Skip to main content

Spanning Tree Protocol

Spanning Tree Protocol
7.2.2 This page will explain how STP can be used to create a loop free network.
Ethernet bridges and switches can implement the IEEE 802.1d Spanning-Tree Protocol and use the spanning-tree algorithm to construct a loop free shortest path network. 
Shortest path is based on cumulative link costs. Link costs are based on the speed of the link. 
The Spanning-Tree Protocol establishes a root node called the root bridge. The Spanning-Tree Protocol constructs a topology that has one path for every node on the network. This tree originates from the root bridge. Redundant links that are not part of the shortest path tree are blocked.
It is because certain paths are blocked that a loop free topology is possible. Data frames received on blocked links are dropped.
The Spanning-Tree Protocol requires network devices to exchange messages to detect bridging loops. Links that will cause a loop are put into a blocking state.
Switches send messages called the bridge protocol data units (BPDUs) to allow the formation of a loop free logical topology. BPDUs continue to be received on blocked ports. This ensures that if an active path or device fails, a new spanning-tree can be calculated.
BPDUs contain information that allow switches to perform specific actions:
  • Select a single switch that will act as the root of the spanning-tree.
  • Calculate the shortest path from itself to the root switch.
  • Designate one of the switches as the closest one to the root, for each LAN segment. This switch is called the designated switch. The designated switch handles all communication from that LAN segment towards the root bridge.
  • Choose one of its ports as its root port, for each non-root switch. This is the interface that gives the best path to the root switch.
  • Select ports that are part of the spanning-tree. These ports are called designated ports. Non-designated ports are blocked. 
The Interactive Media Activity will teach students about STP.
The next page will describe the features of a spanning-tree network.

Comments

Post a Comment

Popular posts from this blog

OSI layers / Peer-to-peer communications / TCP/IP model

OSI layers 2.3.4 This page discusses the seven layers of the OSI model. The OSI reference model is a framework that is used to understand how information travels throughout a network. The OSI reference model explains how packets travel through the various layers to another device on a network, even if the sender and destination have different types of network media. In the OSI reference model, there are seven numbered layers, each of which illustrates a particular network function. - Dividing the network into seven layers provides the following advantages: • It breaks network communication into smaller, more manageable parts. • It standardizes network components to allow multiple vendor development and support. • It allows different types of network hardware and software to communicate with each other. • It prevents changes in one layer from affecting other layers. • It divides network communication into smaller parts to make learning it easier to understand. In the foll...
Post a Comment
Read more

Advantages and disadvantages of link-state routing

Advantages and disadvantages of link-state routing 2.1.5  This page lists the advantages and disadvantages of link-state routing protocols. The following are advantages of link-state routing protocols:  Link-state protocols use cost metrics to choose paths through the network. The cost metric reflects the capacity of the links on those paths. Link-state protocols use triggered updates and LSA floods to immediately report changes in the network topology to all routers in the network. This leads to fast convergence times. Each router has a complete and synchronized picture of the network. Therefore, it is very difficult for routing loops to occur. Routers use the latest information to make the best routing decisions. The link-state database sizes can be minimized with careful network design. This leads to smaller Dijkstra calculations and faster convergence. Every router, at the very least, maps the topology of it...
Post a Comment
Read more

PC Basic...

• Backplane – A backplane is an electronic circuit board containing circuitry and sockets into which additional electronic devices on other circuit boards or cards can be plugged; in a computer, generally synonymous with or part of the motherboard. • Network interface card (NIC) – An expansion board inserted into a computer so that the computer can be connected to a network. • Video card – A board that plugs into a PC to give it display capabilities. • Audio card – An expansion board that enables a computer to manipulate and output sounds. • Parallel port – An interface capable of transferring more than one bit simultaneously that is used to connect external devices such as printers. • Serial port – An interface that can be used for serial communication in which only one bit is transmitted at a time. • Mouse port – A port used to connect a mouse to a PC. • USB port – A Universal Serial Bus connector. A USB port connects devices such as a mouse or printer to the computer ...
Post a Comment
Read more