1. Chapter 9 Copyright 2001 Prentice-Hall
Wide Area Networking
Chapter 9
Copyright 2001 Prentice-Hall

2. Wide Area Networks WANs Link Sites (Locations)
Usually sites of the same organization
Sometimes, sites of different organizations
Site B
Site A
Site C
WAN

3. Carriers You can only install wires on your own property
Called your customer premises
To send signals between sites or to customers, you must use a carrier
Customer
Premises
Carrier

4. Carriers
Carriers transport data and voice traffic between customer premises, charging a price for their services
Receive rights of way from the government to lay wires and radio links
Carrier

5. Carrier Regulation Traditionally, Carriers Have been Regulated
Given rights of way
Given monopoly protection from competition
In return, services normally must be tariffed
Tariff specifies exact terms of the service to be provided, and
Tariff specifies price to be charged
Prevents special deals, which would be inappropriate for a regulated monopoly
Regulators must approve price for reasonableness

6. Carrier Regulation There is a Strong Trend Toward Deregulation
Gradual removal of monopoly protections
Allows competition, so lower prices and more service options
Fewer services need to be tariffed, allowing price negotiation

7. Carrier Regulation Service Level Agreements (SLAs)
Even under competition, carriers may guarantee specific levels of service for certain service parameters in an SLA
Throughput
Latency
Availability
Error Rates, etc.
Penalties are paid to customers if carrier fails to meet agreed-upon service levels

8. High Cost of Long-Distance
LAN Communication is Inexpensive per Bit Transmitted
So most LANs operate at 10 Mbps to a few gigabits per second
Long-Distance Communication is Very Expensive per Bit Transmitted
So Most WANs use low speeds
Most WAN demand is 56 kbps to a few Mbps