Chapter 25: WAN Configuration Guide340 SmartSwitch Router User Reference Manualworks with IP Precedence or priority, as defined in the qos configuration command line,to provide preferential traffic handling for higher-priority traffic.The CLI commands related to RED in both the Frame Relay and PPP protocolenvironments allow you to set maximum and minimum threshold values for each of thelow-, medium-, and high-priority categories of WAN traffic.Adaptive ShapingAdaptive shaping implements the congestion-sensitive rate adjustment function and hasthe following characteristics:• No blocking of data flow under normal condition if the traffic rate is below Bc+Be• Reduction to a lower CIR upon detection of network congestion• Progressive return to the negotiated information transfer rate upon congestionabatementThe CLI command related to adaptive shaping allows you to set threshold values fortriggering the adaptive shaping function.Frame Relay OverviewFrame relay interfaces are commonly used in a WAN to link several remote routerstogether via a single central switch. This eliminates the need to have direct connectionsbetween all of the remote members of a complex network, such as a host of corporatesatellite offices. The advantage that Frame Relay offers to this type of geographic layout isthe ability to switch packet data across the interfaces of different types of devices likeswitch-routers and bridges, for example.Frame Relay employs the use of Virtual Circuits (VCs) when handling multiple logicaldata connections over a single physical link between different pieces of networkequipment. The Frame Relay environment, by nature, deals with these connections quitewell through its extremely efficient use of precious (sometimes scarce) bandwidth.You can set up frame relay ports on your SSR with the commands described in Chapter 15:“frame-relay Commands” in the SmartSwitch Router Command Line Interface ReferenceManual.Virtual CircuitsYou can think of a Virtual Circuit (VC) as a “virtual interface” (sometimes referred to as“sub-interfaces”) over which Frame Relay traffic travels. Frame Relay interfaces on theSSR use one or more VCs to establish bidirectional, end-to-end connections with remoteend points throughout the WAN. For example, you can connect a series of multi-protocolrouters in various locations using a Frame Relay network.
