IP-Access Network (IP-AN)

An IP-AN1 is a set of functions implemented on the transfer plane over which user data passes,

and on the control plane. Generally, IP-ANs offering the same services have the same functions.

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CHAPTER 1. ARE CURRENT MOBILE NETWORKS READY FOR THE NEW ECOSYSTEM?

Although their organic architecture may differ regarding their node types and number, and the way their nodes implement functions and interact, their organic architectures obey to the same model.

This section details the IP-ANs transfer and control planes functions; then it provides a model for their organic architectures, on the transfer plane. The model for the control plane will be given in section 1.3, while describing the different IP-ANs examples.

1.2.1.1 IP-AN control and transfer plane functions Transfer plane functions

• These functions include basically the means to transfer data to the MN whatever be its location in the coverage of the IP-AN. It may also encompass header compression, data anchoring,

policy enforcement, and data ciphering functions. Control plane functions

• Access control: is the process by which a network deduces whether and how a user is allowed to access the services of an IP-AN. It includes authentication functions (secure identification of the service requester), authorization functions (determination of the services the requester can access to), admission control functions (determine if the requested resources are avail- able). It also comprises IP address allocation mechanisms, responsible for allocating an IP address to the MN once it is authenticated and authorized to use the IP-AN services. • Mobility management: when a user is moving during a communication, two functions

are involved: handover decision and handover execution. Handover is executed thanks to signalling protocols updating the route information in the network towards the new MN location. The node in the network, receiving handover execution signalling is called signalling

mobility anchor.

When a user is in idle state, mobility management includes the tools for user reachability, that determine its location in case of incoming calls. Reachability function is very tied to

registration and location update functions, that update the mapping between the user

identity and its physical location.

• Radio resource management: these are functions related to radio resource allocation, according to the radio conditions, service type, user priority, load criterion, etc.

• Network management: these functions include inter-node load balancing and anchor node selection.

1.2.1.2 A model for IP-AN organic architectures

Figure 1.2 presents a model for the IP-AN organic architectures on the transfer plane. It also shows that control plane functions can be implemented in the same nodes as the transfer plane nodes, or in separate nodes.

The model is centralized and hierarchical. It is constituted of different nodes on different levels. A

node on level x is called Nodex. A Nodex connects and manages a number of Nodex-1.

Within a Nodex, data traffic related to a given MN may be identified by: the IP address allocated

1.2. IP-AN//PCC//IMS MODEL 17

IMS SIP proxy IMS SIP proxy

IMS SIP proxy

Function in the policy control interaction layer

Interface carrying transfer plane and possibly control plane data Interface carrying control plane data

First IP router

MN

IMS: Service control overlay network

Policy control interaction layer

IP-AN: IP Access Network PCEF

Nodex-1

Node1 (CoN)

Connectivity Node

Nodek= first IP router

Nodex

Nodex+1

Node performing transfer plane and possibly control plane functions Node performing only control plane functions

BBERF DNS Application Server SLF S-CSCF P-CSCF I-CSCF HSS/HLR PCEF BBERF AF AF PCRF PCRF

IP-AN: IP Access Network

Figure 1.2: A common mobile networks layered model: IP-AN//PCC//IMS

When a MN moves between two Nodex-1, there are many possibilities for routing the traffic to the

MN:

• If the two Nodex-1are managed by the same node Nodex, then traffic continues to pass through

Nodex, which takes the role of a data anchor for mobility between Nodex-1.

• If the two Nodex-1 are managed by two different Nodex:

– either the old Nodexremains on the data route and forwards the traffic to the new Nodex,

which itself forwards the traffic to the new Nodex-1;

– or the old Nodex is no more on the data route, and data traffic passes through the

new Nodex, which forwards the traffic to the new Nodex-1. This imposes that Nodex+1

managing the two Nodex acts as a data anchor for mobility between Nodex.

In the IP-AN organic architecture, there are two particular Nodex:

• The First IP router is the upper node within the IP-AN architecture. Within this node, a MN is mainly identified by its IP address making it reachable from the internet. The first IP router anchors data traffic between the internet and MNs, and even between MNs attached to the same IP-AN.

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CHAPTER 1. ARE CURRENT MOBILE NETWORKS READY FOR THE NEW ECOSYSTEM?

• The Connectivity Node (CoN) is the lower node within the IP-AN. It is the first hop connecting the MN to the IP-AN (e.g. eNB).