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Portfolio: Spanning Tree Essay
Scott Whitton
CMIT 225 T1 - Routing and Switching Fundamentals
Instructor: Scott Fortin
Date: 04/21/2016

SPANNING TREE PROTOCOL

Introduction

STP is composed of many elements that interact with one another in order to function properly. In order for STP to function. Primarily, switches communicate protocol information with the exchange of Bridge Protocol Data Units (BPDU). BPDU contain information related to ports, switches, port priority and addresses. Switches use BPDU to configure and maintain the spanning tree's topology. Switches do not forward received BPDU's along. Instead, switches use them for comparison and calculation of their own BPDU before passing them along to a neighboring switch.

To establish a Spanning tree, an administrator must first select a root switch with the network. The selection of a root switch is important because switch dictates all of the subsequent decisions about how the spanning tree expands throughout a network. Typically, the most centralized switch, which has the most amount of connections to other network regions, becomes the root switch of the spanning tree. The location of a root switch is important because it determines what ports forward data and which ports will be blocked and used for redundancy within the network's topology. It is important to note that within a VLAN environment, because each VLAN is a separate broadcast domain, each VLAN has discrete root switch as its focal point.

Once the root switch is established, switches exchange and compare data parameters within BPDU. Switches use compare incoming BPDU to its own data to determine which of its ports will be a part of primary active routes for data forwarding, and which ports to deactivated and used for redundancy in the case of a primary link failure. Establishing roles for ports eliminates loops within the topology and increases performance by reducing the resources needed for moving data inefficiently over the network.

The Need for Spanning Tree Protocol

STP ability to eliminate loops and generate redundant back up loops has been critical in the development and proliferation of the modern switched network. The development and growth of the modern network grew out of the need to connect more devices to the network. In order to scale to meet these needs, layer 2 switches became important infrastructure devices that expanded networking possibilities. Layer 2 Switches allowed more devices to connect to a network. By connected more switches to one another, networks are now able to scale to incredible sizes.

A problem with extensive connectivity creates data loops, which result in Broadcast storms, which cripple a network performance and render it unusable. When a loop exists, L2 switches will continually receive and regenerate broadcast and multicast data packets between its neighboring switches. This is as a broadcast storm. When a broadcast storm occurs data, traffic quickly exceed the capabilities of the network and the network becomes unstable. The use of STP ensures network stability through the prevention of data loops occurring, which in turn prevents broadcast storms from developing.

In addition, STP is critical to supporting network resilience by enabling redundancy in the case of a link failure within a network topology. Instead of simply generating a single pathway for data to travel and discarding all other possible routes, STP is able to put these alternative pathways into a backup state. These backup routes activate automatically if a primary path happens to go into a fault state. Enabling backup links in the case of network failure is crucial to keeping a network in and operational up state.

Spanning Tree's Components and Co-operation

A Spanning Tree is composed of many elements that interact with one another in order to function properly. In order for STP to function. Primarily, switches communicate protocol information with the exchange of Bridge Protocol Data Units (BPDU). BPDU contain information related to ports, switches, port priority and addresses. Switches use BPDU to configure and maintain the spanning tree's topology. Switches do not forward received BPDU's along. Instead, switches use them for comparison and calculation of their own BPDU before passing them along to a neighboring switch.

To establish a Spanning tree, an administrator must first select a root switch with the network. The selection of a root switch is important because switch dictates all of the subsequent decisions about how the spanning tree expands throughout a network. Typically, the most centralized switch, which has the most amount of connections to other network regions, becomes the root switch of the spanning tree. The location of a root switch is important because it determines what ports forward data and which ports will be blocked and used for redundancy within the network's topology. It is important to note that within a VLAN environment, because each VLAN is a separate broadcast domain, each VLAN has discrete root switch as its focal point.

Once the root switch is established, switches exchange and compare data parameters within BPDU. Switches use compare incoming BPDU to its own data to determine which of its ports will be a part of primary active routes for data forwarding, and which ports to deactivated and used for redundancy in the case of a primary link failure. Establishing roles for ports eliminates loops within the topology and increases performance by reducing the resources needed for moving data inefficiently over the network.

A Network without STP

It almost impossible imagine any of the advances in technology and society that we have come to realize if it were not for the existence of STP. Without the STP, there would be no way to expand beyond the simple hub networks. Every end-device would require a dedicated connection one another in order communicate, no routing and switching would exist within a network. Networks with so many end-to-end connections would be cost prohibitive, would be impossible to scale and maintain. Without STP, networks would never be able to evolve and develop into the complex and advance networks that they are today. Thanks to STP, we are able to live in connected society and are able to realize amazing achievements and benefits that have become central to living in the modern digital age.