VICE LAYER Among the six segments in the service grouping, transactional services and messaging services are very much dependent on the service layer for their implementation. Service Implementation WAE = Wireless application environment WSP = Wireless session protocol WTP = Wireless transaction protocol WTLS = Wireless transport layer security WDP = Wireless datagram protocol Voice Voice WWWWAP browsing video Applications Camera WWW/WAP video Mobile Application (programming) interface commerce Java SIM Device Messaging Location (HLR/GPS) VAS enablers management services middleware H.323 H.323 IPv4, IPv6 numbering & routing IPv4, IPv6 numbering and routing AAL 1 Encapsu- IP/WLAN AAL 1 Encapsu- IP/WLAN lation IP/GPRS lation IP/GPRS PLMN/PSTN/ IP/WCDMA PLMN/PSTN/ IP/WCDMA Ethernet PDH/SDH/ Radio bearers, IP/CDMA Ethernet PDH/SDH/ Radio bearers, IP/CDMA SONET PDH/SDH/SONET/xDSL IP/DWDM SONET PDH/SDH/SONET/xDSL IP/DWDM Figure 8.21 An all-access architecture where the service groups are carried by IP or ATM transfer mode. The figure also shows some stratification possibilities, for example IP over ATM over SDH Transactional Services Transactional services are considered to have a very large potential. Standardization, accuracy and security are key enablers. Transactional services are very dependent on appli- cation support servers at the service layer for e-commerce, micro-payments for parking, cinema tickets etc. The services are not time critical, but the accuracy in the transaction must be very high. Transactional services should be protected as close to the application as possible. IPsec has many advantages, but it is located at the network level. Two closer protocols are secure socket layer (SSL) and S-HTTP, which complement each other. Whereas SSL is designed to establish a secure connection between two computers, S-HTTP is designed to send individual messages securely. An e-commerce service could work like this (see also Figure 8.22). 1. You want to buy something from the Internet and give the shop your card nu