provides transportservice


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to convey Diameter messages between a particular client and aserver,


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a session is referred to be a logical concept at theapplication


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layer. A connection is established between a client and aserver and


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is used in a shared manner. A session is established on aper-user


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basis and is not shared to signal context of multiple users.


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This document proposes an enhancement to the originalDiameter


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session concept and specifies the use of a dedicated Diametersession


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in the context of multiple users or application specificcontext.


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Figure 4 depicts one possible interpretation of the proposedDiameter


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GP Session. A Diameter client establishes user-specificsessions


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with the Diameter server. Each session is identified by aSession


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ID, which uniquely identifies a user. The Diameter GPSession is


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established without linking the session and the associatedSession ID


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to a particular user. The Diameter client may make use of avirtual


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user and associated identifiers, keys etc. to open the GPSession


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with the Diameter server. Important is that client andserver are


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aware of the meaning and use of the virtual user's sessionfor


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general purpose signaling. Details about authentication and


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authorization of the virtual user behind the GP Session isout of


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scope of this version of the document.


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+-----+


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|User1|-+ +---------------+ +---------------+


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+-----+ | | +----+ +----+ |===Session ID 1===| +----++----+ |


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| | |App1| |App2| |===Session ID 2 | |App1||App2| |


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+-----+ +-------| +----+ +----+ | : | +----++----+ |


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|User2|---------|+-------------+| - -connection - -|+-------------+|


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+-----+ +-------|| Diameter || : ||Diameter ||


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: | || Client ||===Session ID N===||Server ||


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+-----+ | |+-------------+|===GPSession ID===|+-------------+|


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|UserN|-+ +---------------+ +---------------+


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+-----+


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Client-Server Application &


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GPSession ID


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Figure 4: General Purpose Session in the context of theDiameter


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Client-Server association


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4.2. Setting up the General Purpose Session


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In order to avoid breaking the Diameter User Session concept,a


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General Purpose Session is interpreted as an additional UserSession


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between the Diameter Client and the Diameter Server, whereasthe user


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behind this session is virtual. The GP Session ID can be


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administratively configured or well known (static GPSession).


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Alternatively, the Diameter client may bootstrap a GP Sessionby


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means of a authentication/authorization procedure, e.g.according to


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the authorization procedure specified in [RFC4005]. In suchcase, a


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unique and temporary Session ID is assigned to a GP Session.The


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Diameter client and server may add an Authorization-LifetimeAVP to


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the authorization signaling to negotiate a limited lifetimeof the GP


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Session.


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The GP Session ID meets the format of the Diameter Session ID


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according to [RFC3588]. During dynamic set up of a GPSession


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according to the Authentication/Authorization procedure, theAAR/AAA


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may indicate the special type of Diameter session. TheDiameter base


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specification as well as the NASREQ specification provideseveral


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means to allow such indication. For example, the DiameterSession


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AVP could carry an indicator in the optional value field,which


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classifies the Session ID as GP Session. The set of high/low64 bits


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identify the GP Session. Details about the setup as well asthe


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indication of the Session ID type are out of scope of thisversion of


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the document and are for further study.


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5. Message Extensions


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Details about extensions to Diameter messages and associatedAVPs to


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handle GP Sessions are for further study and will bedescribed in


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future versions of this document.


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6. Security Considerations


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The GP Session concept relies on the trust relationship and


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associated security association between a Diameter client anda


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server. Hence, security considerations do not go beyond whatis


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covered in [RFC3588].


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7. IANA Considerations


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If the option field in the Session ID AVP is being used toidentify a


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GP Session, no additional IANA requirements will be added bythis


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specification. Future details about the specification andmessage


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format definitions may require IANA actions.


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8. References


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8.1. Normative References


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[RFC2119] Bradner, S., "Key words for use in RFCs toIndicate


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Requirement Levels", BCP 14, RFC 2119, March 1997.
http://tools.ietf.org/html/bcp14http://tools.ietf.org/html/rfc2119http://tools.ietf.org/html/rfc2119http://tools.ietf.org/html/bcp14


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[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G.,and J.


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Arkko, "Diameter Base Protocol", RFC 3588,September 2003.


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8.2. Informative References


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[3GPP-DIAM]


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"3GPP TS 29.272 Mobility Management Entity (MME)and


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Serving GPRS Support Node (SGSN) relatedinterfaces based


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on Diameter protocol", .
http://www.3gpp.org/http://www.3gpp.org/


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[3GPP-EPC]


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"3GPP TS 23.401 General Packet Radio Service(GPRS)


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enhancements for Evolved Universal TerrestrialRadio


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Access Network (E-UTRAN) access",.


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[3GPP-PCRFFR]


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"3GPP TS 29.816 3GPP TS 29.272 Study on PRCFFailure and


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Restoration", .


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[RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton,


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"Diameter Network Access Server Application", RFC4005,
http://tools.ietf.org/html/rfc4005http://tools.ietf.org/html/rfc4005http://tools.ietf.org/html/rfc4005http://tools.ietf.org/html/rfc4005


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August 2005.


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[RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura,M., and J.


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Loughney, "Diameter Credit-Control Application",RFC 4006,


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August 2005.


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Authors' Addresses


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Marco Liebsch


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NEC Laboratories Europe


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NEC Europe Ltd.


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Kurfuersten-Anlage 36


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D-69115 Heidelberg,


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Germany


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Phone: +49 6221 4342146


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Email: [email protected]


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Gottfried Punz


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NEC Laboratories Europe


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NEC Europe Ltd.


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Kurfuersten-Anlage 36


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D-69115 Heidelberg,


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Germany


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Phone: +49 6221 4342119


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Email: [email protected]


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