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Content for  TR 23.897  Word version:  12.0.0

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1 Scope  2 References  3 Definitions, symbols and abbreviations  4 Use cases  5 Architecture Requirements 
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1  Scope  p. 6

During the production of the 3GPP Release 7 specifications it was recognized that the IP Multimedia Subsystem was suitable for serving both mobile and fixed installations and a number of specifications developed by ETSI TISPAN were therefore embedded in the 3GPP specifications to form the Common IMS. Among other aspects, Common IMS requires that the IMS is able to connect with Next Generation Corporate Networks (NGCN), also known as IP-PBXs (see ETSI TS 181 019 [3]).
Managing the connection to IP-PBXs which do not use registration procedures when connecting to the IMS and operate in a static mode that is to enable the IMS to receive and send traffic to an IP-PBX, is realized by means of configuration within the network. The static mode of operation can be used in 2 scenarios, peering based business trunking and subscription based business trunking. The static mode of operation for both of the above mentioned scenarios can be studied in this TR.
It was however observed that the number of implementations of IP-PBXs that are operated in a static mode (e.g. based on the SIPConnect specifications recently released by the SIP Forum) increases.
The purpose of this study is to enable the IMS to manage connections to a large number of IP-PBXs that are operated in a static mode, with minimized configuration in the network.
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2  References  p. 6

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
  • References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
  • For a specific reference, subsequent revisions do not apply.
  • For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
[1]
TR 21.905: "Vocabulary for 3GPP Specifications".
[2]
TS 41.001: "GSM Release specifications".
→ to date, withdrawn by 3GPP
[3]
ETSI TS 181 019: "Business Communications Requirements".
[4]
TS 33.310: "Network Domain Security (NDS); Authentication Framework (AF)".
[5]
TS 23.228: "IP Multimedia Subsystem (IMS) Stage 2".
[6]
TS 23.167: "IP Multimedia Subsystem (IMS) emergency sessions".
[7]
TS 24.229: "IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3".
[8]
ETSI TS 182 025: "Business trunking; Architecture and functional description".
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3  Definitions, symbols and abbreviations  p. 7

3.1  Definitions  p. 7

For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.
IP-PBX in Static Mode of Operation:
an IP-PBX (Next Generation Corporate Network) where the IP-PBX does not initiate any IMS level registration procedure for its users or itself towards the operator IMS, but rather the IP-PBX maintains a static connection to the IMS.
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3.2  Abbreviations  p. 7

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply.
IP-PBX:
Internet Protocol Private Branch eXchange

4  Use cases  p. 7

4.1  Small enterprise with single point of access  p. 7

The PBX is connected via a single point of access, via a xDSL access with a static IP address. Typically around 100 ports are operated at the PBX, but only a very small number of users are connected simultaneously.
This scenario has the following characteristics:
A significant number of PBXs of this class are connected in total to the network.
This class of PBXs has the following characteristics:
  • The dimension of the occurrence in the network will approximate that of a normal UE.
  • The customer has a service profile in the HSS.
  • The generated traffic per customer is low.
  • The operator has to fulfil regulatory requirements for the customer.
  • Typically several services, beyond those usually considered for a Business Trunking application, are executed by the network for this PBX type.
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4.2  Medium enterprise with single point of access  p. 7

The PBX is connected via a single point of access, via a fibre access with a static IP address. Around 100 to 1000 ports are operated at the PBX. A very large number of PBXs of this class are connected in total to the network.
This class of PBXs has the following characteristics:
  • The customer has a service profile in the HSS.
  • The generated traffic per customer is relevant.
  • The operator has to fulfil regulatory requirements for the customer.
  • Typically several services, beyond those usually considered for a Business Trunking application, are executed by the network for this PBX type.
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4.3  Large enterprise with multiple points of contact with the network  p. 8

The PBX is connected via multiple access points, via Ethernet accesses with static IP addresses. More than 1000 ports are operated at the PBX. Only a small number of PBXs of this class are connected in total to the network.
This class of PBXs has the following characteristics:
  • The customer does not have a service profile in the HSS.
  • only a few services are executed in the network for this customer (e.g. call diversion in case of error conditions).
  • The generated traffic per customer is huge.
  • In most cases the operator has to fulfil regulatory requirements for the customer.
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5  Architecture Requirements  p. 8

The solution shall:
  • allow the IMS to handle sessions directed to the IP-PBX users and originated from the IP-PBX users.
  • allow the IMS to execute functions subject to regulatory requirements (emergency calling, legal interception).
  • be scalable.
  • be resilient against a single failure in the operator's network: the IP-PBX users shall still be able to originate and receive new sessions during such outage.
  • allow the IMS to authenticate the IP-PBXs and provide security according to the network domain security TS 33.310.
  • allow for the invocation of application servers in the operator's IMS network to IP-PBX users.
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