Cisco Hierarchical Network Model-

Cisco Hierarchical Network Model--

CORE LAYERà  Responsible for fast and reliable transportation of data across a network. It reduced the latency time in the delivery of packet. It does not route traffic to the network. Also referred to as the backbone layer.

Functions include of core layer---

High data transfer rate.

Low latency period

High reliability

Devices include

Cisco Switches in the 7000, 7200, 7500 and 12000 series for connecting to the WAN devices

Catalyst Switches in the 6000, 5000 and 4000 series for connecting to the LAN devices

DISTRIBUTION LAYERà  Responsible for routing and managing network traffic. Also called Workgroup layer.

Functions include--

Packet filtering

Access layer aggregation point

Control broadcast and multicast

Application gateways

Access layerà This Layer ensures that the packets are delivered to the destination computers. Also called Desktop layer.

Functions include---

Address filtering

Separate collisions domain

Share bandwidth

Handle switch bandwidth

Core layer-- Also referred to as the backbone layer. It is responsible for transferring large

amounts of traffic reliably and quickly – switches traffic as fast as possible. A failure in the core can affect many users; hence fault tolerance is the main concern in this layer. The core layer should be designed for high reliability, high availability, high redundancy, high speed, and low convergence. Do not support workgroup access, implement access lists, VLAN routing, and packet filtering which can introduce latency to this layer.

Distribution layer---

Also referred to as the workgroup layer. Its primary functions are routing, Inter-VLAN routing, defining or segmenting broadcast and multicast domains, network security and filtering with firewalls and access lists, WAN access, and determining (or filtering) how packets access across the core layer.

Access layer---

Also referred to as the desktop layer. Here is where end systems gain access to the network. The access layer (switches) handles traffic for local services (within a network) whereas the distribution layer (routers) handles traffic for remote services. It mainly creates separate collision domains. It also defines the access control policies for accessing the access and distribution layers.