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www.tech-faq.com/cisco-three-layer-model-vs-osi-model.shtml
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www.semsim.com/ccna/ccna-study-guide.asp?ain=57 -

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Posted by crouse

www.tech-faq.com/understanding-the-cisco-three-layer-hierarchical-model.shtml

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Posted by crouse

Please visit:

http://www.tech-faq.com/cisco-three-layer-model-vs-osi-model.shtml

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Posted by sagitraz

Access Layer
The access layer is the point that connects end users to the network. This can be achieved by a hub or switch to which PCs are connected, a wireless access point, a remote office connection, a dial-up service, or a VPN tunnel from the Internet into the corporate network.
Distribution Layer
The distribution layer provides routing, packet filtering, WAN access, and QoS (Quality of Service). The access layer devices (usually switches) connect to a router or Layer 3 switch so that traffic can be routed to another network. Packet filtering refers to the use of access control lists to identify certain types of traffic and control where it might go—or block it altogether.
Traditional WAN access usually involves a specialized interface—perhaps a serial port or ISDN Primary Rate Interface controller. These specialized functions are found on Distribution layer devices such as routers. If our network needs to use QoS features to make it run well, these features are typically first implemented at the distribution layer.
If our network includes different LAN technologies (Token Ring, Fiber-Distributed Data Interchange, and Ethernet, for example), the translation between these different media types is usually done by a distribution layer device. Because these devices are typically routers and Layer 3 switches, this is also where broadcast domain segmentation happens.
Core Layer
The Core layer is all about speed. Here, we typically find big, fast switches that move the data from the distribution layer to centralized resources such as mail and database servers, or to other distribution layer devices, as quickly as possible. The core does not usually do any routing or packet filtering, but it might do QoS if that is an important part of the network (if using Voice over IP [VoIP], for example).

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Posted by griffinLincoln

articles.techrepublic.com.com/5100-10878_11-5032795.html

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Posted by crouse