IMS in Converged Networks

Market and Requirement

It has become evident in recent years that a number of forces were leading operators towards convergence. Services can be accessed from a range of devices and users were rightly questioning why they could not have uniform access to services regardless of the type of access network being used. Upon seeing declining revenues, wireline providers started to consider ways to access wireless revenues. Wireless operators, in turn, have seen handset sales peak in several countries and must now consider ways to expand their markets as well; the most obvious area being converged business services.

The IP Multimedia Subsystem (IMS) defined by 3GPP provides an enabling architecture that is access independent. This is central in the move towards convergence. Now each access type is being 'enabled' to work with an IMS core, be it DSL, WLAN, GPRS or any emerging technology, such as WiMAX.

Newport Networks 1460 sits at the border between IMS core and access networks, and between IMS cores in the case of interconnect. In terms of IMS and TISPAN standards definitions, it performs the following:

These functions are deployed on a distributed architecture with the Newport Networks Signalling proxy providing the P-CSCF, PDF and IBCF. Newport Networks MediaProxy provides the BGF function.

Deployments in a Converged network require that the SignallingProxy and MediaProxy functionality adapt to the type of access networks to which they attach. For example DSL and WiFi Networks are insecure and do not have managed QoS. In addition they operate in IPv4 environments where overlapping address spaces are common place. These access types will require both a SignallingProxy and MediaProxy to be deployed with QoS, security and NAT/firewall functions deployed. In the case of wireless 3G access, security at the transport layer and QoS for the media is provided by the wireless access network. Consequently these networks only require SIP security and an interface from the SignallingProxy to the access network to communicate quality requirements. No MediaProxy is required in this case.

Key Newport Networks 1460 IMS Capabilities

Future Proof Investment

• The 1460 can be deployed as a traditional session border controller or it can be physically separated into a MediaProxy and SignallingProxy. This architectural flexibility allows Newport Networks product to be deployed in converged networks today or migrate to them when required by the operator.
• Common hardware is used in combined Session Border Control deployments and separated signalling and media deployments.
• Both combined session border control deployments and separated signalling and media deployments can be upgraded for IMS and converged network use as required by the network operator ensuring maximum investment reuse.

Access Reach

• Secure traversal of NAT and firewall devices when interfacing to IPv4 networks
• Scaling from 5,000 to 100,000 simultaneous bi-directional calls on a single chassis
• Support for up to 1 million concurrent registered subscribers

Quality of Service

• Type of Service (ToS) and DiffServe Code Point (DSCP) remapping on a per-user and per-session basis ensuring that users do not exceed negotiated/specified quality.
• Session Admission Control applied to physical interfaces, VLANs and IP address groupings, ensuring that Service Level Agreements are met.
• Bandwidth Policing on a per-session basis to ensure sessions to not exceed negotiated rate.

Security

• Network Address and Port Translation (NAPT) provides Topology Hiding for core network.
• Malformed or 'illegal' SIP signalling discarded.
• Rate limiting of Registration messages to protect core network Softswitches/Proxies.
• All media traffic from non-registered IP addresses discarded at line rate.
• Policing of signalling traffic, media traffic and quality monitoring (RTCP) stream. This prevents inappropriate use (fraud).

Regulatory

• Lawful Intercept for CALEA and ETSI.
• Supported national variants include USA, Canada, UK, Germany, Italy.
• Emergency Call handling facilities allowing Session Admission Control to be suspended for emergency calls and calls to be passed to designated Emergency Call Handling Proxies.

Resilience

• The 1460 has no single point of failure providing in excess of 99.999% availability.
• All system modules are 1 + 1 resilient including power distribution units, fans and disks.
• Physical link aggregation (802.3-2002) provides link resilience and load balancing.