The Story Thus Far

As a refresher for readers, the first article in this series, (Sys Admin Vol 9, Issue 9) provided an overview of QoS and various methods that could be used to differentiate types of network traffic. In the second article in this series (Sys Admin Vol 9, Issue 10), I discussed QoS with the data link layer, outlining the role of the IEEE 802.1p standard in a switched-based LAN environment. The third (Sys Admin Vol 9, Issue 11) and fourth (Sys Admin Vol 9, Issue 12) articles comprised a two-part mini-series that described how traffic can be differentiated as it flows into a WAN. The third article focused on router queues and described different queuing methods, as well as illustrated relevant Cisco router commands to effect such methods. I concluded that article with an examination of the Type of Service (ToS) byte in the IP header, which paved the way for the second article that focused upon QoS into the network. That article covered the manner by which the use of the ToS byte was revised by the Internet Engineering Task Force (IETF). That revision, which was the focus of the fourth article, examined how the ToS byte was used to provide differentiated service (DiffServ) information to routers to expedite the flow of traffic through a network.