Chapter 31. The Congested Network
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 fix it.
Determining Whether the Network Is Congested
How do you know if your network is congested? Let’s look at our favorite two-building company again (Figure 31-1).
Figure 31-1. Typical two-building network
Users 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 the
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 Keepalive set (10 sec) LCP Open Open: IPCP, CDPCP Last input 00:00:00, output 00:00:00, output hang never Last clearing of "show interface" counters 3w4d
Queueing strategy: fifo
Output queue 0/40, 548941 drops; input queue 0/75, 3717 ...