Page 141 - Handout Computer Network.

Computer Network 2026

D. How to locate recipients of the updates

6.6 How Distances on Network Paths Are Determined by Various Metrics

When a routing algorithm updates a routing table, its primary objective is to determine
the best information to include in the table. Each routing algorithm interprets what is best in its
own way. The algorithm generates a number called the metric value for each path through the
network. Typically, the smaller the metric number is, the better the path is, as shown in Figure
6-12 shown a Metric Used to Define Best Path.

Figure 6-12 shown a Metric Used to Define Best Path

You can calculate simple metrics based on a single characteristic such as path, or you can
calculate more complex metrics by combining several characteristics.

The metric characteristics that most commonly are used by routers are as follows:

• Bandwidth—The data capacity of a link. (Normally, a 10-Mbps Ethernet link is
preferable to a 64-kbps leased line.)

• Delay—The length of time required to move a packet along each link from source
to destination.

• Load—The amount of activity on a network resource such as a router or a link.

• Reliability—Usually a reference to the error rate of each network link.

• Hop count—The number of routers that a packet must travel through before
reaching its destination.
• Ticks—The delay on a data link using IBM PC clock ticks (approximately 55
milliseconds, or 1/18 second).

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