Ex3 Chapter 1 - LAN Design

Hierarchical network design (Cisco) model involves dividing the network into discrete layers. Each layer provides specific functions that define its role within the overall network.
The typical hierarchical design model is broken up in to three layers:
 - access,
 - distribution,
 - core.

An example of a three-layer hierarchical network design is displayed in the figure.


Access Layer - provide a means of connecting devices to the network and controlling which devices are allowed to communicate on the network
Devices: PCs, printers, and IP phones, routers, switches, bridges, hubs, and wireless access points (AP)

Distribution Layer - aggregates the data received from the access layer switches before it is transmitted to the core layer for routing to its final destination.The distribution layer controls the flow of network traffic using policies and delineates broadcast domains by performing routing functions between virtual LANs (VLANs) defined at the access layer.Devices: high-performance switches to ensure reliability

Core Layer - high-speed backbone of the internetwork
Devices: routers, switches capable of forwarding large amounts of data quickly

Benefits of a Hierarchical Network
 - Scalability / Hierarchical networks scale very well
 - Redundancy / Double distribution and core switches
 - Performance / High-performance distribution and core switches guarantee wire speed between all devices
 - Security / Various policies at access , advanced security policies at distribution
 - Manageability / Fast new deployment and simplified troubleshooting
 - Maintainability / Scale very easily

Network Design Principles
Network Diameter - the number of devices that a packet has to cross before it reaches its destination. Keeping the network diameter low ensures low and predictable latency between devices.

Bandwidth Aggregation - allows multiple switch port links to be combined so as to achieve higher throughput between switches (called EtherChannel from Cisco).

Redundancy - double up the network connections between devices, or you can double the devices themselves.

Convergence is the process of combining voice and video communications on a data network.

Switches
Layer 3 switches are also known as multilayer switches - filter and forward packets based on L2 addresses (MAC) and L3 addresses (IP).

Acces layer switch features:
 - port security
 - VLAN's
 - FastEthernet / GigabitEthernet
 - Power over Ethernet (PoE)
 - Link aggregation
 - Quality of Services (QoS)

Distribution/Core layer switch features:
 - L3 (IP) support
 - High/VeryHigh forwarding rate
 - GigabitEthernet / TenGigabitEthernet
 - Redundant components
 - Security policies / Acces Control Lists (ACL)
 - Link aggregation
 - Quality of Services (QoS)

Switch Form Factors
 - Fixed Configuration Switches / Features or options cannot be added to the switch beyond those that originally came with the switch
 - Modular Switches / Offer flexibility in their configuration (installation of different numbers of modular line cards)
 - Stackable Switches / Can be interconnected using a special cable (backplane - physical connection between CPU/card and data/power buses into a Cisco switch chasis) that provides high-bandwidth throughput between the switches, effectively operate as one large switch.
(StackWise technology allows up to nine switches to be interconnected )

Cisco switches (details)