 network assistance is security. So, also in a 'stupid' network there is a need for assistance to the end user from the network operator. This assistance means at the same time that the operator gains control of the subscriber calls. A key component for awareness in the new horizontal networks is called the call session control server (CSCF). The CSCF will gather charging information and send it to a billing server. See Chapter 14 and Figure 3.5. Control signalling is transported in very different ways in circuit and packet-mode networks. In circuit-switched networks control messages are normally handled and trans- ported separately from user traffic by the well-standardized separate sub-network Sig- nalling System 7 (SS7). For further study of this important standard see Understanding Telecommunications books 1 and 2. In packet-switched networks data of the control plane and the user plane are transported in the same messages. This fact may have added to the impression that packet-switched networks lack control planes. In the horizontal networks the separation is not just logical (as in ISDN) but there is also a physical implementation defined called the gateway control protocol, GCP/H.248. Understanding Changing Telecommunications - Building a Successful Telecom Business Billing Telecom business Charging info Service, security, QoS Control Traffic resources M = Management system Traffic system = Network Figure 3.5 Control, traffic resources and charging based on control 3.3 WHAT IS A VERTICAL NETWORK? Today, almost all networks are 'vertically integrated' single-service networks where the operator offers everything from subscriber access to service creation and service deliv- ery across a wholly owned network infrastructure, optimized for a particular service category. Each vertically integrated network has its own protocols, nodes, end-user equip- ment/terminals and builds on different principles and practices to ensure reliability of a single service. These vertical 'monolithic' networks have basically their 