Configuring IOS as a Proxy for Path and Resv Messages
Cisco ICS can send Path and Resv messages on behalf of clients. This proxy capability is useful for testing RSVP when you don't have any RSVP-enabled clients available. Figure 5-8 depicts such a scenario. Figure 5-8 Router A Can Proxy Path Messages for a Non-RSVP Client (Client A) Client A (sender) 192.168.20.1 non-RSVP Client A (sender) 192.168.20.1 non-RSVP Client B (receiver) 192.168.10.2 non-RSVP Client B (receiver) 192.168.10.2 non-RSVP Client A does nol support RSVP, so it cannot generate...
Effects of Global Synchronization and TCP Slow Start
Global synchronization combined with TCP slow starts can lead to some very undesirable results. When many TCP flows have one or more packets dropped in a tail drop, they all go through TCP slow start at the same time. This means these flows all slow down at the same time, and traffic on the network as a whole drops abruptly. The network gets significantly quieter than it was before the tail drop (again, this assumes most of the traffic is TCP). Next, because the flows are synchronized, they all...
How RED Works
RED randomly drops packets based on the number of packets queued on an interface As a queue reaches its maximum capacity, RED drops packets more aggressively to avoid a tail drop. RED throttles back Mows and takes advantage of TCP slow start. Rather than tail-dropping all packets when the queue is full. RED manages queue depth by randomly dropping some packets as the queue fills (past a certain threshold). As packets drop, the applications associated with those dropped packets slow down and go...
Configuring RSVP
Configuring RSVP is simple so simple, in fact, that the temptation is to enable RSVP without fully understanding how it works. This is not a good idea, which is why this chapter covers the mechanics before it discusses the configuration. RSVP is enabled on router interfaces, not on the router as a whole. This gives you the flexibility to enable RSVP on some interfaces but leave other interfaces alone. Figure 5-7 WFQ on Outbound Interfaces Ensures Data Is Delivered at the Desired QoS To...
Configuring CBWFQ
Configuring CBWTQ comprises three basic steps Step 1 Separate your traffic into classes with class maps. Step 2 Define the QoS for each class using policy maps. Step 3 Apply the policy map to an interface. The following sections demonstrate each of these steps using an example. Separate Your Traffic Into Classes with Class Maps The first step in CBWFQ is to separate your traffic into different classes so you can later apply QoS to those classes. Class maps define the names of your classes and...
