computer that is designed to transfer datagrams from one network to another. The IP protocol routes datagrams by hopping from network to network. The router acts as a connection point between networks, or a gateway. Software hides the underlying routing process from the user and thereby makes the process transparent. H.323 H.323 Public Workstation Workstation Switched Telephone Network H.323 Workstation Internet Ethernet H.320 H.323 IP Phone Workstation Workstation Router H.323 Workstation Ethernet Gateway Switch Ethernet H.323 Gatekeeper Database Application H.323 Server Server Workstation Multipoint Control Unit Fileserver H.323 IP Phone Workstation Figure 10-2. An H.323 Network. Routers perform their task by using IP addresses. IP addresses are actually 32-bit strings that identify specific network devices. To make them easier to remember and understand, people express IP addresses in dotted decimal notation, (e.g., 134.13.9.6). When conveyed across a network, these addresses are converted to hexadecimal notation (hence, the 32 bits). Special database servers, or DNS (Domain Name System, RFC 1034, 1035) servers, translate IP addresses into more recognizable Internet addresses. An example of this is name@company.com. Video Communications: The Whole Picture Application Messages or Streams Transport Transport Protocol Packets Internet IP Datagrams Network-Specific Transport Frames Figure 10-3. Layering in the TCP/IP Protocol Stack (Laura Long). The component of the address to the left of the @ character is the local part of an address, and identifies a user. The component to the right side of the @ character identifies the domain, or the name of the system (whether that person's company or an Internet service provider) that provides services for the user. A domain name such as company.com refers to the company, company, in the commercial (com) sector. Other suffixes include org for non-profit organizations, edu for educational institutions, gov for government agencies, and net for network services providers. The 