 network, network address, access point name and radio priority. Largely, we are again back to the fundamental plans. Service Implementation PS domain transport, IP end-to-end CS domain transport Header PAYLOAD bytes UDP/TCP Common transport for the PAYLOAD Header CS & PS bytes domain (AMR) Transport backbone Figure 8.15 Packets travelling in the network, example The basic packet typically consists of: Checksum Payload Address Control OSI 2 OSI 4 -7 OSI 2, 3 OSI 2 Checksum Payload Address Control Figure 8.16 Basic packet composition IP infrastructure The overall requirements on an IP backbone is to provide connectivity services embracing: - IP address assignment DHCP/RADIUS - domain name translation - routing Routers - address transparency (tunnelling) NAT, NAS - user authentication RADIUS, certificate server - user authorization RADIUS, firewall, proxies - accounting RADIUS - data authentication (digital signature, key management) Security gateway - data confidentiality (encryption, key management) Security gateway - data integrity (hash algorithms) Security gateway - filtering, proxies Proxies Figure 8.17 IP network support functions Understanding Changing Telecommunications - Building a Successful Telecom Business 8.6 THE ROLE OF FUNDAMENTAL TECHNICAL PLANS IN PACKET DESIGN From Figures 8.15 and 8.17 it is easy to recognize the following fundamental technical plans: routing, QoS (= checksum), numbering/addressing, security, charging and accounting. When extending the capabilities the QoS plan is even more important. From the PDP (packet data protocol) context information interconnection needs may obviously be involved, such as foreign operator identification (numbering) and a gateway. One might simply say that the packet propagation in the network is a teamwork between the packet design and its data, possible signalling, and the programming of the network elements, including the participating servers. The packet end-to-end transfer work should be as cheap as possible for the actors in the value chain, and as v