A congested network is one where there’s too much data and not enough bandwidth 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 bandwidth 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 ease the pain using QoS.
How do you know if your network is congested? Let’s look at our favorite two-building company again (Figure 33-1).
Figure 33-1. Typical two-building network
Users at each building have been complaining that access to the
other building is slow. So, let’s take a look at the interfaces on one of
the routers that connects the T1 between buildings. Here’s the output from
show interface command
for the serial interface on Building B’s router:
sho int s0/0Serial0/0 is up, line protocol is up Hardware is PowerQUICC Serial Description: <[
T1 WAN Link]> Internet address is 10.10.10.2/30 MTU 1500 bytes,
BW 1544 Kbit, DLY 20000 usec, reliability 255/255,
txload 42/255, rxload 249/255Encapsulation PPP, loopback not set ...