Quality of Service (QoS)

This chapter describes the approaches for prioritizing. Queuing methods such as priority queuing and custom queuing have their own approaches to moving key traffic to the head of the line. Internet protocol (IP) can enter the fray by enabling its packets marked with higher than normal precedence to get better service. Without explicit configuration, Cisco routers default to either a FIFO basis, or in certain mixes of hardware and software, to weighted fair queuing. This chapter emphasizes that bandwidth is limited, and any opportunity to conserve should be considered. Compression can reduce packet sizes, which can translate into faster transmittal as smaller packets take less time. Compression can place a burden on routers, so one should consider hardware options that offload this task. Routing via protocols such as routing information protocol (RIP) or open shortest path first (OSPF) is usually easy. If not, one can always modify routing behavior using policy based routing and adjusting attributes with route maps. Ultimately, all these tools are designed to give the control needed over the network.