4.6 Explain different methods and rationales for network performance optimization.
QoS stands for quality of service. In SOHO environment, QoS is normally set at router level. If you want to enforce QoS policies in your network, make sure you use a router, which is equipped with QoS software.
Load balancing is the process of distributing a server or network load over a multiple servers or networks. An example of load balancing is a clustered solution where each server in a clustered pool shares the load as per the design parameters.
High availability is incorporated in the system design so that the uptime of a system is maintained as per the designed standards under all circustances. High availability is usually design specific where as the fault tolorence is device or network specific.
Caching improves network performance by locally caching content, thereby limiting surges in traffic.
A VoIP telephony solution hosted by a service provider, which interconnects with a company's existing telephone system is known as Virtual PBX. A hosted PBX is one that is hosted by the telephone company on behalf of its customer. The important elements and the functions of a VOIP network are given below:
IP phone: An IP phone is a telephone with an integrated Ethernet connection. Although users speak into a traditional analog handset (or headset) on the IP phone, the IP phone digitizes the spoken voice, packetizes it, and sends it out over a data network (via the IP phone's Ethernet port).
Call agent A call agent is a repository for a VoIP network's dial plan. For example, when a user dials a number from an IP phone, the call agent analyzes the dialled digits and determines how to route the call toward the destination.
Gateway A gateway in a VoIP network acts as a translator between two different telephony signaling environments. In the figure, both gateways interconnect a VoIP network with the PSTN. Also, the gateway on the right interconnects a traditional PBX with a VoIP network. PBX A Private Branch Exchange (PBX) is a privately owned telephone switch traditionally used in corporate telephony systems. Although a PBX is not typically considered a VoIP device, it can connect into a VoIP network through a gateway.
Analog phone An analog phone is a traditional telephone, like you might have in your home. Even though an analog phone is not typically considered a VoIP device, it can connect into a VoIP network via a VoIP or, as shown in the figure, via a PBX, which is connected to a VoIP network.
SIP Session Initiation Protocol (SIP) is a VoIP signaling protocol used to set up, maintain, and tear down VoIP phone calls. Notice in the figure that SIP is spoken between the IP phone and the call agent to establish a call. The call agent then uses SIP to signal a local gateway to route the call, and that gateway uses SIP (across an IP WAN) to signal the remote gateway (on the right) about the incoming call.
RTP Real-time Transport Protocol (RTP) is a Layer 4 protocol that carries voice (and interactive video). Notice in the figure that the bi-directional RTP stream does not flow through the call agent.
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