ations use the following to ensure voice quality and security. Adequate capacity If there is congestion due to inadequate capacity, the network will discard packets and voice quality will be degraded. QoS solutions Solutions that mark and prioritize voice are important to ensure minimal delays for acceptable voice quality. See the upcoming sec- tions "Assessing Network Quality by Using Voice Quality Measurements" and "Prioritizing Voice and Video on a VLAN" for information about voice quality measurements and Virtual LANs (VLANs). Compression Compressing and digitizing voice signals impacts qual- ity. For example, the recently developed compression algorithm, Adaptive Multi-Rate Wideband (AMR-WB), based on the G.722.2 standard, is able to compress 16,000 samples of voice per second to lower rates, including 12.65 kilobits per second. At this rate, each voice session uses only 12.65KB of bandwidth, but provides better audio than earlier compression standards, Data Centers and IP Private Branch Exchanges including G.711, which required more capacity. G.722.2 provides high-defi- nition (HD) voice and is used for some mobile voice traffic. Security against viruses, worms, and distributed Denial of Service (DoS) Worms are malicious programs that attempt to disrupt normal com- puter and network operation by duplicating themselves on multiple comput- ers. Worms, which are also known as bots, are like viruses except that they are programmed to start infecting computers or other devices on networks at a predetermined future date. In distributed DoS attacks, hackers send millions of simultaneous messages to networks in attempts to disrupt their capability to cope with that level of traffic. Security Monitoring Services Organizations subscribe to security moni- toring services to receive patches that prevent attacks from newly discovered viruses, worms, and distributed DoS attacks. In addition to the preceding, proxy servers authenticate callers to verify that they are who they say they are before being sent to their destin