Switching concepts
Download
1 / 22

Switching Concepts - PowerPoint PPT Presentation


  • 110 Views
  • Uploaded on

Switching Concepts. Introduction to Ethernet/802.3 LANs Introduction to LAN Switching Switch Operation. Switching Concepts. Introduction to Ethernet/802.3 LANs. Ethernet Technology Overview. Ethernet multi-access broadcast technology Uses CSMA/CD Collisions impact on network performance

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Switching Concepts' - king


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Switching concepts

Switching Concepts

Introduction to Ethernet/802.3 LANs

Introduction to LAN Switching

Switch Operation


Switching concepts1

Switching Concepts

Introduction to Ethernet/802.3 LANs


Ethernet technology overview
Ethernet Technology Overview

  • Ethernet multi-access broadcast technology

  • Uses CSMA/CD

  • Collisions impact on network performance

  • Layer 2 devices can improve performance

  • Media includes CAT5(e), fibre, wireless

  • Speeds from 10Mbps to 10,000 Mbps


Network growth
Network Growth

  • Bandwidth needs have increased

    • Internet/intranet/email

    • Multimedia

    • Increasing use of enterprise servers

  • Ethernet has developed to meet challenge

    • 10Mbps, 100Mbps, 1000Mbps, 10Gbit

    • Coaxial, Twisted Pair, Fibre Optic, Wireless

    • Repeaters, hubs, bridges, switches, routers

  • BUT you must understand the features of all this technology to gain best performance in your network design!


Switching concepts
Hubs

thick Ethernet or thin Ethernet infrastructures

  • Layer 1 devices

  • Regenerate, retime, amplify signals

  • 1 collision/bandwidth domain

  • Broadcasts propagated out of every port

  • Only 1 device can transmit at a time

  • Only 50-60% bandwidth available


Bridges
Bridges

  • Layer 2 device

  • Splits network into 2 collision/bandwidth domains

  • Broadcasts are forwarded

  • Local traffic stays local

  • Checks Layer 2 MAC addresses in 802.3 frame


Switches
Switches

  • Layer 2 device

  • Learns MAC addresses of devices attached to each port

  • Each switchport is a collision domain

  • More collision domains BUT smaller collision domains

  • Broadcasts still sent out of every port

  • Each switchport has dedicated bandwidth

  • 100% bandwidth available



Elements of ethernet 802 3 networks
Elements of Ethernet/802.3 networks

  • Broadcast data frame delivery of Ethernet/802.3

  • The carrier sense multiple access/collision detect (CSMA/CD) method allows only one station to transmit at a time.

  • Multimedia applications with higher bandwidth demand such as video and the Internet, coupled with the broadcast nature of Ethernet, can create network congestion.

  • Normal latency as the frames travel across the layers

  • Extending the distances and increasing latency of the Ethernet/802.3 LANs by using Layer 1 repeaters.


Transmission time latency
Transmission Time & Latency

  • Bit time – time taken to recognise 1 bit

  • Minimum frame size - 64 bytes – 512 bits

  • Maximum frame size – 1518 bytes – 12,144 bits

  • Transmission time is always 512 bit times

  • 10Mbps – 64 byte frame - 51,200 ns (100ns bit time)

  • 100Mbps – 64 byte frame 5,120 ns (10 ns bit time)

  • 1000Mbps – 64 byte frame – 512 ns (1ns bit time)

    Times above do not include

  • Time taken to propagate signal along medium

  • Delays introduced by hubs/switches/routers/NICs etc


Types of transmission
Types of Transmission

Half-duplex

  • Host checks medium for signal – if clear host transmits

  • Only 1 host can transmit at a time

  • Collisions – jam signal generated, back-off algorithm before retransmission

  • 50-60% bandwidth available

Full duplex

  • Host can transmit immediately

  • 2 hosts can transmit simultaneously

  • No collisions

  • 100% bandwidth available

  • Requires dedicated connection to a switchport


Switching concepts2

Switching Concepts

Introduction to LAN Switching

Switch Operation


Overview
Overview

  • Maximum availability for the least cost

    • Reduce the effects of collisions on available bandwidth

    • Reduce the effect of broadcasts on available bandwidth

    • Deploy network hardware (media/switches/routers) to overcome bottlenecks & meet bandwidth requirements


Lan segmentation bridges
LAN Segmentation - bridges

  • A bridge splits a LAN into 2 segments

  • It creates 2 collision domains

  • Adds 10-30% latency

  • Learns MAC addresses

  • Keeps local traffic local

  • Forwards broadcasts


Lan segmentation with bridges
LAN Segmentation With Bridges

  • Segmentation provides fewer uses per segment

  • Bridges store, then forward frames based on Layer 2 addresses (CRC verified)

  • Layer 3 protocol-independent

  • Increase latency on the network


Lan segmentation switches
LAN Segmentation - Switches

  • Each switchport is a collision domain – “micro-segmentation”

  • 100% bandwidth available to each switchport

  • Every switchport can send/receive simultaneously

  • Host to switch/switch to switch connection creates full duplex link


Lan segmentation with routers
LAN Segmentation With Routers

  • More manageable, greater functionality, multiple active paths

  • Smaller broadcast domains

  • Operates at Layer 3


Lan switch operation 1
LAN Switch Operation - 1

  • When a switch starts up it sends a broadcast out of all ports to learn host MAC addresses

  • When a frame is received for an unknown destination a broadcast is sent to discover

  • Addresses are added to a switching table mapping them to the port on which they were learned

  • When a frame is received for a known destination it is switched to the appropriate port


Lan switch operation 2
LAN Switch Operation - 2

  • Switches contain RAM – known as CAM “Content Addressable Memory”

  • Stores MAC address table

  • Used as frame buffer

  • Used to queue frames in asymmetric switching – switchports operating at different speeds e.g. 10 and 100 Mbps


Switching methods
Switching Methods

Cut-through Switching

  • Fast-forward – as soon as destination address is read switching starts

  • Fragment-free – after 64 bytes have been received (minimum valid frame size) frame is switched

    Store & Forward Switching

  • Entire frame is received before switching

Increased Latency


Terminology
Terminology

  • Ignoring a frame – filtering

  • Copying a frame – forwarding

  • Microsegmentation – dividing a network into smaller segments (using a switch)


Broadcasts
Broadcasts

  • Bridges & switches cannot block layer 2 or layer 3 broadcasts

  • Adding bridges or switches to a network extends the broadcast domain but creates additional collision domains – a 24 port switch creates 24 collision domains

  • Routers can inspect layer 3 packets and create broadcast domains – a router with 3 ports creates 3 broadcast domains