rnet Protocol Different players of the telecommunications business ecosystem may be divided according to the different layers of the IP suite. The infrastructure layer businesses are active in the network access/physical layer, providing a mechanism for packets to be sent to the retail layer. The retail layer business serves customers using the TCP/IP internet and transport layers and con- nects them to the application and content providers in the application layer, as illustrated in Figure 8.14. Switching and Routing As discussed above internet packets are individually and independently forwarded at each network node. Two modes exist for forwarding packets at a network node: switching; and routing. Broadband Telecommunications Technologies and Management Content and services layer Transport header Connectivity retail layer IP data header Network Infrastructure layer Frame data header Subscriber/End-user Figure 8.14 Telecommunications business ecosystem and IP suite layers Server Printer Figure 8.15 Local switching through a hub In practice, any packet from a local device is sent to a local switch. If the receiver is also within the local network, the switch knows its network (MAC) address and therefore can switch the message directly to the recipient. Switches therefore operate at the link layer. An example of a switching operation could be a file sent to the local network printer. At times the switch, sometimes called a hub, broadcasts the received message to all its devices including the destination device. This is illustrated in Figure 8.15. If the packet is intended for an address outside the local network, the destination MAC address is a gateway device to which the packet is sent. The local gateway then forwards it to the edge router of the internet service provider (ISP). A router receives packets from a number of nodes and forwards them to another node depending on the destination IP address. This is illustrated in Figure 8.16. Each router maintains a routing table which it updates regularly to determine