Summary

QoS is the ability to define a specified level of network performance, enabling certain (customer specified) applications to have better service than others. QoS provides priority to customer traffic across a network by dedicating bandwidth, controlling jitter and latency (required by some real-time and interactive traffic), and improving loss characteristics.

CoS differentiates traffic based on priority. Labels or tags can be added to the packets to identify such classes, but CoS does not guarantee traffic delivery; whereas QoS does provide for such a guarantee.

There are currently four WAN technologies that have some provisions for QoS/CoS:

• ATM

• Frame Relay

• IP

• MPLS/MPLS-TE

Each of these technologies enables QoS/CoS support in different ways that are specific and limited to the constraints of the technology itself. For example, IP does not provide for a CIR in the way that Frame Relay does or for the several Classes of Service that ATM provides.