nnot create this class, but you should configure it in your policy maps. Service Policies service-policy is simply the command that applies your class maps and policy maps to an interface. Because we're looking to improve performance on the WAN link, we'll apply our service-policy statement to the T1 interfaces on the WAN routers: int So/o service-policy output WAN-Edge Service policies are applied on the output side of an interface. Remember that we're trying to affect how packets are sent onto a link. Received packets have already traversed the link, SO there's nothing we can do about them on the receive side. Be warned that when you change the service policy on an interface, you clear the interface SO it can apply the new queuing mechanism. For IP data traffic this is not usually a problem, but it may disconnect, or, at the very least, cause audible gaps in voice calls. Chapter 30: Designing a QoS Scheme Once you apply the service policy, all of your policies are in effect. Our final configuration is as follows: class-map match-any Mail-Traffic description [ [ Any Mail Traffic (Set on WAN Router) ]---] match protocol smtp match protocol pop3 match protocol imap match protocol exchange policy-map WAN-Link description [---[ --- Apply Treatment for Classes ]---] class Voice-Calls priority 148 class Voice-Control bandwidth 30 class Telnet-Traffic bandwidth 64 class HTTP-Call-Center bandwidth 384 class Mail-Traffic bandwidth 128 class class-default fair-queue int So/o service-policy output WAN-Edge Configuring the Routers CHAPTER 31 The Congested Network A congested network is one where there's too much data, and not enough band- width to support it. QoS can help with a congested network, but it cannot cure the root problem. The only ways to cure congestion on a network are to add more band- width, or reduce the amount of data trying to flow over it. That being said, let's look at a congested network, and see how we might fix it. Determining Whether the Network Is Congested How do you know if your network is conges