Ethernet Basics 10 Hubs Switches Hubs Switches q

Ethernet Basics -10 Hubs & Switches

Hubs & Switches q There is only so much available bandwidth, in some instances it can be dynamic q An overabundance of data on the network, not only affects the infrastructure equipment tasked with its distribution, but also the end devices or nodes meant to receive it. q Once a node has been overwhelmed, it needs to recuperate or recover and so called “time outs” can occur.

Hubs & Switches q To understand the differences between Hubs, Switches, and Managed switches, the 3 types of traffic must be understood There are 3 types of ‘traffic’ 1. 2. 3. Unicast Multicast Broadcast q

Traffic Types - Unicast q Unicast = 1 to 1 communication. Traffic generated by one device meant specifically for another.

Traffic Types - Multicast q Multicast = 1 to many nodes communication. Traffic generated by one device meant for multiple nodes but not necessarily all nodes

Traffic Types - Broadcast q Broadcast = 1 to all nodes communication. Traffic generated by one device and sent to all other devices.

Traffic Types – Unicast, Multicast and Broadcast q The type of traffic directly effects the amount of traffic on a Network or "Networking" device q The amount of traffic directly effects the bandwidth utilization of that device. q The bandwidth utilized on the device effects the device’s ability to transmit and receive data in an efficient manner. q Network performance will degrade if too much bandwidth is used because of too much of the wrong kind of traffic

Hubs q Devices which regenerate incoming signals (frames) and distribute them to all other ports. (Broadcast) q Considered to be “dumb” devices (indiscriminately send data everyone with no means to filter it) q Do not support 10/100 auto-sensing (either 10 BASE OR 100 BASE) q Subject to rules of Propagation Equivalent and Variability Value (Calculations necessary for a “collision domain”)

Operating mode of a Hub From I/O 1 To PLC 1 From I/O 1 PLC 1 To PLC 1 From I/O 1 To PLC 1 Data Storage server

Operating mode of a Hub From PLC 1 To I/O 1 From PLC 1 To I/O 1 Data Storage server

Operating method of a Hub

Unmanaged Switches q A Device which delivers a received Unicast data packet only to that port on which the destination station is connected. q ALL switches on the network instantly recognize newly attached devices, read MAC address and records that into its address table q RJ 45 ports are typically 10/100 auto-negotiation/crossing q Multiple versions for variety of RJ 45/Fiber port configurations q It is a good practice to keep extra ports for expansion, laptop access and networking to rest of network

Managed Switches q Managed switches can operate on a network without any set up programming as do Unmanaged switches q Managed switches can be given their own IP address, permitting custom configuration of ports and overall control of switch q SNMP software as well as other methods allow for the monitoring and configuration of (alarming, bandwidth utilization, security, etc. )

Operating mode of a Switch q On a switch, each port is a Collision Domain q Can communicate @ 10/100 mbps Half or Full Duplex q Unicast traffic is sent only to the port it is destined to go From PC 12 To PLC B PLC A

Operating mode of a Switch q How does a switch direct Unicast traffic efficiently? Address table Port 1 Port 2 Port 3 Port 4 Port 5 PC 1 RC 11 PLC C PLC B PLC A RC 12 RC 13 P 1 PC 1 P 5 P 4 P 2 PLC A PLC C PLC B RC 11 RC 12 RC 13

Operating mode of a switch Address table Port 1 Port 2 Port 3 Port 4 Port 5 From PC 1 RC 11 PLC C PLC B PLC A RC 12 RC 13 To PLC C P 3 P 1 PC 1 P 5 P 4 P 2 From PC 1 PLC A To PLC C PLC B RC 11 RC 12 RC 13

Operating mode of a Switch Address table Port 1 Port 2 Port 3 Port 4 Port 5 From PC 1 P 3 To PLC C P 1 PC 1 From PLC A PLC 1 RC 11 PLC C PLC B RC 12 RC 13 P 5 P 4 P 2 From PLC 1 To RC 11 From PC 1 To PLC C To RC 11 PLC A PLC C PLC B RC 11 RC 12 RC 13

Managed vs. Unmanaged Switches

Switches – unmanaged q Device which delivers a received Uni-Cast data packet only to that port on which the destination station is connected. q ALL switches on the network instantly recognize newly attached devices, read MAC address and records that into its address table (no manual configuration needed) q RJ 45 ports are typically 10/100 auto-sensing q Multiple versions for variety of RJ 45/Fiber port configurations

Switches – Managed q Device which delivers a received Uni-Cast data packet only to that port on which the destination station is connected. q ALL switches on the network instantly recognize newly attached devices, read MAC address and records that into its address table (no manual configuration needed) q RJ 45 ports are typically 10/100 auto-sensing q Multiple versions for variety of RJ 45/Fiber port configurations

Managed Vs Non-Managed q Can be programmed using Serial, Web interface, or SNMP software q Port security - Security functionality is important in terms of awareness and prevention of unwanted access to devices as well as the network as a whole. q Port mirroring - necessary for accurate network diagnostic monitoring and troubleshooting by allowing you to copy the Unicasts traffic from one port to another. q Multicast Filtering - provides for the proper management of IP multicast traffic. It ensures that not only Unicasts but multicast traffic is properly directed only where it is meant to go. q Remote monitoring – Allows for the capability of remotely monitoring conditions and criteria of the "goings on" of the switch. q Spanning Tree Protocol facilitates redundant back bone connections and loop free networks. q Prioritization support, ensures that frames tagged with higher priority will be handled quickly and efficiently. q Broadcast Limiters which allow the administrator to filter the amount of broadcast traffic on a packets per second per port basis.

Remember the traffic? q Unicast traffic, through a hub, is like broadcast traffic q Multicast traffic through a hub or “unmanaged Switch” is like broadcast traffic q Broadcast traffic when not controlled, can affect overall network performance as well as your network nodes ability to perform its primary process causing “time outs” which lead to communication failures and ultimately process failure

Managed Vs Non-Managed Features Managed l Prevent collisions l Auto-polarity, -sensing l Auto-negotiation, -MDI/MDIX l Web interface l Port security l Port mirroring l Multicast Filtering/IGMP l Remote monitoring l Redundancy l SNMP l Broadcast Limiter Unmanaged

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