Monday, October 11, 2010
OSI Model Network Layer
The network layer defines the network address, which differs from the MAC address. Some network layer implementations, such as the Internet Protocol (IP), define network addresses in a way that route selection can be determined systematically by comparing the source network address with the destination network address and applying the subnet mask. Because this layer defines the logical network layout, routers can use this layer to determine how to forward packets. Because of this, much of the design and configuration work for internetworks happens at Layer 3, the network layer.
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Review Questions
Q—What are the layers of the OSI model?
A—Application, presentation, session, transport, network, data link, physical. Remember the sentence "All people seem to need data processing."
Q—Which layer determines path selection in an internetwork?
A—Layer 3, the network layer.
Q—What types of things are defined at the physical layer?
A—Voltage levels, time of voltage changes, physical data rates, maximum transmission distances, physical connectors, and type of media.
Q—What is one method of mapping network addresses to MAC addresses?
A—ARP, Hello, predictable.
Q—Which includes more overhead, connection-oriented or connectionless services?
A—Connection-oriented.
For More Information
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A—Application, presentation, session, transport, network, data link, physical. Remember the sentence "All people seem to need data processing."
Q—Which layer determines path selection in an internetwork?
A—Layer 3, the network layer.
Q—What types of things are defined at the physical layer?
A—Voltage levels, time of voltage changes, physical data rates, maximum transmission distances, physical connectors, and type of media.
Q—What is one method of mapping network addresses to MAC addresses?
A—ARP, Hello, predictable.
Q—Which includes more overhead, connection-oriented or connectionless services?
A—Connection-oriented.
For More Information
Cisco's web site (www.cisco.com) is a wonderful source for more information about these topics. The Documentation section includes in-depth discussions on many of the topics covered in this chapter.
Teare, Diane. Designing Cisco Networks. Indianapolis: Cisco Press, July 1999.
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