The scope of this TR is to capture the results of a study into the feasibility of enhancing IMS network
architecture. This report intends to study the feasibility of enhancing IMS network architecture as follows:
Investigating architectural improvements to reduce the complexity of signalling procedures by reducing the
signalling hops, or the number of options and combinations (by looking at different groupings of combining
Investigating means to improve system-level load balancing and reliability;
Investigating possibilities for reducing configuration workload to save OPEX.
Investigating the introduction of IMS Overload Control mechanisms.
Backward compatibility with current IMS specifications shall be ensured.
NOTE: overlap with SA5 and CT4 work need to be monitored.
This report is intended to explore potential architecture improvements and also provide conclusions on the above
aspects with respect to potential future normative specification work.
There are a number of functions involved in call session setup in IMS network. Interfaces and interactions between
network elements may be a little complicated and not that efficient. It is deemed beneficial to review the current IMS architecture including aspects such as the possible optimization of interfaces/reference points (by looking at different groupings of combining existing entities), reducing options of solutions for the same issues, relevancy of certain functions etc.
IMS network service availability largely relies on the reliability of network entities. If some network elements
implementing critical functions (e.g. S-CSCF, HSS) fail, service availability may be impacted. Moreover network
elements may not be fully utilized because network load may not be well distributed, e.g. some nodes may be
overloaded due to sudden traffic increase, while others may be under loaded to some extent. Though there are some
element level approaches to solve these problems, some system level solutions should be studied, for example, the
method to distribute load between network elements in different geographical locations especially when a disaster
happens, such as earthquake.
Network expansion may require significant manual configurations, and the network maintenance and upgrade may be
time-consuming and also may be costly for operators. Introducing self-organization features may improve the network intelligence and reduce the efforts of manual configuration.
The objectives of the study for investigating the introduction of IMS Overload Control mechanisms are to:
Determine the parts of IMS architecture for which overload control mechanisms are needed;
Evaluate the applicability of candidate solutions for Overload Control to the SIP entities of the IP multimedia
core network architecture, including:
mechanisms having already been specified or studied within 3GPP and their possible enhancements,
mechanisms specified or studied by other bodies (e.g. ETSI TISPAN, IETF) and their possible enhancements,
other mechanisms, if proposed within this work item;
Provide recommendations based on analysis.