h ensures that a call's or connection's underlying signaling information gets commu- nicated between gateways. The signaling information may include automatic num- ber identifiers, billing data, or other call triggers. Softswitches must communicate with packet switches, VoIP gateways, media gateways, and SS7 networks by using standardized protocols. A number of differ- ent technical specifications, protocols, and standards are involved in delivering these services and the desired end functions. As discussed in more detail later in this chapter, they include H.323, Megaco and MGCP, SIP, Real-Time Transport Proto- col (RTP), Real-Time Transport Control Protocol (RTCP), RTCP Reporting Exten- sion (RTCP XR), and Secure Real-Time Transport Protocol (SRTP). IP Devices A number of IP devices are available: Legacy support-Simple terminal adapters are available for standard telephones. IP hard phones-These are IP phones that look and work just like a tradi- tional multiline business display phone. They plug in to an Ethernet RJ-45 jack. Typically, they're proprietary and part of a vendor's platform. Their original prices were similar to PBX phones, around US$300 and up, but are now down to less than US$100. Emerging IP phone-on-a-chip technologies promise dramatically lower prices in the near future. IP soft phones-IP soft phones are software that runs on a user's PC and graphically resembles a phone. The key advantage of this approach is its low price. IP soft phones are gaining acceptance because applications such as presence management and IM are much better on a PC than on other devices. The disadvantages lie in the fact that an IP soft phone relies on the PC sound card, which can create problems with the volume level when switching between the soft phone and other applications that use the PC sound card. However, products such as the Clarisys USB handset (www.clarisys.com) overcome these problems. This device replaces the headset, rings audibly, includes a speakerphone, and, as a USB device, avoids the PC sound card.