tocols required for managing and con- trolling the ATM network. PNNI allows for the establishment and support of on- demand, switched connections, and the mechanisms that enable every node in the Understanding Changing Telecommunications - Building a Successful Telecom Business Other network Terminal Content Content (CPN, if any) Service network Protocol such asHHTP, Applications Service enablers Service enablers Access dependent SIP, H.323, BICC, ISUP IW sign signalling, or SIP (H.323) Gateway control protocol UNI(ATM) PNNI(ATM), OSPF, RIP Access Core connectivity Media gateway Might be one network element, only Figure 8.26 Signalling and routing systems, overview Management Traffic system system IN service control, HTTP, SMTP etc Control servers Connection control CO, CL Connectivity layer Traffic resources Figure 8.27 There are control functions in the connectivity and control layer network to maintain up-to-date information about any changes in every other node in the particular network. Note similarities with OSPF. B-ICI - The signalling and routing protocol for managing on-demand, switched con- nections between two ATM networks. B-ICI can also be used within an ATM network to improve control of traffic routing. Other protocols can be found in ATM as well as IP networks: BICC - The bearer independent call control protocol is used at the control layer. It is based on ISUP and is used for signalling between telephony servers. See more in Chapter 14. The H.248 protocol is used by the telephony server to control the media gateways, as described in Chapter 3. Service Implementation Private ATM network ATM network Dynamically calculated route for SVC Interconnected network B-ICI UNI signalling link File server Figure 8.28 Common signalling protocols in ATM IP-Oriented Control Layer Protocols Some short facts about H.323: A collection of standards: H.225 for session administration; H.245 for multimedia control; T.120 for sharing of data (whiteboard); H.235 for security; H.450 for addi- tional services Complex stand