Practical TCP/IP and Ethernet Networking for Industry

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100 000 km WAN: Propagation delay about 0.5–2 seconds, a packet of 128 bytes

takes about 10 ms to transmit at 1 Mbps.

Therefore α is about 1 S/10 ms or 100. This means that for a WAN the packet reaches

the destination after a delay of 100 times the packet length.

Figure 2.4

Coupling ratios

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A cheaper alternative to a WAN, which uses dedicated packet switched links (such as

X.25) to interconnect two or more LANs, is the virtual private network, which

interconnects several LANs by utilizing the existing Internet infrastructure.

A potential problem is the fact ...