Many enterprise network products vendors including Cisco use the ToS header data to define the Quality of Service (QoS) parameters and options (Bartolini, Casalicchio, 2006). Cisco and others are doing this to increase the performance of QoS implementations on IPv4 and IPv6-based networks. Traffic conditioning, congestion avoidance and congestion management all also must be included on QoS planning for IPV4 versus IPv6 implementations as well. Cisco and IBM are beginning to use constraint-based modeling approaches to streamline the configuration of IPv4 and IPv6 parameters in these specific options for traffic conditioning and congestion avoidance (Bartolini, Casalicchio, 2006). These constraint-based software engines are allowing for low-priority packets to be dropped from traffic workflows when there is a high probability of packet collision or congestion in lighter duty-cycle networks (Bartolini, Casalicchio, 2006). Congestion management strategies are critical for QoS to deliver high performance across IPv4 and IPv6 networks...

It is critically important that IPv4-based configuration of QoS parameters take full advantage of Network-based application recognition and Generic Traffic Shaping (GTS), two options not available on many implementations of IPv6 networks (Bianchi, Blefari-Melazzi, Chan, Holzbock, Fun Hu, Jahn, Sheriff, 2003). Priority Queuing and Custom Queuing in IPv4 networks is also critical for setting the foundation for effective QoS levels over the long-term as well (Bartolini, Casalicchio, 2006).