A 155-Mbps ATM OC-3 network module is available on the Cisco 3825 and 3845 integrated services routers, starting with Cisco IOS Software Release 12.4(3) Mainline. The network module supports the ATM forum standard ATM Adaptation Layer 5 (AAL5) with the following ATM quality of service (QoS) traffic classes: unspecified bit rate (UBR), UBR+, real-time variable bit rate (VBR-rt), non-real-time VBR (VBR-nrt), available bit rate (ABR), and constant bit rate (CBR). Voice over IP (VoIP) and H.323 over ATM is supported over the WAN using the currently available onboard voice digital signal processors (DSPs), analog voice and fax network modules, and voice interface cards.