ndicators. When this traffic is based on the SIP protocol, it is easy to extend the borders of trunking between appli- cations to include these nonvoice, nonvideo applications. It is important that these com- munications do not get siloed or require special translations to enable them to intercon- nect, which is why these other methods transition to SIP. In summary, you need to be aware of the important trends for trunking in an enterprise: Transition from traditional methods, such as TDM or H.323, to SIP for voice commu- nications Adoption of SIP as a method to interconnect various video endpoints within an enterprise 22 SIP Trunking Expansion of SIP to interconnect nonvoice/video traffic such as instant messaging and presence indicators Feature Trends in SIP Trunking Between Enterprises As multiple companies adopt IP telephony, a natural trend toward federation occurs. Federation is the capability to enable rich communications between companies without the use of an SP that offers anything beyond basic IP connectivity. The types of companies that want to form federations vary. At one end of the scale are two companies that are close for a long period of time. A good example is the out- sourced legal counsel of an organization. These companies are often close for a long peri- od of time and would benefit from integration of their UC infrastructures, but because they want to maintain independence, wholesale adoption of the other party's UC infra- structure is not possible. At the other end of the spectrum are companies that come together for a short period of time to collaborate for a specific service or function. The level of collaboration between the federated entities would greatly benefit from rich communications, but the standard method for collaboration with people outside of an organization is to use the PSTN for a phone call to collaborate via audio and use the Internet connection to collaborate via a shared web experience such as WEBEX from Cisco. However, this communication often takes place outside the