typically used in a carrier's older networks. See Table 5-2 in the "Appendix" sec- tion of Chapter 5 for a description of ATM services. Edge routers also use addressing information to determine how to handle the data. Figure 6-1 presents a detailed look at a router that can be used at the edge or in the core portion of networks. Services on edge routers include the following (if a router is used in the core, it does not require the extensive services listed here). Authentication that verifies the sender is indeed who he identifies himself to be when he logs on to networks. Protected session setup that confirms that each multimedia session conforms to the features and QoS allowed to the computer making the request. This protects against fraud and ensures accurate billing. Network Address Translation (NAT) addressing that translates external IP addresses to internal IP addresses, and vice versa. Support for IPv4 and IPv6 addressing. IPv6 is designed to replace IPv4; it supports many more IP addresses than IPv4. Layer 2 switching for creating Virtual Private Line Service (VPLS) to communicate directly with databases and applications in data centers. (See Chapter 5 for a description of VPLS.) Firewall software that protects networks from hackers. Accounting to track subscriber packet usage in the event that carriers charge for usage. QoS per application and per user for VoIP and video. In addition to more intelligence, there are requirements for greater capacity in routers. This is caused by increasing use of video conferencing, greater demand for video by residential customers, access to cloud-based services, and growth in mobile smartphone Internet browsing. Router ports now commonly support 1Gbps as well as speeds up to 10Gbps. Total capacity of edge routers ranges from 1 to 3 terabits per second (Tbps). A terabit is the equivalent of 1,000 gigabits. The Structure of the Internet Juniper Networks Modular MX80 Router Twenty-port modular card for connections Two-port modular card that to optical networks; each port 