IP exchange or (IPX) is a telecommunications interconnection model for the exchange of IP based traffic between customers of separate mobile and fixed operators as well as other types of service provider (such as ISP), via IP based Network-to-Network Interface. IPX is developed by GSM Association.
IPX is not intended to replace or compete with the Internet but it does offer an alternative option for service providers. The intent of IPX is to provide interoperability of IP-based
services between all service provider types within a commercial
framework that enables all parties in the value chain to receive a
commercial return. The commercial relationships are underpinned with
service level agreements which guarantee performance, quality and
security.
It may not be evident to end-users whether their service provider
utilises the IPX model or not, however, the ability for service
providers to differentiate services using the flexibility provided by
the IPX model, ultimately provides for end-user choice.
High-level architecture of IPX network connecting various operators
& service providers together for the exchange of different IP based
traffic
Background
Traditionally, voice traffic interconnection between different operators has utilized the international SS7/TDM networks. However, lately the all-IP paradigm with VoIP is being rapidly introduced by different operators in various forms, such as IMS. In order to minimize the number of conversions between packet-switched voice and circuit-switched
voice there is a clear need to deploy an IP based NNI
(Network-to-Network Interface) and therefore an IP based interconnection
network.
It is also evident that a large number of IP based services (such as Presence or IM)
simply cannot be interconnected using a SS7/TDM network, further
increasing the need for evolution into an IP based interconnection
network.
Since the year 2000 GSM operators have been using GRX (GPRS Roaming
Exchange) network for routing the IP based commercial roaming traffic
between visited and home operators. Mainly 2.5G and 3G
data roaming has been using GRX. GRX is a private IP network (separated
from internet) consisting of multiple different GRX carriers that are
connected to each other via peering points. However, GRX is limited only
to GSM operator community and not all GRX's are capable of meeting the
demands of real-time services.
Even though the GRX environment is not entirely suitable as a common
IP network for interconnection and roaming, it offers a good starting
point for the development of IPX. IPX development has been done in
various GSM Association projects and working groups since 2004.
Need for a private backbone
IP based interconnection could be handled with Internet, since
Internet natively supports the IP protocol and offers the required
global connectivity. But there are issues when using Internet for this
particular purpose. As Alex Sinclair of GSMA put it,[1]
"The open Internet is a wonderful thing, but when it comes to providing
a guaranteed quality of service, particularly for time-critical
services, there is still a long way to go".
Naturally operators and other service providers are free to choose
which interconnection option to use. It is also possible to use multiple
different options at the same time (although this will lead to
increased complexity).
Architecture
IPX architecture consists of different IPX Providers connecting
together via an IPX peering point for traffic exchange. Both signaling
(such as SIP) and media (such as RTP) is transported end-to-end in
accordance with IPX specifications. A typical end-to-end path of traffic
in a fixed to mobile interconnection scenario is illustrated below:
X is a peering point where IPX Provider A and IPX Provider B exchange traffic
IPX offers both bilateral and multilateral interconnection. Bilateral
means the traditional model of two operators bilaterally writing an
interconnection contract prior to setting up a connection to each other
themselves. Multilateral on the other hand means that the IPX provider
to some extent takes care of both handling the contract and connectivity
set-up on behalf of the operators. Setting up bilateral interconnection
contracts & connections with tens/hundreds of other operators can
be a major burden. Therefore the multilateral option, which allows an
operator to open multiple connections by making a single contract and
single technical connection with the IPX provider, makes interconnection
deployment easier and faster.
Key features
- Open - open to any fixed operator, mobile operator or other service provider (such as ISP or cable operator) willing to adopt the necessary common IPX technical and commercial principles and sign in
- Quality - support for QoS ensured by usage of combination of technical features in the network and an enforceable contract model among all the players involved (end-to-end Service Level Agreements)
- Cascading payments – the cascading responsibility in IPX means each party is responsible for the performance of the next party in the transit chain. Because all participants make this commitment, the financial benefits of providing the service are cascaded through the value chain, enabling all involved to receive a commercial return for their participation
- Efficient connectivity - operator connecting to IPX can choose a multilateral interconnection mode where one interconnection contract opens multiple interconnection partners
- All IP - supporting natively IP based protocols (such as SIP, RTP, GTP, SMTP, SIGTRAN etc.)
- Secure - completely separated from the public internet, both logically and physically. IPX is not addressable nor visible from the internet
- Global - not restricted to a certain geographical area
- Backwards compatible - IPX specifications are compliant with the existing specifications and recommendations. There is no need to upgrade for example, a 3GPP compliant IMS core system with the implementation of a IPX compliant Network-to-Network Interface (NNI)
- NNI only - IPX requirements address NNI only. The User-to-Network Interface (UNI) is out of scope
- Common technical specifications used end-to-end
- Interconnection and roaming - IPX covers both interconnection and roaming scenarios
- Competitive environment - IPX services are provided by a number of competing international IP carriers all connected to each other via dedicated IPX peering points
Status
Principles of IPX have been successively tested and validated by
GSMA. From 2004 onwards, GSMA SIP Trials tested IP-based NNI with
numerous IMS based services. IPX Pre-commercial Implementation[2] trials have been ongoing since April 2007 focusing especially on packet switched voice service.
GSMA press release[3]
in February 2008 explains that IPX trials have been completed
successfully. A number of international carriers are preparing to roll
out IPX services, such as IPX Voice, Belgacom International Carrier
Services, BT, CITIC 1616, Deutsche Telekom ICSS, iBasis, Reach, SAP
Mobile Services, Syniverse, Tata Communications, Telecom Italia Sparkle,
Telecom New Zealand International, Telefónica International Wholesale
Services, Telekom Austria, Telenor Global Services, TeliaSonera
International Carrier. These companies will function as IPX Providers
towards fixed and mobile operators and other service provider types.
GSMA is open to support further trials on demand.[4]
See also
References
- ^ High-Quality Global IP Network Prepares To Go Commercial, February 12, 2008
- ^ IPX Pre-commercial Implementation Project information
- ^ High-Quality Global IP Network Prepares To Go Commercial Press Release
- ^ How to Join IPX Pre-Commercial Implementation Trials Document
- GSMA IR.34 - Inter-Service Provider IP Backbone Guidelines
- GSMA AA.80 - Non-Binding Template Agreement for IP Packet Exchange (IPX) Services
- GSMA IR.77 - Inter-Operator IP Backbone Security Requirements
- GSMA IR.40 - Guidelines for IPv4 Addressing and AS Numbering for GRX/IPX Network Infrastructure and User Terminals
