r (+ possibly IN service logic) Large/Medium Enterprises Large/Medium Other operator's Enterprises server server Internet network server "LAN" server SGSN/GGSN server "LAN" Access function Ethernet transport Access Packet backbone router transport router (MGW) router (MGW) Access Access transport transport (MGW) (MGW) WLAN hot spot Access Access transport transport Access To be added: transport Cable modem GSM/EDGE Homes & SMEs Copper xDSL Resource sharing Fibre Ethernet DSL WCDMA PSTN/ISDN Figure 14.2 Three control parts or domains in the control layer Control Network Mobile and fixed voice networks ('circuit-switched domain'). ISUP/BICC signalling. Data uses the connectivity layer Mobile data networks ('packet-switched domain') as introduced in GPRS Mobile and fixed IMS multimedia networks. Primarily SIP signalling. Carries media individually and as multimedia Signalling over IP solutions. Gateways SIP-ISUP. Sigtran. 'Softswitch' with SIP/H.323 signalling. See Figure 14.3, central part. Voice trunking with H.323 gatekeepers accord- ing to Chapter 8, Section 8.8.3 Figure 8 will not be further treated (See also Chapter 11, Figure 11.8). 14.2 THE ENVIRONMENT OF THE CONTROL NETWORK The introduction of the horizontal network is performed in an environment dominated by legacy networks with numerous signalling systems, especially on the access side (See Figure 14.3). A mixture of legacy and new (SIP, H.323) signalling systems will be com- mon. This will require signalling gateways. A typical signalling gateway connects ISUP and SIP. ISUP, V5 and Q.931 will be briefly treated when describing the circuit domain. The signalling traffic should be carried in protected paths in the connectivity network. The interfaces upwards and downwards are new. ISUP, V5 and Q931 will be briefly treated when describing the circuit domain. The signalling traffic should be carried in protected paths in the connectivity network. Compare the No 7 network where the user parts are carried by the MTP carrier. The interfaces upwards and downward