Nortel Meridian 1 Description, Installation And Operation page 73

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Packet errors in intranets are generally correlated with congestion somewhere
in the network. Bottleneck links tend to be where the packet errors are high
because packets get dropped when they arrive faster than the link can transmit
them. The task of upgrading highly utilized links should also remove the
source of packet errors on a particular flow. Also an effort to reduce hop count
gives fewer opportunities for routers and links to drop packets.
Other causes of packet errors not related to queueing delay are as follows:
• Poor link quality. The underlying circuit may have transmission
problems, high line error rates, subject to frequent outages, etc. Note
that the circuit may be provisioned on top of other services, such as
X.25, frame relay or ATM. Check with the service provider for
resolution.
• Overloaded CPU. This is another commonly-monitored statistic
collected by network management systems. If a router is overloaded,
it means that the router is constantly performing
processing-intensive tasks, which impedes the router from
forwarding packets. Find out what the threshold CPU utilization
level is, and check if any suspect router conforms to the threshold.
The router may have to be re-configured or upgraded.
• Saturation. Routers can also be overworked when there are too many
high capacity and high traffic links configured on it. Ensure that
routers are dimensioned according to vendor guidelines.
• LAN saturation. Packets may also be dropped on under-engineered
or faulty LAN segments.
• Jitter buffer too small. Packets that arrive at the destination ITG, but
too late to be placed in the jitter buffer are essentially loss packets as
well.
ITG Line 1.0/IP Telecommuter Description, Installation and Operation
IP Telecommuter Engineering Guidelines Page 73 of 262